Science
Natural sciences and scientific concepts
Articles in this category are re-verified roughly every 180 days.
Science
Acoustic levitation
Acoustic levitation uses sound-induced forces to suspend or position objects without physical contact. In a common arrangement, ultrasonic waves form a standing-wave field whose acoustic radiation force can balance gravity and trap a sample. It enables contactless study and handling of droplets and solids, although stable positions depend on the object, acoustic field and operating conditions.
Updated 28 Oct 2026
Science
Acoustic streaming
Acoustic streaming is the time-averaged flow of a fluid generated by sound. Viscous absorption and momentum transfer from an acoustic field can create persistent currents even though the underlying sound oscillates rapidly. The phenomenon occurs in different forms near walls, in sound beams, and around oscillating bubbles, and is used to mix and move fluids in microfluidic devices.
Updated 28 Oct 2026
Science
Action potential
An action potential is a brief, regenerative change in a cell's membrane voltage that carries signals in neurons and other excitable cells. In neurons, voltage-gated sodium channels drive depolarization and potassium channels help repolarize the membrane; refractory periods and myelin shape how signals travel along axons.
Updated 31 Oct 2026
Science
Aharonov–Bohm effect
The Aharonov–Bohm effect is a quantum phenomenon in which electromagnetic potentials can contribute to the relative phase of charged-particle waves, even when the particles travel through regions where the corresponding electric and magnetic fields vanish. In its magnetic form, the phase difference depends on the magnetic flux enclosed by the alternative paths. Electron-interference experiments, including a 1986 test using a superconducting shield, have confirmed this prediction. The effect is commonly described using the vector potential, though it can also be formulated using gauge-invariant field variables for the complete system.
Updated 25 Oct 2026
Science
Airglow
Airglow is the faint, widespread light emitted by a planet's upper atmosphere through processes involving sunlight and atmospheric chemistry. Unlike auroras, which are powered by energetic particles associated with space weather, Earth's airglow is a persistent glow linked to ordinary solar radiation and chemical reactions. Its color and brightness carry information about atmospheric composition, temperature, density and motion, making it useful to researchers studying the boundary between Earth and space.
Updated 28 Oct 2026
Science
Albedo
Albedo is the fraction or percentage of incoming light or solar energy reflected by a surface or body. It helps describe Earth's energy balance: snow and clouds generally reflect more sunlight than dark ocean, forests or many urban surfaces. When snow and ice melt, darker surfaces can absorb more solar energy, creating an ice–albedo feedback that amplifies an initial warming. Scientists use ground observations and satellite measurements of reflectance to study Earth's changing land surfaces and climate.
Updated 22 Oct 2026
Science
Anammox
Anammox, short for anaerobic ammonium oxidation, is a microbial process in which ammonium and nitrite are converted mainly into nitrogen gas under oxygen-poor conditions. Carried out by specialized bacteria, it removes biologically available nitrogen from natural waters and is used in engineered wastewater treatment. Its role in the nitrogen cycle and its distinctive metabolism have made anammox important to ecology and environmental engineering.
Updated 25 Oct 2026
Science
Archimedes' principle
Archimedes' principle states that the buoyant force on a body in a fluid equals the weight of the fluid displaced by the body. It explains why submerged objects appear lighter and, together with an object's weight and average density, helps determine whether it sinks, floats or remains suspended.
Updated 31 Oct 2026
Science
Arctic amplification
Arctic amplification is the tendency for the Arctic to warm more rapidly than the global mean as the climate warms. It arises from interacting processes rather than a single cause. Retreating snow and sea ice expose darker surfaces that absorb more sunlight, while atmospheric and oceanic heat transport, cloud and water-vapour effects, and vertical temperature structure also shape the response. The strength of these processes varies by season and location.
Updated 26 Oct 2026
Science
Arecibo Observatory
Arecibo Observatory in Puerto Rico was a major center for radio astronomy, planetary radar and atmospheric research. Its 305-meter radio telescope made influential contributions to astronomy before collapsing in December 2020; the site continues to support science and education activities.
Updated 9 Nov 2026
Science
Asthenosphere
The asthenosphere is a mechanically weak, slowly deforming region of Earth's upper mantle beneath the rigid lithosphere. Although its rocks are mostly solid, elevated temperature and pressure allow them to flow over geological timescales. This contrast in mechanical behaviour helps explain how tectonic plates move, while seismic and geodynamic observations show that the asthenosphere is not a simple, uniformly molten layer with one universally fixed boundary.
Updated 26 Oct 2026
Science
Atmospheric refraction
Atmospheric refraction is the bending of light as it travels through air whose refractive index changes with altitude and atmospheric conditions. It shifts the apparent position of celestial objects, with the largest ordinary effects near the horizon. The phenomenon makes the Sun and stars appear higher than their geometric positions and affects observed sunrise and sunset times.
Updated 30 Oct 2026
Science
Aurora
An aurora is a natural light display in a planet's upper atmosphere. On Earth, auroras form when energetic particles in near-Earth space collide with atmospheric gases, which then emit light. The solar wind and solar eruptions transfer energy into Earth's magnetosphere, helping drive this activity around the magnetic poles. Known as the aurora borealis in the north and aurora australis in the south, the displays vary in color and shape with atmospheric composition and conditions. Bright auroras are one visible expression of space weather.
Updated 14 Oct 2026
Science
Aurora australis
Aurora australis, or the southern lights, is a natural luminous display produced when energetic electrons in Earth's magnetosphere travel along magnetic field lines and excite gases in the upper atmosphere. The emissions form an oval around the southern magnetic pole, most often over Antarctica and the Southern Ocean. Its colors depend on atmospheric gas and altitude, while its extent and brightness vary with solar-wind-driven geomagnetic activity.
Updated 28 Oct 2026
Science
Auroral electrojet
Auroral electrojets are powerful, horizontally flowing electrical currents in the ionosphere, concentrated around the auroral oval. They arise from the coupling between Earth's magnetosphere and upper atmosphere, and their changing magnetic fields can be detected by ground magnetometers and satellites. Scientists monitor electrojet activity to study geomagnetic disturbances and space weather; the aurora and the currents are related features, but not the same phenomenon.
Updated 25 Oct 2026
Science
Auroral oval
An auroral oval is a broad, roughly ring-shaped zone around each of Earth's geomagnetic poles where auroras occur most frequently. It is produced by charged particles guided and accelerated along magnetic field lines into the upper atmosphere, where collisions generate light. The oval is not fixed: geomagnetic activity can brighten it and expand its equatorward boundary, while its location differs from the geographic polar circle. Similar auroral ovals occur around other magnetized planets, including Jupiter and Saturn.
Updated 24 Oct 2026
Science
Axolotl
The axolotl (Ambystoma mexicanum) is an aquatic salamander native to wetlands around Xochimilco in Mexico City. Unlike most salamanders, it typically reaches reproductive maturity without undergoing metamorphosis, retaining external gills and an aquatic lifestyle. Its capacity to regenerate complex tissues has made it an important research animal, while habitat degradation, pollution and invasive fish threaten its small wild population; the IUCN Red List classifies it as Critically Endangered.
Updated 7 Nov 2026
Science
Bacterial cellulose
Bacterial cellulose is cellulose synthesized by bacteria. Chemically similar to plant cellulose, it can form highly pure, nanofiber-based networks and is studied and produced for food, biomedical, personal-care and materials applications.
Updated 10 Nov 2026
Science
Bacterial conjugation
Bacterial conjugation is a form of horizontal gene transfer in which DNA moves from a donor bacterium to a recipient through a contact-dependent process. Often mediated by conjugative plasmids, it can spread traits between cells and contribute to bacterial adaptation, including the dissemination of antibiotic-resistance genes.
Updated 24 Oct 2026
Science
Baily's Beads
Baily's beads are brief points of sunlight visible along the Moon's edge just before and after the total or annular phases of a solar eclipse. They form because the Moon's mountainous, uneven limb has valleys and low points through which sunlight can still pass as the lunar disk moves across the Sun. The pattern changes quickly with the geometry of the eclipse and the Moon's topography.
Updated 28 Oct 2026
Science
Ball lightning
Ball lightning is a rare atmospheric phenomenon described by observers as a luminous, roughly spherical object, often appearing during thunderstorms. Despite historical reports and laboratory experiments that reproduce some similar effects, its origin and the mechanism behind natural sightings remain unexplained.
Updated 7 Nov 2026
Science
Banded Iron Formation
Banded iron formations are ancient marine sedimentary rocks marked by alternating iron-rich and silica-rich layers. Most large deposits formed in Precambrian oceans, and their minerals and chemistry preserve evidence about early ocean conditions, iron cycling and the changing availability of oxygen. Although often linked to oxygen-producing microbes and Earth’s oxygenation, the processes that formed the rocks and their fine-scale bands remain subjects of scientific research.
Updated 23 Oct 2026
Science
Barkhausen effect
The Barkhausen effect is the stepwise change in magnetization observed when a ferromagnetic material is magnetized or demagnetized. As its magnetic domains shift and change size in sudden increments, they produce small changes in magnetic flux; a coil can convert these changes into electrical pulses, which can be amplified and heard as clicks. Heinrich Barkhausen reported the phenomenon in 1919, providing experimental evidence for the domain structure of ferromagnets.
Updated 24 Oct 2026
Science
Baryon acoustic oscillations
Baryon acoustic oscillations (BAO) are a faint, large-scale pattern in how matter—visible today through the distribution of galaxies—is clustered. The pattern originated as pressure waves in the hot early universe, where gravity drew matter inward and radiation pressure pushed it outward. When the plasma cooled and neutral atoms formed, the waves ceased to travel and left a characteristic scale in the matter distribution. By measuring this scale at different cosmic distances, astronomers can test how the universe expanded over time.
Updated 24 Oct 2026
Science
Bell's theorem
Bell's theorem shows that predictions of quantum mechanics for certain entangled-particle experiments cannot be reproduced by theories that satisfy specified local-causality assumptions. John Bell derived inequalities in 1964 that let experiments test this distinction. Repeated experiments have found violations of Bell inequalities consistent with quantum theory, deepening understanding of entanglement and enabling work in quantum information science.
Updated 29 Oct 2026
Science
Bengal tiger
The Bengal tiger is a tiger population native to the Indian subcontinent, found in a range of habitats including forests, grasslands and mangrove landscapes. The common name is widely used for tigers in the region, though taxonomic treatments of tiger subspecies have changed as genetic evidence has accumulated. Like other tigers, it is a largely solitary ambush predator. Its long-term survival depends on protection of prey and habitat, connected landscapes, and measures addressing poaching and conflict with people.
Updated 27 Oct 2026
Science
Benguela Niño
A Benguela Niño is an episodic period of unusually warm sea-surface temperatures in the coastal upwelling region off Angola and Namibia in the southeastern tropical Atlantic. Events can arise through different combinations of local winds, ocean waves, currents and, in some cases, freshwater-related processes. They affect marine productivity and fisheries and may influence rainfall over southwestern Africa. Despite the name, a Benguela Niño is a regional Atlantic event, distinct from Pacific El Niño.
Updated 8 Nov 2026
Science
Berezinskii–Kosterlitz–Thouless transition
The Berezinskii–Kosterlitz–Thouless (BKT) transition is a topological phase transition found in certain two-dimensional systems. In the classic XY model, it occurs when bound vortex–antivortex pairs separate into free defects as temperature rises, changing the system from a low-temperature phase with quasi-long-range order to a disordered phase.
Updated 31 Oct 2026
Science
Bernoulli's principle
Bernoulli's principle describes how pressure, speed and elevation are related in a flowing fluid. In its familiar horizontal-flow case, faster-moving fluid corresponds to lower static pressure along a streamline. It follows from energy conservation under idealized conditions and is used to understand effects such as flow through constrictions and pressure-based velocity measurement.
Updated 30 Oct 2026
Science
Bhabha Atomic Research Centre
The Bhabha Atomic Research Centre (BARC) is an Indian multidisciplinary nuclear research institution based at Trombay, Mumbai. Founded in 1954 as the Atomic Energy Establishment, Trombay, and renamed after Homi J. Bhabha in 1966, it conducts research and development across nuclear science and engineering, reactor technologies, isotope applications, radiation technologies, materials science and related fields. Its research reactors support basic science, neutron-beam research, isotope production, training and materials studies.
Updated 31 Oct 2026
Science
Biology
Biology is the natural science that studies living organisms, their life processes, and their relationships with one another and the environment. Its subject ranges from molecules and cells to organisms, populations, ecosystems, and the biosphere. Ideas such as cellular organization, inheritance, evolution, energy use, and ecological interaction help biologists explain both the shared features and diversity of life, while research in the field informs health, food, biotechnology, and conservation.
Updated 12 Oct 2026
Science
Bioluminescence
Bioluminescence is light generated by a living organism through a chemical reaction. It occurs in many ocean organisms and also on land, including in fireflies and some fungi. Species use their light in different ways—to attract prey or mates, deter predators, or hide in dim surroundings—and their biochemical systems have become useful tools in laboratory research.
Updated 16 Oct 2026
Science
Biosphere
The biosphere is the global zone of Earth where life exists, spanning parts of the land, water and atmosphere rather than forming a separate shell. It comprises organisms and their interactions with one another and with their surroundings, organized into ecosystems. Through processes such as photosynthesis, feeding, respiration and decomposition, living systems transfer energy and cycle matter among Earth’s spheres.
Updated 23 Oct 2026
Science
Biosphere 2
Biosphere 2 is a large, controlled ecological research facility in Arizona, built to explore interactions among living systems and the physical environment. Its best-known early experiments sealed crews inside the structure from 1991 to 1994, revealing practical difficulties in maintaining a materially closed environment. Now operated by the University of Arizona, it supports research on ecosystems, climate, and Earth-system processes.
Updated 24 Oct 2026
Science
Bjerknes feedback
The Bjerknes feedback is a reinforcing interaction between tropical Pacific Ocean temperatures and the atmosphere that helps amplify El Niño and La Niña. Changes in sea-surface temperature alter tropical rainfall and pressure patterns, which influence the equatorial trade winds; those winds then change ocean currents and upwelling, reinforcing the initial temperature pattern. It is a key mechanism within the El Niño–Southern Oscillation (ENSO), but it does not by itself explain the irregular timing or eventual reversal of events.
Updated 24 Oct 2026
Science
Black smoker
A black smoker is a deep-sea hydrothermal vent that releases hot, mineral-rich fluid through a chimney on the ocean floor. Its dark plume forms as dissolved minerals precipitate when the fluid meets colder seawater. The vent systems occur in geologically active settings and support communities whose food webs are based largely on microbial chemosynthesis rather than sunlight.
Updated 29 Oct 2026
Science
Bose–Einstein condensate
A Bose–Einstein condensate (BEC) is a state in which a large fraction of a dilute gas of bosons occupies the same lowest-energy quantum state. Predicted by Satyendra Nath Bose and Albert Einstein in the 1920s, the phenomenon was first clearly demonstrated in a dilute atomic gas in 1995. Ultracold atomic condensates provide a controllable setting for studying collective quantum behaviour, coherence and related phenomena.
Updated 29 Oct 2026
Science
Boyle's law
Boyle's law describes the inverse relationship between the pressure and volume of a fixed amount of gas when its temperature remains constant. In this condition, the product of absolute pressure and volume is constant: P₁V₁ = P₂V₂. The law is a useful approximation for real gases under appropriate conditions and follows from the ideal gas law.
Updated 30 Oct 2026
Science
Braess's Paradox
Braess's paradox is a result in traffic-network theory: under some conditions, adding a road can worsen travel times once drivers independently choose routes that seem best for them. The added link changes route incentives and redistributes traffic, potentially producing a less efficient equilibrium. The effect depends on network structure and congestion; it is not a general argument against building roads.
Updated 7 Nov 2026
Science
Bragg's law
Bragg's law relates the wavelength of a wave diffracted by regularly spaced crystal planes to the plane spacing and diffraction angle. In its common form, nλ = 2d sin θ, it expresses the geometric condition for constructive interference and is central to interpreting X-ray diffraction patterns and determining crystalline structure.
Updated 23 Oct 2026
Science
Brewster angle
The Brewster angle is the angle of incidence at which an ideal, smooth interface between two transparent, non-magnetic media does not reflect p-polarized light. For unpolarized light incident at that angle, the reflected beam is completely linearly polarized perpendicular to the plane of incidence. The angle depends on the refractive indices of the two media.
Updated 27 Oct 2026
Science
Brinicle
A brinicle is a downward-growing tubular ice structure that forms beneath sea ice when cold, concentrated brine drains into near-freezing seawater. The descending brine is denser than the surrounding water and, because salt lowers its freezing point, can remain liquid at temperatures below the seawater’s freezing point. Heat transfer at the plume’s boundary freezes surrounding seawater into a hollow ice tube. Brinicles have been observed in polar oceans and recreated in laboratory experiments; research examines their growth, salt transport and possible relevance to icy ocean worlds.
Updated 24 Oct 2026
Science
Brownian motion
Brownian motion is the irregular, random movement of microscopic particles suspended in a fluid. It results from many uneven collisions with the fluid’s molecules and links observable particle motion to molecular-scale thermal activity. Its mathematical description is also central to models of diffusion and stochastic processes.
Updated 24 Oct 2026
Science
Burgess Shale
The Burgess Shale is a fossil-bearing unit in the Canadian Rockies, especially known for exceptionally preserved marine organisms from the Cambrian Period. Its fossils include soft-bodied animals rarely represented in the fossil record, offering evidence about the diversity, anatomy and ecology of early animal communities. Discovered by Charles Doolittle Walcott in 1909, the site has become a major reference for studying Cambrian life and fossil preservation.
Updated 28 Oct 2026
Science
C4 Photosynthesis
C4 photosynthesis is a carbon-fixation pathway that concentrates carbon dioxide near Rubisco, reducing photorespiration in many warm, high-light environments. It spatially coordinates initial carbon fixation and the Calvin cycle, commonly across mesophyll and bundle-sheath cells.
Updated 10 Nov 2026
Science
Capacitance
Capacitance measures how much separated electric charge a system of conductors carries for a given potential difference. In a linear capacitor, it is the ratio of charge to voltage and is determined by the conductors' geometry and the material between them. The SI unit is the farad (F), equal to one coulomb per volt. Capacitance governs how capacitors store energy in electric fields and behave in circuits, including filters, timing networks and resonant systems.
Updated 17 Oct 2026
Science
Catatumbo lightning
Catatumbo lightning is recurrent thunderstorm activity concentrated near the mouth of Venezuela’s Catatumbo River, where it enters Lake Maracaibo. The surrounding mountains, moisture-bearing winds and nighttime atmospheric circulation help focus storms in this basin. Its occurrence varies seasonally and from year to year, and research combines satellite observations, meteorological data and models to understand and forecast that variability.
Updated 29 Oct 2026
Science
Cavendish experiment
The Cavendish experiment is a precision laboratory measurement of the weak gravitational attraction between known masses, performed by Henry Cavendish in 1797–1798 using a torsion balance devised by John Michell. Cavendish used the measured attraction to estimate Earth's mean density, reporting about 5.48 times that of water. The experiment is now recognized as an early way to determine the strength of gravity and is commonly presented in modern versions as a measurement of the universal gravitational constant, G.
Updated 30 Oct 2026
Science
Chemistry
Chemistry is the natural science concerned with the composition, structure and properties of substances, the changes they undergo, and the energy involved in those changes. By studying atoms, molecules and their interactions, chemists explain material behaviour and develop ways to identify, make and improve substances. The field spans areas from medicines and biological processes to materials, manufacturing and environmental analysis, while also examining how chemical products and processes can be made safer.
Updated 12 Oct 2026
Science
Cherenkov radiation
Cherenkov radiation is electromagnetic radiation emitted when a charged particle moves through a transparent medium faster than light's phase velocity in that medium. The effect produces a characteristic cone of light, often perceived as a blue glow in water. First observed by Pavel Cherenkov in 1934 and explained by Igor Tamm and Ilya Frank in 1937, it is now used in particle-identification detectors, radiation monitoring, and astrophysical observations.
Updated 25 Oct 2026
Science
Chladni figures
Chladni figures are the visible patterns formed when fine particles collect along nodal lines on a vibrating plate. Each pattern corresponds to a particular vibration mode, shaped by the plate’s geometry, material and boundary conditions. Ernst Chladni made the method famous in the late eighteenth century, turning otherwise invisible motion into a tool for acoustics and musical-instrument study.
Updated 26 Oct 2026
Science
Circadian rhythm
A circadian rhythm is a roughly 24-hour pattern in biological processes. In humans, a central clock in the brain coordinates timing across the body, while light and darkness are the strongest environmental cues that align this clock with the day. Circadian rhythms influence sleep and wakefulness as well as processes such as hormone release, body temperature, appetite and digestion. Their timing can shift when environmental cues change, including through exposure to light at different times of day.
Updated 22 Oct 2026
Science
Cloud condensation nuclei
Cloud condensation nuclei (CCN) are atmospheric aerosol particles on which water vapour can condense to form cloud droplets when air becomes sufficiently saturated. Their ability to activate depends on particle size and chemical composition as well as the supersaturation in rising air. CCN influence cloud droplet populations and are one pathway through which aerosols affect clouds and climate, although the magnitude and regional effects remain uncertain.
Updated 26 Oct 2026
Science
Cloud iridescence
Cloud iridescence, also called irisation, is a colorful optical effect seen in parts of a cloud when sunlight is diffracted by small water droplets or ice crystals of similar size. It most often appears as delicate bands or patches near thin, newly forming cloud edges, often close to the Sun.
Updated 8 Nov 2026
Science
Cloud seeding
Cloud seeding is a weather-modification technique that introduces particles into suitable clouds to influence processes involved in precipitation or, in some settings, fog and hail. Its effects are conditional: the right cloud and atmospheric conditions must already exist, and distinguishing an effect from natural variability is difficult. Recent field research has documented a physical pathway for wintertime seeding of certain mountain clouds, but results do not imply that seeding can create storms or reliably control severe weather.
Updated 26 Oct 2026
Science
Coandă effect
The Coandă effect is the tendency of a fluid jet to bend toward and follow a nearby surface, often a curved wall. Entrainment of surrounding fluid and the resulting pressure field help draw the jet toward the surface, while viscosity and flow conditions influence whether attachment persists. The phenomenon is studied in aerodynamics, fluidic control and, more recently, shallow-water jets.
Updated 27 Oct 2026
Science
Coconut Crab
The coconut crab (Birgus latro), also called the robber crab, is a large terrestrial hermit crab found on islands across the Indian and Pacific Oceans. Adults live on land, while the species’ early development depends on the sea. Coastal habitat loss and harvesting have contributed to declines in many populations, and the species is classified as Vulnerable on the IUCN Red List.
Updated 10 Nov 2026
Science
Cocos Plate
The Cocos Plate is a young oceanic tectonic plate beneath the eastern Pacific, west of Central America. It moves toward and subducts beneath the North American and Caribbean plates along the Middle America Trench, contributing to earthquakes and volcanic activity. Its geology also records the influence of the Galápagos hotspot and seafloor spreading.
Updated 8 Nov 2026
Science
Continental drift
Continental drift is the historical geological hypothesis that continents have changed position over time. Alfred Wegener assembled evidence including the fit of continental margins, matching fossils and rock formations, and traces of past climates to argue that continents were once joined in a supercontinent. His proposed mechanism was inadequate and the idea was rejected by many geologists during his lifetime. Later evidence from the ocean floor helped establish plate tectonics, the broader modern theory that explains the movement of continents as parts of moving lithospheric plates.
Updated 23 Oct 2026
Science
Convectively coupled equatorial waves
Convectively coupled equatorial waves are large-scale atmospheric disturbances near the equator whose circulation is linked to organized tropical cloud and rainfall. Several wave types travel eastward or westward, shaping tropical rainfall variability and sometimes influencing weather systems beyond the tropics.
Updated 28 Oct 2026
Science
Coral bleaching
Coral bleaching is a stress response in which corals lose or expel much of the microscopic algae living in their tissues, revealing a pale or white appearance. The algae provide food through photosynthesis and contribute to coral color, so their loss can leave a coral vulnerable, but bleaching does not mean it is already dead. Heat stress is the main driver of widespread bleaching, although cold, pollution, freshwater influx, intense light and exposure to air can also stress corals. Recovery is possible if conditions improve; prolonged or repeated stress raises the risk of disease and death.
Updated 26 Oct 2026
Science
Coriolis effect
The Coriolis effect is an apparent deflection of motion observed in a rotating reference frame. On Earth, it makes moving air, water and other objects appear to veer to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. It is important in large-scale atmospheric and oceanic motion, but negligible in everyday systems such as sinks and drains.
Updated 19 Oct 2026
Science
Coriolis force
The Coriolis force is an apparent, or inertial, force used to describe motion from a rotating reference frame. On Earth it makes large-scale moving air and water appear to deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Its influence grows with the speed of the motion and varies with latitude; it is important in weather systems and ocean circulation, but usually negligible for short, small-scale motions.
Updated 25 Oct 2026
Science
Coulomb's law
Coulomb's law describes the electrostatic force between two stationary point charges: its magnitude is proportional to the product of their charge magnitudes and inversely proportional to the square of the distance between them. The force acts along the line joining the charges; like charges repel and unlike charges attract. Charles-Augustin de Coulomb's 18th-century experiments with a torsion balance helped establish this quantitative relationship.
Updated 29 Oct 2026
Science
CRISPR gene editing
CRISPR gene editing uses components of microbial immune systems to target and alter genetic material. In the best-known CRISPR-Cas9 method, a designed guide RNA directs the Cas9 enzyme to a matching DNA sequence, where it makes a cut; the cell's repair processes then determine the resulting edit. The technology has transformed biological research and entered clinical medicine, but intended changes are not guaranteed and safety, delivery and ethical questions remain important.
Updated 14 Oct 2026
Science
Cryoconite hole
A cryoconite hole is a water-filled depression in glacier ice formed when dark windblown or locally deposited sediment absorbs sunlight and melts the ice beneath it. Its sediment and meltwater create a small, variable habitat for microorganisms and influence how dust, nutrients and carbon move across glacier surfaces. Hole size, persistence and biology differ with local ice conditions and climate.
Updated 29 Oct 2026
Science
Curie–Weiss law
The Curie–Weiss law is a mean-field model describing how the magnetic susceptibility of many paramagnetic materials changes with temperature. It expresses susceptibility as χ = C/(T − θCW), where C is the Curie constant and θCW is the Curie–Weiss temperature. The temperature dependence can reveal information about magnetic interactions, but the law is an approximation and must be applied only over a temperature range where its assumptions are reasonable.
Updated 27 Oct 2026
Science
Dallol (hydrothermal system)
Dallol is a geothermal and hydrothermal complex in Ethiopia's Danakil Depression, known for its salt-rich, highly acidic hot springs, fumaroles and mineral formations. Its unusual geology reflects interactions among evaporite deposits, groundwater and magmatic activity in the Afar Rift region.
Updated 9 Nov 2026
Science
Dew point
Dew point is the temperature to which an air parcel must be cooled, at constant pressure and without changing its water-vapour content, for saturation to occur. It helps describe the actual moisture in air, unlike relative humidity, which also depends strongly on temperature. When air cools to its dew point, water vapour can condense as liquid droplets or, below freezing, deposit as ice; this underlies dew, fog, cloud formation and frost-related processes.
Updated 24 Oct 2026
Science
Diamond dust
Diamond dust is precipitation made up of tiny ice crystals that fall through clear or nearly clear air, often appearing to sparkle near the ground. It is most characteristic of very cold polar and alpine environments. Although sometimes confused with ice fog, it is a distinct atmospheric ice-crystal phenomenon whose formation and visibility depend on fine-scale conditions.
Updated 29 Oct 2026
Science
Diatom
Diatoms are single-celled photosynthetic algae whose glass-like silica walls help define their form and ecological role. Found in marine and freshwater environments, they contribute to aquatic food webs and the cycling of silicon and carbon. Their abundance, physiology and sinking behavior vary among species and with environmental conditions.
Updated 29 Oct 2026
Science
Diel vertical migration
Diel vertical migration (DVM) is the recurring movement of aquatic organisms between deeper and shallower water over a 24-hour cycle. In the common nocturnal pattern, animals spend daylight at depth and move toward food-rich surface waters after dusk, then descend before daylight. Light, feeding opportunities and predator risk shape the behaviour, which influences food-web interactions and the transport of carbon and nutrients through the ocean.
Updated 25 Oct 2026
Science
Dielectric absorption
Dielectric absorption is a memory-like effect in real capacitors: after a capacitor has been charged and then briefly discharged, some voltage can reappear when it is left open-circuit. Also called dielectric relaxation or soakage, it results from delayed polarization and charge redistribution in the dielectric. It can introduce errors in precision sample-and-hold and switched-capacitor circuits, and its magnitude depends on the dielectric material and measurement conditions.
Updated 29 Oct 2026
Science
Dirac equation
The Dirac equation is a relativistic quantum equation developed by Paul Dirac in 1928 to describe the electron. It brought quantum mechanics into agreement with special relativity, accounts naturally for the electron's spin, and led Dirac to a prediction of a positively charged counterpart to the electron, later identified as the positron.
Updated 29 Oct 2026
Science
Discrete time crystal
A discrete time crystal is a nonequilibrium phase in which a periodically driven many-body system responds with a stable period longer than that of its drive, spontaneously breaking discrete time-translation symmetry. Interactions help make this subharmonic response robust to imperfections. Experiments have investigated such behavior in platforms including trapped ions, diamond defects and superconducting qubits.
Updated 7 Nov 2026
Science
DNA replication
DNA replication is the cellular process of copying DNA before cell division. In the usual semiconservative model, each parental strand serves as a template for a new complementary strand; replication proteins unwind the double helix, and DNA polymerases build new DNA in the 5′-to-3′ direction.
Updated 31 Oct 2026
Science
Dollo's law
Dollo's law is an evolutionary principle that complex traits are unlikely to return in precisely their former form after they have been lost, because evolutionary changes accumulate along lineages. Modern biology treats it as a useful statement about historical constraint rather than an absolute ban on resemblance or trait reappearance: retained genes and developmental pathways can enable partial or apparent reversals.
Updated 27 Oct 2026
Science
Doppler Effect
The Doppler effect is the change in a wave's observed frequency caused by motion between its source and an observer. It explains the pitch shift of a siren as it passes, and it also applies to light: spectral lines from an approaching object shift toward shorter wavelengths, while those from a receding object shift toward longer wavelengths. The effect is used to measure motion in astronomy and radar, and to assess blood flow with Doppler ultrasound.
Updated 18 Oct 2026
Science
Double-slit experiment
The double-slit experiment sends light or particles toward a barrier with two narrow openings and records what reaches a detector beyond it. With both paths available, an interference pattern can form; in quantum experiments, individual detections accumulate into that pattern even when particles are sent one at a time. Experiments that obtain information about which path was taken change or remove the interference, making the setup a foundational demonstration of wave behavior and quantum measurement.
Updated 29 Oct 2026
Science
Drake equation
The Drake equation is a framework for estimating how many civilizations in the Milky Way might produce signals detectable from Earth. Introduced by astronomer Frank Drake in 1961 as a way to structure discussion at a meeting on the search for extraterrestrial intelligence, it multiplies estimates for star formation, planets, life, intelligence, detectable technology and the duration of signal production. Several terms remain highly uncertain, so the equation organizes questions rather than yielding a settled count.
Updated 29 Oct 2026
Science
Earth's magnetosphere
Earth's magnetosphere is the region around the planet where Earth's magnetic field dominates over the interplanetary magnetic field. Shaped by the solar wind, it is compressed on the Sun-facing side and stretched into a long tail on the night side. It deflects much of the solar wind and traps charged particles, but it is dynamic rather than an impermeable shield; interactions with solar plasma drive space-weather effects and contribute to auroras.
Updated 25 Oct 2026
Science
Earthquake
An earthquake is ground shaking caused by a sudden release of energy within Earth, usually when rocks slip along a fault. Seismic waves from the rupture are recorded by instruments and help scientists locate and measure the event. Magnitude describes the size of an earthquake at its source, while shaking intensity varies from place to place. Most earthquakes occur on faults near tectonic plate boundaries; some undersea ruptures can displace the ocean floor and generate tsunamis.
Updated 14 Oct 2026
Science
Eddington limit
The Eddington limit is a theoretical luminosity threshold at which outward radiation pressure balances the inward pull of gravity in a radiating object or accreting system. It provides a useful reference for stellar stability and the growth of compact objects, including black holes. The estimate depends on assumptions about opacity and geometry; observed or modeled super-Eddington behavior does not automatically violate physics, but signals that additional transport, geometry or dynamical effects matter.
Updated 27 Oct 2026
Science
Ediacaran biota
The Ediacaran biota is a diverse assemblage of mostly soft-bodied organisms preserved in rocks from the late Precambrian, before the Cambrian diversification of animal life. Its fossils, found at sites around the world, record seafloor communities with varied body forms and ecological roles. Many organisms remain difficult to classify, so their relationship to modern animal groups and the causes of their disappearance near the end of the Ediacaran are subjects of continuing research.
Updated 22 Oct 2026
Science
Ekman spiral
The Ekman spiral is an idealized pattern describing how wind-driven ocean currents change in speed and direction with depth. Wind transfers momentum to the sea surface; friction passes some of it to deeper water, while Earth’s rotation deflects the moving layers. In the classical description, each deeper layer moves more slowly and is turned relative to the layer above, producing a spiral-shaped current profile. Integrated over the Ekman layer, the net transport is approximately perpendicular to the wind, with its direction depending on the hemisphere.
Updated 23 Oct 2026
Science
Electret
An electret is an insulating material that retains a quasi-permanent electric field through stored electric charge or aligned electric dipoles. Electrets convert this persistent polarization into useful electrostatic effects without requiring a continuously applied polarizing voltage. Their best-known application is the electret microphone, while modern research also explores sensors, energy harvesters and other devices.
Updated 29 Oct 2026
Science
Electric current
Electric current is the rate at which electric charge passes a chosen cross-section. Its SI unit is the ampere (A), equal to one coulomb of charge per second. Current may be carried by electrons, ions or other charge carriers; conventional current is defined in the direction positive charge would move, and may be steady or periodically reverse direction.
Updated 6 Nov 2026
Science
Electric field
An electric field is a vector quantity that describes the electric force a charge would experience at each point in space. It is produced by electric charges and, in changing electromagnetic situations, by changing magnetic fields. The field concept makes it possible to describe forces on charges without recalculating the influence of each source for every test charge.
Updated 6 Nov 2026
Science
Electrocaloric effect
The electrocaloric effect is the reversible change in a dielectric material's temperature or entropy when an electric field is applied or removed. In ferroelectrics, the field changes dipole order, coupling electrical work to heat. The effect is being explored for solid-state cooling and thermal management, though practical systems must address heat transfer, operating fields, efficiency, durability and scale.
Updated 27 Oct 2026
Science
Electromagnetic induction
Electromagnetic induction is the production of an electromotive force when the magnetic flux linked with a circuit changes. Faraday’s law relates the induced voltage to the rate of change of flux, while Lenz’s law determines its direction: the induced effect opposes the change that produced it. First investigated experimentally by Michael Faraday in 1831, induction is the operating principle behind electric generators, transformers, many motors and wireless charging systems.
Updated 20 Oct 2026
Science
Electromagnetism
Electromagnetism is the branch of physics that studies electric and magnetic fields, their sources, and their interactions with matter. Maxwell’s equations bring the two phenomena into a unified theory: changing electric and magnetic fields are linked, and together they can propagate as electromagnetic waves. These waves include radio signals, visible light, X-rays and gamma rays, which differ in wavelength and frequency.
Updated 13 Oct 2026
Science
Electrostatic induction
Electrostatic induction is the redistribution of electric charge in an object caused by the electric field of a nearby charged body, without direct contact. In a conductor, mobile electrons shift so that a neutral object becomes polarized while its total charge remains unchanged. With an appropriate grounding and separation procedure, induction can also leave an object with a net charge opposite to the nearby charged body.
Updated 29 Oct 2026
Science
Enzyme
Enzymes are biological catalysts that accelerate particular chemical reactions in living organisms without being consumed overall. Most are proteins, although some RNA molecules are catalytic. By binding substrates and helping reactions pass through lower-energy pathways, enzymes regulate processes from digestion and DNA replication to metabolism; their activity can be affected by temperature, pH, inhibitors and other conditions.
Updated 30 Oct 2026
Science
Eötvös effect
The Eötvös effect is the change in apparent gravity measured by a moving observer on Earth, caused by the planet’s rotation. Motion eastward increases the observer’s speed around Earth’s axis and generally lowers the measured vertical gravity; motion westward has the opposite effect. The size of the correction depends chiefly on east–west speed and latitude, so it must be accounted for in gravity surveys made from ships, aircraft and other moving platforms.
Updated 29 Oct 2026
Science
Epigenetics
Epigenetics studies molecular marks and processes that regulate gene activity without changing the underlying DNA sequence. These mechanisms help explain how cells with the same genome take on different roles, how gene expression changes through development and exposure, and how altered patterns can be associated with disease. Some marks persist through cell divisions; inheritance across generations is possible in some cases but is limited and biologically complex.
Updated 18 Oct 2026
Science
Euphotic zone
The euphotic zone is the upper part of a body of water where sunlight is sufficient for photosynthesis. In the open ocean it is commonly described as extending to roughly 200 metres, although its depth varies with water clarity, location and the definition used.
Updated 7 Nov 2026
Science
Evolution
Biological evolution is the change in inherited characteristics of populations across generations. It explains how lineages diversify and how organisms share common ancestry. Mutation, natural selection and genetic drift alter the genetic composition of populations in different ways; evidence from fossils, comparative biology, geography and DNA supports the history of evolutionary change.
Updated 13 Oct 2026
Science
Faraday cage
A Faraday cage is a conducting enclosure that reduces the electric fields and electromagnetic signals reaching its interior. Charges in the conductor redistribute to shield the inside from external electric fields, while time-varying fields can induce currents that oppose some incoming waves. The degree of shielding depends on the enclosure's material, continuity, openings and the frequency of the field.
Updated 23 Oct 2026
Science
Fata Morgana
A Fata Morgana is a complex superior mirage formed when atmospheric refraction bends light through layers of air with sharply differing temperatures. Seen in a narrow region near the horizon, it can distort distant coastlines, islands or ships into rapidly changing, stacked images that appear elevated, inverted or stretched. The effect depends on a strong temperature inversion and an atmospheric duct; an inversion by itself does not guarantee a Fata Morgana.
Updated 23 Oct 2026
Science
Fermi's golden rule
Fermi's golden rule is a result of time-dependent quantum perturbation theory that estimates the rate of transitions from an initial state to a continuum or dense set of final states under a weak interaction. In its common form, the rate is proportional to the squared transition matrix element and the density of available final states at the initial energy. It is widely used to analyze processes such as atomic transitions, scattering and decay, provided the assumptions behind the approximation are appropriate.
Updated 30 Oct 2026
Science
Ferrel cell
The Ferrel cell is the conventional name for the mean atmospheric circulation in Earth's mid-latitudes, between the tropical Hadley circulation and the polar circulation. In the simplified three-cell model, surface air flows poleward and eastward while the upper return flow is equatorward. Unlike the thermally direct Hadley cell, this mid-latitude circulation is maintained largely by weather systems and atmospheric eddies, so the idealized diagram is not a literal, steady overturning cell.
Updated 25 Oct 2026
Science
Ferroelectricity
Ferroelectricity is the property of certain insulating materials whose spontaneous electric polarization can be reversed by an applied electric field. The polarization arises from an internal arrangement of electric dipoles, often grouped into domains, and its switching produces a characteristic polarization–electric-field hysteresis loop. Ferroelectric behavior generally disappears above a material-specific Curie temperature; the effect is used in capacitors, sensors, actuators and non-volatile memory research.
Updated 27 Oct 2026
Science
Ferrofluid
A ferrofluid is a liquid containing stable, nanoscale magnetic particles dispersed in a carrier fluid. A magnetic field can shape or move the liquid, while surfactants or other surface coatings help keep the particles from clumping and settling. Developed in the 1960s during research into handling liquid rocket propellant, ferrofluids later found practical uses including seals for rotating shafts and loudspeaker components; current research explores medical, environmental and engineering applications.
Updated 26 Oct 2026
Science
Fick's laws of diffusion
Fick's laws are mathematical descriptions of how particles diffuse in response to concentration differences. The first law relates diffusive flux to a concentration gradient under steady-state conditions; the second describes how concentration changes with time, under the usual constant-diffusivity assumption.
Updated 31 Oct 2026
Science
Fizeau experiment
The Fizeau experiment was an 1851 interferometric test of how flowing water affects the propagation of light. Hippolyte Fizeau sent light in opposite directions through moving water and measured a shift in the interference fringes. The result was inconsistent with simple classical addition of the water's speed to light's speed and agreed approximately with Augustin Fresnel's partial-drag prediction. In 1907, Max von Laue showed how the result follows from relativistic velocity transformation, making the experiment an important precursor to experimental tests of special relativity.
Updated 26 Oct 2026
Science
Fog
Fog is a suspension of tiny water droplets, or sometimes ice particles, near the ground that reduces horizontal visibility. It forms when air close to Earth's surface becomes saturated, commonly through cooling or the addition and mixing of moisture.
Updated 7 Nov 2026
Science
Foucault Pendulum
A Foucault pendulum is a long, freely swinging pendulum whose apparent rotation of its oscillation plane, viewed from the rotating Earth, demonstrates Earth's rotation. First publicly demonstrated by French physicist Léon Foucault in 1851, the effect varies with latitude: it is greatest at the poles and vanishes at the equator.
Updated 23 Oct 2026
Science
Fourier's law of heat conduction
Fourier's law describes conductive heat transfer: heat flux is proportional to the negative temperature gradient, with thermal conductivity setting the proportionality. In a simple, isotropic material, it predicts heat flow from warmer to cooler regions. The law is central to classical heat-transfer modelling, while advanced settings such as very short timescales or nanoscale structures can require more detailed models.
Updated 29 Oct 2026
Science
Fresnel equations
The Fresnel equations describe the amplitudes of light reflected and transmitted at an interface between optical media. They account for the incident angle, refractive indices and polarization, distinguishing s-polarized light from p-polarized light. From the amplitude coefficients, reflectance and transmittance can be calculated; the equations also explain effects such as the disappearance of p-polarized reflection at Brewster's angle.
Updated 30 Oct 2026
Science
Fresnel lens
A Fresnel lens is a lens whose optical surface is divided into concentric steps or zones, reducing bulk while retaining much of the focusing or beam-forming effect of a conventional lens. Developed for lighthouse illumination in the early 19th century, it is also used in searchlights, imaging systems and other applications where a thin, light-gathering optic is useful.
Updated 28 Oct 2026
Science
Frost flower
Frost flowers are delicate, short-lived clusters of ice crystals that can grow on very young sea ice in cold, calm conditions. They form at the boundary between brine-wetted ice and the atmosphere and can concentrate salts and host microbes, making them of interest to polar atmospheric chemistry and sea-ice ecology.
Updated 29 Oct 2026
Science
Frost flowers
Frost flowers are delicate clusters of ice crystals that develop on newly formed sea ice and, more rarely, on frozen lakes. Their growth depends on cold surface and atmospheric conditions, and laboratory work shows they can form on solid ice even when the surrounding air is unsaturated. On sea ice, the crystals can become coated with concentrated brine, making them chemically distinct from ordinary frost. Researchers study their possible influence on polar aerosols and atmospheric chemistry, as well as the microbial communities found in their brine channels.
Updated 24 Oct 2026
Science
Fulgurite
A fulgurite is a natural glassy structure formed when a lightning discharge melts material at the ground surface. Fulgurites can develop as tubes or branching forms in sand and soil, or as glassy veins and crusts in rock. Their shapes and composition preserve evidence of a brief, intense interaction between lightning and the substrate; researchers also study them as records of past environments and as products that can be reproduced experimentally.
Updated 29 Oct 2026
Science
Fungi
Fungi are a diverse group of eukaryotic organisms that includes yeasts, molds and mushrooms. They obtain nutrients by absorbing organic material, often after releasing digestive enzymes, and most have cell walls containing chitin. As decomposers, partners in plant symbioses, pathogens and sources of food and medicines, fungi play varied roles in ecosystems and human life.
Updated 16 Oct 2026
Science
Gaganyaan
Gaganyaan is the Indian Space Research Organisation’s human-spaceflight programme, designed to demonstrate India’s ability to send astronauts to low Earth orbit and return them safely. Its architecture combines a human-rated launch vehicle, a crewed orbital module, life-support and crew-escape systems, and a sequence of uncrewed tests intended to validate safety-critical technologies before human flight.
Updated 8 Nov 2026
Science
Gaia hypothesis
The Gaia hypothesis, developed by James Lovelock and Lynn Margulis in the 1970s, proposes that life and Earth's nonliving environment interact in ways that can help maintain conditions suitable for life. It drew attention to possible biosphere-wide feedbacks, but its broad claims and explanations remain debated; it is not a claim that Earth is literally a living organism.
Updated 31 Oct 2026
Science
Gauss's law
Gauss's law relates the net electric flux through a closed surface to the net electric charge enclosed by it. It is one of Maxwell's equations and can be expressed in integral or differential form. The law applies to any charge distribution, while its use to calculate an electric field directly is especially powerful when the distribution has strong symmetry.
Updated 29 Oct 2026
Science
Gegenschein
The gegenschein, or counterglow, is a faint brightening of the night sky near the point directly opposite the Sun. It is part of the zodiacal light produced when sunlight scatters from interplanetary dust. Near the antisolar direction, the viewing geometry and a narrow backscattering enhancement make the dust appear brighter against the surrounding sky. Dark, clear conditions are needed to observe it, and high-resolution studies use its shape and brightness to investigate dust in the inner Solar System.
Updated 28 Oct 2026
Science
Gene drive
A gene drive is a natural or engineered inheritance-biasing system that increases the chance a genetic element is passed to offspring, allowing it to become more common over generations than ordinary Mendelian inheritance alone would predict. Gene drives have attracted research interest in population genetics, vector-borne disease control and conservation, but proposed uses also raise ecological, ethical and governance questions, especially where a system may spread beyond an intended location.
Updated 28 Oct 2026
Science
General relativity
General relativity is Albert Einstein's theory of gravitation, whose field equations he published in 1915. It describes gravitational effects through the geometry of spacetime: matter and energy shape that geometry, while freely moving bodies and light follow paths within it. The theory explains observations such as the precession of Mercury's orbit and the bending of light, and its predictions must be accounted for alongside special relativity in precise satellite navigation timing.
Updated 22 Oct 2026
Science
Geomagnetic jerk
A geomagnetic jerk is a relatively abrupt change in the time evolution of Earth's main magnetic field, identified as a sharp change in its secular variation or, equivalently, a short-lived change in secular acceleration. These features are associated with rapid changes in fluid motion at the top of the liquid outer core, but their physical causes, global extent, timing and detection remain subjects of research.
Updated 28 Oct 2026
Science
Geomagnetic reversal
A geomagnetic reversal is a change in Earth’s magnetic field in which magnetic north and south exchange polarity. The field is generated by motion in the liquid outer core, and its long geological record is preserved in magnetized rocks and sediments. Reversals occur irregularly, take far longer than an ordinary human event, and should not be confused with temporary magnetic excursions or the ongoing drift of the magnetic poles.
Updated 24 Oct 2026
Science
Geothermal energy
Geothermal energy is heat from within the Earth that can be used directly for heating and cooling or converted into electricity. Conventional power plants draw on naturally permeable hot-water or steam reservoirs, while newer designs seek to reach heat in less permeable rock. Ground-source heat pumps use the relatively stable temperature of shallow ground to exchange heat with buildings. The technology can provide steady power or useful heat, but its potential depends on geology, drilling, project costs, environmental safeguards and access to suitable sites.
Updated 26 Oct 2026
Science
Gibbs free energy
Gibbs free energy, also called Gibbs energy, is a thermodynamic state function combining enthalpy and entropy. At constant temperature and pressure, changes in Gibbs energy provide a criterion for the direction of spontaneous change and equilibrium. In chemistry it also connects reaction conditions with equilibrium constants and, for electrochemical cells, with electrical work.
Updated 8 Nov 2026
Science
Glacier
A glacier is a persistent body of land ice formed from accumulated snow that has compacted over time and moves under its own weight. Glaciers flow downhill through internal deformation of ice and, in some conditions, sliding at their base. Their mass changes as snowfall and other inputs are balanced against melting, sublimation and, for glaciers that reach water, the calving of icebergs. This balance influences glacier growth or loss and connects glacier change to water supplies, landscapes and sea level.
Updated 26 Oct 2026
Science
Graphene
Graphene is a two-dimensional form of carbon in which atoms occupy a single, honeycomb-like layer. Its unusual electronic structure gives it high carrier mobility and tunable electrical behavior, while its thinness, strength, flexibility, transparency, and thermal conductivity have made it important in materials research. Potential applications include sensors, electronics, energy technologies, composites, and biomedical devices, although large-scale production and the absence of a natural band gap complicate some uses.
Updated 18 Oct 2026
Science
Gravitational lensing
Gravitational lensing is the bending, magnification and distortion of light from a distant source by the gravity of matter between the source and an observer. Predicted by general relativity, it can produce multiple images, arcs or rings and helps astronomers study distant galaxies and the distribution of matter, including dark matter.
Updated 1 Nov 2026
Science
Gravitational Waves
Gravitational waves are propagating changes in spacetime geometry predicted by general relativity. Strong waves are produced by rapidly changing, compact mass systems such as pairs of black holes or neutron stars. Laser interferometers first detected them directly in 2015, opening a way to study cosmic events that is distinct from observing electromagnetic radiation.
Updated 19 Oct 2026
Science
Great Attractor
The Great Attractor is a broad region of enhanced gravitational influence in the nearby Universe, associated with galaxy motions toward the Norma Cluster and embedded in the larger Laniakea Supercluster. Its study is complicated by foreground stars and dust in the Milky Way, which obscure much of the region at visible wavelengths.
Updated 10 Nov 2026
Science
Great Indian bustard
The great Indian bustard (Ardeotis nigriceps) is a large ground-dwelling bird of the Indian subcontinent and one of the world’s most threatened bird species. It is now associated chiefly with dry grasslands and open landscapes in India. Its decline reflects habitat change and direct human-caused mortality, including collisions with overhead power lines. Recovery efforts combine habitat protection, field research, threat reduction and conservation breeding; the long-term challenge is to secure viable, connected habitat as well as maintain birds in managed breeding facilities.
Updated 27 Oct 2026
Science
Great Oxidation Event
The Great Oxidation Event (GOE) was a major transition in Earth's early history, when oxygen began accumulating in the atmosphere on a lasting, large scale about 2.4 billion years ago. Oxygenic photosynthesis supplied molecular oxygen, but its atmospheric rise depended on interactions among life, oceans, rocks and chemical sinks that consumed oxygen. Geological evidence indicates that some marine environments may have contained oxygen before the atmosphere changed substantially, while the timing and conditions of that earlier oxygenation remain subjects of research.
Updated 21 Oct 2026
Science
Green flash
A green flash is a brief optical phenomenon sometimes visible at the upper edge of the Sun as it rises or sets. Atmospheric refraction bends different wavelengths by slightly different amounts, while scattering and absorption shape which colours reach an observer. With a clear, unobstructed horizon and suitable atmospheric conditions, the final visible sliver may appear green; mirages can alter or intensify the effect. The appearance is fleeting and is not a flash produced by the Sun itself.
Updated 24 Oct 2026
Science
Greenwich Mean Time
Greenwich Mean Time (GMT) is mean solar time associated with the Prime Meridian at Greenwich, England. It helped provide a shared reference for navigation and civil timekeeping as railways and communications expanded in the nineteenth century, and served as an international standard from 1884 until the adoption of Coordinated Universal Time (UTC) in 1972. The name remains in everyday use and denotes the United Kingdom's standard time in winter, although UTC is the modern international time standard.
Updated 23 Oct 2026
Science
Gutenberg discontinuity
The Gutenberg discontinuity is the seismic boundary between Earth's silicate mantle and liquid outer core, about 2,900 kilometres below the surface. Seismic-wave behaviour changes sharply across it: shear waves do not pass through the liquid outer core, while compressional waves are strongly refracted. These observations reveal a major boundary deep inside Earth and help scientists infer its layered structure.
Updated 26 Oct 2026
Science
Haber–Bosch process
The Haber–Bosch process is an industrial method for making ammonia from atmospheric nitrogen and hydrogen. Developed through the work of Fritz Haber and Carl Bosch in the early 20th century, it enabled large-scale production of nitrogen fertilizers and became a foundation of modern chemical manufacturing. Its energy-intensive production is now a focus of efforts to make lower-carbon ammonia.
Updated 20 Oct 2026
Science
Hadley cell
A Hadley cell is a large-scale tropical circulation in which air rises near the equator, moves poleward at altitude, descends in the subtropics and returns toward the equator near the surface. Operating in both hemispheres, it helps explain the trade winds and broad patterns of tropical and subtropical weather.
Updated 22 Oct 2026
Science
Hall effect
The Hall effect is the appearance of a voltage across a current-carrying material when a magnetic field is applied perpendicular to the current. The Lorentz force pushes moving charge carriers sideways, creating a transverse electric field until the electrical and magnetic forces balance. The voltage's size and polarity can reveal properties such as magnetic-field strength, carrier density, and whether electrons or holes dominate conduction. The effect underlies Hall probes and is also a foundation for studying quantum Hall phenomena.
Updated 25 Oct 2026
Science
Hall–Petch relationship
The Hall–Petch relationship is an empirical relation in materials science connecting grain size with the yield strength of many polycrystalline metals. In its common form, yield strength increases approximately with the inverse square root of grain size, a trend associated with grain boundaries impeding dislocation motion. Its usefulness has limits, especially in very fine-grained materials and in plastically deformed microstructures.
Updated 31 Oct 2026
Science
Harmonic oscillator
A harmonic oscillator is a system that, when displaced from a stable equilibrium, experiences a restoring force proportional to its displacement. In the ideal undamped case, it undergoes periodic motion at a natural frequency determined by the system's physical parameters, not by the amplitude. Harmonic oscillators are useful models across mechanics, acoustics, electrical systems and quantum physics, although real systems may also be damped, driven or nonlinear.
Updated 30 Oct 2026
Science
Hawking radiation
Hawking radiation is the thermal emission that quantum field theory predicts from black holes. Proposed by Stephen Hawking in 1974, it links quantum physics, gravity and thermodynamics: an isolated black hole that emits energy loses mass, and its predicted temperature is inversely related to its mass.
Updated 31 Oct 2026
Science
Heat capacity
Heat capacity describes how much heat must be transferred to change the temperature of a specified body or amount of substance. It depends on the material and, for gases, on the conditions of the process; specific heat capacity expresses the quantity per unit mass, while molar heat capacity expresses it per mole. These properties are used in calorimetry, thermal design and the study of how materials respond to heating and cooling.
Updated 30 Oct 2026
Science
Helioseismology
Helioseismology uses oscillations measured at the Sun’s visible surface to infer conditions inside the Sun. Turbulent convection excites sound waves that travel through the solar interior and form resonant modes; their frequencies and patterns depend on properties of the regions they cross. By analyzing these signals, researchers investigate solar structure, rotation and subsurface flows, including areas that cannot be observed directly. The method relies on models and extended, precise observations, so its inferences have limits and uncertainties.
Updated 26 Oct 2026
Science
Higgs boson
The Higgs boson is an elementary particle associated with the Higgs field, a field that is part of the Standard Model of particle physics. Its discovery by the ATLAS and CMS experiments at CERN in 2012 provided evidence for the field and the Brout–Englert–Higgs mechanism, which accounts for the masses of several elementary particles. Studying the Higgs boson also tests how well the Standard Model describes nature and where it may be incomplete.
Updated 20 Oct 2026
Science
Hofstadter butterfly
The Hofstadter butterfly is the intricate, recursively structured energy spectrum predicted for electrons moving through a two-dimensional periodic lattice in a perpendicular magnetic field. It arises from the competition between the lattice's periodicity and the magnetic field's quantization of electron motion. Experiments using graphene moiré superlattices made the spectrum accessible by providing a relatively long periodic length scale, and revealed associated quantum Hall features and recursive structure.
Updated 26 Oct 2026
Science
Homo floresiensis
Homo floresiensis is an extinct human species known from fossils on the Indonesian island of Flores. Named in 2004 after remains were discovered in Liang Bua cave, it was small-bodied and made stone tools. Finds from other sites on Flores point to a much older hominin presence on the island, while the exact relationship between those remains and the Liang Bua population remains a subject of research.
Updated 22 Oct 2026
Science
Horseshoe crabs
Horseshoe crabs are marine arthropods whose lineage extends deep into the fossil record. They are ecologically important because their spawning eggs feed migratory shorebirds, and their blood-derived lysate is used in tests for bacterial endotoxins in medicines and medical devices. Harvest for bait and biomedical use, along with habitat pressures, has prompted fisheries management and conservation work; the status of individual species varies.
Updated 27 Oct 2026
Science
Hubble tension
The Hubble tension is the persistent difference between estimates of the present-day expansion rate of the universe, the Hubble constant, obtained from observations of the nearby universe and values inferred from observations of the early universe using a cosmological model. Local distance-ladder measurements generally give a higher value than cosmic-microwave-background-based estimates within the standard ΛCDM model. Independent telescope observations have tested measurement uncertainties, but the cause of the discrepancy remains unsettled.
Updated 25 Oct 2026
Science
Hubble's law
Hubble's law, also known as the Hubble–Lemaître law, describes the large-scale relationship between a galaxy's distance and its recession rate: the farther away a galaxy is, the faster it generally recedes as the universe expands. In its simple form, the law is written v = H₀d, where H₀ is the present expansion-rate parameter. The relation links astronomical redshift and distance and provides a foundational observational description of cosmic expansion.
Updated 21 Oct 2026
Science
Human Genome Project
The Human Genome Project (HGP) was an international research effort formally launched in 1990 and declared complete in April 2003. It produced the first widely usable reference sequence of the human genome, alongside sequences for several model organisms, and helped establish large-scale, collaborative genomics. Its 2003 completion was a project milestone, not a claim that every human DNA region had been read without gaps: later work, using newer methods, resolved substantial remaining sequence, including the human Y chromosome.
Updated 20 Oct 2026
Science
Human microbiome
The human microbiome is the collection of microorganisms associated with the human body and, in common usage, their genes and functional potential. Microbial communities inhabit distinct body sites, including the gut, mouth, skin and nasal passages, and vary among people and over time. Research links these communities to processes such as digestion, immune development and resistance to pathogens, while also investigating their associations with disease. Because many findings are observational and the microbiome is highly variable, an association does not by itself show that microbes caused a condition.
Updated 19 Oct 2026
Science
Hydraulic jump
A hydraulic jump is a rapid rise in the water surface where fast, shallow, supercritical flow changes into slower, deeper, subcritical flow in an open channel. The turbulent transition dissipates part of the flow's mechanical energy and is deliberately used in hydraulic structures to reduce high-speed outflow and limit downstream erosion.
Updated 28 Oct 2026
Science
Hydrothermal Vents
Hydrothermal vents are openings in the seafloor where heated, chemically altered seawater returns to the ocean. Common along mid-ocean ridges and other tectonically active areas, they release mineral-rich fluids that can build chimney-like deposits. Microorganisms use chemical energy at many vents, supporting distinctive deep-sea food webs without relying directly on sunlight.
Updated 21 Oct 2026
Science
Ice core
An ice core is a cylindrical sample drilled from a glacier or ice sheet. Its layered ice preserves clues to past climate, including isotope ratios, dust and other particles, while air bubbles trapped during snow compaction preserve samples of ancient atmosphere. Scientists combine these measurements with dating methods to reconstruct environmental change over time.
Updated 29 Oct 2026
Science
Ice disk
An ice disk is a floating, roughly circular sheet of ice that can rotate on a river or lake. Naturally occurring disks have been reported in cold waterways, sometimes reaching tens of metres across. Their formation and rotation depend on local conditions, and laboratory studies have investigated how melting-related water flows can contribute to rotation.
Updated 8 Nov 2026
Science
Ice Shelves
An ice shelf is a floating extension of land ice where a glacier or ice sheet flows into the ocean. Ice shelves gain ice from landward glaciers and snowfall, and lose it through basal melting and iceberg calving. Though already afloat and therefore not a direct source of sea-level rise when they break up, shelves can buttress inland ice; their thinning or collapse can speed the flow of grounded ice into the sea.
Updated 7 Nov 2026
Science
Ice spikes
Ice spikes are hollow, upward-pointing projections that sometimes form as water freezes in an open container or small body of water. In the usual ice-cube explanation, a surface layer of ice leaves a small opening through which expanding water is pushed; the water freezes at the opening and extends a tube-like spike. Their formation depends on details of freezing and crystal growth, and they do not appear in every freezing event.
Updated 29 Oct 2026
Science
IceCube Neutrino Observatory
The IceCube Neutrino Observatory is a particle detector embedded in Antarctic ice near the South Pole. By recording faint Cherenkov light from charged particles produced when neutrinos interact in the ice, it studies high-energy neutrinos and their possible cosmic sources. Its observations helped establish neutrino astronomy and contributed to identifying the blazar TXS 0506+056 as a likely source of high-energy cosmic neutrinos.
Updated 26 Oct 2026
Science
Indian Ocean Dipole
The Indian Ocean Dipole (IOD) is a recurring climate pattern defined by differences in sea-surface temperature between the western and eastern tropical Indian Ocean. Its positive, negative and neutral phases are associated with shifts in tropical winds, ocean temperatures and rainfall. The IOD influences regional climate, but its effects vary by region and can interact with other climate patterns such as El Niño–Southern Oscillation.
Updated 22 Oct 2026
Science
Indian Space Research Organisation
The Indian Space Research Organisation (ISRO) is India's space agency and a major constituent of the Department of Space. Established in 1969, it develops and applies space technology for national needs, including communications, meteorology, resource monitoring and navigation, and conducts scientific and planetary missions. Its work includes satellites, launch vehicles and ground-based systems, carried out through centres across India.
Updated 30 Oct 2026
Science
Inductance
Inductance is a property of an electrical circuit or conductor that quantifies the electromotive force induced when current changes. Self-inductance describes this effect within the same circuit, while mutual inductance describes the coupling between separate circuits. Measured in henries, inductance depends on circuit geometry and nearby materials, and is central to devices such as inductors and transformers.
Updated 30 Oct 2026
Science
International System of Units
The International System of Units (SI) is the internationally agreed system used to express measurements in science, industry, trade and everyday life. It organizes measurement around seven base units and defines units through exact values of physical constants, while derived units and decimal prefixes allow quantities to be expressed consistently across scales. Established in 1960, the SI is maintained through international metrology institutions and was substantially revised in 2019.
Updated 15 Oct 2026
Science
Interstellar medium
The interstellar medium (ISM) is the gas, dust, radiation, magnetic fields and energetic particles occupying the space between stars within a galaxy. In the Milky Way, it is structured rather than uniform: diffuse material and dense clouds coexist, and matter cycles between the medium and stars. Dense interstellar clouds can collapse to form stars, while stellar winds and supernovae return processed material to space.
Updated 27 Oct 2026
Science
Ionosphere
The ionosphere is a region of Earth’s upper atmosphere containing electrically charged particles formed when solar and other high-energy radiation ionizes atmospheric gases. Its electron density varies with sunlight, solar activity, and atmospheric conditions. These changes affect radio-wave propagation and satellite-navigation signals, making the ionosphere important to communications, navigation, and space-weather science.
Updated 26 Oct 2026
Science
Isostasy
Isostasy is the gravitational balance that helps explain broad differences in Earth's surface elevation. In simplified models, columns of lithosphere are supported by the denser, deformable mantle beneath them; their elevations depend on the density and thickness of the rocks and on the loads they carry. The concept explains why high mountain belts can have deep crustal roots and why land deforms under large ice sheets and slowly rebounds after they melt.
Updated 24 Oct 2026
Science
Jantar Mantar, Jaipur
Jantar Mantar in Jaipur is an early-18th-century astronomical observatory built under Maharaja Sawai Jai Singh II. Its monumental fixed instruments were designed to observe celestial positions with the naked eye and apply astronomical methods through architecture. Recognized as a UNESCO World Heritage property in 2010, the site reflects the scientific interests and cosmological ideas of Jai Singh II’s court in late Mughal-era India.
Updated 29 Oct 2026
Science
Joule heating
Joule heating is the conversion of electrical energy into thermal energy when current flows through electrical resistance. In an ohmic resistor, the rate of heat production is the electrical power P = I²R, also expressible as VI or V²/R under Ohm's law. It is useful in devices such as heating elements, but unwanted resistive losses can warm wires and electrical components.
Updated 30 Oct 2026
Science
Joule–Thomson effect
The Joule–Thomson effect is the temperature change that a real fluid can undergo when its pressure changes at constant enthalpy, as in flow through a throttling valve or porous plug. A pressure drop may cool or warm the fluid depending on its state; ideal gases show no temperature change in this process. The effect is used in refrigeration and gas liquefaction.
Updated 30 Oct 2026
Science
Kapitza resistance
Kapitza resistance is a thermal resistance at a boundary that impedes heat flow across an interface. First associated with heat transfer between solids and liquid helium, the phenomenon also describes interfaces between solid materials and is important in cryogenics and nanoscale heat transport. Its magnitude depends on the materials, temperature and microscopic condition of the boundary.
Updated 27 Oct 2026
Science
Kármán vortex street
A Kármán vortex street is a repeating wake pattern in which vortices form alternately on opposite sides of an obstacle in a moving fluid. It occurs in suitable flow conditions behind objects such as cylinders, islands, or mountains, and can appear in clouds when moist air flows around elevated terrain. Its periodic shedding is important in fluid mechanics and atmospheric observation.
Updated 24 Oct 2026
Science
Keeling Curve
The Keeling Curve is the long-running record of atmospheric carbon dioxide measurements begun by Charles David Keeling at Hawaii's Mauna Loa Observatory in 1958. Its distinctive seasonal oscillation reflects the annual growth and decay of Northern Hemisphere vegetation, while its persistent upward trend records the accumulation of carbon dioxide in the atmosphere. The measurements became a foundational dataset for understanding the global carbon cycle and human-driven climate change.
Updated 23 Oct 2026
Science
Kelvin water dropper
The Kelvin water dropper is an electrostatic generator in which falling water droplets acquire and transfer charge through induction. Two linked streams and collecting vessels form a positive-feedback loop that amplifies a tiny initial charge imbalance, producing a high voltage that can discharge as a spark. The device demonstrates electrostatic induction and the conversion of gravitational potential energy into electrical potential energy.
Updated 27 Oct 2026
Science
Kelvin–Helmholtz instability
Kelvin–Helmholtz instability is the growth of waves and rolling billows when adjacent parts of a fluid move at different speeds. In the atmosphere and ocean, shear can disturb an interface or stratified layer; the resulting billows may break down and promote mixing and turbulence. Visible cloud formations are one atmospheric example, while oceanic billows help connect internal waves to mixing in the water column.
Updated 27 Oct 2026
Science
Kerguelen Plateau
The Kerguelen Plateau is a vast submarine volcanic plateau in the southern Indian Ocean, on the Antarctic Plate. Together with nearby Broken Ridge, it forms a large igneous province built by extensive magmatism over a prolonged period. Ocean drilling recovered volcanic rocks and sediments that record its complex formation, former episodes when parts stood above sea level, and later environmental changes. The plateau is also a distinctive Southern Ocean marine region, where studies have examined benthic species and their responses to changing conditions.
Updated 25 Oct 2026
Science
Kibble balance
A Kibble balance is a precision instrument that realizes or measures mass by comparing mechanical power with electrical power. Its two operating modes relate the force on a test mass to the motion-induced voltage in a coil, allowing mass to be determined using electrical measurements linked to fixed quantum constants, including the Planck constant.
Updated 28 Oct 2026
Science
Kibble–Zurek mechanism
The Kibble–Zurek mechanism describes how defects can form when a system is driven through a continuous phase transition too quickly to remain in equilibrium. Near the critical point, relaxation slows and correlations cannot spread without limit; separated regions can settle into different ordered states, leaving defects where they meet. The framework connects ideas first developed for the early universe to experiments in condensed matter and ultracold gases.
Updated 26 Oct 2026
Science
Kīlauea Iki
Kīlauea Iki is a volcanic crater on Hawaiʻi Island that became the site of an unusually well-observed eruption in 1959. Seventeen episodes of lava fountaining built a cinder cone and filled the crater with a thick lava lake. Subsequent drilling into the cooling lake gave volcanologists a rare record of how basalt crystallizes and develops crust over decades.
Updated 27 Oct 2026
Science
Kilonova
A kilonova is a short-lived astronomical transient powered by radioactive material expelled when compact objects—most clearly, a pair of neutron stars—merge. The expanding ejecta produces a changing glow across optical and infrared wavelengths. Observations of GW170817 in 2017 linked gravitational waves from a neutron-star merger with electromagnetic light from a kilonova and showed that such events synthesize heavy elements through rapid neutron capture.
Updated 29 Oct 2026
Science
Kinetic isotope effect
A kinetic isotope effect (KIE) is a change in a reaction's rate constant associated with isotopic substitution in a reactant. Comparing the rates of isotopically distinct molecules can help chemists investigate bond changes and reaction mechanisms, though interpreting a measured effect requires care about the reaction's steps and conditions.
Updated 31 Oct 2026
Science
Kinetic Theory of Gases
The kinetic theory of gases explains measurable properties such as pressure and temperature by modelling a gas as a large number of moving particles. In its simplest form, it treats particles as widely separated, moving randomly and colliding elastically, with negligible intermolecular forces. The model derives useful gas laws and connects molecular motion with macroscopic behaviour, while remaining an approximation rather than a complete description of real gases.
Updated 19 Oct 2026
Science
Kirchhoff's circuit laws
Kirchhoff's circuit laws are two rules for analyzing electrical networks. The junction rule states that the total current entering a junction equals the total current leaving it, expressing conservation of electric charge. The loop rule states that the signed changes in electric potential around a closed circuit path sum to zero, reflecting energy conservation in the lumped-circuit model. Together, they allow unknown currents and voltages to be determined in networks that cannot be simplified as simple series and parallel combinations.
Updated 30 Oct 2026
Science
Köhler illumination
Köhler illumination is an optical alignment method used in light microscopy to create an evenly illuminated specimen field while keeping the image of the light source out of focus at the specimen. By adjusting the field diaphragm and condenser, microscopists can reduce stray light and balance contrast with resolution.
Updated 8 Nov 2026
Science
Kola Superdeep Borehole
The Kola Superdeep Borehole (SG-3) was a Soviet scientific drilling project on Russia’s Kola Peninsula that investigated the deep continental crust. Begun in 1970, it reached a maximum vertical depth of 12,262 metres in 1989, making it the deepest borehole by vertical depth. The project provided rock and fluid samples from deep crustal rocks, while unusually high temperatures and technical and financial constraints prevented the planned deeper drilling.
Updated 25 Oct 2026
Science
Kramers–Kronig relations
The Kramers–Kronig relations connect the real and imaginary parts of a system’s frequency-dependent response when that response is causal and satisfies suitable mathematical conditions. They link effects such as dispersion and absorption, allowing one part of a response to be inferred from measurements of the other. The relations are widely used in optics and spectroscopy, although finite measurement ranges and extrapolations can affect practical estimates.
Updated 27 Oct 2026
Science
Lagrangian mechanics
Lagrangian mechanics is a formulation of classical mechanics that describes a system's motion using a scalar function, the Lagrangian, and generalized coordinates. For many conservative systems the Lagrangian is kinetic energy minus potential energy; applying the Euler–Lagrange equations yields the equations of motion. The method is especially effective for systems with constraints and connects mechanics to the principle of stationary action.
Updated 25 Oct 2026
Science
Lake Vostok (Antarctica)
Lake Vostok is a large subglacial lake beneath the East Antarctic ice sheet, buried beneath several kilometres of ice. First accessed by drilling in 2012, it is an important site for studying Antarctic subglacial environments and the challenges of investigating isolated water without contaminating samples. Claims about microbial life there remain subject to strict scientific scrutiny.
Updated 6 Nov 2026
Science
Landauer's principle
Landauer's principle connects logical information erasure with thermodynamics: resetting an unknown, equally likely bit in a system coupled to a heat bath at temperature T requires at least kBT ln 2 of work in the ideal limit and releases a corresponding minimum amount of heat to the surroundings. The bound applies to logically irreversible operations under specified conditions, not indiscriminately to every computation. Experiments with a one-bit memory have tested the predicted limit, while reversible computation provides a way to avoid erasing intermediate information unnecessarily.
Updated 26 Oct 2026
Science
Landauer's principle
Landauer's principle links information erasure to thermodynamics: resetting one unknown bit in an environment at temperature T requires at least kBT ln 2 of heat to be dissipated in the ideal limit. Proposed by Rolf Landauer in 1961, it concerns logically irreversible operations—not every computation or every act of information processing—and gives a physical lower bound that practical devices generally exceed.
Updated 29 Oct 2026
Science
Langmuir circulation
Langmuir circulation is a pattern of parallel, wind-aligned rotating cells in the upper layer of a lake or ocean. Neighboring cells rotate in opposite directions, creating alternating surface convergence and divergence zones that can gather foam, algae, and floating debris into long streaks called windrows.
Updated 7 Nov 2026
Science
Large Hadron Collider
The Large Hadron Collider (LHC) is a particle accelerator operated by CERN near Geneva. Its 27-kilometre ring uses superconducting magnets to guide counter-circulating beams of protons or ions to high energies, where collisions are studied by international experimental collaborations. Results include the 2012 discovery of a new particle consistent with the Higgs boson by ATLAS and CMS.
Updated 10 Nov 2026
Science
Laser cooling of atoms
Laser cooling reduces the motion of atoms by using the momentum carried by light. In Doppler cooling, laser beams tuned slightly below an atomic resonance preferentially slow atoms moving toward them, while repeated photon scattering removes kinetic energy. Further techniques and trapping methods made ultracold atomic gases important tools in precision measurement and quantum physics.
Updated 27 Oct 2026
Science
Lazarus taxon
In palaeontology, a Lazarus taxon is a group known from fossils, absent from the sampled record for a substantial interval, and later represented again by fossils or living members. The name refers to apparent disappearance and return, not literal resurrection: the gap may reflect rare preservation, restricted habitats, limited geographic distribution or sparse sampling rather than extinction. The coelacanth is a prominent example, while the term also describes taxa that reappear in strata after major extinction events.
Updated 26 Oct 2026
Science
Leidenfrost effect
The Leidenfrost effect is a form of film boiling in which vapor generated beneath a liquid separates it from a much hotter surface. The vapor layer reduces direct contact and heat transfer, allowing droplets to move across the surface and evaporate more slowly than they do at lower temperatures. The transition temperature depends on the liquid, surface and operating conditions.
Updated 8 Nov 2026
Science
Lenticular cloud
A lenticular cloud is a lens-shaped cloud that can form when moist air flows over hills or mountains and oscillates in atmospheric waves. Condensation in the rising parts of the wave creates the visible cloud, while evaporation or sublimation in descending air dissipates it. The cloud may appear nearly stationary even as strong winds move through it, and its presence can signal mountain-wave turbulence relevant to aviation.
Updated 28 Oct 2026
Science
Lichen
A lichen is a stable association built around a fungus and a photosynthetic partner—green alga, cyanobacterium, or both. The fungal partner provides much of the structure, while the photobiont supplies photosynthetic carbon. Lichens grow in varied habitats and forms, reproduce through fungal spores or vegetative dispersal, and are used in ecological studies, including monitoring air quality.
Updated 30 Oct 2026
Science
Lichtenberg figure
A Lichtenberg figure is a branching pattern left by electrical discharge on or within an insulating material. Named for physicist Georg Christoph Lichtenberg, who recorded such patterns in the eighteenth century, the term now encompasses discharge structures that are studied in electrostatics and high-voltage engineering as well as celebrated as natural-looking forms.
Updated 28 Oct 2026
Science
Light echo
A light echo is the delayed or apparently moving illumination produced when light from a brief stellar outburst reaches surrounding dust or gas and is scattered or re-emitted toward an observer. Because the extra path through the surrounding material takes time, a light echo can reveal both the geometry of that material and a view of an event long after its direct light has passed.
Updated 26 Oct 2026
Science
LIGO (Laser Interferometer Gravitational-Wave Observatory)
The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a U.S.-based scientific project that uses laser interferometers to detect gravitational waves. Its two widely separated detectors in Hanford, Washington, and Livingston, Louisiana, jointly observed the first direct gravitational-wave signal, GW150914, in 2015, opening a new way to study the universe.
Updated 31 Oct 2026
Science
Lunar regolith
Lunar regolith is the loose, fragmented layer of rock, mineral grains, glass and dust that covers the Moon’s bedrock. It forms chiefly through repeated meteoroid impacts and is continually altered by solar and cosmic radiation. Unlike terrestrial soil, it contains no organic matter and is not shaped by wind or flowing water; its angular grains and fine dust create both scientific opportunities and practical challenges for lunar exploration.
Updated 24 Oct 2026
Science
Mach number
The Mach number is the ratio of an object's speed relative to a fluid, or the fluid's flow speed, to the local speed of sound in that fluid. It is a dimensionless measure used to characterize compressible flow and distinguish regimes such as subsonic, transonic and supersonic. Because sound speed changes with the fluid and its temperature, a Mach number is not a fixed speed in kilometres or miles per hour.
Updated 25 Oct 2026
Science
Madden–Julian oscillation
The Madden–Julian oscillation (MJO) is a large-scale pattern of tropical atmospheric variability marked by eastward-moving regions of enhanced and suppressed cloud and rainfall. Its active pattern typically circles the tropics in about 30–60 days, affecting weather on weekly-to-monthly timescales and modulating rainfall and other weather systems.
Updated 28 Oct 2026
Science
Magnetic hysteresis
Magnetic hysteresis is the dependence of a material’s magnetization on its magnetic history: when an applied field is cycled, magnetization does not simply retrace its path. The resulting loop describes properties such as remanence and coercivity and helps distinguish soft from hard magnetic materials.
Updated 7 Nov 2026
Science
Magnetic reconnection
Magnetic reconnection is a process in electrically conducting plasma in which magnetic fields change their connections and release some of their stored energy. The energy can heat plasma and accelerate charged particles. It occurs in settings including Earth’s magnetosphere, the Sun and laboratory fusion plasmas; spacecraft such as NASA’s Magnetospheric Multiscale mission study the small regions where the process takes place.
Updated 23 Oct 2026
Science
Magnetotactic bacteria
Magnetotactic bacteria are diverse microorganisms that align their swimming with magnetic fields using chains of membrane-bound mineral crystals called magnetosomes. In many aquatic habitats, this orientation helps them move along oxygen gradients toward favorable microenvironments. Their biominerals also affect sediment records and biogeochemical cycling, while prospective technological applications remain an active area of research.
Updated 27 Oct 2026
Science
Mammatus clouds
Mammatus are rounded, pouch-like cloud features that hang beneath a larger cloud, most often the anvil of a cumulonimbus. Their appearance is associated with particular patterns of sinking air and evaporation or sublimation, but no single explanation accounts for every observation. Despite their frequent association with thunderstorms, mammatus themselves do not produce severe weather and are not a reliable sign that a tornado will occur.
Updated 24 Oct 2026
Science
Mantis Shrimp Vision
Mantis shrimps (stomatopod crustaceans) have unusually elaborate compound eyes, with photoreceptor systems that can support colour, ultraviolet and polarization vision. Research shows that visual abilities vary by task and species: specialized receptors do not mean they necessarily distinguish colours better than humans, and one object-recognition experiment found shape more salient than colour.
Updated 10 Nov 2026
Science
Mantle plume
A mantle plume is a proposed upwelling of unusually hot rock within Earth’s mantle. Plume models have been used to explain some volcanic hotspots and age-progressive island and seamount chains, including Hawaii. The plume hypothesis remains an active scientific model rather than a directly observed structure, and it does not account equally well for every volcano formed within a tectonic plate.
Updated 24 Oct 2026
Science
Marangoni effect
The Marangoni effect is fluid motion driven by a gradient in surface or interfacial tension. Differences in temperature or in the concentration of surface-active substances can create such a gradient, which pulls liquid along an interface and can generate circulation in the fluid. The effect appears in everyday phenomena and is important in industrial processes and microgravity research.
Updated 27 Oct 2026
Science
Marine snow
Marine snow is a continuous downward flux of particles through the ocean, especially organic debris from surface waters. Made up of material such as dead plankton, fecal pellets and shed tissue, these particles may aggregate as they sink. Some are consumed or decomposed in the water column; a fraction reaches the seabed, feeding deep-sea communities and carrying organic carbon and nutrients to depth. Its formation and fate depend on interactions among particle physics, microbes and marine food webs.
Updated 24 Oct 2026
Science
Maunder Minimum
The Maunder Minimum is the name given to an interval, conventionally dated about 1645–1715, when telescopic records show unusually few sunspots. Modern studies compare historical observations with indirect solar-activity records to assess how quiet the Sun was. The interval overlapped part of the Little Ice Age, but that overlap alone does not establish that low solar activity caused the wider period of cooler climate; reconstructions point to multiple influences.
Updated 22 Oct 2026
Science
Maxwell stress tensor
The Maxwell stress tensor is a mathematical representation of electromagnetic momentum flow used to calculate the force and torque exerted by electric and magnetic fields on matter. In vacuum, integrating its traction over a closed surface enclosing an object gives the net electromagnetic force for static fields; for time-varying fields, the momentum stored in the enclosed field must also be accounted for. Its use is especially convenient when the field is known on a surrounding surface, though interpretation in material media requires care.
Updated 28 Oct 2026
Science
Maxwell's equations
Maxwell's equations are four relations that describe how electric charges and currents generate electric and magnetic fields, and how changing fields are linked. Together with the Lorentz force law, they form the classical foundation of electromagnetism and predict electromagnetic waves, including light.
Updated 31 Oct 2026
Science
Meiosis
Meiosis is a specialized form of cell division that reduces the number of chromosome sets by half. In sexually reproducing organisms, it helps produce haploid reproductive cells or spores from diploid cells. Two successive divisions follow one round of DNA replication: homologous chromosomes separate in meiosis I, then sister chromatids separate in meiosis II. Recombination and the independent assortment of chromosomes create genetic variation.
Updated 30 Oct 2026
Science
Mendelian inheritance
Mendelian inheritance describes how genes and their alleles are passed from parents to offspring through predictable patterns, especially the segregation of allele pairs during gamete formation and the independent assortment of unlinked genes. Gregor Mendel inferred these patterns from controlled crosses of pea plants in the nineteenth century. His principles explain many inheritance patterns, but observed traits can also be shaped by linkage, interactions among genes, and other biological processes.
Updated 30 Oct 2026
Science
Metamaterial
A metamaterial is an engineered structure whose designed internal architecture produces effective properties not ordinarily found in naturally occurring materials. First developed around unusual electromagnetic responses, the field now also includes optical, acoustic, mechanical and thermal systems.
Updated 10 Nov 2026
Science
Michelson–Morley experiment
The Michelson–Morley experiment was an 1887 optical test by Albert A. Michelson and Edward W. Morley that sought evidence of Earth's motion relative to the hypothesized luminiferous ether. Using an interferometer to compare light along perpendicular paths, they found no expected shift in the interference fringes. The null result challenged prevailing ether models and became an important episode in the development of modern physics, although its relationship to the later creation of special relativity is historically nuanced.
Updated 30 Oct 2026
Science
Mie scattering
Mie scattering is the solution of the electromagnetic scattering problem for a homogeneous sphere illuminated by a plane wave. It provides a quantitative account of how the sphere scatters and absorbs light, including dependence on wavelength, particle size and refractive index. The framework is used in atmospheric science, cloud optics and particle characterization; its classical form assumes spherical geometry, although extensions handle more complex particles and illumination.
Updated 26 Oct 2026
Science
Milankovitch cycles
Milankovitch cycles are long-term variations in Earth's orbital shape, axial tilt and rotational-axis orientation that alter the distribution of incoming sunlight. Operating over tens of thousands to hundreds of thousands of years, they help pace glacial–interglacial climate cycles. They are a natural influence on long-term climate, not an explanation for the rapid global warming observed in the modern era.
Updated 26 Oct 2026
Science
Miller–Urey experiment
The Miller–Urey experiment was a 1953 laboratory study by Stanley Miller and Harold Urey that tested whether organic compounds could form from simpler substances under simulated early-Earth conditions. An electric discharge passed through a mixture of gases and water vapour above heated water; the collected products included amino acids and other organic molecules. The experiment demonstrated that some biological building blocks can form abiotically under particular conditions, not that it recreated the full early Earth or explained how life began.
Updated 30 Oct 2026
Science
Mima mounds
Mima mounds are low, rounded hills of soil found in the southern Puget Lowland of Washington State. At their best-known locality near Olympia, the mounds form a distinctive prairie landscape over glacial deposits. Their precise origin remains debated: proposed explanations include biological soil movement by burrowing animals and several glacial, sedimentary and seismic processes. Evidence constrains the possibilities, but no single explanation is accepted for all mound fields.
Updated 28 Oct 2026
Science
Minoan eruption
The Minoan eruption was a major Late Bronze Age volcanic event at Thera (Santorini), Greece. It buried settlements including Akrotiri, generated widespread volcanic deposits and a tsunami, and remains debated in its precise date and wider effects.
Updated 9 Nov 2026
Science
Mitochondria
Mitochondria are membrane-bound organelles found in most eukaryotic cells. They produce much of the cell's ATP through aerobic respiration and also contribute to metabolism, signaling, and cell regulation. Their small genome and several bacterial-like characteristics support the widely accepted endosymbiotic explanation for their evolutionary origin.
Updated 16 Oct 2026
Science
Mitochondrion
Mitochondria are membrane-bound organelles found in almost all human cells. They produce most of the chemical energy cells use, storing it in adenosine triphosphate (ATP), and also take part in other cellular processes. They have their own DNA, and evidence from mitochondrial genomes supports an evolutionary origin from bacteria through endosymbiosis.
Updated 21 Oct 2026
Science
Mitosis
Mitosis is the division of a eukaryotic cell’s nucleus, during which replicated chromosomes are separated into two nuclei. The cell copies its DNA earlier, in the S phase of interphase; mitosis then organizes and distributes those copies. Mitosis supplies new cells for growth and replacement of worn cells and, in some eukaryotes, is a means of asexual reproduction. When followed by cytokinesis—the division of the cytoplasm—it typically produces two daughter cells with the same chromosome number as the parent cell.
Updated 17 Oct 2026
Science
Moiré pattern
A moiré pattern is a larger-scale pattern that appears when two similar periodic structures are overlaid with a small relative rotation or spacing difference. The resulting bands or fringes are a geometric beat pattern, not necessarily a new physical structure. Moiré patterns are used to detect small displacements and strain, and in layered two-dimensional materials they can create a long-period modulation that influences electronic behavior.
Updated 24 Oct 2026
Science
Molecular clock
A molecular clock uses genetic differences among organisms to estimate evolutionary rates or the timing of divergence. Because molecular rates vary among lineages, modern analyses use models that can relax a single constant-rate assumption and rely on calibration evidence—often fossils—to express estimates in absolute time. Results remain dependent on data, model choice and calibration assumptions.
Updated 28 Oct 2026
Science
Molybdenum
Molybdenum (Mo) is a silvery, high-melting transition metal with atomic number 42. First isolated in 1781, it is best known for strengthening steels and other alloys, while its compounds and trace biological roles give it additional industrial and natural significance.
Updated 9 Nov 2026
Science
Monsoon
A monsoon is a large-scale seasonal shift in winds and rainfall, producing distinct wet and dry periods in many tropical regions. Seasonal heating differences between land and ocean contribute to changing pressure and wind patterns; the movement of tropical rain belts and regional geography also shape where and when rain falls. Monsoons support agriculture and water supplies, but their variable timing and intensity can bring drought, flooding and other hazards.
Updated 13 Oct 2026
Science
Monsoon trough
The monsoon trough is an elongated, semi-permanent low-pressure zone associated with the South Asian summer monsoon. Extending across the northern part of the subcontinent, its position and strength are linked to where monsoon rainfall occurs. Shifts in the trough accompany changes between active and break conditions, although rainfall also depends on other atmospheric processes and weather systems.
Updated 23 Oct 2026
Science
Moon illusion
The Moon illusion is the familiar impression that the Moon appears larger near the horizon than high in the sky. Photography and direct size comparisons show that its apparent angular width changes little with elevation; atmospheric refraction slightly compresses, rather than magnifies, the low Moon. Researchers have proposed perceptual explanations involving distance, size constancy and visual context, but no single account has achieved consensus.
Updated 25 Oct 2026
Science
Mössbauer effect
The Mössbauer effect is the recoil-free emission and resonant absorption of gamma rays by nuclei bound in a solid. By avoiding the energy loss that normally shifts nuclear emission away from absorption, it creates exceptionally narrow resonance lines. Mössbauer spectroscopy uses these lines to probe nuclear and local material environments, especially the oxidation state, coordination and magnetic behavior of iron-bearing substances.
Updated 27 Oct 2026
Science
Mulliken electronegativity
Mulliken electronegativity is an atomic electronegativity scale based on the average of an atom's first ionization energy and electron affinity. Unlike the Pauling scale, which is inferred from bond energies, it is calculated from properties of isolated atoms and is commonly expressed in energy units. Proposed by Robert S. Mulliken in 1934, it connects electron attraction with the energetic cost of removing an electron and the energy change when an atom accepts one; comparisons require care about electron-affinity sign conventions and scale normalization.
Updated 26 Oct 2026
Science
Mycorrhizal symbiosis
Mycorrhizal symbiosis is an association between fungi and plant roots in which fungal hyphae extend into the soil and exchange resources with the plant. Fungi commonly improve access to nutrients such as phosphorus and can aid water uptake; plants provide the fungi with carbon compounds made through photosynthesis. The benefits and form of the association vary among fungal groups, plant species and environmental conditions.
Updated 25 Oct 2026
Science
Nacre
Nacre, commonly called mother-of-pearl, is an iridescent biomineral that lines the shells of many molluscs and forms much of the material in some pearls. It is a composite built mainly from microscopic aragonite crystals, a form of calcium carbonate, arranged with a small amount of organic material. This layered architecture helps nacre resist fracture more effectively than the mineral alone and produces its characteristic optical effects. Researchers study how molluscs control its formation and how its structure might inspire engineered materials.
Updated 26 Oct 2026
Science
Nacreous clouds
Nacreous clouds are rare, vividly iridescent ice clouds in the polar stratosphere, also called mother-of-pearl clouds. They form in exceptionally cold winter conditions, often in air disturbed by gravity waves, and can remain brightly coloured after sunset. Their chemistry and relationship to other polar stratospheric clouds are important to stratospheric ozone science.
Updated 24 Oct 2026
Science
Negative capacitance
Negative capacitance describes a regime in which a change in charge is associated with a voltage change opposite to that of an ordinary positive capacitor. In ferroelectrics, researchers investigate whether this response can be stabilized in a material or heterostructure, potentially amplifying voltage in electronic devices. Its microscopic interpretation and practical use remain subjects of active debate.
Updated 28 Oct 2026
Science
Nernst effect
The Nernst effect is a transverse thermoelectric phenomenon: a temperature gradient and a magnetic field in a conducting material can generate an electric field perpendicular to both. It provides a way to investigate charge transport and magnetic materials, and underlies research into transverse thermoelectric energy conversion. In magnetic materials, a related anomalous Nernst effect can arise from spontaneous magnetization even without an applied magnetic field.
Updated 27 Oct 2026
Science
Nernst equation
The Nernst equation relates the potential of an electrochemical cell or electrode under specified conditions to its standard potential, temperature, electron transfer and reaction quotient. It follows from the relationship between Gibbs energy and electrical potential and is used to calculate cell potentials away from standard-state conditions. At equilibrium, the cell potential is zero and the reaction quotient equals the equilibrium constant.
Updated 30 Oct 2026
Science
Neutrino
A neutrino is an electrically neutral elementary particle in the lepton family. Neutrinos have very small, nonzero masses and interact so rarely with matter that they are difficult to detect. Their ability to change among three known flavors as they travel—neutrino oscillation—has reshaped particle physics and made them useful probes of the Sun, Earth’s atmosphere, supernovae and other astrophysical environments.
Updated 16 Oct 2026
Science
Neutrino oscillation
Neutrino oscillation is the quantum-mechanical change in the probability of detecting a neutrino in a particular flavour—electron, muon or tau—as it travels. It occurs because flavour states are mixtures of states with different masses, whose quantum phases evolve differently. Experiments observing solar and atmospheric neutrinos established oscillations and showed that at least some neutrinos have non-zero mass, requiring an extension to the minimal Standard Model.
Updated 24 Oct 2026
Science
NISAR
NISAR (NASA-ISRO Synthetic Aperture Radar) is a joint Earth-observation mission developed by NASA and the Indian Space Research Organisation. Launched in 2025, the satellite uses L-band and S-band synthetic aperture radar to repeatedly map changes in Earth's land and ice-covered regions. Its observations support research on surface deformation, ecosystems, ice, water and natural hazards.
Updated 8 Nov 2026
Science
Nitrogen cycle
The nitrogen cycle is the movement of nitrogen among the atmosphere, soils, waters and living organisms. Microbes, lightning and industrial processes convert atmospheric nitrogen gas into reactive forms that organisms can use, while other transformations return nitrogen to the atmosphere. Fertilizer use and fuel combustion have altered this cycle, bringing agricultural benefits as well as air- and water-quality impacts.
Updated 21 Oct 2026
Science
Nuclear fission
Nuclear fission is a reaction in which an atomic nucleus splits into smaller nuclei, releasing energy and often additional neutrons. In suitable fuel, those neutrons can sustain a chain reaction; power reactors regulate the process and use its heat to generate electricity. Fission can also occur spontaneously in some unstable nuclei, while radioactive fission products and spent fuel require careful management.
Updated 17 Oct 2026
Science
Nuclear fusion
Nuclear fusion occurs when light atomic nuclei combine to form a heavier nucleus, releasing energy because of changes in nuclear binding energy. Fusion powers stars, while research on Earth seeks to create and control it in extremely hot plasma. Magnetic-confinement machines and laser-driven inertial-confinement experiments have achieved important scientific milestones, but producing reliable net electricity still requires advances in fuel handling, materials, heat management and integrated plant design.
Updated 15 Oct 2026
Science
Nuclear magnetic resonance
Nuclear magnetic resonance (NMR) is a physical phenomenon in which certain atomic nuclei respond to radiofrequency energy in a magnetic field. Because their resonance frequencies depend on the nucleus and its local molecular environment, NMR spectroscopy is widely used to investigate chemical structure and molecular behaviour. Magnetic resonance imaging (MRI) applies related principles to produce spatially resolved images, especially of hydrogen-rich tissues.
Updated 28 Oct 2026
Science
Octopuses
Octopuses are marine cephalopod mollusks distinguished by eight flexible, sucker-lined arms and soft bodies. They occur in oceans worldwide and use a beak to feed on prey such as crustaceans and mollusks. Many species can change skin appearance, hide in small spaces, or propel themselves with a jet of water. Their nervous systems combine a central brain with extensive neural networks in the arms, supporting flexible movement and complex interactions with their surroundings.
Updated 16 Oct 2026
Science
Oklo natural nuclear reactors
The Oklo natural nuclear reactors are ancient uranium deposits in present-day Gabon where self-sustaining nuclear fission occurred without human intervention. Discovered through unusual uranium isotope measurements in 1972, the reactors formed when uranium-rich geology and groundwater created conditions that allowed a chain reaction. The site is a rare natural record of nuclear processes and geological history.
Updated 6 Nov 2026
Science
Olbers' paradox
Olbers' paradox asks why the night sky is dark if an infinite, static and eternal universe filled uniformly with stars would seem to make every sightline end on a star. Modern cosmology resolves the apparent contradiction: the universe has a finite age, so light from every possible source has not had time to reach us, and cosmic expansion stretches much distant light to wavelengths beyond human vision.
Updated 29 Oct 2026
Science
Olympus Mons
Olympus Mons is a vast shield volcano on Mars and the largest known volcano in the Solar System. Its broad, gently sloping flanks were built by fluid lava flows, while a complex summit caldera and steep peripheral escarpment record a long volcanic and geological history. Spacecraft observations and geological mapping have helped scientists characterize this major feature of the Tharsis region.
Updated 30 Oct 2026
Science
Orographic lift
Orographic lift is the forced ascent of air over elevated terrain such as hills or mountains. As moist air rises, it expands and cools; if it reaches saturation, clouds form and precipitation may develop, often increasing on windward slopes. Air descending on the far side is commonly drier, creating a rain-shadow effect, though the outcome depends on moisture, wind and terrain.
Updated 26 Oct 2026
Science
Osmoregulation
Osmoregulation is the control of water and dissolved-solute balance in an organism. It helps maintain conditions needed for cells and tissues despite changes in intake and surroundings. Animals achieve it through processes such as membrane transport, excretion, and—in many vertebrates—kidney and hormonal regulation; strategies differ among species and environments.
Updated 30 Oct 2026
Science
Osmosis
Osmosis is the net movement of a solvent—usually water in living systems—through a selectively permeable membrane when conditions differ across it. When water can pass more readily than particular dissolved solutes, it moves toward the side with lower water potential, often the more concentrated solution. Osmosis influences cell volume and plant water balance and underlies processes such as reverse osmosis for water treatment.
Updated 21 Oct 2026
Science
Oxygen minimum zone
An oxygen minimum zone (OMZ) is a persistent midwater region where dissolved oxygen reaches a minimum relative to surrounding layers. OMZs form when oxygen-consuming processes, especially microbial decomposition of sinking organic matter, outpace oxygen supply by circulation and mixing. Their low-oxygen conditions shape marine habitats and microbial carbon and nitrogen cycling; their extent and intensity vary across ocean basins and over time.
Updated 25 Oct 2026
Science
Paleocene–Eocene Thermal Maximum
The Paleocene–Eocene Thermal Maximum (PETM) was a major global warming event about 56 million years ago, near the boundary between the Paleocene and Eocene epochs. It is identified in geological records by a large negative carbon-isotope excursion and is associated with substantial carbon release, rapid warming, and changes in ocean chemistry and ecosystems. Researchers study the event as a natural example of how the climate system responds to a major carbon perturbation, while continuing to investigate its sources, timing, and sequence of feedbacks.
Updated 25 Oct 2026
Science
Paleomagnetism
Paleomagnetism is the study of magnetic signals preserved in rocks and other materials, which record aspects of Earth's ancient magnetic field. By measuring the direction and strength of this remanent magnetization and establishing the material's age, researchers investigate geomagnetic reversals, past plate motions, seafloor spreading, and volcanic histories. The field links small-scale magnetic minerals to large-scale reconstructions of Earth's geological past.
Updated 25 Oct 2026
Science
Paleontology
Paleontology is the scientific study of past life through fossils and their geological context. It examines preserved remains and traces of organisms—from microscopic fossils and plants to large animals—to investigate the history and diversity of life, evolutionary change, extinction, and ancient environments. Because fossil preservation depends on particular conditions, the fossil record is incomplete and must be interpreted alongside geology.
Updated 14 Oct 2026
Science
Pando aspen clone
Pando is a large clonal colony of quaking aspen (Populus tremuloides) in Utah's Fishlake National Forest. Genetic testing has confirmed that its many trunks belong to one genetic individual connected through an extensive root system. Covering roughly 43 hectares, it is often called one of the world's largest organisms by area or mass. Its long-term persistence depends on continual replacement of aging stems, a process challenged by browsing and other pressures on young growth.
Updated 28 Oct 2026
Science
Pangaea
Pangaea was a geologically recent supercontinent that brought together nearly all of Earth's major landmasses. It was surrounded by the global ocean Panthalassa and assembled by the Early Permian, roughly 300 million years ago. Beginning about 200 million years ago, it gradually broke apart as tectonic plates moved, giving rise to the continents and ocean basins recognizable today. Evidence of matching continental margins and geological formations helped inform the theory of continental drift and, later, modern plate tectonics.
Updated 22 Oct 2026
Science
Pangolin
Pangolins are eight species of Asian and African mammals in the family Manidae, order Pholidota. Their keratin scales, long tongues and ant- and termite-based diets distinguish them among mammals. All eight species face a high risk of extinction, chiefly from overexploitation and habitat loss, despite restrictions on commercial international trade.
Updated 21 Oct 2026
Science
Parhelion
A parhelion, commonly called a sun dog or mock sun, is a bright atmospheric optical effect that appears beside the Sun. It is produced when sunlight is refracted and dispersed by ice crystals, most often in high clouds; its position and visibility depend on crystal geometry, cloud conditions and the Sun’s elevation.
Updated 27 Oct 2026
Science
Pasteurization
Pasteurization is a controlled heat treatment used to reduce disease-causing microorganisms in foods and drinks, especially milk. It uses a specified combination of temperature and time; it is not the same as sterilization and does not make a product immune to later contamination or spoilage. The process is named for Louis Pasteur, whose nineteenth-century work showed that heating could prevent unwanted fermentation.
Updated 30 Oct 2026
Science
Pauli exclusion principle
The Pauli exclusion principle states that identical fermions cannot occupy the same quantum state simultaneously. Proposed by Wolfgang Pauli in 1925 to explain electron arrangements in atoms, the principle helps account for the structure of the periodic table and many properties of matter. It applies to fermions such as electrons, protons and neutrons, but not to bosons such as photons.
Updated 29 Oct 2026
Science
Peltier effect
The Peltier effect is the reversible heating or cooling that occurs at a junction between dissimilar materials when electric current passes through it. It underlies solid-state thermoelectric modules, which pump heat from one face to another without moving mechanical parts and can be used for both cooling and heating.
Updated 24 Oct 2026
Science
Periodic table
The periodic table organizes chemical elements by increasing atomic number—the number of protons in an atom’s nucleus—and displays recurring patterns in their properties. In the familiar long form, its seven rows are periods and its 18 columns are groups; elements in a group often share chemical traits because of related electron configurations. Dmitri Mendeleev’s influential 1869 table left gaps for elements he predicted, while Henry Moseley’s work in 1913 established atomic number as the sound basis for ordering. The table is a compact guide for comparing elements and anticipating chemical behavior, not a substitute for the detailed data about each substance.
Updated 17 Oct 2026
Science
Phonon
A phonon is the quantum of a collective vibrational mode in a solid, especially a crystal lattice. It provides a useful particle-like description of quantized atomic vibrations and helps explain how heat and sound travel through materials. Phonons also influence thermal conductivity and can mediate interactions between electrons in some superconductors.
Updated 27 Oct 2026
Science
Photomultiplier tube
A photomultiplier tube (PMT), also called a photomultiplier, is a highly sensitive vacuum photodetector that converts light into electrons and amplifies the resulting signal through secondary emission at dynodes.
Updated 8 Nov 2026
Science
Photonic crystal
A photonic crystal is a material or engineered structure whose optical properties vary periodically on a scale that affects light. This repeating pattern can shape how electromagnetic waves propagate, sometimes creating frequency ranges called photonic band gaps in which light cannot travel through the structure. By controlling propagation and localizing light, photonic crystals underpin research into optical waveguides, resonators, filters, sensing, and other photonic devices.
Updated 28 Oct 2026
Science
Photosynthesis
Photosynthesis is the set of biological processes that capture light energy and convert it into chemical energy stored in organic compounds. In oxygenic photosynthesis, used by plants, algae, and cyanobacteria, water supplies electrons and oxygen is released as carbon dioxide is incorporated into carbohydrates. Other photosynthetic bacteria use different electron donors and do not release oxygen. By supporting primary production and influencing atmospheric chemistry, photosynthesis shapes most food webs and has profoundly affected Earth's history.
Updated 12 Oct 2026
Science
Photovoltaic effect
The photovoltaic effect is the generation of an electrical voltage and current in a material when it absorbs light. In a solar cell, light creates mobile charge carriers and a built-in electric field or junction helps separate them, allowing an external circuit to draw direct-current electricity. It is the physical principle behind photovoltaic power generation.
Updated 27 Oct 2026
Science
Phyllotaxis
Phyllotaxis is the arrangement of leaves, flowers or other repeated organs around a plant axis. It ranges from alternate and opposite leaves to whorls and spiral patterns. Many spiral arrangements are associated with Fibonacci numbers, while successive organs near the growing shoot tip often form at an angle close to 137.5 degrees. These patterns emerge through plant development, including local signaling at the shoot apical meristem; the exact mechanisms and evolutionary explanations remain active research topics.
Updated 27 Oct 2026
Science
Physics
Physics is a natural science that seeks quantitative explanations of matter, energy, motion and their interactions, from subatomic particles to the universe. It combines observation and experiment with mathematical models, testing predictions and revising explanations when evidence requires. Classical physics describes many everyday systems; quantum theory and relativity extend the framework to very small scales, high speeds and strong gravity, while a complete unification of known interactions remains unresolved.
Updated 12 Oct 2026
Science
Piezoelectricity
Piezoelectricity is the coupling between mechanical deformation and electrical polarization in certain materials. In the direct effect, pressure or strain produces an electrical response; in the converse effect, an applied electric field causes deformation. First demonstrated in crystals by Pierre and Jacques Curie in 1880, the phenomenon underlies sensors, sound transducers, ultrasonic devices and other technologies.
Updated 23 Oct 2026
Science
Planetary defense
Planetary defense is the scientific and international effort to find and characterize near-Earth objects that could threaten Earth, assess any impact risk, and prepare potential responses. It combines astronomical surveys and orbit analysis with public communication and research into mitigation methods. NASA's DART mission demonstrated that a spacecraft impact can alter an asteroid moonlet's orbit, while international networks coordinate observations and response planning.
Updated 6 Nov 2026
Science
Plate tectonics
Plate tectonics is the scientific framework describing how Earth's rigid outer shell is divided into moving plates. Their interactions shape ocean basins and mountains and are closely associated with earthquakes and volcanoes. Most movement and its most visible effects occur at plate boundaries, where plates diverge, converge, slide past one another, or interact across broader zones.
Updated 23 Oct 2026
Science
Poynting–Robertson effect
The Poynting–Robertson effect is a subtle force on small particles that absorb and re-emit starlight while orbiting a luminous body. In the Solar System it gradually removes orbital energy and angular momentum from many dust grains, causing their orbits to shrink and usually become more circular. Its influence accumulates over long periods and helps explain how interplanetary dust evolves under radiation as well as gravity.
Updated 25 Oct 2026
Science
Precession of the equinoxes
The precession of the equinoxes is the slow shift in the orientation of Earth's rotational axis, which causes the equinox points to move along the ecliptic relative to the stars. Driven mainly by the gravitational pull of the Sun and Moon on Earth's equatorial bulge, the cycle takes about 25,772 years. It changes the direction of Earth's axis in the sky and the alignment of the seasons with Earth's orbital position.
Updated 7 Nov 2026
Science
Project Mohole
Project Mohole was a U.S. scientific effort in the late 1950s and 1960s to drill through oceanic crust and obtain a direct sample of the mantle. Although the project was cancelled before reaching its principal target, its 1961 expedition demonstrated that a ship could be held over a deep-ocean drill site using dynamic positioning and recover rock from beneath the seafloor. The engineering achievement helped lay groundwork for later scientific ocean-drilling programs.
Updated 24 Oct 2026
Science
Protein folding
Protein folding is the process by which a newly made or unfolded polypeptide adopts a three-dimensional shape that enables its biological activity. Amino-acid sequence and the surrounding chemical environment constrain this process, while cellular chaperones help many proteins fold, avoid aggregation, or recover from stress. Misfolding can impair function, but folding pathways, intermediate states, and the role of helper proteins vary among proteins and conditions.
Updated 30 Oct 2026
Science
Pulsar timing array
A pulsar timing array (PTA) is a network of regularly observed millisecond pulsars used to search for gravitational waves at nanohertz frequencies. Researchers compare tiny deviations in pulse arrival times across many pulsars: a gravitational-wave background should produce a distinctive pattern of correlated timing residuals across the sky. PTAs reported evidence for such a background in 2023, while the strength and interpretation of the evidence continue to be studied.
Updated 24 Oct 2026
Science
Quantum dots
Quantum dots are semiconductor nanocrystals small enough that quantum confinement changes their electronic and optical behavior. Their absorption and emission depend on particle size, allowing researchers to tune the light they produce. This size-sensitive behavior underpins uses in displays, lighting, biological research and emerging photonic technologies.
Updated 26 Oct 2026
Science
Quantum error correction
Quantum error correction is a set of methods for protecting quantum information from noise, decoherence and imperfect operations. It encodes one logical qubit across multiple physical qubits and detects error patterns through measurements that reveal information about errors without directly reading the encoded quantum state. Quantum error correction is central to fault-tolerant quantum computing, but its performance depends on the code, hardware and error rates.
Updated 6 Nov 2026
Science
Quantum mechanics
Quantum mechanics is the physical theory used to describe matter and light at atomic and subatomic scales. It represents physical systems by mathematical states and predicts probabilities for measurement outcomes; in bound systems, some properties such as energy have discrete allowed values. Concepts including wave–particle duality, superposition, uncertainty and entanglement help explain atomic structure and phenomena that classical physics cannot account for. Quantum mechanics underpins technologies such as semiconductors, lasers and atomic clocks, although questions about how to interpret its mathematical description remain debated.
Updated 15 Oct 2026
Science
Quantum Teleportation
Quantum teleportation is a protocol for transferring an unknown quantum state from one system to another using shared entanglement and classical communication. It does not transport matter or send information faster than light: the receiver needs classical measurement results from the sender to reconstruct the state. The protocol, proposed in 1993, has been demonstrated with photons and other quantum systems and is studied as a tool for quantum communication and computing.
Updated 7 Nov 2026
Science
Quantum tunnelling
Quantum tunnelling is a quantum-mechanical process in which a particle has a nonzero probability of passing through an energy barrier that classical mechanics would make impassable at its energy. It follows from the wave-like description of matter: a particle's quantum state can extend into and beyond a barrier. Tunnelling helps explain phenomena such as alpha decay and enables technologies including the scanning tunnelling microscope.
Updated 25 Oct 2026
Science
Quantum Zeno Effect
The quantum Zeno effect is the inhibition or slowing of transitions between quantum states when a system is measured frequently enough. It arises from quantum dynamics and the interaction involved in measurement, not from human attention or a literal freezing of time. Experiments with trapped ions have demonstrated the effect; under other conditions, measurement can instead accelerate transitions, a related phenomenon called the quantum anti-Zeno effect.
Updated 7 Nov 2026
Science
Quasi-biennial oscillation
The quasi-biennial oscillation (QBO) is a recurring reversal of east–west winds in the tropical stratosphere. Alternating easterly and westerly wind regimes descend through the stratosphere, with a typical full cycle averaging about 28 months. The QBO is generated mainly by atmospheric waves that transfer momentum to the mean flow, and it influences circulation and the transport of ozone and other trace substances beyond the equatorial region.
Updated 25 Oct 2026
Science
Quorum sensing
Quorum sensing is a form of chemical communication used by many bacteria to coordinate changes in gene expression. Bacteria release and detect signaling molecules; when the local signal reaches a threshold, cells can alter collective behaviors such as light production, biofilm development or virulence-factor secretion. The systems vary among species, and population density is only one influence on their activity.
Updated 24 Oct 2026
Science
Radioactive Half-Life
Radioactive half-life is the time in which, on average, half the unstable nuclei in a sample of a particular radioisotope decay. It is characteristic of that radioisotope and supports calculations of activity, radioactive change and radiometric dating.
Updated 7 Nov 2026
Science
Radiometric dating
Radiometric dating is a group of methods for estimating the age of rocks, minerals and other materials by measuring radioactive isotopes and their decay products. Because isotopes decay at characteristic rates, their measured proportions can act as clocks, provided the sample's geological history and the method's assumptions are understood. Geologists use radiometric dates alongside other evidence to reconstruct Earth's history and time geological events.
Updated 6 Nov 2026
Science
Rafflesia arnoldii
Rafflesia arnoldii is a parasitic flowering plant native to Sumatra, famous for producing a single flower that can reach about one metre across. It lives within Tetrastigma vines, lacks ordinary leaves, stems and roots, and uses a carrion-like scent to attract insect pollinators.
Updated 9 Nov 2026
Science
Raman effect
The Raman effect is the change in energy of a small fraction of light scattered by molecules or materials. The shifted light reflects energy exchanged with molecular or material vibrations, so its spectrum can reveal information about a sample’s composition and structure. Discovered by C. V. Raman and K. S. Krishnan in 1928, the effect underlies Raman spectroscopy, a widely used analytical technique.
Updated 24 Oct 2026
Science
Rayleigh criterion
The Rayleigh criterion is a conventional way to describe when two nearby point sources are just distinguishable in a diffraction-limited imaging system. For an ideal circular aperture, the criterion places their angular separation at approximately 1.22 times the wavelength divided by the aperture diameter. It is a useful benchmark, not a universal boundary on every imaging method.
Updated 27 Oct 2026
Science
Rayleigh–Bénard convection
Rayleigh–Bénard convection is buoyancy-driven motion in a fluid layer heated from below and cooled from above. When the imposed temperature difference is large enough to destabilize the conductive state, the fluid develops organized circulation cells; as driving increases, the flow can become turbulent. The Rayleigh number measures the relative strength of buoyancy against viscous and thermal diffusion, while the onset and pattern depend on boundaries and container geometry.
Updated 30 Oct 2026
Science
Rayleigh–Taylor instability
The Rayleigh–Taylor instability is a fluid instability that develops when a denser fluid is accelerated into a less-dense one, or equivalently when a density interface experiences acceleration in an unfavorable direction. Small disturbances can grow into rising and sinking structures, promoting mixing. The process occurs in laboratory flows and in astrophysical settings such as supernova remnants.
Updated 27 Oct 2026
Science
Red sprites
Red sprites are brief flashes of light produced high above thunderstorms in Earth’s middle atmosphere. A member of the wider family called transient luminous events, they can appear as red columns, tendrils or diffuse plumes, and are associated with powerful lightning strokes. Their fleeting nature and complex electrical physics make them challenging to observe and study.
Updated 29 Oct 2026
Science
Reynolds number
The Reynolds number (Re) is a dimensionless quantity used in fluid mechanics to compare inertial effects with viscous effects. For a flow with characteristic speed U, length scale L, fluid density ρ and dynamic viscosity μ, it is commonly written Re = ρUL/μ, or Re = UL/ν using kinematic viscosity ν. It helps characterize flow behavior and compare physically similar flows, but transition thresholds depend on geometry and disturbances.
Updated 30 Oct 2026
Science
Rime ice
Rime ice is a rough, opaque deposit that forms when supercooled liquid droplets freeze onto cold exposed surfaces. It is common on windward branches, structures and aircraft in cloud or freezing-fog conditions. Its texture and aerodynamic effects differ from smoother glaze ice and from frost formed directly from water vapour.
Updated 29 Oct 2026
Science
RNA editing
RNA editing is a set of processes that alter an RNA molecule's nucleotide sequence after it has been transcribed. Depending on the organism and pathway, editing can substitute, insert, or delete nucleotides. In animals, adenosine-to-inosine editing by ADAR enzymes is widespread; inosine is generally interpreted like guanosine in many cellular processes. Editing can affect protein coding, RNA regulation, and other transcript functions without changing the corresponding DNA sequence.
Updated 30 Oct 2026
Science
RNA interference
RNA interference (RNAi) is a sequence-guided process in which small RNA molecules help reduce gene expression, often by directing the destruction or repression of matching messenger RNA. It occurs in many eukaryotes and contributes to gene regulation and genome defence. Researchers also use engineered RNAi triggers to investigate gene function and develop targeted medicines, although its effectiveness and safety depend on delivery and biological context.
Updated 25 Oct 2026
Science
Rossby wave
A Rossby wave, or planetary wave, is a large-scale disturbance in a rotating fluid whose dynamics are influenced by changes in the Coriolis effect with latitude. On Earth, Rossby waves occur in both the atmosphere and the oceans. Atmospheric waves shape broad meanders in the mid-latitude circulation, while oceanic waves propagate slowly across basins and are often detected through satellite measurements of sea-surface height.
Updated 28 Oct 2026
Science
Rössler attractor
The Rössler attractor is a bounded, aperiodic solution of a three-dimensional continuous-time dynamical system introduced by Otto E. Rössler in 1976. Its equations are deterministic, but for appropriate parameter values their trajectories display chaos and approach a characteristic folded, ribbon-like set in phase space.
Updated 31 Oct 2026
Science
Rydberg atom
A Rydberg atom is an atom with at least one electron excited to a state of very high principal quantum number. The electron occupies a much more spatially extended orbit-like state than in low-lying atomic states, making the atom unusually sensitive to electric fields and strongly interacting with other Rydberg atoms. These properties underpin research in quantum information, simulation and sensing.
Updated 26 Oct 2026
Science
Saffir-Simpson Hurricane Wind Scale
The Saffir-Simpson Hurricane Wind Scale is a five-category classification based on a hurricane's maximum sustained wind speed. Used by the U.S. National Hurricane Center, it conveys the potential for wind damage, with Categories 3–5 designated as major hurricanes. The scale does not rate storm surge, rainfall flooding, or tornadoes, which can cause severe impacts at any category.
Updated 26 Oct 2026
Science
Sagnac effect
The Sagnac effect is a rotation-dependent phase or arrival-time difference between waves traveling in opposite directions around a closed interferometer. Because the difference depends on the loop's enclosed area and rotation rate, the effect underlies ring-laser and fiber-optic gyroscopes. Experiments have also observed it with matter waves, extending the phenomenon beyond light.
Updated 24 Oct 2026
Science
Salt fingering
Salt fingering is a form of double-diffusive convection that can occur when relatively warm, salty seawater overlies cooler, fresher water. Because heat diffuses through water much faster than salt, small rising and sinking motions develop, transporting heat and salt at different rates. In some ocean regions, the process contributes to vertical mixing and layered temperature–salinity structures, although its strength and wider effects vary with local conditions and interactions with turbulence and waves.
Updated 24 Oct 2026
Science
Sastrugi
Sastrugi are ridges and grooves sculpted into snow by wind, especially common across polar landscapes. Their shape and orientation reflect interactions between wind, drifting snow and surface roughness; they can influence near-surface airflow and snow transport as well as provide clues to local wind history.
Updated 29 Oct 2026
Science
Schrödinger's cat
Schrödinger's cat is a 1935 thought experiment that explores the difficulty of applying quantum superposition to familiar macroscopic objects. A hypothetical radioactive decay triggers a mechanism that may kill a sealed cat, coupling a microscopic quantum event to a visible outcome. The example was devised to expose questions about quantum measurement and interpretation, not as a proposal to perform the experiment on a real cat.
Updated 29 Oct 2026
Science
Schumann resonances
Schumann resonances are extremely low-frequency electromagnetic resonances in the cavity between Earth's surface and the lower ionosphere. Excited mainly by lightning, they appear as a set of broad spectral peaks, with the lowest near 8 Hz. Researchers use their measured characteristics to study lightning and the electrical environment of the atmosphere.
Updated 8 Nov 2026
Science
Seebeck effect
The Seebeck effect is the generation of an electromotive force in a circuit when its conductors experience a temperature difference. Discovered by Thomas Johann Seebeck in 1821, it underlies thermocouples, which convert a temperature difference between two junctions into a measurable voltage. The effect is also used to convert heat directly into electrical energy in thermoelectric generators.
Updated 27 Oct 2026
Science
Seismic waves
Seismic waves are elastic vibrations that carry energy through Earth or along its surface after an earthquake or another disturbance. Body waves include compressional P waves and shear S waves; surface waves include Love and Rayleigh waves. Their speeds, paths, and arrival times at seismometers help scientists investigate Earth's interior and locate earthquakes.
Updated 30 Oct 2026
Science
Semiconductor
A semiconductor is a material whose electrical conductivity lies between that of a conductor and an insulator and can be deliberately adjusted. Silicon is the most widely used example. By controlling charge carriers through doping and by arranging semiconductor regions into devices, engineers make diodes, transistors, solar cells and integrated circuits—the building blocks of much modern electronics.
Updated 22 Oct 2026
Science
Shape-memory alloy
A shape-memory alloy (SMA) is a metal that can recover a trained shape after deformation when exposed to a suitable stimulus, commonly heating. This behavior arises from a reversible solid-state transformation between crystal structures, rather than melting. Nickel–titanium is a widely used SMA; the materials are valued for compact actuation and have applications in areas such as medical devices and engineering, while their performance and manufacture depend on composition, processing and operating conditions.
Updated 28 Oct 2026
Science
Siberian Traps
The Siberian Traps are a vast large igneous province in what is now Siberia, formed by extensive magmatism near the end of the Permian Period about 252 million years ago. Their emplacement coincided with Earth’s most severe mass extinction. Research links volcanic activity and greenhouse-gas release to environmental disruption, while the precise causal chain and contributions of different magmatic phases remain subjects of scientific study.
Updated 10 Nov 2026
Science
Sleep
Sleep is a recurring, naturally regulated state marked by changes in awareness and brain activity. Human sleep alternates between non-rapid eye movement (NREM) and rapid eye movement (REM) stages, under the combined influence of circadian timing and a sleep drive that builds while awake. Sleep supports learning, memory, mood and other bodily functions, though its full biological purposes remain under study; persistent deficiency is associated with risks to health and everyday performance.
Updated 14 Oct 2026
Science
Solar dynamo
The solar dynamo is the process by which moving, electrically conducting plasma inside the Sun generates and sustains its large-scale magnetic field. Differential rotation, convection and meridional circulation reshape magnetic fields over time, producing the Sun's recurring pattern of magnetic activity. The broad sunspot cycle lasts about 11 years; the magnetic field's polarity reverses over that cycle, so it takes roughly 22 years to return to its original orientation. The precise balance of physical processes that drives the cycle remains an active research question.
Updated 26 Oct 2026
Science
Solar prominence
A solar prominence is a large structure of relatively cool, dense plasma suspended in the Sun’s hot corona by magnetic fields. Seen against the dark background beyond the Sun’s edge, it appears bright and arching; the same structure viewed against the solar disk appears dark and is called a filament. Some prominences remain stable for months, while others become unstable and erupt, sometimes in association with a coronal mass ejection.
Updated 26 Oct 2026
Science
Sonoluminescence
Sonoluminescence is the emission of brief flashes of light by bubbles in a liquid when they undergo intense acoustic or other rapid collapses. In single-bubble experiments, a sound field can trap and drive a gas bubble through repeated expansion and compression. The collapse concentrates energy, heating the bubble contents; the detailed processes that produce the light remain an active subject of study.
Updated 27 Oct 2026
Science
Soret effect
The Soret effect, or thermodiffusion, is the redistribution of components in a mixture caused by a temperature gradient. It can create a concentration gradient that opposes or balances ordinary diffusion, and its magnitude and direction depend on the mixture and conditions. The phenomenon is studied in liquids, gases and other systems, with applications ranging from separation science to geophysical and industrial processes.
Updated 27 Oct 2026
Science
Space weather
Space weather describes changing conditions in the space environment, especially disturbances driven by the Sun. Solar flares, energetic particles, and coronal mass ejections can affect Earth's ionosphere, magnetosphere, upper atmosphere, and technological systems. The same interactions that produce auroras can also disrupt radio links and satellite navigation, increase drag on low-orbit spacecraft, and induce currents in power infrastructure. Monitoring and forecasting help operators prepare for these effects.
Updated 25 Oct 2026
Science
Stellar nucleosynthesis
Stellar nucleosynthesis is the formation of chemical elements through nuclear reactions in stars and stellar explosions. Fusion in stellar interiors builds many nuclei from lighter ones, while neutron-capture and other processes in evolved stars, supernovae and neutron-star mergers produce or transform additional elements. Ejected material enriches interstellar gas and contributes to the chemical composition of later generations of stars and planets.
Updated 25 Oct 2026
Science
Stochastic resonance
Stochastic resonance is a counterintuitive effect in which a suitable amount of random noise helps a nonlinear system detect or transmit a weak signal. It is most often discussed in systems with a threshold or energy barrier: fluctuations that are too small to cross the barrier alone can become synchronized with a weak input when noise is added. The benefit is limited; excess noise masks the signal. The phenomenon has been studied in physical, biological and engineered systems.
Updated 26 Oct 2026
Science
Sundial
A sundial indicates local apparent solar time by using the Sun’s changing position to cast a shadow or illuminate a marked surface. Its gnomon and hour lines are arranged for a particular latitude and orientation. Because apparent solar time differs from standardized clock time, a sundial reading generally needs corrections for longitude, time zone and the seasonal equation of time.
Updated 27 Oct 2026
Science
Superconductivity
Superconductivity is a physical state in which certain materials, cooled below a characteristic critical temperature, conduct direct current without electrical resistance and expel magnetic fields from their interiors. The state also has limits: excessive temperature, magnetic field or current can destroy it, and practical devices often need cryogenic cooling. Superconducting magnets are used in technologies such as MRI systems and particle accelerators. Quantum theory explains conventional superconductors, while the mechanisms of some unconventional, higher-temperature materials remain an active area of research.
Updated 14 Oct 2026
Science
Supercritical Carbon Dioxide
Supercritical carbon dioxide (scCO₂) is carbon dioxide held above its critical temperature and pressure, where liquid and gas are no longer distinct phases. Its density and transport properties make it useful as a solvent in extraction and as a working fluid studied for power cycles, though these applications require specialized high-pressure equipment and careful process design.
Updated 7 Nov 2026
Science
Synesthesia
Synesthesia is a perceptual trait in which a stimulus or concept produces an additional, automatic experience, such as letters evoking colours or words evoking tastes. Researchers describe dozens of forms, and experiences vary between individuals. Evidence supports its consistency and involuntary character, while proposed explanations for its neural and genetic basis remain under investigation.
Updated 30 Oct 2026
Science
Tardigrade
Tardigrades, often called water bears, are microscopic, eight-legged invertebrates found in marine, freshwater and terrestrial habitats. Some species can enter cryptobiosis, a reversible state of greatly reduced activity that helps them endure stresses such as drying. Their tolerance varies by species and condition; recent research links survival to protective proteins and DNA-repair responses rather than to a single universal mechanism.
Updated 24 Oct 2026
Science
Tata Institute of Fundamental Research
The Tata Institute of Fundamental Research (TIFR) is an Indian research institution founded in Mumbai in 1945 with support from the Sir Dorabji Tata Trust. Initiated by physicist Homi J. Bhabha, it began with cosmic-ray research and developed into a multidisciplinary centre whose work includes mathematics, natural sciences, biology, technology and computer science. TIFR's main campus is in Colaba, Mumbai, and the institute operates within India's Department of Atomic Energy framework.
Updated 31 Oct 2026
Science
Tektite
Tektites are natural, silica-rich glass bodies formed when high-energy impacts melt terrestrial rocks and eject droplets that cool rapidly. Often shaped during flight through the atmosphere, they occur in geographically broad, age-related deposits called strewn fields. Their detailed source rocks and impact craters are well established for some groups but remain uncertain for others.
Updated 28 Oct 2026
Science
The Wow! signal
The Wow! signal was a brief, unusually strong narrowband radio signal detected by Ohio State University’s Big Ear radio telescope on 15 August 1977. Astronomer Jerry Ehman marked the computer printout with “Wow!”, giving the signal its name. Although it has attracted interest in searches for extraterrestrial intelligence, it has never been detected again and its origin remains uncertain.
Updated 6 Nov 2026
Science
Theory of relativity
The theory of relativity comprises two connected frameworks developed by Albert Einstein: special relativity, introduced in 1905, and general relativity, completed in 1915. Special relativity links measurements of space and time to an observer's motion and establishes the constancy of light's speed in a vacuum. General relativity describes gravity through the geometry of spacetime. Both theories have been tested extensively and underpin explanations of phenomena ranging from fast-moving particles to black holes; a complete theory uniting general relativity with quantum physics remains an open problem.
Updated 15 Oct 2026
Science
Thermal expansion
Thermal expansion is the change in a material’s dimensions as its temperature changes. It is commonly described by linear and volumetric expansion coefficients, which relate fractional changes in length or volume to a temperature interval. The amount and direction of expansion depend on the material and its structure; engineers account for it in structures, instruments and components exposed to changing temperatures.
Updated 30 Oct 2026
Science
Thermal runaway in lithium-ion batteries
Thermal runaway is an uncontrollable self-heating condition in a lithium-ion cell: heat is generated faster than it can be dissipated, allowing the cell’s temperature and internal reactions to escalate. Faults such as internal short circuits, overcharging, external damage or extreme operating conditions can initiate it. A failing cell may vent hot gases, smoke or fire, and heat from one cell can trigger neighboring cells in a battery pack.
Updated 6 Nov 2026
Science
Thermal stress
Thermal stress is mechanical stress caused when temperature changes make a material expand or contract unevenly, or when its dimensional change is restrained. It is important in structures and components exposed to heating, cooling, or temperature gradients.
Updated 7 Nov 2026
Science
Thermochromism
Thermochromism is a material's change in colour caused by a change in temperature. The effect can be reversible, with colour returning as temperature cycles, or irreversible, when heating or cooling produces a lasting change. It arises through temperature-dependent changes in a material's molecular or structural state that alter how it interacts with visible light, and is used in indicators, inks, textiles and other responsive materials.
Updated 28 Oct 2026
Science
Thermocline
A thermocline is a layer in a body of water where temperature changes rapidly with depth, separating warmer surface water from colder water below. Its depth and strength vary with location and season. Ocean thermoclines influence vertical mixing and the exchange of heat and materials between surface and deeper waters; they are also relevant to interpreting ocean conditions such as the depth of warm water beneath a storm.
Updated 25 Oct 2026
Science
Thermodynamics
Thermodynamics is the branch of physics that studies heat, work, temperature and energy, especially how energy moves and changes form. Its four laws describe thermal equilibrium, conservation of energy, the direction and limits of energy transformations, and the behavior of entropy near absolute zero. Developed in large part through the study of heat engines, thermodynamics now helps explain and design processes in physics, chemistry, engineering and materials science.
Updated 17 Oct 2026
Science
Thermoelectricity
Thermoelectricity describes the direct coupling of heat and electrical effects in materials. A temperature difference can generate a voltage through the Seebeck effect, while an electric current can heat or cool a junction through the Peltier effect; the Thomson effect describes related heat absorption or release along a current-carrying conductor with a temperature gradient. These effects underpin thermocouples, solid-state temperature-control devices and thermoelectric generators, whose practical performance depends on materials and system design.
Updated 25 Oct 2026
Science
Tidal heating in planetary satellites
Tidal heating is the conversion of orbital and rotational energy into internal heat when gravity repeatedly deforms an astronomical body. In the Solar System, it helps explain Io’s intense volcanism and contributes heat to icy moons such as Europa. The amount and distribution of heating depend on orbital motion and the internal properties of the body.
Updated 27 Oct 2026
Science
Tin pest
Tin pest is the deterioration of tin caused by its transformation from metallic white β-tin to brittle gray α-tin at low temperatures. The transformation is thermodynamically possible below about 13.2 °C in pure tin, but it may take a long and unpredictable time to begin. Expansion and embrittlement can make affected objects crumble, so the phenomenon matters in cold-exposed electronics and materials conservation.
Updated 28 Oct 2026
Science
Topological insulator
A topological insulator is a quantum material with an insulating interior and conducting states at its edges or surface. The unusual boundary states arise from the topology of the electronic bands and, in time-reversal-symmetric systems, can be robust against many non-magnetic disturbances.
Updated 7 Nov 2026
Science
Tornado
A tornado is a violently rotating column of air that extends from a storm cloud to the ground. Many develop with rotating thunderstorms called supercells, though other forms occur; their intensity is commonly estimated from surveyed damage, and they are reported in many parts of the world.
Updated 20 Oct 2026
Science
Triboelectric effect
The triboelectric effect, also called contact electrification or triboelectrification, is the transfer of electric charge when materials make contact and separate, often after rubbing. The materials can acquire opposite charges, although the sign and amount depend on their surfaces and conditions. Familiar static-electricity demonstrations illustrate the effect; researchers also study its mechanisms and applications in triboelectric nanogenerators.
Updated 30 Oct 2026
Science
Tropical cyclone
A tropical cyclone is an organized, rotating low-pressure storm that forms over warm tropical or subtropical waters. Called hurricanes, typhoons or cyclones in different regions, these systems draw energy from the ocean and can bring destructive winds, heavy rain, storm surge and flooding.
Updated 16 Oct 2026
Science
Tropical wave
A tropical wave, also called an easterly wave, is a westward-moving disturbance in the tropical easterlies associated with an elongated region of relatively low pressure. Such disturbances can organize clouds, showers and thunderstorms, and many tropical cyclones develop from them, although most waves do not become cyclones. Their development depends on environmental conditions such as ocean heat, moisture, atmospheric instability and wind shear.
Updated 8 Nov 2026
Science
Tsunami
A tsunami is a series of long waves caused by a sudden displacement of a large volume of water, most often by an undersea earthquake. Tsunamis can cross ocean basins with little sign at sea, then grow in height and produce powerful flooding and currents in shallow coastal waters. Landslides, volcanic activity and some atmospheric disturbances can also generate tsunami waves. Their effects depend on the source, ocean depth and coastal shape, while monitoring networks and warning systems help communities prepare.
Updated 22 Oct 2026
Science
Tsunami warning system
Tsunami warning systems combine seismic and sea-level monitoring, forecasting, communications, and community preparedness to reduce harm from tsunami hazards. Regional service providers assess disturbances and distribute alerts, while national authorities decide and communicate protective actions to their populations. Their effectiveness depends not only on detecting waves but also on timely local response and public readiness.
Updated 28 Oct 2026
Science
Tunguska Event
The Tunguska event was a powerful atmospheric explosion over a remote region of central Siberia on 30 June 1908. The blast flattened and scorched a vast area of forest but left no widely accepted impact crater. Evidence points to an asteroid or similar small cosmic body exploding above the ground; the exact object and details of its breakup remain uncertain.
Updated 22 Oct 2026
Science
Turbidity current
A turbidity current is a gravity-driven flow of water and sediment that moves downslope because the sediment makes it denser than surrounding water. Such flows can erode submarine slopes and channels, carry sediment into deeper basins and leave layered deposits. Field studies show that some powerful currents also move water-saturated sediment along the seabed, making their dynamics more complex than a simple cloud of muddy water.
Updated 28 Oct 2026
Science
Turing pattern
A Turing pattern is a spatial pattern that can emerge in a system of interacting substances that react and diffuse at different rates. In Alan Turing's 1952 theory of morphogenesis, diffusion can destabilize an otherwise uniform chemical state and amplify small variations into organized structures such as spots or stripes. Reaction–diffusion models help researchers investigate biological pattern formation, although the mechanisms behind particular patterns must be tested in each system.
Updated 25 Oct 2026
Science
Turritopsis dohrnii
Turritopsis dohrnii is a small hydrozoan jellyfish widely called the immortal jellyfish because, under certain stressful conditions, its adult medusa can reverse development into a polyp stage. This life-cycle reversal can be repeated in observations, but it does not make the animal invulnerable to predators, disease, or other causes of death.
Updated 8 Nov 2026
Science
Tyndall effect
The Tyndall effect is the scattering of light by particles suspended in a medium, making a beam visible from the side. It is commonly seen when sunlight enters a dusty room or when a beam passes through fog or a colloid. The effect can help distinguish many colloidal dispersions from true solutions, whose much smaller dissolved particles generally do not scatter visible light strongly. It is named after physicist John Tyndall, who investigated light scattering in the nineteenth century.
Updated 23 Oct 2026
Science
Type Ia supernova
A Type Ia supernova is a thermonuclear explosion associated with a white dwarf in a binary star system. Its light output can be standardized using features of its light curve, making these events important tools for measuring astronomical distances and tracing the expansion of the universe. The exact pathways that lead to the explosions remain an active area of research.
Updated 1 Nov 2026
Science
Vernalization
Vernalization is the promotion of flowering by prolonged exposure to low temperatures. In plants that use this seasonal cue, winter cold helps ensure that reproduction occurs after winter rather than during it. The underlying responses differ among species; in the model plant Arabidopsis, cold exposure establishes an epigenetic state that silences a flowering-repressor gene, while other plants use distinct genetic pathways.
Updated 24 Oct 2026
Science
Vestibular system
The vestibular system is a network of sensory organs in the inner ear and neural pathways that helps the brain detect head movement and orientation, maintain balance, and stabilize vision during motion. Its peripheral organs comprise three semicircular canals and two otolith organs—the utricle and saccule. The brain combines their signals with information from vision and body senses to guide posture, gaze and spatial orientation.
Updated 23 Oct 2026
Science
Volcanic lightning
Volcanic lightning is electrical discharge associated with some explosive volcanic eruptions. Charge can develop as magma fragments and ash particles collide or rub together in an eruption column; ice and water-related processes may add to electrification higher in the plume. The discharges are both a hazard and a potential source of information about eruption activity, though the exact charging processes vary and remain an active research subject.
Updated 28 Oct 2026
Science
Volcanic winter
A volcanic winter is a period of regional or global cooling that can follow a major explosive eruption. Sulfur dioxide injected high into the atmosphere can form sulfate aerosols that scatter sunlight and alter circulation, temporarily changing temperatures and rainfall patterns. The 1815 eruption of Mount Tambora is a prominent historical example: climatic effects contributed to the unusually cold conditions of 1816 known as the Year Without a Summer. The strength and duration of these effects depend on the eruption and atmospheric conditions; volcanic cooling is temporary and differs from long-term human-driven climate change.
Updated 28 Oct 2026
Science
Vredefort Impact Structure
The Vredefort impact structure in South Africa is the deeply eroded remnant of an enormous meteorite impact about 2.02 billion years ago. Recognized as a UNESCO World Heritage property, it preserves geological evidence of impact processes and ancient crust. Estimates of the original crater size vary, and modern impact simulations continue to test the impactor parameters that best match the surviving geological record.
Updated 10 Nov 2026
Science
Vulcanization
Vulcanization is a chemical process that improves rubber by forming links between its long polymer molecules. The best-known method heats rubber with sulfur, producing a network that generally increases strength, resilience and resistance to wear and swelling. Developed in the nineteenth century, vulcanization made rubber far more useful in manufactured goods; modern formulations use carefully controlled ingredients and curing conditions, and not all rubbers use sulfur chemistry.
Updated 22 Oct 2026
Science
Walker circulation
The Walker circulation is an east–west atmospheric overturning pattern along the equatorial belt, most commonly described across the tropical Pacific. In typical conditions, near-surface trade winds carry air westward; air rises over warm western Pacific waters, flows eastward aloft, and descends over the cooler eastern Pacific. Its strength and position vary with the El Niño–Southern Oscillation (ENSO), affecting tropical winds, rainfall and ocean conditions.
Updated 23 Oct 2026
Science
Water cycle
The water cycle, or hydrologic cycle, is the continuous movement of water through the atmosphere, oceans, land, underground stores and living things. Solar energy and gravity drive processes including evaporation, transpiration, condensation, precipitation, runoff and groundwater flow. Water is stored in reservoirs for different lengths of time, and natural processes and human activities change where it is found, how it moves and its quality.
Updated 17 Oct 2026
Science
Water ice on Mercury
Despite Mercury's proximity to the Sun and its extreme surface temperatures, observations indicate that water ice is preserved in permanently shadowed craters near the planet's poles. MESSENGER data found polar deposits consistent with ice, some exposed at the surface and some buried beneath darker material. These deposits are possible because sunlight never reaches certain crater floors, where temperatures can remain low enough for ice to persist.
Updated 6 Nov 2026
Science
Wave–particle duality
Wave–particle duality is the experimentally grounded feature of quantum physics in which entities such as light and electrons display effects that classical physics associates with both waves and particles. Interference and diffraction reveal wave-like behavior, while energy exchange and detections occur in discrete, localized events. The duality is not a claim that quantum objects are ordinary waves and tiny classical balls at once; quantum theory provides a framework that predicts the outcomes of different measurements.
Updated 25 Oct 2026
Science
Wet-bulb globe temperature
Wet-bulb globe temperature (WBGT) is an environmental heat-stress index used to assess conditions for people working or exercising in heat. It combines measurements that account for air temperature, humidity, radiant heat and air movement, offering a more complete picture than air temperature alone.
Updated 7 Nov 2026
Science
Wiedemann–Franz law
The Wiedemann–Franz law describes a relationship between the electrical conductivity and the electronic contribution to thermal conductivity of many metals. In its usual form, the ratio of thermal conductivity κ to electrical conductivity σ is proportional to absolute temperature T, with proportionality constant L, the Lorenz number. The law reflects the role of mobile electrons in transporting both charge and heat, but its accuracy depends on material and scattering conditions; it is not a universal rule for all solids or all temperature ranges.
Updated 28 Oct 2026
Science
Wilson cloud chamber
The Wilson cloud chamber is a particle detector that makes the paths of ionising particles visible as lines of tiny droplets. A charged particle passing through a supersaturated vapour leaves ions that seed condensation along its path. Developed by physicist C. T. R. Wilson, the device became an important early tool in particle physics and helped researchers observe phenomena including the positron.
Updated 26 Oct 2026
Science
Wolbachia
Wolbachia is a genus of bacteria that live inside the cells of many arthropods and some nematodes, often passing from mother to offspring through eggs. Some strains alter host reproduction, while others can reduce the ability of mosquitoes to transmit certain viruses. These properties have led to distinct mosquito-control approaches: establishing virus-blocking infections in local mosquito populations, or using incompatible matings to suppress populations. Results depend on the bacterial strain, host and deployment strategy.
Updated 24 Oct 2026
Science
Xylem cavitation and embolism
Xylem cavitation is the formation of a gas-filled void in a plant’s water-conducting tissue; when a conduit becomes blocked by gas, the condition is called embolism. These events can reduce water transport, especially under drought or freeze–thaw stress. Plant anatomy, water tension and environmental conditions influence both the risk and spread of hydraulic failure.
Updated 27 Oct 2026
Science
Yarkovsky effect
The Yarkovsky effect is a small non-gravitational force on a rotating asteroid or other small Solar System body, produced when it absorbs sunlight and later emits heat unevenly. The resulting thermal-radiation recoil can gradually change an object's orbital semimajor axis. Its size and direction depend on factors such as rotation, shape, size, and thermal properties, making it important in long-term asteroid-orbit calculations and some impact assessments.
Updated 26 Oct 2026
Science
Yerkes Observatory
Yerkes Observatory is an astronomical observatory in Williams Bay, Wisconsin, established by the University of Chicago and opened in 1897. Its historic Great Refractor, a 40-inch lens telescope, became a landmark instrument in observational astronomy. The observatory also supported research, photographic work and education, and is associated with generations of astronomers, including Edwin Hubble, Nancy Grace Roman and Carl Sagan.
Updated 22 Oct 2026
Science
Zeeman Effect
The Zeeman effect is the splitting of an atom's spectral line into components with slightly different frequencies when the emitting or absorbing atoms are placed in a magnetic field. It arises because the field shifts atomic magnetic energy sublevels, changing the energies of allowed transitions. The pattern helps researchers study atomic structure and measure magnetic fields, including those of the Sun and other stars.
Updated 28 Oct 2026
Science
Zener diode
A Zener diode is a semiconductor diode designed to operate in reverse bias near a specified breakdown voltage. In that region, its voltage changes comparatively little as current varies within rated limits, making it useful for voltage references, clamping and simple regulation. Breakdown may be dominated by quantum-mechanical Zener tunnelling or by avalanche multiplication, depending on junction properties and voltage.
Updated 27 Oct 2026