42,772 articles
Fire (πῦρ) (classical element)
Fire (πῦρ, pyr) is one of the four classical elements of ancient Greek philosophy, first set out by Empedocles and defined by Aristotle as hot and dry.
Fire brick
Fire brick, also called refractory brick or firebrick, is a ceramic block made from heat-resistant fireclay with 25% to 45% alumina, used to line furnaces, kilns, ovens, and fireplaces where ordinary brick would fail.
Fire triangle
The fire triangle is a teaching and investigative model in which the three sides represent fire's requirements: fuel, an oxidizing agent, and heat, and removing any one extinguishes the fire.
Fire Weather Index
The Fire Weather Index (FWI) is a numeric rating of wildfire danger calculated from daily weather observations, introduced across Canada in 1971 and shown on public fire danger signs.
Fire whirl
A fire whirl, also called a fire devil or firenado, is a spinning vortex of hot air and flame rising from a fire, with large whirls having tornado-like intensity.
Fireclay refractory
A fireclay refractory is a dense alumina-silica refractory product, most commonly a brick, made from fireclays with 25 to 45 percent alumina and used to line boilers, kilns, and furnaces.
Firestorm
A firestorm is a fire so intense that it generates its own wind system, sustaining and spreading the flames, sometimes producing its own pyrocumulonimbus cloud, lightning, and tornadoes.
Firewall (physics)
In theoretical physics, a firewall is a proposed high-energy barrier at an old black hole's event horizon that burns an infalling observer, proposed in 2012 as the AMPS paradox.
Firn air
Firn air is the atmosphere trapped in the porous layer of compacting snow between fresh snowfall and glacial ice on polar ice sheets, preserving a record of atmospheric composition covering roughly the last century.
First G-APD Cherenkov Telescope
The First G-APD Cherenkov Telescope (FACT) is a Cherenkov telescope on La Palma, Spain, the first with a camera of silicon Geiger-mode photodiodes instead of photomultiplier tubes.
First GARP Global Experiment (FGGE)
The First GARP Global Experiment, also called the Global Weather Experiment, was a year-long international program of global atmospheric observation in 1978–1979 involving more than 140 countries.
First law of black hole mechanics
The first law of black hole mechanics is a 1973 result by Bardeen, Carter, and Hawking relating changes in a black hole's mass, angular momentum, and horizon area.
First law of thermodynamics
The first law of thermodynamics is the statement of energy conservation for thermodynamic systems: a system's internal energy changes by the heat added minus the work done.
First Majestic Silver
First Majestic Silver is a publicly traded Canadian silver and gold mining company, founded by Keith Neumeyer in 2002 and headquartered in Vancouver, that operates underground mines in Mexico.
First observation of gravitational waves
The first observation of gravitational waves, also called the first detection of gravitational waves, was LIGO's detection of signal GW150914 on September 14, 2015, from two merging black holes 1.3 billion light-years away.
First passage and overshoots of Lévy processes
First passage and overshoots of Lévy processes study when a Lévy process first exceeds a fixed level; the overshoot is its excess at that moment, analyzed via the quintuple law and Wiener–Hopf factorisation.
First principle
A first principle is a foundational proposition that cannot be deduced from any other in a system of knowledge, a concept originating with Aristotle's account of scientific knowledge.
First-order logic
First-order logic, also called first-order predicate calculus, is a formal logical system whose quantifiers range over individual objects only; it is the standard language for formalizing mathematics.
First-order theory
A first-order theory is a set of sentences in a first-order language, typically given by a signature and axioms, and is the standard way to axiomatize parts of mathematics.
Fischer 344 rat
The Fischer 344 rat (F344) is an inbred albino laboratory rat developed at Columbia University in the 1920s and used for decades as the principal rat strain of the US National Toxicology Program.
Fischer carbene
A Fischer carbene is an electrophilic metal carbene complex of a low-valent late transition metal, typically bearing alkoxy or amino groups, first reported by Ernst Otto Fischer in 1964.
Fischer projection
The Fischer projection, or Fischer notation, is a two-dimensional drawing convention showing stereochemistry at chiral centers, proposed by Emil Fischer in 1891 and still used for carbohydrates.
Fischer–Speier esterification
Fischer–Speier esterification, also called Fischer esterification, is the acid-catalyzed reaction of a carboxylic acid with an alcohol to form an ester and water, reported by Emil Fischer and Arthur Speier in 1895.
Fisetin
Fisetin is a plant flavonol found in fruits and vegetables, especially strawberries, known as the most potent senolytic flavonoid in cell studies, with limited human evidence.
Fisher information
Fisher information is a statistical quantity that measures how much a set of data carries about an unknown parameter of a probability distribution, introduced by Ronald Fisher in 1922.
Fisher transformation
The Fisher transformation, also known as Fisher's Z-transform, converts a Pearson correlation coefficient into a statistic with an approximately normal distribution, introduced by Ronald Fisher in 1915.
Fisher–Tippett–Gnedenko theorem
The Fisher–Tippett–Gnedenko theorem is a probability theory result stating that normalized maxima of random variables can only converge to the Gumbel, Fréchet, or Weibull types.
Fisher's exact test
Fisher's exact test, also called the Fisher-Irwin test, is a statistical test for association in a 2 × 2 table, introduced by R. A. Fisher in 1935.
Fishfinder
A fishfinder is a marine sonar instrument that transmits ultrasonic waves and displays their echoes, showing fish schools, water depth, and the seabed on a screen.
Fission barrier
A fission barrier is the energy a heavy atomic nucleus must overcome or tunnel through before dividing into two fragments, governing whether it survives or undergoes spontaneous fission.