42,772 articles
Eccentricity (mathematics)
Eccentricity, in mathematics, is a single number measuring how much a conic section deviates from a circle: 0 is a circle, 1 a parabola, above 1 a hyperbola.
Ecdysone
Ecdysone, also known as α-ecdysone, is a steroid prohormone that regulates molting and metamorphosis in insects. It was first isolated in crystalline form from silkworm pupae in 1954.
Ecdysterone
Ecdysterone, also known as 20-hydroxyecdysone or β-ecdysone, is a polyhydroxylated steroidal hormone that regulates molting and reproduction in arthropods and also occurs in plants; it is sold as a dietary supplement and monitored by anti-doping authorities.
Echelle grating
An echelle grating is a diffraction grating with coarsely spaced, steeply blazed grooves, operated in high orders to reach very high spectral resolving power, mainly in astronomical spectroscopy.
Echelle spectrometer
An echelle spectrometer, often called an echelle spectrograph, is an optical instrument that records high-resolution spectra using an echelle grating plus a cross disperser; it was devised by George R. Harrison at MIT in 1949.
Echo
An echo is a repetition of a sound reflected from a surface, arriving at least about 50 ms after the original to be heard as a separate event.
Echo sounding
Echo sounding, also called depth sounding, measures water depth by timing a sound pulse's return from the seabed; it replaced the lead line in the early twentieth century.
Echolocation
Echolocation is a form of active sensing in which animals emit sounds and use the returning echoes to determine the location and distance of objects, best known in bats and toothed whales.
Eckard Münck
Eckard Münck is a bioinorganic chemist and emeritus Professor of Chemistry at Carnegie Mellon University, known for applying Mössbauer spectroscopy to iron-sulfur clusters and high-valent iron intermediates in metalloenzymes.
Eclipse
An eclipse occurs when the Sun, Moon, and Earth line up: a solar eclipse at new moon, and a lunar eclipse when the full Moon enters Earth's shadow.
Eclipse chasing
Eclipse chasing, also called umbraphilia, is traveling to the narrow path of totality of a solar eclipse, which crosses any given spot on Earth only about every 375 years.
Eclipse mapping
Eclipse mapping is an exoplanet astronomy technique that uses the changing shape of a secondary eclipse to reconstruct a two-dimensional map of a planet's dayside brightness or temperature.
Eclipse of Thales
The Eclipse of Thales, also called the Battle of the Eclipse, is the total solar eclipse of 28 May 585 BCE that interrupted a battle between the Lydians and the Medes.
Eclipses used for scientific discovery
Eclipses used for scientific discovery are solar and lunar eclipses exploited as natural experiments, most famously for observing the Sun's corona and testing general relativity in 1919.
Eclipsing binary
An eclipsing binary is a pair of stars that alternately pass in front of each other as seen from Earth, causing periodic dips in brightness.
Ecliptic
The ecliptic is the plane of Earth's orbit around the Sun, seen from Earth as the great circle the Sun follows yearly, tilted 23.4° to the celestial equator.
Ecliptic coordinate system
The ecliptic coordinate system specifies positions on the celestial sphere by ecliptic longitude and latitude, measured from the ecliptic plane of Earth's orbit, and is widely used for solar system science.
Eclogite
Eclogite is a dense metamorphic rock composed of red garnet and green omphacite, formed when basalt or gabbro is buried deep during subduction of oceanic crust.
ECMWF Ensemble Prediction System
The ECMWF Ensemble Prediction System (ENS) runs many parallel forecasts at the European Centre for Medium-Range Weather Forecasts to estimate probabilities of future weather, operational since 1992.
Ecological fallacy
The ecological fallacy is the error of treating a relationship observed between groups as holding for the individuals within them, as in Robinson's 1950 census study.
Ecological status
Ecological status is a five-class measure of surface water ecosystem quality under the EU's 2000 Water Framework Directive, rating rivers, lakes, and coastal waters from high to bad.
Econazole
Econazole is an imidazole antifungal drug used topically against dermatophyte and yeast infections of the skin, developed by Janssen Pharmaceutica in Belgium and marketed in 1974 as one of the first azole antifungals.
Economic Census (United States)
The Economic Census is the official five-year measure of American business conducted by the U.S. Census Bureau for years ending in 2 and 7, benchmarking GDP and the Producer Price Index.
Economic Geology (journal)
Economic Geology is a peer-reviewed scientific journal covering mineral deposits and their origin, description, and exploration. Published since 1905, it is the flagship journal of the Society of Economic Geologists.
Economics and regulation of carbon capture and storage
The economics and regulation of carbon capture and storage cover capture costs from $15 to $120 per metric ton, tax credits and carbon pricing, storage liability, and project deployment.
Econophysics
Econophysics is the application of statistical physics methods to economic systems, a field named by Eugene Stanley in 1995 and known for findings like fat tails and scaling laws.
Ecosystem respiration
Ecosystem respiration is the oxidation of organic matter to inorganic carbon by all organisms in an ecosystem, measured in streams and rivers from daily dissolved oxygen records.
ECTS grading scale
The ECTS grading scale was a letter-based A–E scale ranking passing students by their position in the cohort; it was replaced in 2009 by the ECTS grading table.
Ed Scheinerman
Ed Scheinerman, born 1957, is an American mathematician at Johns Hopkins University known for work in discrete mathematics, especially graph theory, and for inventing random dot product graphs.
Eddington experiment
The Eddington experiment, also called the Dyson-Eddington-Davidson experiment, was the 1919 solar eclipse test of Einstein's general relativity by two British expeditions whose results made Einstein world-famous.