94 relations: Albert Einstein, Alfonsine tables, Apollo 11, Aries (astrology), Astronomical Almanac, Astronomy in the medieval Islamic world, Atomic clock, Axial precession, Bighorn sheep, Calendar reform, Celestial equator, Celestial mechanics, Centre national de la recherche scientifique, Charles-Eugène Delaunay, Computus, Coordinated Universal Time, Copernican heliocentrism, December solstice, Degree (angle), Earth, Earth's orbit, Ecliptic, Edmond Halley, Ephemeris day, Ephemeris time, Equinox, First Council of Nicaea, Fixed stars, Galaxy, General Conference on Weights and Measures, General relativity, Global Positioning System, Greek language, Gregorian calendar, Hipparchus, IBM SSEC, International Atomic Time, International Bureau of Weights and Measures, International Celestial Reference Frame, International Earth Rotation and Reference Systems Service, International System of Units, Isaac Newton, ΔT, Jet Propulsion Laboratory, Johannes Kepler, Joseph-Louis Lagrange, Julian calendar, June solstice, LAGEOS, Latitude, ..., Libra (astrology), Longitude, Louis Essen, Lunar Laser Ranging experiment, March equinox, Mars, Mercury (planet), Moon, Nicolaus Copernicus, Numerical integration, Nutation, Perturbation (astronomy), Philosophiæ Naturalis Principia Mathematica, Pierre-Simon Laplace, Pioneer 4, Planet, Position of the Sun, Prime meridian (Greenwich), Prutenic Tables, Ptolemy, Quartz clock, Quasar, Radar astronomy, Retroreflector, Rudolphine Tables, Season, September equinox, Shortt–Synchronome clock, Sidereal and tropical astrology, Sidereal year, Solar time, Standard error, Summer solstice, Sun, Terrestrial Time, Time, Tropic of Cancer, Tropic of Capricorn, Tycho Brahe, United States Naval Observatory, Universal Time, Urbain Le Verrier, Venus, Very-long-baseline interferometry. Expand index (44 more) » « Shrink index
Albert Einstein (14 March 1879 – 18 April 1955) was a German-born theoretical physicist who developed the theory of relativity, one of the two pillars of modern physics (alongside quantum mechanics).
The Alfonsine tables (Tablas alfonsíes, tabulae alphonsinae), sometimes spelled Alphonsine tables, provided data for computing the position of the Sun, Moon and planets relative to the fixed stars.
Apollo 11 was the spaceflight that landed the first two humans on the Moon.
Aries (♈) (meaning "ram") is the first astrological sign in the zodiac, spanning the first 30 degrees of celestial longitude (0°≤.
The Astronomical AlmanacThe Astronomical Almanac for the Year 2015, (United States Naval Observatory/Nautical Almanac Office, 2014).
Islamic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age (9th–13th centuries), and mostly written in the Arabic language.
An atomic clock is a clock device that uses an electron transition frequency in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element.
In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis.
The bighorn sheep (Ovis canadensis) is a species of sheep native to North America named for its large horns.
Calendar reform, properly calendrical reform, is any significant revision of a calendar system.
The celestial equator is the great circle of the imaginary celestial sphere on the same plane as the equator of Earth.
Celestial mechanics is the branch of astronomy that deals with the motions of celestial objects.
The French National Center for Scientific Research (Centre national de la recherche scientifique, CNRS) is the largest governmental research organisation in France and the largest fundamental science agency in Europe.
Charles-Eugène Delaunay (9 April 1816 – 5 August 1872) was a French astronomer and mathematician.
Computus (Latin for "computation") is a calculation that determines the calendar date of Easter.
Copernican heliocentrism is the name given to the astronomical model developed by Nicolaus Copernicus and published in 1543.
The December solstice, also known as the southern solstice, is the solstice that occurs each December, typically between the 20th and the 22nd day of the month according to the Gregorian calendar.
A degree (in full, a degree of arc, arc degree, or arcdegree), usually denoted by ° (the degree symbol), is a measurement of a plane angle, defined so that a full rotation is 360 degrees.
Earth is the third planet from the Sun and the only astronomical object known to harbor life.
Earth's orbit is the trajectory along which Earth travels around the Sun.
The ecliptic is the circular path on the celestial sphere that the Sun follows over the course of a year; it is the basis of the ecliptic coordinate system.
Edmond (or Edmund) Halley, FRS (–) was an English astronomer, geophysicist, mathematician, meteorologist, and physicist.
An ephemeris day is a period of 86,400 SI seconds.
The term ephemeris time (often abbreviated ET) can in principle refer to time in connection with any astronomical ephemeris.
An equinox is commonly regarded as the moment the plane (extended indefinitely in all directions) of Earth's equator passes through the center of the Sun, which occurs twice each year, around 20 March and 22-23 September.
The First Council of Nicaea (Νίκαια) was a council of Christian bishops convened in the Bithynian city of Nicaea (now İznik, Bursa province, Turkey) by the Roman Emperor Constantine I in AD 325.
The fixed stars (stellae fixae) comprise the background of astronomical objects that appear to not move relative to each other in the night sky compared to the foreground of Solar System objects that do.
A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter.
The General Conference on Weights and Measures (Conférence générale des poids et mesures – CGPM) is the supreme authority of the International Bureau of Weights and Measures (Bureau international des poids et mesures – BIPM), the inter-governmental organization established in 1875 under the terms of the Metre Convention (Convention du Mètre) through which Member States act together on matters related to measurement science and measurement standards.
General relativity (GR, also known as the general theory of relativity or GTR) is the geometric theory of gravitation published by Albert Einstein in 1915 and the current description of gravitation in modern physics.
The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Air Force.
Greek (Modern Greek: ελληνικά, elliniká, "Greek", ελληνική γλώσσα, ellinikí glóssa, "Greek language") is an independent branch of the Indo-European family of languages, native to Greece and other parts of the Eastern Mediterranean and the Black Sea.
The Gregorian calendar is the most widely used civil calendar in the world.
Hipparchus of Nicaea (Ἵππαρχος, Hipparkhos) was a Greek astronomer, geographer, and mathematician.
The IBM Selective Sequence Electronic Calculator (SSEC) was an electromechanical computer built by IBM.
International Atomic Time (TAI, from the French name temps atomique international) is a high-precision atomic coordinate time standard based on the notional passage of proper time on Earth's geoid.
The International Bureau of Weights and Measures (Bureau international des poids et mesures) is an intergovernmental organization established by the Metre Convention, through which Member States act together on matters related to measurement science and measurement standards.
In astrometry, an International Celestial Reference Frame (ICRF) is a realization of the International Celestial Reference System (ICRS) using reference celestial sources observed at radio wavelengths.
The International Earth Rotation and Reference Systems Service (IERS), formerly the International Earth Rotation Service, is the body responsible for maintaining global time and reference frame standards, notably through its Earth Orientation Parameter (EOP) and International Celestial Reference System (ICRS) groups.
The International System of Units (SI, abbreviated from the French Système international (d'unités)) is the modern form of the metric system, and is the most widely used system of measurement.
Sir Isaac Newton (25 December 1642 – 20 March 1726/27) was an English mathematician, astronomer, theologian, author and physicist (described in his own day as a "natural philosopher") who is widely recognised as one of the most influential scientists of all time, and a key figure in the scientific revolution.
In precise timekeeping, ΔT (Delta T, delta-T, deltaT, or DT) is the time difference obtained by subtracting Universal Time (UT) from Terrestrial Time (TT):.
The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in Pasadena, California, United States, with large portions of the campus in La Cañada Flintridge, California.
Johannes Kepler (December 27, 1571 – November 15, 1630) was a German mathematician, astronomer, and astrologer.
Joseph-Louis Lagrange (or;; born Giuseppe Lodovico Lagrangia, Encyclopædia Britannica or Giuseppe Ludovico De la Grange Tournier, Turin, 25 January 1736 – Paris, 10 April 1813; also reported as Giuseppe Luigi Lagrange or Lagrangia) was an Italian Enlightenment Era mathematician and astronomer.
The Julian calendar, proposed by Julius Caesar in 46 BC (708 AUC), was a reform of the Roman calendar.
The June solstice, also known as the northern solstice, is the solstice on the Earth that occurs each June falling on the 20th to 22nd according to the Gregorian calendar.
LAGEOS, Laser Geodynamics Satellite or Laser Geometric Environmental Observation Survey, are a series of two scientific research satellites designed to provide an orbiting laser ranging benchmark for geodynamical studies of the Earth.
In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface.
Libra (♎) is the seventh astrological sign in the Zodiac.
Longitude, is a geographic coordinate that specifies the east-west position of a point on the Earth's surface.
Louis Essen FRS O.B.E. (6 September 1908 – 24 August 1997) was an English physicist whose most notable achievements were in the precise measurement of time and the determination of the speed of light.
The ongoing Lunar Laser Ranging experiment measures the distance between Earth and the Moon using laser ranging.
The March equinox or Northward equinox is the equinox on the Earth when the subsolar point appears to leave the southern hemisphere and cross the celestial equator, heading northward as seen from Earth.
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System after Mercury.
Mercury is the smallest and innermost planet in the Solar System.
The Moon is an astronomical body that orbits planet Earth and is Earth's only permanent natural satellite.
Nicolaus Copernicus (Mikołaj Kopernik; Nikolaus Kopernikus; Niklas Koppernigk; 19 February 1473 – 24 May 1543) was a Renaissance-era mathematician and astronomer who formulated a model of the universe that placed the Sun rather than the Earth at the center of the universe, likely independently of Aristarchus of Samos, who had formulated such a model some eighteen centuries earlier.
In numerical analysis, numerical integration constitutes a broad family of algorithms for calculating the numerical value of a definite integral, and by extension, the term is also sometimes used to describe the numerical solution of differential equations.
Nutation (from Latin nūtātiō, "nodding, swaying") is a rocking, swaying, or nodding motion in the axis of rotation of a largely axially symmetric object, such as a gyroscope, planet, or bullet in flight, or as an intended behavior of a mechanism.
In astronomy, perturbation is the complex motion of a massive body subject to forces other than the gravitational attraction of a single other massive body.
Philosophiæ Naturalis Principia Mathematica (Latin for Mathematical Principles of Natural Philosophy), often referred to as simply the Principia, is a work in three books by Isaac Newton, in Latin, first published 5 July 1687.
Pierre-Simon, marquis de Laplace (23 March 1749 – 5 March 1827) was a French scholar whose work was important to the development of mathematics, statistics, physics and astronomy.
Pioneer 4 was an American spin-stabilized unmanned spacecraft launched as part of the Pioneer program on a lunar flyby trajectory and into a heliocentric orbit making it the first probe of the United States to escape from the Earth's gravity.
A planet is an astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.
The position of the Sun in the sky is a function of both the time and the geographic location of observation on Earth's surface.
A prime meridian, based at the Royal Observatory, Greenwich, in London, England, was established by Sir George Airy in 1851.
The Prutenic Tables (Tabulae prutenicae from Prutenia meaning "Prussia", Prutenische oder Preußische Tafeln), were an ephemeris (astronomical tables) by the astronomer Erasmus Reinhold published in 1551.
Claudius Ptolemy (Κλαύδιος Πτολεμαῖος, Klaúdios Ptolemaîos; Claudius Ptolemaeus) was a Greco-Roman mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology.
A quartz clock is a clock that uses an electronic oscillator that is regulated by a quartz crystal to keep time.
A quasar (also known as a QSO or quasi-stellar object) is an extremely luminous active galactic nucleus (AGN).
Radar astronomy is a technique of observing nearby astronomical objects by reflecting microwaves off target objects and analyzing the reflections.
A retroreflector (sometimes called a retroflector or cataphote) is a device or surface that reflects light back to its source with a minimum of scattering.
The Rudolphine Tables (Tabulae Rudolphinae) consist of a star catalogue and planetary tables published by Johannes Kepler in 1627, using some observational data collected by Tycho Brahe (1546–1601).
A season is a division of the year marked by changes in weather, ecology, and amount of daylight.
The September equinox (or Southward equinox) is the moment when the Sun appears to cross the celestial equator, heading southward.
The Shortt–Synchronome free pendulum clock was a complex precision electromechanical pendulum clock invented in 1921 by British railway engineer William Hamilton Shortt in collaboration with horologist Frank Hope-Jones, and manufactured by the Synchronome Co., Ltd.
Sidereal and tropical are astrological terms used to describe two different definitions of a year.
A sidereal year (from Latin sidus "asterism, star") is the time taken by the Earth to orbit the Sun once with respect to the fixed stars.
Solar time is a calculation of the passage of time based on the position of the Sun in the sky.
The standard error (SE) of a statistic (usually an estimate of a parameter) is the standard deviation of its sampling distribution or an estimate of that standard deviation.
The summer solstice (or estival solstice), also known as midsummer, occurs when one of the Earth's poles has its maximum tilt toward the Sun.
The Sun is the star at the center of the Solar System.
Terrestrial Time (TT) is a modern astronomical time standard defined by the International Astronomical Union, primarily for time-measurements of astronomical observations made from the surface of Earth.
Time is the indefinite continued progress of existence and events that occur in apparently irreversible succession from the past through the present to the future.
The Tropic of Cancer, also referred to as the Northern Tropic, is the most northerly circle of latitude on Earth at which the Sun can be directly overhead.
The Tropic of Capricorn (or the Southern Tropic) is the circle of latitude that contains the subsolar point on the December (or southern) solstice.
Tycho Brahe (born Tyge Ottesen Brahe;. He adopted the Latinized form "Tycho Brahe" (sometimes written Tÿcho) at around age fifteen. The name Tycho comes from Tyche (Τύχη, meaning "luck" in Greek, Roman equivalent: Fortuna), a tutelary deity of fortune and prosperity of ancient Greek city cults. He is now generally referred to as "Tycho," as was common in Scandinavia in his time, rather than by his surname "Brahe" (a spurious appellative form of his name, Tycho de Brahe, only appears much later). 14 December 154624 October 1601) was a Danish nobleman, astronomer, and writer known for his accurate and comprehensive astronomical and planetary observations.
The United States Naval Observatory (USNO) is one of the oldest scientific agencies in the United States, with a primary mission to produce Positioning, Navigation and Timing (PNT) for the United States Navy and the United States Department of Defense.
Universal Time (UT) is a time standard based on Earth's rotation.
Urbain Jean Joseph Le Verrier (11 March 1811 – 23 September 1877) was a French mathematician who specialized in celestial mechanics and is best known for predicting the existence and position of Neptune using only mathematics.
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days.
Very-long-baseline interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy.