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240 BCE
Eratosthenes
Several astronomers and mathematicians before and after Eratosthenes tried to accurately measure the circumference of the Earth, but is was Eratosthenes that came through. He found the circumference of the Earth to be nearly 25,000 miles -
150 BCE
Claudius Ptolemy
Claudius Ptolemy compiled a star catalog and the earliest surviving table of a trigonometric function and established mathematically that an object and its mirror image must make equal angles to a mirror. -
Period: 1508 to 1514
Nicolaus Copernicus
Nicolaus Copernicus discovered the heliocentric system, that the planets orbit around the Sun and that Earth is a planet which, besides orbiting the Sun annually, also turns once daily on its own axis and that very slow changes in the direction of this axis account for the precession of the equinoxes. -
Period: Feb 15, 1564 to
Galileo Galilei
Galileo Galilei discovered craters and mountains on the Moon, the phases of Venus, Jupiter’s moons, the stars of the Milky Way and the first pendulum clock -
Nov 11, 1572
Tycho Brahe
Brahe showed irregularities in the Moon's orbit and discovered a new star in the Cassiopeia formation. Brahe invented many instruments such as the Tyconian Quadrant which were widely copied and led to the invention of improved observational equipment. In 1600, Tyco Brahe hired Johannes Kepler as his assistant. -
Period: to
John Baptist Riccioli
He is known, among other things, for his experiments with pendulums and with falling bodies, for his discussion of 126 arguments concerning the motion of the Earth, and for introducing the current scheme of lunar nomenclature. He is also widely known for discovering the first double star. -
Johannes Kepler
Kepler discovered three major laws of planetary motion.
(1) The planets move in elliptical orbits with the Sun at one focus.
(2) The time necessary to traverse any arc of a planetary orbit is proportional to the area of the sector between the central body and that arc.
(3) There is an exact relationship between the squares of the planets’ periodic times and the cubes of the radii of their orbits -
Sir Isaac Newton
Newton discovered the laws of gravity and motion and invented calculus. He helped to shape our rational world view. -
Period: to
Anders Jonas Ångström
Anders Jonas Ångström made significant contributions to several areas of physics, but is most known as one of the founders of optical spectroscopy. He introduced a unit for electromagnetic wavelength, equivalent to 0.1 nanometers, which later on was adopted as an international standard under the name ångström. -
Period: to
Daniel Kirkwood
Known as the "Kepler of his time," Daniel Kirkwood changed astronomy with his discovery of "Kirkwood Gaps" and research on meteors during his time at Indiana University. -
Period: to
Henry Draper
American physician and amateur astronomer who made the first photograph of the spectrum of a star in 1872. He was also the first to photograph a nebula, the Orion Nebula, in 1880. -
Albert Einstein
Albert Einstein is best known for his equation E = mc2, which states that energy and mass are the same thing, just in different forms. He is also known for his discovery of the , for which he won the Nobel Prize for Physics in 1921. -
Period: to
Tadashi Nakajima
Waiting for one year, I confirmed the same movement of the primary star and companion star candidate in the star field, and found the luminosity of the companion star was 6% of the darkest star's luminosity. Then I released the discovery of the brown dwarf. -
Charles Thomas Bolton
Charles Thomas Bolton is an American astronomer who was one of the first astronomers to present strong evidence of the existence of a stellar-mass black hole. -
Period: to
James Ludlow Elliot
The American astronomer James L. Elliot and colleagues discovered the ring system from Earth in 1977, nine years before the Voyager 2 encounter, during a stellar occultation by Uranus -
Alan H. Guth
Guth and Tye began a search for alternatives that might avoid the magnetic monopole overproduction problem, and from this work Guth invented a modification of the big bang theory called the inflationary universe. -
Neil deGrasse Tyson
Tyson's research has focused on observations in cosmology, stellar evolution, galactic astronomy, bulges, and stellar formation. He has held numerous positions at institutions including the University of Maryland, Princeton University, the American Museum of Natural History, and the Hayden Planetarium. -
Stephen Hawking
Hawking is best known for his discovery that black holes emit radiation which can be detected by special instrumentation. His discovery has made the detailed study of black holes possible.