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Period: Jan 1, 1500 to
10 Astronomers
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Giovanni Cassini
Italian astronomer Giovanni Cassini (1625–1712) measured how long it took the planets Jupiter and Mars to rotate. He also discovered four moons of Saturn and the gap in the planet's rings. When NASA launched a satellite to orbit Saturn and its moons in 1997, it was fittingly dubbed Cassini. -
Sir Isaac Newton
English astronomer Sir Isaac Newton (1643–1727) is most famous for his work on forces, specifically gravity. Building on the work of those who had gone before him — he is quoted as saying, "If I have seen further, it is by standing upon the shoulders of giants" — he calculated three laws describing the motion of forces between objects, known today as Newton's laws. -
Charles Messier
French astronomer Charles Messier (1730–1817) composed a database of objects known at the time as "nebulae," which included 103 objects at its final publication, though additional objects were added based on his personal notes. Many of these objects are often listed with their catalog name, such as the Andromeda Galaxy, known as M31. Messier also discovered 13 comets over the course of his lifetime. -
Albert Einstein
In the early 20th century, German physicist Albert Einstein (1879–1955) became one of the most famous scientists ever after proposing a new way of looking at the universe that went beyond current understanding. Einstein suggested that the laws of physics are the same throughout the universe, that the speed of light in a vacuum is constant, and that space and time are linked in an entity known as space-time, which is distorted by gravity. -
Harlow Shapley
American astronomer Harlow Shapley (1885–1972) calculated the size of the Milky Way galaxy and general location of its center. He argued that the objects known as "nebulae" lay within the galaxy, rather than outside of it, and incorrectly disagreed with Hubble's observations that the universe boasted galaxies other than the Milky Way. -
Edwin Hubble
At the same time Einstein was expanding man's view of the universe, American astronomer Edwin Hubble (1899–1953) calculated that a small blob in the sky existed outside of the Milky Way. Prior to his observations, the discussion over the size of the universe was divided as to whether or not only a single galaxy existed. Hubble went on to determine that the universe itself was expanding, a calculation which later came to be known as Hubble's law. -
Frank Drake
Frank Drake (born 1930) is one of the pioneers in the search for extraterrestrial intelligence. He was one of the founders of the Search for Extraterrestrial Intelligence (SETI) and devised the Drake equation, a mathematical equation used to estimate the number of extraterrestrial civilizations in the Milky Way galaxy able to be detected. -
Carl Sagan
American astronomer Carl Sagan (1934–1996) may not have been a great scientist in comparison to some on this list, but he is one of the most famous astronomers. Sagan not only made important scientific studies in the fields of planetary science, he also managed to popularize astronomy more than any other individual. Sagan founded the Planetary Society, a nonprofit organization devoted to advancing space science and exploration. -
William K. Hartmann
American astronomer William K. Hartmann (born 1939) put forth the most widely accepted theory on the formation of the moon in 1975. He proposed that, after a collision with a large body scooped, debris from the Earth coalesced into the moon. -
Stephen Hawking
Stephen Hawking (1942-2018) has made many significant insights into the field of cosmology. He proposed that, as the universe has a beginning, it will likely also end. He also suggested that it has no boundary or border. Despite being viewed as one of the most brilliant minds since Einstein, many of Hawking's books and lectures are steered toward the general public as he seeks to educate people about the universe they live in.
