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Period: 276 BCE to 195 BCE
Erathosthenes
Eratosthenes (276–195 B.C.) used the sun to measure the size of the round Earth, according to NASA.
His measurement of 24,660 miles (39,690 kilometers) was only 211 miles (340 km) off the true measurement. -
Period: 90 BCE to 168 BCE
Claudius Ptolemy
Claudius Ptolemy (A.D. 90–168)-Ptolemy's writings stood as authoritative for more than 1,200 years. However, his model, which was incorrect, later fell out of use as the heliocentric view of the solar system came into being. -
Period: 1473 to 1543
Nicolaus Copernicus
Nicolaus Copernicus (1473–1543) proposed a model of the solar system that involved the Earth revolving around the sun, according to NASA. The model wasn't completely correct, as astronomers of the time struggled with the backward path Mars sometimes took, but it eventually changed the way many scientists viewed the solar system. -
Period: 1546 to
Tycho Bache
Tycho Brahe (1546-1601), from a rich Danish noble family, was fascinated by astronomy but disappointed with the accuracy of tables of planetary motion at the time Tycho built vast instruments to set accurate sights on the stars, and used multiple clocks and timekeepers. -
Period: 1564 to
Galileo Galilei
Galileo Galilei (1564–1642) is often credited with the creation of the optical telescope, though in truth he improved on existing models. According to Rice University's Galileo Project, "Galileo made his first telescope in 1609, modeled after telescopes produced in other parts of Europe that could magnify objects three times. He created a telescope later that same year that could magnify objects twenty times." -
Period: 1571 to
Johannes Kepler
Johannes Kepler (1571–1630) determined that planets traveled around the sun not in circles, as Copernicus had thought, but in ellipses. In so doing, he calculated three laws involving the motions of planets that astronomers still use in calculations today. However, closed minds put Kepler's work at risk. -
Period: to
Sir Issac Newton
Sir Isaac Newton (1643–1727) is most famous for his work on forces, specifically gravity today as Newton's laws. 1) an object at rest tends to stay at rest and an object in uniform motion tends to stay in uniform motion unless acted upon by a net external force. 2) The net force on an object is equal to the rate of change of its linear momentum in an inertial reference frame, or if a body is accelerating, there a force is acting on it. 3) For every action there is an equal and opposite action. -
Period: to
Albert Einstein
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.