' Planetary Motion: The History of an Idea That Launched the Scientific Revolution (opens in new tab)'.Additionally, you can read about the life of Nicolaus Copernicus at the New World Encyclopedia website (opens in new tab). To read more about the heliocentric model, and to learn about retrograde motion, visit this page at the Penn State University College of Earth and Mineral Sciences website (opens in new tab). According to NASA, Kepler and Newton worked out precise measurements of the planets' movements around the sun, while Galileo used his telescope to prove heliocentrism. When on one side of the sun, the light hitting the planets gave them a crescent shape.Īlmost a century after Copernicus' theory was released, scientists such as Johannes Kepler, Galileo Galilei and Isaac Newton were able to use the heliocentric model to make new findings. When the planets were on the far side of the sun relative to the position of Earth, these planets were much smaller in the sky. Mercury and Venus' orbits were placed between the sun and Earth, which revealed to astronomers why they appeared so different in size and shape over time, according to Universe Today (opens in new tab). Greek astronomer Aristarchus of Samos suggested that this object was the sun two centuries later.īy answering the question of what was at the center of the solar system, astronomers were able to find the answers to other questions, too. As early as a thousand years before that, the 5th century Greek philosophers Philolaus and Hicetas suggested that the Earth could be circling a fiery object, according to the American Philological Association (opens in new tab). However, Nicolaus Copernicus wasn't the first person to suggest this. The Copernican heliocentric model was the first widely accepted idea that the sun was the center of the solar system, rather than Earth. The positions of planets were predicted largely by observing their position and size against the stars, according to the book The Solar System (opens in new tab) (Jones & Bartlett Learning, 2010). Because the heliocentric model was initially pieced together without a telescope, all observations had to be made with the naked eye and simple instruments. While the theory of the sun being central was correct, the model in its entirety held many inaccuracies.

Nicolaus Copernicus proposed the heliocentric model in his work published in 1543, according to NASA Earth Observatory (opens in new tab).

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