Ancient Astronomers

Eratosthenes

276 BCE

Eratosthenes, a Greek mathematician, geographer, and astronomer, lived from 276-195 B.C. He proposed the idea that the world was not flat, but round in 240 B.C. He made this idea by using the measurements of the sun to to measure the size of Earth. His measurements, in fact, were only 211 miles off the true size. His discovery is important because he was the first to discover the circumference of the Earth accurately.

Claudius Ptolemy

90

Claudius Ptolemy, a Greek mathematician and astronomer, lived from 90-168. He created a model in which the sun, stars, and planets revolved around the Earth. This was known as the Ptolemaic System and it was created around the 2nd century A.D. This model was thought to be right for hundreds of years and it served as an important representation for other astronomers from the time period.

Nicolaus Copernicus

1473

Nicolaus Copernicus, an astronomer from Poland, lived from 1473-1543. He proposed the idea of what he imagined the solar system to look like through a model which was published in 1543. Although his model wasn't absolutely correct, but it changed the way other astronomers viewed and studied the universe. His model was correct, though, in the way he placed the sun in the center of the universe rather than Earth.

Tycho Brahe

1546

Tycho Brahe, a Danish astronomer, lived from 1546-1601. He dedicated his life research to discovering planetary positions with help from the king of Denmark. He was gifted an island by the king in 1576 that allowed him to build instruments that could see the universe and helped him to achieve his goal of measuring one minute of arc. This was an astonishing discovery considering there were no telescopes yet and he still managed to see the stars and planets.

Johannes Kepler

1571

Johannes Kepler, a German astronomer, lived from 1571-1630. Kepler believed that God had a reason for placing the planets a certain distance from the sun. He is best known for his laws of planetary motion that explain why there are 6 planets and why they orbit the way they do. In 1609 when he made this discovery, he published his writing titled "Astronomia Nova" which explain his first two laws of planetary motion.

Sir Isaac Newton

1643

Isaac Newton, an English astronomer, lived from 1643-1727. He is best known for calculating his three laws known as "Newton's Laws" that describe the motion of forces between objects. His laws were published in 1687 and they served as an important piece of writing for other astronomers and scientists and they helped better the understanding of motion and force.

Albert Einstein

1879

Albert Einstein, a German physicist, lived from 1879-1955. Einstein proposed the idea that speed is constant, laws and physics are the same throughout the universe, and space and time are linked by an entity "space-time." His idea was considered important because it went beyond his time's current understanding of the universe.