Ancient Astronomers

By abbybrewer27
  • 100 BCE

    Eratosthenes

    Around 100 BC, Eratosthenes attempted to measure the circumference of the Earth. Although he was off by 16%, he made important assumptions during his calculations and was extremely accurate for the time period.
  • Period: 100 to 170

    Claudius Ptolemy

    From 100 to 170, Claudius Ptolemy developed many different books and collections of astrological observations, data, and tables. Many of these instruments are still used today. Most importantly, he describes a physical realization of the universe as a set of nested spheres,in which he used the epicycles of his planetary model to compute the dimensions of the universe.
  • Period: 1500 to

    Nicolaus Copernicus

    During the 1500s, Nicolaus Copernicus presented his idea of a heliocentric solar system. Until then, the accepted theory was that the solar system revolved around the Earth. His theory was the first (correct) theory with the Sun at the center.
  • 1572

    Tycho Brahe

    In 1572, Tycho Brahe observed a supernova in the constellation of Cassiopeia. Current theory taught that it was a disturbance in the atmosphere. However, Brahe's precise measurements revealed differently. He proved that the supernova never changed with regard to the surrounding stars, changing how supernovas were viewed for the rest of history.
  • Period: to

    Johannes Kepler

    As Johannes Kepler published his work from 1609 to 1619, he developed Kepler's Laws. The three laws describe the movement of the planets around the Sun, and are still used today.

  • Sir Isaac Newton

    In 1687, Sir Isaac Newton published The "Principa". In this work, Newton stated the three universal laws of motion, describing the relationship between any object, the forces acting upon it and the resulting motion, defining universal gravitational.

  • Albert Einstein

    In 1917, Albert Einstein applied the general theory of relativity to the structure of the universe as a whole. He discovered that the general field equations predicted a universe that was dynamic, either contracting or expanding. Observational evidence for a dynamic universe was not known at the time, and was not discovered until many years after.