Ancient Astronomers Timeline

Eratosthenes

200 BCE

(276 - 195 BCE) Eratosthenes used math to disprove the common belief that the world is flat. He used the sun to measure the size of the round Earth. His measurement was so close to the actual distance, that his theory the Earth was round had been proven, changing the way people thought of our planet and other planets.

Claudius Ptolemy

160

(~100-170 AD) Ptolemy is credited with the first geocentric model of our solar system. His model showed that Earth was a stationary object that all other planets and stars revolve around. This was incorrect and later disproven, but it was believed by many scientists for a very long time.

Nicolaus Copernicus

1543

(1473-1543) Copernicus is credited with originating the theory of a heliocentric system, which was the first theory to challenge Ptolemy's geocentric theory. This meant he believed that the Sun was the center of our system instead of the Earth. With his theory, he was able to explain the movements of other planets, and better understand Earth's movements. He also first mentioned the spinning of planets on their axis, and that Earth's was tilted.

Tycho Brahe

1560

(1546-1601) Brahe believed Earth was the center of the universe, and spent thirty years observing the sky in hopes of proving his theory. He is credited with having the greatest observations made with the naked eye, and his observations were used by Kepler to create his laws of planetary motion.

Johannes Kepler

1600

(1571-1630) Kepler wrote his three laws of planetary motion, which are still used today.The laws are:
1. The planets move in elliptical orbits with the sun at a focus
2. In their orbits around the sun, the planets sweep out equal areas in equal times
3. The squares of the times to complete one orbit are proportional to the cubes of the average distances from the sun
These laws were used by Newton to establish universal gravitation.

Sir Isaac Newton

1666

(1643-1727) Newton is known for his three laws of gravity that describe the forces between objects. Newton used Kepler's laws to calculate and prove his own series of laws now known as Newton's laws. These laws are critical to the understanding of gravity and are sill used and taught today.

Albert Einstein

1912

(1879-1955) Einstein suggested that the laws of physics are the same throughout the entirety of the universe, the speed of light found in a vacuum is constant, and that space and time, which is altered by gravity. This made him extremely famous because his ideas meant looking at the universe in a way that is beyond current understanding.