-
Period: 276 BCE to 194 BCE
Eratothenes
He is best known for being the first person to calculate the circumference of the Earth, which he did by comparing angles of the mid-day Sun at two places the North and South poles. He was also the first to calculate the tilt of the Earth's axis. Additionally, he may have calculated the distance from the Earth to the Sun and invented the leap day. He created the first map of the world, incorporating parallels and meridians based on the available geographic knowledge of his era. -
Period: 90 to 168
Claudius Ptolemy
He believed that the Earth was the center of the Universe. Even though he was false, he was able to combine what he saw of the stars' movements with mathematics, to predict the movements of the planets. In order to make his predictions true, he worked out that the planets must move in epicycles, and the Earth itself moved along an equant. None of this was true, but it made the math work for his predictions. This flawed view of the Universe was accepted for many centuries. -
Period: 1473 to 1543
Nicolaus Copernicus
Proposed a model of the solar system that involved the Earth revolving around the sun. He was a mathematician, physicist and philosopher. Discovered the 4 primary moons of Jupiter and the rings of Saturn. Heliocentric system put the Sun at the center of our system. He brought the new model into the the world of the Renaissance and used his own observations of the movements of the planets to back up his ideas, including the revelation that the Earth rotates on its axis. -
Period: 1546 to
Tycho Brahe
Tycho Brahe was fascinated by astronomy and decided to dedicate his life and considerable resources to recording planetary positions ten times more accurately than the best previous work. Tycho built vast instruments to set accurate sights on the stars, and used multiple clocks and timekeepers. He achieved his goal of measuring to one minute of arc. His aim was to confirm his own picture of the universe, which was that it was Earth-centered. -
Period: 1571 to
Johannes Kepler
He founded his three laws of planetary motion:
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.
Kepler was the first to state clearly that the way to understand the motion of the planets was in terms of some kind of force from the sun. -
Period: to
Sir Isaac Newton
He calculated three laws describing the motion of forces between objects, known today as Newton's laws. -
Period: to
Albert Einstein
He 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.