by Hayzelle Lababit
He proposed a Sun centered(aka heliocentric) solar system in the 1500's.
Objections to Copernicus
- How could Earth be moving at huge speeds when we don't feel it?
- He didn't know about inertia.
- Why can't we detect Earth's motion against the background stars (stellar parallax)?
- His model did not fit the observational data very well.
- In the late 1500's, the Danish nobleman Tycho Brahe went to make the most accurate measurements of planetary motions to date, in order to prove his own ideas of planetary motion.
- His data was successfully understood by the German mathematician and scientist Johannes Kepler in the early 1600's.
- He made a firm decision that the orbits of the planets weren't perfect circles, but ellipses, with the Sun at one focus.
- Another firm decision he made was that a planet moves faster when near the Sun, and slower when far from the Sun.
- His laws gave a complete kinematic description of planetary motion(like planetary satellites, like the Moon)- but why did the planets move like that?
- He discovered that the motion of a falling apple and the motion of the Moon were both actually the same motion, caused by the same force - which is the gravitational force.
- His idea was that gravity is a universal force acting between any 2 objects.
- He knew that the gravitational force of the apple equals the apple's weight, mg, where g=9.8 m/s²
- He explained that the centripetal force on the moon was also supplied by the Earth's gravitational force.
- Newton's Law of Universal Gravitation is often called an inverse square law, since force is inversely proportional to the square of the distance.
- It also allowed extremely precise predictions of planetary orbits.