Quote:
The rotation of Earth can be proven in several ways. One is the Foucault experiment. This was first conducted in 1851, by the Frenchman Léon Foucault. He suspended a heavy iron ball from a 200 ft (61 m) wire, creating a pendulum, from the dome of the Pantheon in Paris. He put sand underneath the pendulum, and placed a pin on the bottom of the ball, so it would leave a mark on its swing from side to side. On each swing, over the course of 24 hours, the mark in the sand would move to the right. The direction in the path showed movement of the earth against the swing of the pendulum.
Read more: Earth's Rotation
Quote:
There was no straightforward proof for the motion of Earth until 1725 when James Bradley discovered stellar aberration. This is (apparent) yearly change in positions of all stars in the sky due to Earth's own motion. Aberration arises due to adding up of the speed of light coming from the star and Earth's own speed. This is a very complex phenomenon and its description requires some math.
Another, much simpler, consequence of Earth's motion is stellar parallax. If Earth changes its position relative to the stars, than the stars should appear to change position in the course of the year.....
...Parallax of a star was first measured by Bessel in 1838. It was not measured before because this change of star's apparent position is very small (the stars are very far from us). This was a very important discovery because Aristotle himself mentioned the lack of observable stellar parallax as the proof that the Earth is not moving (he didn't have a telescope and didn't know that the stars are so distant).
A third discovery proving Earth's motion was that of Doppler effect. Wavelength of the light that we receive from objects moving relative to us becomes a little shorter (i.e. bluer) when we approach the source and becomes longer (i.e. redder) when we move away from the source. When Earth moves toward a star, the star will appear slightly bluer (only high-tech instruments can measure this) while it will appear redder when Earth is on the other side of the orbit and moves in the opposite direction. This effect proves that Earth has a velocity relative to the stars, similar to aberration.