How Earth is rotating and revolving , how to show it with simple experiment ?

Hello student,

Let''s understandt about the reotation of earth. Suppose that you''re standing in the rain, and there''s no wind. Since the rain will fall vertically, you have to hold your umbrella straight up. But now start running. What happens? From your point of view, the rain will no longer fall vertically: you have to tilt your umbrella forward to keep your head dry. A similar phenomenon happens with light: the direction in which you see a beam of light depends on your velocity. This effect is called aberration.

For instance, suppose you have two stars, separated by an angle θ in a rest frame. If an observer is moving towards the star on the horizontal axis, then he will see the second star at an angle φ, instead of θ. If the velocity of the observer changes, then the angle φ changes, and the star will appear to ''wobble'' with respect to stars at different positions.

The orbital velocity v≈30km/s of the Earth around the Sun causes an annual aberration: over the period of a year, every star and galaxy will appear to wobble on an ellipse, with a maximum displacement of v/c≈20.5′′ around their mean position, regardless of their distance to the Earth (unlike parallax, which does depend on distance). It was first observed by James Bradley in 1725, and is direct proof that the Earth orbits the Sun.

But there''s another, much smaller aberration: a diurnal aberration, caused by the rotation of the Earth around its axis. The effect is greatest for an observer on the equator, who has an equatorial speed of v=0.465km/s, while an observer on the poles will see no effect. For an observer on the equator, the position of every star wobbles on a daily basis, with a maximum displacement of v/c≈0.32′′. It''s an incredibly small effect, but it is measurable, and it has to be taken into account when doing high-precision astrometry. Moreover, it proves that the Earth does rotate.