Question

How can I prove that the earth rotates around the sun?

Asked by: Brad Simpson

Answer

The Earth ROTATES on its axis every 24 hours (relative to the Sun) and REVOLVES in orbit around the Sun once every year.

The most direct evidence of daily rotation is via a Foucault pendulum, which swings in the same plane as the Earth rotates beneath it. At either pole, the swinging plane mirrors the Earth's 24 hour period. Some rotation is observed at all other locations on the Earth's surface as well, except for the equator.

The most direct observational evidence for Earth's orbital motion is the apparent shift of nearby stars after six months, as the Earth moves from one side of its orbit to the other. Because of the large distance to even the nearest start, this parallax shift is too small to been seen without a telescope. You can see how parallax works by moving your head from side to side and observing how nearby objects appear to move relative to the background.

Answered by: Paul Walorski, B.A. Physics, Part-time Physics Instructor

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