# Foucault pendulum explanation, rotating earth or rotating universe?

If we start from the assumption that all frames of reference are valid for describing motion, how can a foucault pendulum either prove or disprove that the earth rotates or is stationary?

Couldn't it just as easily prove that the earth is stationary and that the whole universe (including the earth's atmosphere) rotates? what would be the difference in the observed Foucault pendulum? How can the observation prove one explanation over the other in light of my assumption? Is the rotating Earth model preferred for the sake of simplicity?

• Would this mean there was no conservation of angular momentum and everything had a preferred spin? – DWin Jan 3 '14 at 7:27
• This is basically another way of asking about Mach's principle, and in particular the bucket experiment (search the article I've linked for "bucket"). The question has no answer. – John Rennie Jan 3 '14 at 8:19