From: utzoo!utcsrgv!donald Newsgroups: net.misc Title: Ants on spinning wheels Article-I.D.: utcsrgv.489 Posted: Mon Aug 2 13:37:34 1982 Received: Mon Aug 2 14:28:57 1982 The ant on the rotation wheel problem is a variation on Newton's bucket and brings up the ugly question of Mach's principle. The argument is that if you have a spinning bucket full of water, inertial effects cause the surface of the water to become concave, thus showing that it is the bucket, not the rest of the universe that is "really" moving. If I recall Gardner's "Relativity for the Million" correctly, General Relativity comes to the rescue with the following explanation: the rest of the universe is rotating about the bucket, which generates a gravitational field (indistinguishable from accelaration according to the General theory), thus causing the surface of the water to go concave. Note that this does not violate Special Relativity by requiring the rest of the universe to spin faster than light: the requirement that no signal be propagated faster than C is satisfied. Contrary to Doug Lerner's statements, the inertial effects caused by the spinning bucket (or wheel) are not a property of movement "relative to space time" (whatever that means). Consider this though: what if the bucket were the only object in the universe and it was started spinning (relative to what, you might ask!), would the surface go concave? Don Chan