Harvey13

DH PHYSICS EXPERT, I worry about your use of 'necromanced'. According to my dictionary, magicians practise necromancy, which is the pretended art of revealing the future by communicating with the dead. 'Extra mass' is the relativistic mass and since E = mc^2, I see no reason why energy 'outdates' mass. My red statement is in agreement with Nigel Calder's remarks. Perhaps a read of his excellent book would modify your misunderstandings. Have you read that Einstein claimed that a rest mass on the surface of a gravitating body is less than it would be out in 'flat space'? He thought rest mass was variable. I have not the foggiest idea of the meaning of your last sentence. PHYSICS EXPERT, you have put out 643 postings since March 2006 (about 1 every 30 hours) and I suspect that you are neglecting to read some learned physics books.

Einstein's relativity tells us that an accelerated body gains mass, the extra mass being that of the KE; it has been verified countless times with accelerators. This theory would be problematic if we applied it to gravitational acceleration. What did Einstein mean by 'the equivalence principle'? 'Gravitional Fields' have the property of converting particle rest mass into KE mass so that a falling body does not change its total mass as seen in an accelerator. Hence: "A falling stone gathers no mass". Nigel Calder expressed the same idea in his book "Einstein's Universe" in Chapter 7: Shells of Time: "As no force acts on the apple, it cannot gain or lose energy". There are no freebies in the energy game - with gravity (a conservative force) you add rest mass (most refer to this as potential energy) to the particle by raising it and you get it back when it falls. If we knew how to make the rest mass of a particle propel itself (gravity does just that) and then slow down withot ANY loss then we might almost have perpetual motion!