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Dec14-05, 12:37 PM
P: 22
Quote Quote by Norman
Smaller in what sense? The less massive a particle is the easier it is to accelerate. But special relavtivity tells us that it would take an infinite amount of energy to accelerate a particle with mass (no matter how little or how close to zero the mass is) to the speed of light, c. The graviton is thought to be a spin 2, massless particle. It has zero rest mass and therefore travels at the same speed as a photon, c.
Since Mass and Energy are different manifestation of the same thing, yet Mass and Gravity are inter-related, I guess the better question would be "What is Mass?" Given that Mass, however small, is bound by speed of light and does contribute to Gravity while its altered-ego (Energy) does not (travels at c and causes no Gravity, although it does follow Geodesic path), what is it about Mass that shows these properties?

Also, just for fun, is this possible? If one were to be able to convert Energy to Mass and back at will, wouldn't a Gravity-Drive be possible by repeatedly creating Mass (and converting back to Energy) in front of a spaceship? Of course, we are talking about huge amount of Energy and efficiency is always a concern, but I suppose it is possible.