Stan Shannon wrote: It is my understanding that it does not predict that. That, in fact, quantum mechanics and realativity contridict each other in ways significant enough that both cannot be valid. From wilipedia[^]: Mechanics can be subdivided into classical mechanics, relativistic mechanics, non-relativistic quantum mechanics, and relativistic quantum mechanics (quantum field theory). Dirac came up with the first successful relatvisic quantum wave equation, which not only required a particle with half integer spin like the electron, but predicted anti-matter before it was discovered in cosmic rays. Also, the entire field of particle physics is based on the mass-energy relationship and is one of the strongest validations of the principle. Also, decay times of particles and the energy to velocity relationship for particles going something like .999999999c are verified in particle accelerators all the time. Special relativity and qunatum mechanics agree to a level of precision unrivaled by any other physical science. In fact, all the units of measure except mass are based on relativistic quantum mechanics. Here is where the theory breaks down. Predicting the masses of particles, and quantum gravity. Field theory predicts that particles will have infinite mass, but if you replace the infities with the measured values, everything works out. So, it's predictive power is limited, but it agrees completely with the measured values. Which is ok because plain general and special relativity just accept masses as input values anyway. You need quantum theory to have "quantized" masses to begin with. As far as quantum gravity goes, we are somewhere in the ether stages. There are a number of competing theories, each one stranger then the last. I've only studied quantum mechanics for 4 semseters, which just got me to somewhere in the mid-1920's level of knowledge. Someone like John could tell you alot more about this stuff, but from the way I understand it, Quantum Mechanics only deals with particles in a space as distributions in that space. It doesn't have any way to treat changes to the geometry of the space that it is emeded in. General Relativity is a theory that couples the geometry of a space to the masses that are embeded in it. I think that is what must be overcome. What really suc