## How do you reconcile classical quantum mechanics with
general relativity?

In may, in fact, not be possible to do this at all, however there are
a growing number of theoretical physicists who believe they are on the
verge of finding a 'Theory of Everything' that does just this.

The problem is that quantum mechanics is a non-local theory involving
wave functions. General relativity is a classical theory of fields that has
nothing to say about the behavior of wave functions, or the structure of
matter. It says nothing about how the gravitational field is generated by
matter and energy, and it is a global theory of space-time, not a local theory
of space-time. One can scarcely imagine two great theories that have less to
say to one another than quantum mechanics and general relativity!

Physicists are convinced that the general relativistic treatment of gravity
must be replaced by one in which the gravitational force is replaced by one
dealing with a quantum field theory. The prototypes are the quantum field
theories for the other three forces in nature which have proven to be very
successful in the 'Standard Model'. It is a very vexing challenge, however,
to find the right mathematics to bridge the conceptual gap between classical
gravity and space-time, and a quantum description of gravity and space-time.

Still, in the last 10 years there have been many 'miraculous' theories that
have shown that under certain circumstances this gap can be bridged. It
remains to see whether any experiments can be devised to prove which of the
many prototypical theories are correct.

Return to the Special & General Relativity Questions and Answers page.

All answers are provided by Dr. Sten Odenwald (Raytheon STX) for the NASA Astronomy Cafe, part of the NASA Education and Public Outreach program.