Re: Why doesn't the grand unification theory (proposed) link everything?

Richard, You are entirely correct that any theory that purports to explain all of physics must include space and time as well as matter and energy. But present theories do attempt to include this; I hinted at this in my answer to a related question you asked.

This web page has a nice description of the four fundamental forces and physicists' attempts to unify them. As you can see, a successful theory exists which unifies quantum electrodynamics (QED) and the weak force. This theory is compatible with special relativity, so it does include considerations of space and time as well as matter and energy.

A successful Grand Unified Theory (GUT) would unify the electroweak theory with the theory of the strong force, quantum chromodynamics (QCD). This would also be compatible with special relativity since the electroweak theory already is. The final theory, called a Theory of Everything, or TOE, would unify the other three forces with what we think is the correct theory of gravity - Einstein's general relativity. As the MADSci answer I referred to above states, GR is very much concerned with the relation between spacetime and matter/energy, so again, any TOE would have to include both.

But I don't know if even a TOE will answer some of the questions you raise, such as "what is space, really?" Physical theories are pretty good at describing how things work, and sometimes at describing things as being made of other things (eg, atoms as collections of protons, neutrons, and electrons). But it may be that there are no simpler way to describe concepts like spacetime, matter, and energy, than the quantities that appear in the equations.

The question of what happened before the Big Bang is another question that may not be answerable. We currently think that spacetime came into existence with the Big Bang, so asking what came before it is like asking what's north of the North Pole: it's a meaningless question. But a TOE might change this view, and then the question might have an answer.

References: your local public or university library should have some popular books on general relativity and comsology. Books on particle physics ("The God Particle", by Leon Lederman, is a good one), generally cover the territory of GUTs and TOEs, as does "The Elegant Universe" (a book on string theory, the best current TOE candidate) by Brian Greene. This particular area is one where searching the Internet may not be all that helpful; I did so and found a lot of "alternative" physics theories (mostly gibberish with a sprinkling of jargon, in my opinion).

Pauline

[Moderator's note: for a general introduction to the concepts behind string theory, you could look at http://www.superstringtheory.com.]