|MadSci Network: Physics|
I'll assume you mean subspace as in what's referred to in Star Trek. The simple answer is that I don't know, and I think I can generalize to say that we, as scientists, don't know, either. None of our current theories postulate the existence -- or even the need -- for a subspace. Also, the subspace as used in Star Trek is a vague and mysterious thing. So.... perhaps you can refine your question. What does subspace do? Why is it there? If you can answer those questions, perhaps we can help. Write back if you want to pursue this!
Try the links in the MadSci Library for more information on Physics.