The
theoretical plane of existence below the
quantum level in
Star Trek. According to that source,
subspace occupies the same
time and space as conventional space, but with a separate set of
physical laws; even though in glimpses of that
reality, it was shown to have a
compatible set of laws to our own (the
subspace creatures that stolen various crew members for experimentation – including
Riker who’s arm was
surgically removed and reattached).
I personally believe that this is non-plausible because of the vast difference between realities with different governing laws. No parallel could be drawn between that plane and ours (due to the different of basic laws).