Peter Crisp wrote:Science fiction often contains references and entire plot devices for something called Subspace so does Subspace exist even in theory and if so can we somehow travel to it or through it?
My example is Babylon 5 where ships fly though subspace which isn't in normal space and travel through it is massively faster.
Something like 'subspace' - an alternate space we could dip into where distances are shorter - doesn't really exist, as far as we can tell.
But, space is malleable: gravity operates by compressing and bending space. What might be possible is a form of the 'warp bubble' from Star Trek, where the space in front of a craft is compressed and the space behind expanded, pushing the craft along -- in a way that wouldn't involve any actual velocity, so wouldn't be limited by the speed of light. (This is called an Alcubierre drive). The JPL at NASA were conducting warp field tests using similar methods a few years ago; as far as I know their results were inconclusive and research is still ongoing.
Wormholes might also exist, if you could bend two very separate regions of space 'into' each other. Much like Star Trek's take on it (it really made some great predictions!), it would be at best extremely rare to find a stable wormhole in the wild, and extremely difficult to create one.
I actually don't think warp drives or wormholes are possible at all, because they both offer opportunities for time travel and I believe there are tantalising hints in the mathematics of quantum field theory and general relativity that our Universe simply doesn't work that way. (But I hear about those hints second-hand because I'm not a practising theoretical physicist, so my opinion should be taken with a pinch of salt!)