In a dynamic universe matter, anti-matter and energy are moving, colliding and interacting with each other, the number of possible resulting configurations is virtually infinite. This cosmic kaleidoscope is of such a chaotic complexity that, when looking at the complete thing, it seems practically impossible to make accurate predictions as seems everything is uncertain and unstable.
Something only has meaning if it can be related to something else. Although everything constantly changes in the universe, all things within it are relative. Unfortunately this would mean nothing to two different observers trying to communicate with each other about the universe surrounding them. Truth may be in the eye of the beholder, but there are many people living in that universe, and they're all beholding from their own point of view; each person has his or her own perspective on matters, and with both perspective and matters constantly undergoing change, so what makes this small miracle possible for two people to be able to agree on anything at all? Ignorance probably plays quite a big part here, but somehow it seems that between two people there's usually enough common ground for them to be able to relate to one another. Quite a strange thing, if you think about it, considering theoretically there can be no real certainty about anything in the universe at all! Or can there?
Our two observers need to have at least ONE thing to which they attribute exactly the same meaning; ONE thing they both associate with the same concept. As mentioned before though, one concept can have a completely different meaning different observers (while two completely different concepts can be mistaken by two people to be one and the same thing). There is an exeption though. A 'thing', or 'concept' that is not changed, mutated or otherwise affected by the constant interaction within the universe. No matter what state the universe might be in tomorrow, this 'thing' remains unaltered, for it possesses no properties whatsoever, and thus none of it's properties can ever change. It is, of course, 'nothing'. That which does not exist anyway can never be changed or destroyed.
You're best off believing in nothing, for no matter what, it will be there for you! (or rather... it won't... and that's what's so reliable and reassuring about it).