I've been thinking today about the Big Bang theory and how I've heard people claim that before the big band there was "nothing". And that when we die, there is nothing. No more life, etc.
But is that logical? If our entire (and other) universes can suddenly exist (from nothing), is it not possible that we can live once again, from nothing?
According to the standard theory, it is not true that there was nothing before the big bang, because there simply was no "before the big bang". The universe exists since the beginning of time; it's just that this beginning of time was about 13 billion years ago. Since there is no "before the big bang", the statement "there was nothing before the big bang" becomes meaningless because it presupposes that there was a "before the big bang" when there could have been either something or nothing.
Note however that this is not evidence-backed knowledge. We can get evidence for things happening only fractions of seconds after big bang, but we simply do not have knowledge about what happened at big bang, or even whether such an event actually happened (note, however, that often when people speak about the big bang, they don't actually mean that point, but the processes after; in that sense big bang theory is scientifically confirmed). Indeed, there are some theories which suggest that the "big bang" may actually have been a "big bounce". In which case there certainly would have been a time before the big bang, and there clearly was not nothing back then, but a complete universe that collapsed.
As of death, it is obvious that in this universe you don't exist any more after the death (both the matter and the information which happened to make up you do still exist, but they are no longer organized in a way that would be you). Even if somewhere in the universe there should by chance happen to be an exact copy of you at the time of your death, it would still be a copy of you, it would not be you. Whether you continue to exist outside the universe is something which we cannot find out as long as we live inside the universe, and therefore we can only believe or disbelieve, at least until we actually die.
The notion that the universe - including space and time - had a beginning is, when taken in conjunction with a restricted version of the Principle of Sufficient Reason (PSR), the basis of the Kalam cosmological argument: since entities do not pop into existence out of nothing (not to confuse with quantum particles popping into and out of existence from existing quantum fields, which are not "nothing"), the beginning of the existence of the universe can be explained only by its creation by the Absolute Being, Whose essence is Absolute Existence Itself (Ipsum Esse Subsistens, for the scholastically-minded).
Alternatively, the notion that the universe had a beginning is, when NOT taken in conjunction with the PSR, the basis of fanciful magical thinking: since the universe popped into existence out of nothing, anything can pop into existence anywhere, anytime!
Dawkins offered a rather challenging reason for this: information theory (I believe this was in "God Dilemma").
If you put the parts that make up a chair into a large bag, and shake it, it is unlikely that they will assemble themselves into a chair. There is some possibility, but it is very small. One way of looking at why is because a chair is a complicated object that requires a good deal of information to assemble properly.
In your question, given that the universe came from nothing "is it not possible that we can live once again from nothing?" a similar argument can be applied. Taking the fact that the universe "came from nothing" as a given, we can ask what that means. The universe took a while to organize itself - in the mean time there was little "information" there. It took a long time for that "information" to be present by the rules of physics organizing things into place. If all one admits is the laws of physics as know them, then this makes arguing for a "life after death" based on the Big Bang quite difficult.
It's worth nothing that those who claim that there is life after death probably wouldn't claim that that life comes from "nothing" either. Many religions believe in the existence of the soul that can survive bodily death (a soul, since it exists, is not "Nothing"). Since the soul is not nothing, it wouldn't make sense to say that an afterlife comes from nothing.
So, there are at least two ways of thought that address your question.
