I don't believe in an 'afterlife', because it's a complete oxymoron. :P

If there's something after life, then it's not life. If life never ceases, then there's no such thing as death. (either way, the term 'life after death' contradicts itself).

Also, the big bang theory doesn't say that the universe came out of nothing, it says that the universe came out of a singularity. Big difference.