Naturalism

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The big bang for creationists,

Darwins theory of evolution by natural selection is not the Big Bang, Abiogenesis or Atomic theory.

The big bang is sometimes described as a titanic explosion that happened 13.7 billion years ago. 'Explosion' is a misnomer since the Big Bang happened everywhere at once and there was no pre-existing void into which the Universe erupted. Space and time and energy all came into being in the Big Bang. The Universe began in a super-dense, super-hot state 13.7 billion years ago and has been expanding and cooling ever since.

Just because you don't understand it, doesn't mean it never happened. Fortunately your belief isn't a prerequisite for the truth.