Big bang background cosmic microwave radiation?

I've heard of the concept of astronomers detecting microwave radiation from the big bang. But I don't know how this could be. If everything was created in the big bang, which was an explosion from a single point, and nothing can travel faster than the speed of light, and the microwave radiation travels at... show more I've heard of the concept of astronomers detecting microwave radiation from the big bang. But I don't know how this could be. If everything was created in the big bang, which was an explosion from a single point, and nothing can travel faster than the speed of light, and the microwave radiation travels at the speed of light (which it must as it is electromagnetic radiation) then how could we get in front of it so as to receive it now, without us travelling faster than light to get there?

I expect the answer probably involves relativity, which I can't easily get my head round.
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