I know that the universe is 13 billion years old and the fastest anything could be is the speed of light so if the universe is expanding as fast as it could be wouldn’t the universe be 13 billion light years big? But I’ve searched and it’s 93 billion light years big, so is the universe expanding faster than the speed of light?
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>wouldn’t the universe be 13 billion light years big?
Only if it exploded out of a single point within the universe. But the big bang wasn’t all the stuff exploding out of a point in space within the universe, it was an explosion of space. At t+1 nanosecond, space is infinitely big in every direction, all the stuff within it is just really tightly packed together. The big bang is how space expanded and all the stuff had enough room to cool off and form things like atoms.
> But I’ve searched and it’s 93 billion light years big,
That’s likely the **visible** universe. The parts of it we can see. And that’s bigger than 13 billion lightyears because when that early stuff that’s now 93 billion light years away emitted light ~13 billion years ago, it was a lot closer to us. The space between us grew.
>so is the universe expanding faster than the speed of light?
Yes. That part is true. Centered on us, there’s enough distance between us and the edge of the visible universe that the rate of expansion sums up to more than the speed of light. It means stuff on the edge is fading away and getting more and more feint. Matter is falling out of our cone of causality. Which really isn’t a perfect cone anymore, it’s more like a column, and its even getting narrower. Anything past that column, even if it launched itself right at us at the speed of light, like a flashbulb, the space between us grows faster than it travels.
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