LesserEvil: Dumb question.... if the universe is 13.8 billion years old, but 93 billion light years across... how did it expand to that size? If the speed of light is a maximum speed of matter, how did it expand to this size in such a short time?
LDM90: Very helpful, but one small problem. He says the longer we wait, the more stuff we'll be able to see. I thought with the accelerating expansion of the universe, things at the edge would fade away as they moved farther out, meaning the visible universe is getting smaller, not bigger.Am I wrong?
LDM90: LesserEvil: Dumb question.... if the universe is 13.8 billion years old, but 93 billion light years across... how did it expand to that size? If the speed of light is a maximum speed of matter, how did it expand to this size in such a short time?The speed of light is a limit on light, but not on the expansion of the universe. It sounds strange but think of it this way: Space is expanding. If something one LY is moving away at one speed, something 100 LY is moving away 100 times as fast. So something 13 billion LY away is moving away 13 billion times as fast. You can see where this is going. Depending on where you stand, that expansion of space could be faster than the speed of light.
Stridar: LesserEvil: Think of it this way. Suppose that we start at time 0 with one checker. Every second, each checker in the line splits into two checkers, with the new on being placed to the right of the old now. After one second there is two checkers, after 2 seconds we have four, after 8 seconds, there will be 64 checkers. But if we can only count one checker every second, we will never get to the end of the line of checkers.
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