Thread: I have a Cosmology question

Originally Posted by wopmanfixit

I’ve heard this (I'm paraphrasing)- “expansion of the universe is accelerating, scientists don’t know why.”

It really depends on when in the universe's history you are talking about. IIRC, and I could be wrong here as this was explained to me some years ago, is that the expansion of the universe works in an unintuitive way. It was space that was expanding, and all space was expanding. That's probably not very clear.

Consider the time shortly after the Big Bang (if it did indeed happen), and imagine that you are at the outer limit of the universe. Since it is all of space that is expanding, as opposed to you moving away from the center at a constant velocity, your velocity will increase as you move farther away, because as you move farther away there is more space between you and the center and that space is expanding.

Or maybe think of 10 people in a line, each one foot apart. So the two people on the end will be... 9 feet apart. But if space doubles, there will be two feet between each person and the ends are 18 feet apart. Double again, and there will be 4 feet between each person and the ends are 36 feet apart. The gain is exponential instead of linear.

...Sorry for not multiquoting