If I'm sitting still and you're sitting still and then an earthquake splits the earth and moves us further apart, you could say that you didn't budge but I moved twice as fast away from you, because reference frames are weird like that.
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- 5 yr. ago
- Posts
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- 5 yr. ago
We don't know if space is a material made of anything, but we treat space as a 4-dimensional coordinate set in our math. We know space is expanding because when we look at things far away, 100% of them are moving away from us, and the farther away they are, the faster they're moving. Some clever people did the math and established that the only reasonable cause for that is space itself expanding, so things that are further away move away faster because there's more space between us to expand.