How can the universe be speeding up in its expansion? Since gravity is the only force that controls wouldn’t the universe ultimately always contract again over time because gravity would eventually win out over the initial acceleration caused by the big bang?
In: Physics
Imagine a stretchy sheet with two rocks on it. The mass of the rocks will distort the sheet around them, and if they’re close enough, they’ll eventually both pull together into the same stretched-out area.
That’s gravity.
Now imagine putting those two rocks on the stretchy sheet, and then pulling the ends of the sheet apart constantly. Each rock is still distorting the sheet around it, but the sheet itself is moving apart more quickly. Even if the rocks started off near each other, they’ll end up in their own little stretched-out areas instead of together, because the sheet pulled them apart more quickly than they rolled together.
That’s the expansion of the universe.
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