(Solved) How does gravity exactly counteract the expanding universe at most scales?

datadisha

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11 years ago

How does gravity exactly counteract the expanding universe at most scales?

We get told that the expanding universe is like the surface of a balloon and we live on one of the little dots on the surface. As the balloon expands, every other dot looks further away. However the dot gets bigger too, and so do I at the same rate.

Why does it seem that gravity completely explains the attraction of objects at laboratory scale up to galactic scale, but then doesn't when you look beyond that? Why isn't the space between my toes getting bigger at exactly the same rate?

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leojesse2

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11 years ago

This is because space is expanding, not matter. If you place a ball on a rubber sheet and stretch the sheet, the sheet is going to expand and not the ball. Gravity is much much stronger then the expansion in small scales, but once you get to scales somewhat larger then galaxy clusters the expansion has much more of an influence.

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tony365

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11 years ago

The strong and weak nuclear forces are probably keeping you together better than gravity does, those are a lot stronger on small scales.

Larger objects, like planets, stars, natural satellites, etc, rely on gravity to keep themselves together.

But if the value for Dark Energy is large enough (and we don't know its exact value) then, eventually, someday, the universe expansion will rip apart things held together by gravity. And eventually, even molecular bonds will separate, and atoms themselves will be ripped apart.

It's just one possible fate of the Universe... they call it the Big Rip, and between that or Heat Death, you have a very dismal very distant future.

If Dark Energy is not strong enough, or if there is more mass in the universe than initially estimated, then perhaps a A Big Crunch will occur, in which gravity wins, and all the matter in the universe will fall back into itself.

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datboililp

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11 years ago

This verified answer contains over 310 words.

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How does gravity exactly counteract the expanding universe at most scales?

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