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Q & A: Expanding universe and gravity?

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Most recent answer: 12/31/2009
Q:
If the universe and everything in it is expanding at an accelerating rate, wouldn't this give the effect of gravity without the need for any more explanation? If you think of gravity as everything pushing agaist everything else, instead of everything pulling everything else in.
- Harriet
New Zealand
A:
Gravitational forces between objects are always attractive, never repulsive.   The expansion of the universe and its acceleration has to do with general relativity and the overall composition of the 'stuff' that makes up the universe.  'Stuff' includes ordinary matter, so-called 'dark matter', and now people are beginning to talk about 'dark energy'.   To be honest we still don't have all the answers.  Many experiments are being planned, like new giant telescopes and space probes, that will attempt to shed new light on the subject.  Just Google 'dark energy' and browse around the first few articles to get some ideas on the subject.

LeeH

Just to reinforce Lee's point, that accelerating expansion has negligible effects on the scale of familiar objects, but gravity has very perceptible effects. So there's no reason to think that the overall acceleration accounts for the local attraction.

Mike W.



(published on 12/18/2009)

Follow-Up #1: expanding

Q:
Thankyou. So the universe is expanding but we (people) are not?
- Harriet
A:
That's an awkward question right after dinner.
We cannot honestly blame our personal expansion on cosmic effects.
Mike W.

Mike means well but apparently he just had a good dinner.  As far as the global universe and local distances are affected you are correct.

LeeH

(published on 12/31/2009)

Follow-up on this answer.