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skrap1r0n
2006-Oct-18, 02:43 AM
the article on the BA homepage today with the galaxies colliding made me question this. Is there an extreme upper bound to gravity? The reason I ask is because aside from the occasional galactic collision, why are galaxies not clustered and spiraling in a "Super Galaxy" like stars do in a galaxy? Does gravity not work at that scale?

PhantomWolf
2006-Oct-18, 03:06 AM
Well my understand is that the big bang was more a big whoomp and occured everywhere at once, so the matter then slowly came togther to forms larger clumps that then formed stars and galaxies.

skrap1r0n
2006-Oct-18, 04:01 AM
ok I understand that, but it still doesn't explain why there are no super galaxies comprised of billions of other galaxies swirling around a core.

Jens
2006-Oct-18, 05:49 AM
There isn't an upper bound to gravity, as far as we know. It just gets weaker and weaker with distance, but never hits zero.

There are two possible answers to your question about super galaxies. One is that if you believe the big bang, there hasn't been enough time for them to form.

If you believe in an infinite universe, then it's possible that there are such super super super clusters or whatever, and that we haven't seen them. Galaxies have been found, then galaxy clusters, then galaxy cluster clusters, and there is something called the "great wall" that I don't really understand. So there are concentrations at higher than the galaxy level.

skrap1r0n
2006-Oct-18, 02:24 PM
oh well I hadn't considered the time factor yet. lol it makes sense though

astro_uk
2006-Oct-18, 04:35 PM
There is another reason, the expansion of the Universe is ongoing (and possibly accellarating) so some objects are so far apart that gravity will never be able to overcome the expansion of the Universe.

There are observed structures with possibly tens of thousands of galaxies, but that is probably near the limit according to Big Bang theory.

Nereid
2006-Oct-18, 11:25 PM
Moved, from the ATM section.

triclon
2006-Oct-18, 11:41 PM
1. The expansion of the universe probably is what is counteracting the fact that everything doesn't just fly together into one giant supergalaxy.
2. Galaxies do form clusters (and superclusters) which are bound together by gravity.