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Brack the Barbarian
2004-May-18, 10:52 PM
[FONT=Times]OK here goes!!

The Earth, Galaxy and Local Group (sorry about the Plethora of Capital letters) are all being pulled in the direction of the Great Attractor - whatever that may turn out to be. BUT, at the same time the universe is expanding, so here is the question. If we hang around long enough (the odd few trillion years) will our part of space 'hit' the Great Attractor or will have expanded away at such a rate that we never catch up with it?

StarLab
2004-May-18, 11:06 PM
Please wouldya mind explaining what this Great Attractor is? A BlackHole, perhaps? God? Well, WHAT?!

TheThorn
2004-May-19, 12:07 AM
We're not actually moving toward the Great Attractor. We're just moving away from it less slowly than we should be given the expansion of the universe. It's not easy to find a source that actually says that in plain English, but
This Page (http://www.solstation.com/x-objects/greatatt.htm) does mention that the distance to the great attractor is a red shift distance of 4350 km/second, and it's "attracting" us at 600 km/second (which means we're actually moving away from it at only 3750 km/second).

The cosmic microwave background actually shows this distortion too - it's a little hotter in the direction of the great attractor than in the opposite direction, which means that it's not as red shifted that way, by htat same amount, 600 km/second.

Billions and billions of years from now, the local group of galaxies, - us, Andromeda, and a few smaller ones like the Magellanic clouds - will be all that's left around these parts. Those are the only objects that are gravitationally bound with us. The rest of the universe, including the Great Attractor will expand off into the distance.

po-
2004-May-19, 04:18 AM
unless the expansion of the universe slows down. I just read from the dark energy article on the front page that the expansion was constant until 6 billion years ago when it began accellerating. If it can accellerate for no reason it could decellerate just as randomly? I wouldn't put a big crunch out of the picture just yet.

Magenta
2004-May-19, 03:23 PM
Because the universe's expansion is accelerating, it is unlikely we will fall into the Great Attractor. It is less clear what will happen on smaller scales. Certainly the Local Group galaxies will stay together, but we may or may not remain part of the Local Supercluster.

A colorful discussion of the discovery of the cluster at the center of the Great Attractor can be found here (http://KenCroswell.com/universeatmidnightexcerpt.html).

Brack the Barbarian
2004-May-19, 06:09 PM
Many thanks to The Thorn, I didn't have access to the figures and you have given me exactly what I wanted to know!

Brack the Barbarian
2004-May-19, 06:14 PM
PS Thanks too to Magenta!