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ejim
2009-Feb-13, 07:37 PM
There is the picture of the large scale structure of the universe as shown by the solan sky survey. It shows this web like structure and says that is how the universe looks. The problem is that this is looking back in time and not out in space. To see how the universe actually looks you would need to find a galaxies speed and direction and alter its position according to that. But this information is not used in the construction of this map.

Now I suppose all this must wash out and the universe is actually web like but let me present how I think you should look at the structure in a naive way.

So if you see a filament along your line of sight what this should actually be is a large clump of galaxies that persist through time. If you see a web parallel to your line of site this should be a set of galaxies that once existed and dispersed.

So in the end I am not sure if that really shows how the universe looks in space but how it looks in time.

If anyone has some insight on this please comment.

astromark
2009-Feb-13, 08:16 PM
Yes 'ejim' I see your point and agree that a scale of relative movement would need to be applied to make such imaging accurate. To do that we would need to know the direction, rate, and effects of local gravity groupings of galactic clusters... I would suspect the end image would be larger, but look the same. The Solan Sky Survey is the best yet work attchieved... Its never finished.

Cougar
2009-Feb-14, 01:50 AM
There is the picture of the large scale structure of the universe as shown by the solan sky survey. It shows this web like structure and says that is how the universe looks. The problem is that this is looking back in time and not out in space....

I'm sure you mean the Sloan Digital Sky Survey or the SDSS. Yes, this is looking back in time, but it also looks out into space. A flat map would be a poor representation of the richness of data that SDSS exhibits. Of course, depth, or distance, is one of those characteristics, and large distances can involve not just space but spacetime.

It's a little tricky, looking back in time, isn't it? A galaxy whose light has been traveling to us 1 billion years appears as it was 1 billion years ago, and a galaxy whose light has been traveling 2 billion years appears as it was 2 billion years ago, but we are seeing them both at once! I don't know, is that weird? Where those galaxies are NOW can be estimated by understanding the rate of change of the universe's expansion to this point and projecting that forward.

loglo
2009-Feb-14, 02:27 AM
Yes 'ejim' I see your point and agree that a scale of relative movement would need to be applied to make such imaging accurate. To do that we would need to know the direction, rate, and effects of local gravity groupings of galactic clusters... I would suspect the end image would be larger, but look the same. The Solan Sky Survey is the best yet work attchieved... Its never finished.

This information is encompassed in the measured redshifts of the galaxies. With redshift they can determine a 3D map not just a 2D one. See for instance figure 4 here (http://www.atnf.csiro.au/pasa/17_1/kraankorteweg/paper.pdf). Now if we just had a 3D display handy...

transreality
2009-Feb-14, 03:35 AM
The webs and threads of galaxies are imbedded in dark matter, aligned and gravitationally connected. They are not chance alignments and should persist over much of the the age of the universe.