Time waits for no quasar – even though it should

[sjastro]

Originally Posted by Robh

The edge of the observable Universe is currently 46.5 billion light years away (or edge diameter 93 billion light years ). The Sloan Great Wall is measured as 1.37 billion light years in length.
This is roughly 1.5% of the edge diameter. I would consider this as a fairly significant percentage.

Regards, Rob.

It has nothing to do with relative size of the object to the Universe.
More important is the age of the object or it's distance to the observer.

As we look further out towards our event horizon the Universe becomes more and more isotropic as galaxies spread out due to the Hubble flow.

Since the Universe is not expanding into existing space and there is no centre, an observer at any point in the Universe will see the Universe as isotropic for the same reasons.

Regards

Steven

[Jarvamundo (Alex)]

Isotropy is based on the entire visible Universe. The structures you refer to represent distances that are a small percentage of the size of the visible Universe. The smaller the distance the less the Universe appears to be isotropic.

Originally Posted by Robh
The edge of the observable Universe is currently 46.5 billion light years away (or edge diameter 93 billion light years ). The Sloan Great Wall is measured as 1.37 billion light years in length.
This is roughly 1.5% of the edge diameter. I would consider this as a fairly significant percentage.

Regards, Rob.

Originally Posted by sjastro

It has nothing to do with relative size of the object to the Universe.
More important is the age of the object or it's distance to the observer.

As we look further out towards our event horizon the Universe becomes more and more isotropic as galaxies spread out due to the Hubble flow.

Since the Universe is not expanding into existing space and there is no centre, an observer at any point in the Universe will see the Universe as isotropic for the same reasons.

Regards

Steven

circles?

age?
http://www.theaustralian.com.au/news...-1225816739412

To our surprise, the results show that these galaxies existed at 700 million years after the Big Bang and must have started forming stars hundreds of millions of years earlier, pushing back the time of the earliest star formation in the universe.

One would be begin to ask... how long does it take coalescing gas to form a star... then get a bunch of mates to make a galaxy... in BB+700M

theres that word again... surprise

[Robh (Rob)]

Originally Posted by sjastro

As we look further out towards our event horizon the Universe becomes more and more isotropic as galaxies spread out due to the Hubble flow.

Since the Universe is not expanding into existing space and there is no centre, an observer at any point in the Universe will see the Universe as isotropic for the same reasons.

Regards

Steven

Homogeneity and isotropism are ideal theoretical assumptions. As we can't obtain observational evidence beyond the event horizon then we have to rely on evidence within it. The Universe is evolving and what we see locally at this time is not necessarily going to match what we see further away as we head back in time to the point of the Big Bang. So, scientists must allow for this by explaining evolutionary changes in star or galaxy formation in line with current assumptions. I would think, conceptually, that the Cosmological Principal is an ideal and appealing assumption and may be supported by evidence (e.g. distribution of galaxies, CMBR) but, in the end, it's still an assumption.

Regards, Rob.

[sjastro]

Originally Posted by Robh

Homogeneity and isotropism are ideal theoretical assumptions. As we can't obtain observational evidence beyond the event horizon then we have to rely on evidence within it. The Universe is evolving and what we see locally at this time is not necessarily going to match what we see further away as we head back in time to the point of the Big Bang. So, scientists must allow for this by explaining evolutionary changes in star or galaxy formation in line with current assumptions. I would think, conceptually, that the Cosmological Principal is an ideal and appealing assumption and may be supported by evidence (e.g. distribution of galaxies, CMBR) but, in the end, it's still an assumption.

Regards, Rob.

The Cosmological principle while being an ideal is consistant with the idea that the BB didn't occur in existing space otherwise a "geometrical centre" can be defined and the principle is violated.

Homogenity and Isotropy are testable outcomes of the Cosmological principle and apply only to the visible Universe.

Examples of observed isotropy are the CMB and the distribution of cosmological redshift of distant galaxies.

Regards

Steven

[Jarvamundo (Alex)]

Examples of observed isotropy are the CMB and the distribution of cosmological redshift of distant galaxies

They are still working on CMB... last year potential WMAP catastrophy was highlighted... http://arxiv.org/abs/0905.0075 ... and this year another has come http://cdsweb.cern.ch/record/1238439?ln=ca

I'd be keen to see Wright's response...

This thread discusses as test where quasars don't fit, regarding cosmological distances implied by redshift.

[sjastro]

Originally Posted by Jarvamundo

This thread discusses as test where quasars don't fit, regarding cosmological distances implied by redshift.

As this thread has shown using quasar data on it's own in an attempt provide an alternative viewpoint is like not seeing the forest for the trees.

Regards

Steven

[Jarvamundo (Alex)]

tis hard to see with all these weird dark lensy things in the way