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Old Sep 24th 2013, 07:01 AM   #11
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Originally Posted by ChipB View Post
The concept of our universe having existed for an infinite amount of time was the dominant thinking back in the 1800's and perhaps up to the 1930's. Part of this static universe theory also included the concept of an infinitely large universe, with an essentially homogeneous distribution of galaxies and stars within it. But then Hubble did his observations that show an expanding universe, and once you accept that data it's not too much of a leap to realize that at one point there must have been a start to the universe as we know it today. That does not mean that this is the first and only universe to have ever existed - perhaps everything goes through a never-ending repeating cycle of expansion followed by contraction. So an infinitely old series of universes is not necessarily wrong, but as Topsquark said there is no way of knowing for sure because the evidence for this can never be observed.
If, however the universe and everything in it were expanding at an accelerating rate, then things would appear to us to remain static... with the exceptions of light and gravity. Light measurements would indicate that the expansion was taking place while gravity would indicate that the expansion was universal (no pun intended), that is that everything, including space and time were also expanding.
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Old Sep 24th 2013, 08:08 AM   #12
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Originally Posted by ChipB View Post
My understandingof Olber's Paradox is that it provides an argument against an infinitely old universe of infinite size with homogenous and static distribution of stars and galaxies. But it doesn't preclude an infinitely old expanding (non-static) universe, or an infinitely old universe without a homogenous distrubution of stars.
What about an infinitely old expanding (appearing to us as static) universe?
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Old Sep 24th 2013, 08:10 AM   #13
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Originally Posted by MBW View Post
I have been considering the "outside the universe" idea.
The simplest answer seems to be that there is no outside, and therefore the question is meaningless.
However there are various "multiverse" theories around that would therefore allow an alternative viewpoint.
And there is the theory of branes drifting in a multidimensional realm where contact between these branes creates universes.
(see also http://www.newscientist.com/article/...bly-birth.html )
One thing that all options that allow an outside to the universe seem to share is that they re-introduce infinity.
This solves one philosophical conundrum in that it removes the beginning and end issues.
But infinity brings it's own philosophical baggage.
By "outside" I mean outside of space/time.
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Old Sep 24th 2013, 08:14 AM   #14
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Originally Posted by MBW View Post
Surely the original observer outside space and time appears in the opening lines of the bible.
And surely that observer is just as inconceivable... so let's not bother with religion and consign ourselves to being deists or atheists.
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Old Sep 24th 2013, 08:25 AM   #15
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Originally Posted by Troll View Post
And surely that observer is just as inconceivable... so let's not bother with religion and consign ourselves to being deists or atheists.
(Ahem) Deism is a religion. And Atheism probably should be considered to be, seeing how difficult it is to argue for no Deity at all.

But I digress...

-Dan
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Old Sep 24th 2013, 08:28 AM   #16
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Originally Posted by Troll View Post
If, however the universe and everything in it were expanding at an accelerating rate, then things would appear to us to remain static... with the exceptions of light and gravity. Light measurements would indicate that the expansion was taking place while gravity would indicate that the expansion was universal (no pun intended), that is that everything, including space and time were also expanding.
We can, as you say, determine that the Universe is expanding. However we are also able to detect that the Universe's size is accelerating when it probably should be decelerating under the influence of gravity. So we can detect that, despite the fact that we are observing from inside the Universe.

We define "dark energy" as the source of the Universal acceleration. We don't know what it is, or what's causing it, but we do know what it does. Dark energy is the tendency for "empty" space to expand. So the expansion of the parts of the Universe between galaxies is larger than the expansion between, say, Chicago and NYC.

-Dan
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Last edited by topsquark; Sep 24th 2013 at 08:33 AM.
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Old Sep 24th 2013, 08:29 AM   #17
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Originally Posted by topsquark View Post
(Ahem) Deism is a religion. And Atheism probably should be considered to be, seeing how difficult it is to argue for no Deity at all.

But I digress...

-Dan
Deism is a belief in God without the need of a religious prescript.
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Old Sep 24th 2013, 08:31 AM   #18
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Originally Posted by topsquark View Post
We can, as you say, determine that the Universe is expanding. However we are also able to detect that the Universe's size is accelerating when it probably should be decelerating under the influence of gravity. So we can detect that, despite the fact that we are observing from inside the Universe.

-Dan
BUT! Can we detect that everything in the universe is expanding at the same rate?
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Old Sep 24th 2013, 08:34 AM   #19
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Originally Posted by Troll View Post
BUT! Can we detect that everything in the universe is expanding at the same rate?
We cross posted. I was editing my previous response, which mentions this.

-Dan
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Old Sep 24th 2013, 08:43 AM   #20
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My intuition says that there should be no distinction between space and "empty" space... I think that to make such a distinction short cuts the evidence in order to preserve the concept of a "Big Bang".

http://www.nobelprize.org/nobel_priz...sprize2011.pdf page 1

Why should the universe take on this shape instead of a simple cone?
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