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shawnhar
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Reged: 06/25/10

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Dark Energy Expansion in the Past - Question
      #5601852 - 01/02/13 07:57 PM

So my understanding is Dark Energy is causing the Universe to expand more rapidly as we move forward in time. My undertanding of the big bang is that it expanded faster than light in the beginning and then slowed down.
My dumb logic says there must have been less dark energy in the past or the further you go back the slower things get, is that wrong? Was there some "hump" which once passed, would allow the expansion to speed up? Or has it always been expanding more rapidly than before? Is it possible dark energy is "leaking" into our space or being created now?
Also, have there been any studies to determine if there is a correlation between the variations in the CMB and Dark Energy?

Edited by shawnhar (01/02/13 08:14 PM)


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Dave Mitsky
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Re: Dark Energy Expansion in the Past - Question new [Re: shawnhar]
      #5603073 - 01/03/13 02:00 PM

According to what I've read, the effect of gravity on cosmological expansion became progressively weaker and that of dark energy grew progressively stronger as the universe evolved. The time at which dark energy began to dominate varies from 5 to 7 billion years ago, depending upon the source. At that point, the slowing of expansion due to gravity was overcome by the repulsive effect of dark energy.

http://hetdex.org/dark_energy/dark_matter.php

http://fire.biol.wwu.edu/trent/alles/Cosmic_Evolution.pdf (page 27)

http://imgsrc.hubblesite.org/hu/db/images/hs-2001-09-g-full_jpg.jpg

http://www.sciencenews.org/view/access/id/43609/description/COSMIC_TUG-OF-WAR

Regarding your final question, browse http://kipac.stanford.edu/collab/research/highlights/tidbits2010/actsz

Dave Mitsky


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Carl Coker
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Reged: 07/30/12

Loc: Ohio
Re: Dark Energy Expansion in the Past - Question new [Re: Dave Mitsky]
      #5603148 - 01/03/13 02:41 PM

Dave has it right. Since the total amount of matter and radiation has remained the same since the Big Bang, they necessarily dilute as the universe gets larger. Dark energy, so far as we can tell, does not do so; or, if it does (i.e., it is not actually a cosmological constant), it does so much more slowly than matter and radiation. Because of this, it eventually comes to dominate over the gravitational influence of matter and radiation.

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Kon Dealer
professor emeritus


Reged: 01/05/11

Loc: Cambridge UK
Re: Dark Energy Expansion in the Past - Question new [Re: Carl Coker]
      #5603447 - 01/03/13 06:05 PM

So we are going out in a big "rip", rather than a big "crunch"

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shawnhar
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Re: Dark Energy Expansion in the Past - Question new [Re: Kon Dealer]
      #5603501 - 01/03/13 06:42 PM

Thanks for the awesome reading Dave! So there was a hump, cool.
One of those articles seems to indicate there was no dark energy right after inflation, but there was lots of dark matter, that seems rather weird. I wonder if the clumping/collapse of hydrogen and other elements somehow spawned the dark energy.
I love the fact that we don't know much about it.


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sirchz
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Reged: 09/21/09

Re: Dark Energy Expansion in the Past - Question new [Re: shawnhar]
      #5604631 - 01/04/13 11:50 AM

Here is a nice talk about dark energy.

http://www-personal.umich.edu/~huterer/EPO/adler.pdf


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