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Author Topic: What happened to all the light emitted from the Big Bang?  (Read 3397 times)

Offline Quark

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I figure at some point we should be able to see it, being that it was the brightest light ever created even if it only lasted a fraction of a second,and also if the universe is finite then it should have an edge where this light, the first ever created is at right now.If not then the universe must be expanding faster than c.


 

Offline imatfaal

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What happened to all the light emitted from the Big Bang?
« Reply #1 on: 16/06/2011 11:21:55 »
The universe was opaque for the first 370,000 years - so any initial radiation was emitted/absorbed/reemitted in this form of superhot plasma.  once the temperature went low enough for hydrogen to form from the disassociated protons and electron then the universe became more transparent - the last light that was generated by the plasma but was not absorbed is what we now see as the Cosmic Microwave Background. 

Your concept of the light from the big bang heading outwards is flawed.  The big bang happened everywhere - it wasn't an explosion outwards from a single point.  We see the CMBR from every direction and at the same distance and time.

Your last sentence is however correct (if possibly for wrong reasons).  Space is expanding - this expansion is a background intrinsic expansion.  Galaxies are not moving through space away from each other, the space in between them is growing.  As the the rate of separation increases with the distance between galaxies then at a certain critical distance two galaxies will be separating faster than the speed of light. This does not cause trouble for einstein's theories because nothing is moving THROUGH space faster than light
 

Offline Quark

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What happened to all the light emitted from the Big Bang?
« Reply #2 on: 16/06/2011 12:18:24 »
O.K. if the space between galaxies is expanding and not the galaxies themselves moving, then how do you explain the fact that our own milky way is getting closer to earth?
 

Offline imatfaal

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What happened to all the light emitted from the Big Bang?
« Reply #3 on: 16/06/2011 12:53:41 »
Because at small distances (and in universe terms the milky way is very small) gravity is strong enough to keep the galaxy together.  At large distances ie between galaxies then the expansion is the dominant effect.

We are actually close enough to Andromeda that we are gravitationally bound with that galaxy - but everything else further out is spreading away
 

Offline Don_1

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What happened to all the light emitted from the Big Bang?
« Reply #4 on: 16/06/2011 13:07:08 »
The universe is not finite, only the matter within it.

Even if there were a central 'big bang' rather than the mass expansion imatfaal has explained, you would only be able to see the light when it reflects off of something.
 

Offline Quark

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What happened to all the light emitted from the Big Bang?
« Reply #5 on: 16/06/2011 20:34:12 »
wouldn't the light be able to reflect off the hubble's lens as in distant stars? or it is possible in some way that over the billions of years the light has simply turned into CMBR? I'm no expert just fascinated by this stuff.
 

Offline imatfaal

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What happened to all the light emitted from the Big Bang?
« Reply #6 on: 16/06/2011 22:25:48 »
or it is possible in some way that over the billions of years the light has simply turned into CMBR? I'm no expert just fascinated by this stuff.
Yes - if you look at my reply.  The last light of the hot universe has been travelling for 13.6 billion years and has been stretched out by the expansion of the universe.  So the last light started off as ultra-violet and has been stretched out to very cold long wavelength microwave - the CMBR
 

Offline Quark

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What happened to all the light emitted from the Big Bang?
« Reply #7 on: 17/06/2011 01:29:03 »
Thanks, Imatfaal for your explanations, I'm just so intrigued by this part of physics since watching all of the episodes of through the wormhole. It's like my brains are scrambled eggs trying to comprehend all of the information I'm taking in, in such a short time, but at the same time it's so fascinating and interesting that I can't stop thinking about all the theories of the origins of our universe.I hope you don't mind me bombarding you with all these questions.
 

Offline imatfaal

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What happened to all the light emitted from the Big Bang?
« Reply #8 on: 17/06/2011 10:27:53 »
Not at all fire away - when they get to obscure I may have to bow down, but there are others here with a really deep grasp of cosmology
 

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What happened to all the light emitted from the Big Bang?
« Reply #8 on: 17/06/2011 10:27:53 »

 

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