Reading the forum on the size of the known universe the term inflation epoch was used. Would someone care to enlighten me as to what this is?
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Reading the forum on the size of the known universe the term inflation epoch was used. Would someone care to enlighten me as to what this is?
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In most of the current big bang models, there was a brief period during which the universe expanded much faster than it is currently expanding. This accounts for certain observed phenomena today, such as the relative anisotropy of the cosmic microwave background.Originally Posted by Ozzy
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Vulcan Administrator
And, to clarify, that period is called the inflationary epoch. It occurred shortly after the Big Bang and only lasted a tiny fraction (10^-32) of a second, but during that time the universe expanded by many, many factors of ten. They're arguing about just how many, but one theoretical estimate is 10^50 times.
Everything I need to know I learned through Googling.
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"the relative anisotropy of the cosmic microwave background".
aaahh enlightened one, could you explain relative anisotropy?
Order of Kilopi
Thank the stars for Google...
Inflation
Anisotropy
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In general, an anisotropy is a difference in the measured values of a system that changes depending on the direction in which the measurement is taken. In the case of the CMBR, the anisotropy is the difference in temperature of the microwave radiation as it is measured in different parts of the sky. Maps such as this one show these temperature anisotropies as color codes with the warmer spots in red and the cooler spots in blue.
Instruments like COBE and WMAP are used to measure these anisotropies.
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At what point in time after the Big Bang did the restriction that nothing could exceed the speed of light come into play?
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It is my understanding that during the inflationary period nothing went faster than the speed of light. It is merely the case that the space between things increased very rapidly, but nothing felt an special acceleration.
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Order of Kilopi
That has always been the case for objects traveling through space. However, General Relativity has no such restriction for space itself expanding faster than the speed of light, which it apparently did for a very brief instant at the start of the inflation epoch.
Everyone is entitled to his own opinion, but not his own facts.
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I get confused about the meaning of the words when we address superluminal expansion. Isn't it true that during inflation, objects within the Hubble sphere (D < c/H) receded at less than the speed of light, while objects beyond the Hubble sphere (D > c/H) receded faster than the speed of light ? Isn't this still true ?
During inflation the Hubble constant was much larger than it has been since.
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Yes, it is still true.
Yes, by the inflation models, that is true too. Currently inflation is 22 millimeters/second per lightyear. In the first 10-35 of a second the universe expanded more than it would have at that rate.
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antoniseb,
You agreed with this and then commented further about inflation. My point, or rather my understanding, is that even currently, with limited or no inflation, objects beyond D > c/H still recede faster than the speed of light.
When you think about it, c/H currently corresponds to a rather modest redshift of z = 1.5 (actually a little less than 1.5). Many supernova lie beyond z = 1.5, and all of them must have been receding faster than the speed of light.
Is this also your understanding ?
My point was that during inflation, while objects certainly must have receded superluminally, that really is no different than the current situation. The principal effect of inflation in this regard was to increase the Hubble constant, and thereby cause even more closely spaced objects to recede faster than the speed of light.
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You aren't taking relativity into account. but is is close to what we seem to be seeing. At z=1 we are looking a little over halfway across the observable universe. Less than twice as far away as that we are seeing z=1100 at the CMB. The current idea is that there was a lot a universe further away than that, but the light hasn't had time to get here yet.
On the other hand, I don't think we've seen any supernovae at z>1.0. So I don't kow what you're talking about there.
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I thought I was. Could you expand on this, or is it too far off topic ?
Vulcan Administrator
We've seen at least one at 1.7.
Everything I need to know I learned through Googling.
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Thanks to ToSeek for the rescue, but in truth I misspoke. I meant to say that many galaxies have been seen that lie beyond z = 1.5, and all of these must have been (and still are) receding faster than the speed of light.
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My! My! Business at the epicycle shop is experiencing an "inflation epoch".
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I asked this before on a different thread, but noone seemed to answer...
Why do we believe that energy cant be created?
If the big bang happened? then why cant i figure out a way to make other things "happen" in my back yard (so to speak) aswell?
If the universe came into existence from nothing, then why do we believe it is impossible to make other elements out of nothing? Clearly our existance proves that there is no such thing as conservation of energy....at least from our big bang model....unless we figured that once something like the universe has been created, nothing else can be created after that.. of that everything that could possibly be created has already been created....
In the BB model, did the universe start out INFINITELY small?
Becasue if it DID, wouldnt it take an infinite amount of time for it to expand into "something" NOT infinitely small?
If not, shouldnt we be able to estimate how small the universe was before the explosion?
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Concerning the very beginning of the universe, we really don't know much, however, I can say two things about your above comment:
- We do not know that it started off infinitely small. It may well be that it started off at the Planck scale.
- Even if it did start off infinitely small, thinking it would take an infinite amount of time to get to a finite size seems like Zeno's paradox in which the runner could never finish the race because he had to go through an infinite series of increasingly smaller fractions of the remaining distance.
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If it started out at Planck scales, then how long do you think it would take for the universe (the matter in he universe), to expand to this size? a few earth years at the speed of light?
Are there any estimates on this out there?
Oh, and what about the other question i had...the creating energy one?
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1. There are too many unknowns to give an answer, but when you say something is expanding at the speed of light, which two parts are you comparing? Two spots very close together would never be expanding apart faster than light.
2. Sure lots of them. Make some assumptions and you can make estimates.
3. We observe that in this era there is no evidence that any energy is created in any process we've observed, and the principle of the conservation of energy has been a very useful tool in figuring out how things work in distant parts of the universe. If at some point, you figure out how to create energy in you back yard (and you survive) you will probably end up being quite well known for centuries to come.
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Yes. A local school board is meeting to determine if the Harry Potter books promote witchcraft.
It's probably good that BB Theory is not taught at that school.
Order of Kilopi
z>2 supernova
There's this, too,... http://arxiv.org/abs/astro-ph/0402512
and this at z>2,... http://www.astro.ucla.edu/~wright/sne_cosmology.html
Pete.
Order of Kilopi
Actually, in a sense, I think energy is being created all the time in the form of virtual particles in the "vacuum" of space. We say that energy on the whole is conserved because (except in the case of Hawking radiation) this energy "loan" is always paid back in the briefest instant -- the bigger the loan, the more brief the instant. Some speculate this phenomenon could have been the impetus behind the big bang - a very large "loan" that underwent a very brief inflation epoch, and then it couldn't be paid back but rather went to a vacation villa in the Bahamas.
Everyone is entitled to his own opinion, but not his own facts.
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