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When was inflation over?

  1. Dec 21, 2011 #1
    As I understand it, very soon after the big bang, the process of inflation took over and caused the super size of the universe in a very short period of time. At some point, I suppose, the inflation process ceased and the universe settled down to a more 'normal' existence with normal expansion.

    When was inflation done related to the age of the universe? Was it all over by 12 billion years ago.....10 billion? What would be a good conservative estimate of how long ago the universe was 'inflation-free' and simply existed in its current form (give or take the differences due to normal expansion)?

    thanks
    tex
     
  2. jcsd
  3. Dec 21, 2011 #2

    e.bar.goum

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    According to conventional theory, inflation started at about 10-37s after the BB, and continued to around 10-33 seconds after the BB.

    AKA: Not long at all.
     
  4. Dec 21, 2011 #3
    So, I guess, when I see a star at 10 billion or ever 12 billion light years distant, whose light has traveled that distance SINCE inflation, Im looking at the star the way it was and in the position it was that long ago. In other words, the transverse of the light from the star 10 billions light years away has been a simple, essentially linear journey, free from the effects of inflation since inflation had long since been completed before the light left the star. Better stated...no inflation has occured since the light left a star 10 or 12 billion light years away. Is this a correct way of thinking of it?
     
  5. Dec 22, 2011 #4

    e.bar.goum

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    Since inflation happened before there were even hadrons, no stars existed then to shine. Inflation happened very very early in the universe. So, stars are unaffected by this initial inflationary period

    However, to say that the star's light is unaffected isn't true, since the universe has changed a lot in 10-12 billion years. The matter dominated universe has given way to the cosmological constant dominated universe, and this changes the rate of expansion of the universe, changing the light (eg redshifts) etc.
     
  6. Dec 22, 2011 #5
    Well, Im just wondering how much we can rely on the information we assume from what we see when we see a star. For example, when we look at a star one billion light years away we are seeing the star as it was 1 billion years ago, right? Also, the star WAS where we see it one billion years ago, right? It might have moved since the light left it as well as ourselves but, in general, it was where we see it now. Where it actually is now we cant know since THAT light wont get here for awhile.

    Correct?
     
  7. Dec 22, 2011 #6

    Chronos

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    Somewhat correct, but, it is a little more complicated than that. The starlight from distant galaxies never actually originated from where [or when] it appears to be now. Imagine a guy in the distance running off into the sunset while sounding a fog horn. Can you positively pinpoint his position at an any given time?
     
  8. Dec 22, 2011 #7
    No, I guess not. But when I see the light from a star 500 light years away I think I can say this.....500 years ago the star was THERE. I dont know where it is now but I know where is was 500 years ago...it was THERE, at that point where I see the light that has traveled for 500 years. Where there IS or WAS in relation to anything else I dont know but I can point my finger and say it was THERE....THEN. Or, saying it a different way.....the light I am now seeing originated from a star that was located at the position indicated by the light 500 years ago.

    This seems to be fundamental and non-dependent on any other idea.
     
  9. Dec 22, 2011 #8
    Could you explain this a little further?

    This hardly makes sense to me as our ears are far less attuned to pinpoint the location of a source of sound than our eyes are at pinpointing a source of light.
     
  10. Dec 22, 2011 #9

    phinds

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    The point where the light APPEARS to us (now) to have originated is a point which is much closer to us now than is the point at which the light originated. This is due to the expansion of the universe, which has carried the point of origin of the photon way out from where it was then the photon was sent.
     
  11. Dec 22, 2011 #10
    This is where the discussion of this topic always gets frustrating to me. We read countless times in magazines, in articles, on TV, thousands of places....that when we see a star we are looking at it as it WAS. This seems simple enough. In fact it is represented as THAT SIMPLE in all of those magazines, articles and TV shows on the universe. But when a simple question is asked all of the sudden it gets complicated. How far is Aldeberan by the current accepted measuring methods? About 65 light years? Ok, that means that it takes about 65 years for light to get here from there....right? What am I missing? Is it any more complicated than that? Im sure that whatever factor has to be added to compensate for normal expansion has been included in the calculation. So, in general, it is 65 light years away. A star that is 100 million light years away is....wait for it.....100 million light years away....or at least was (approximately) 100 million years ago.

    Am I being too simplistic here. When a star is said to be 10 billion light years away just exactly what does that expression mean? Does it mean that it is really 8.5 million light years away....or 12 billion light years away. Why does any scientist make any statement on distance if it doesnt really mean that? Can someone give me a simple answer when I point to a star and ask 'how far away was that star when the light left it?' and it mean just that?

    I need to get this point clarified before I can hope to understand the original point.

    tex
     
  12. Dec 22, 2011 #11

    phinds

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    We ARE looking at it as it was. What we are NOT looking at is the actual place WHERE it was because that PLACE has moved due to the expansion. So if we could triangulate in some way and say THIS is the place where that light originated, we would be wrong because that place isn't where it was. BUT if we had telescopes with so high a resolution that we could see details, they would be exactly the details from the time when we think they are from. It's just that the point from which that light originated would no longer be where our triangulation says it is.
     
  13. Dec 22, 2011 #12
    I understand that. It would be like a having two people stand 20 feet apart with a rubber band stretched between them. On a signal an ant is released to travel the rubber band from person a to person b at exactly 1 millimeter per minute. On that same signal person b begins walking away from person a at 1 inch per minute. It takes the ant a certain amount of time to walk the ever stretching rubber band. We caculate, when the ant reaches person a, that person b is 20 feet from person a when in fact person b is some unknown distance from the point where the ant began its walk.

    Ok, so we dont actually know where person b really is. We just think, based on our information, that he is 20 feet away. Yes, expansion plays a small part. But the rate of expansion when compared to the speed of light is, on average, not a huge factor. So much so that when we say, to close approximation, that when we see light from a star that indicates it is 100 million light years away, it is fairly close to that distance....OR WAS.

    The main point is that when we see a star that is 1 million light years away, we can, to close approximation, state that we are looking at the star the way it was and where it was 1 million years ago.

    Just like we can say that when we look at the sun we are seeing it the way it was and where it was 8 minutes ago, give or take the small amount of expansion that occurs during that time.

    Of course, the farther away a star is the greater the rate of and effect of expansion in the calculation. But eventually we state that star A is X miles away....OR WAS....or even better stated....the light originated from an apparent point....THERE (where Im pointing).

    tex
     
  14. Dec 23, 2011 #13

    phinds

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    WAY wrong. True for things really close, say a few million light years or less, but when you talk about things even a decent fraction of the way out towards the edge of the observable universe, the expansion effect is HUGE. The edge of the OU looks to us right now to be 13.7 Billion light years away when in fact we know it to be almost 50 billion LY away.

    The rest of your post I agree /w.
     
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