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Post by abacus9900 on Nov 7, 2010 11:50:00 GMT 1
Doesn't the CBR just become more diluted the more the universe expands? Ih yes, definitely, but we shouldn't even be seeing it at all. Should we? Well, from my understanding (which could well be wrong) the CBR is everywhere as it is a remnant of the BB and as the universe expands it is carried with it, but in doing so it gets spread over more and more space which I would have thought would have 'stretched' it. I think it is photons that constitute it and as the universe gets bigger the photons become more weakly distributed, but again, I do not claim to be an expert on this.
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Post by typobrane on Nov 7, 2010 17:50:40 GMT 1
I think the problem is the assumption that the universe started from a primordial atom. Personally I think this has to be wrong, as STA has said in the past that if the universe is infinite now then it must have always been infinite and from a personal point of view I think that this must include the moment of creation for our part of the universe. This means that the cosmic background radiation when it first occurred happened everywhere. If we were to travel back in time to this period in the history of our part of the universe we would find ourselves in the middle of something like an infinite sun. Now try this thought experiment, if you had a teleportation device that could instantaneously transport you 13.7 billion light years away you would be no closer to the CMBR than when you left. It is synonymous to chasing a rainbow. The part of the universe you would end up in would look very similar to the part you left with the CMBR 13.7 billion light years away. Below is another excellent answer. www.astro.ucla.edu/~wright/photons_outrun.htmlBelow is what I posted on the Hubble Constant discussion. The visible universe, that is the area of the universe that we can see is increasing. A measured line of sight to the CMB will be getting longer by 186,000 miles every second. In the distant past this meant that more and more of the stars etc. of the universe would become visible as time went on. But now because the recessional velocity of the most distant parts of our visible universe are in effect moving away from us faster than the speed of light the amount of visible material like stars, galaxies and quasars of the universe will become less. The furthest thing on our visible horizon will always be the CMB and has always been so. The interesting thing here is “how will we see it disappear”? Ole Romer first demonstrated that light travelled at a finite speed by observing the movement of Io a moon that orbits Jupiter. The Earth orbits the Sun faster than that of Jupiter and as our obit takes us towards Jupiter, Io appears to orbit Jupiter faster and as our obit takes us away from Jupiter, Io appears to slow down. Either Io gets excited and moves faster as Earth approaches or else it is an effect of light traveling at a finite speed. This gives us a clue to what we shall see, the greater the distance the faster the recessional velocity the slower things will appear to be moving. When we look at distant objects that have a recessional velocity equal to the speed of light they will appear to have no movement. Then from that distance onwards back to the CMB any movements will appear in reverse order and although our telescopes are not capable of seeing such events yet, one day we will see distant quasars explode into behemoth primordial stars and these stars will the accelerate away from us and morph into the CMB.
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Post by Progenitor A on Nov 7, 2010 17:50:45 GMT 1
If you go far enough away, light from very distant objects will do the best it can to reach us, but if space keeps expanding faster than the light can cut down the distance, then light from those objects can NEVER reach us. A diameter (or is it radius) of 46billion light years - that would be the observable universe.
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Post by abacus9900 on Nov 7, 2010 18:06:40 GMT 1
I'm still unclear as to what people really mean when they say the universe may be infinite. STA suggests that this might be possible yet at the same time is quite convinced that it is impossible to indulge in endless regression in regard to finer and finer details of the fundamental constituents of the universe so it appears to me we have a contradiction here. Also, I think we have to be careful when assuming things about the unobservable universe since there might be surprises in store.
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Post by abacus9900 on Nov 7, 2010 18:14:15 GMT 1
If you go far enough away, light from very distant objects will do the best it can to reach us, but if space keeps expanding faster than the light can cut down the distance, then light from those objects can NEVER reach us. A diameter (or is it radius) of 46billion light years - that would be the observable universe. Well, I'm no scientist but one thing I have learned about science is that one should be very cautious about jumping to conclusions as regards things that we have never actually observed. It's all very well making deductions from current knowledge but things might not be quite so simple. This happened to classical physics when the deepest level of matter was examined in the earlier part of the last century; it revolutionized our view of reality.
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Post by Progenitor A on Nov 7, 2010 20:57:18 GMT 1
I think the problem is the assumption that the universe started from a primordial atom. Personally I think this has to be wrong, as STA has said in the past that if the universe is infinite now then it must have always been infinite and from a personal point of view I think that this must include the moment of creation for our part of the universe. I have a great deal of conceptual dificulty in imagining an infinite space Univers expanding into an infinite-space Universe. Surely if you have an infinite space, that's it - no more room for expansion This means that the cosmic background radiation when it first occurred happened everywhere. [/qupte] WEll, almost, it happened in BB + 40,000 years. Then it started expanding. So if our part of theuniverse expandedat the sam etime, then yes, CMBR would be all around us. But so would everyting else and there would be no separation due to expanding space. If we were to travel back in time to this period in the history of our part of the universe we would find ourselves in the middle of something like an infinite sun. yes Now try this thought experiment, if you had a teleportation device that could instantaneously transport you 13.7 billion light years away you would be no closer to the CMBR than when you left. What happened to the expansion?
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Post by abacus9900 on Nov 7, 2010 22:02:18 GMT 1
In any case, I have always thought it was very egotistical on the part of cosmologists to assert that space and time began with the BB, implying that all of reality started at that moment. What are the odds that a puny species like us has been able to work out when everything in creations began; more likely there was something or other existing before the BB and the BB merely introduced a particular 'dimension' into things. It shows you how they come to tie themselves in knots when they actually suggest that we and the rest of the universe came from nothing. Nothing comes from nothing - any child knows this.
Question: If enegy cannot be destroyed, as we are often told by those that should know, how could it have never existed at the time of the BB when everything supposedly came into existence? It must always have existed.
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Post by typobrane on Nov 7, 2010 22:11:09 GMT 1
Naymissus I think your concept of an infinite universe is too finite. It is infinite space there is always more room in an infinite space for more space even infinitely more space.
The universe has always expanded even before first light 40,000 years after BB. When we look at the stars or well anything really we are looking into the past and the CMBR is the oldest visible light (but not to the naked eye) that can be detected and so will always be the furthest visible light. It is not light from our past it is light from a part of the universe that is now much much further away and so yes if you wanted to get to that part of the universe you would have to teleport a lot further than 13.7 billion light years but even if you teleported 200,000 billion light years away you would still be 13.7 billion light years away from the CMBR.
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Post by Progenitor A on Nov 8, 2010 9:22:13 GMT 1
Naymissus I think your concept of an infinite universe is too finite. It is infinite space there is always more room in an infinite space for more space even infinitely more space. Then what is infinite space? Something smaller than infinite space it seems! I am afraid the English language is cracking unde the strain here The universe has always expanded even before first light 40,000 years after BB.When we look at the stars or well anything really we are looking into the past and the CMBR is the oldest visible light (but not to the naked eye) that can be detected and so will always be the furthest visible light. Yes and at 400,000 years that was evidently the limit of its expansion About 4 million years later the first stars were born and we are told that space has expanded so far that these early stars are no lonfer visible But as CMBR is also expanding in the same space, then that too should be keeping pace with those early stars and also be invisible. It is not light from our past it is light from a part of the universe that is now much much further away and so yes if you wanted to get to that part of the universe you would have to teleport a lot further than 13.7 billion light years but even if you teleported 200,000 billion light years away you would still be 13.7 billion light years away from the CMBR. Sorry, do not understand this www.damtp.cam.ac.uk/user/tong/concepts/cosmology.pdf
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Post by Progenitor A on Nov 8, 2010 10:09:49 GMT 1
In any case, I have always thought it was very egotistical on the part of cosmologists to assert that space and time began with the BB, implying that all of reality started at that moment. What are the odds that a puny species like us has been able to work out when everything in creations began; more likely there was something or other existing before the BB and the BB merely introduced a particular 'dimension' into things. It shows you how they come to tie themselves in knots when they actually suggest that we and the rest of the universe came from nothing. Nothing comes from nothing - any child knows this. Question: If enegy cannot be destroyed, as we are often told by those that should know, how could it have never existed at the time of the BB when everything supposedly came into existence? It must always have existed. Here is David Tong being very sensible on that subject Big bang theory has nothing to say about how the universe started. We don’t know the answer to that questionwww.damtp.cam.ac.uk/user/tong/concepts/cosmology.pdf
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Post by abacus9900 on Nov 8, 2010 11:30:30 GMT 1
How refreshing. Why can't more so-called 'experts' be this honest?
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Post by speakertoanimals on Nov 8, 2010 13:16:39 GMT 1
Who said the universe was expanding INTO anything? That is a commoin misconception, as I keep saying, not helped by all those pictures of explosions and expanding balloons...................
Infinite space CAN expand, as I've said many times before. Imagine the plane, with small squares drawn on it. An infinite number, all 1cm across. Now expand, so all squares 2cm across. The plane is as full as it was before, there is no space that was empty of small squares now filled with larger squares.
And the primordial atom idea is just plain wrong if we have an infinite universe, because if infinite, it always was -- what becomes infinite as we roll the film backwards is the density, but that only means goes to a point if we have a finite universe, not an inifinite one.
As regards Tong -- if you look at any timeline of the universe on any reputable cosmology website, we have the classical prediction for the big bang (infinite denisty at t=0), but usually with a hazy bit right near t=0, indicating quantum gravity, unknown physics etc. As I've said before, new physics may modify the infinite denisty prediction. But this doesn't invalidate the big bang per se, which is the overall picture of an expanding universe, and one where the bang is continuing, and still happening. It is not the BANG of an exploding universe, which is then picture some people seem to have, that the Big Bang was some initial explosion, and everything else is just stuff flying outwards from that explosion, hence if we invalidate classical theories at the instant of the bang, the whole big bang model is wrong. This is wrong. THe expansion continues, the universe is still banging, we're just not sure yet of the conditions at the very earliest times.
As regards the CMBm, thinking of the primordial atom and the flash from the explosion gives you the wrong answer. What is expanding is not just matter within some larger empty space, but the whole of space itself. Hence the CMB fills the universe AND ALWAYS DID! Just that as it expands the CMB gets redshifted. So, the CMB that resulted from the matter that now makes up us and the earth has travelled away from us, which is why we don't see it. What we see are photons that have travelled from somewhere else.
Think of it like this. Suppose we had a box filled with gas molecules at speed v, banging into each other, so that all the box is filled with gas. They only travel a short way before collliding with another molecule. Now imagine that there is a change, so that the gas molecules no longer collide. So, sitting in the box, and having a gas molecule detector, after 1s, we detect molecules that have travelled v meters since their last collision. At time t=2s, we detect molecules that have travelled 2v since last collision. Yet as time unrolls, the box is still filled with molecules, they keep travelling, and we keep detecting them. In effect, what we see in terms of the molecules is the last-scattering surface, which at t=1s, is a surface v away. At t=2, sphere 2v in radius, and so on,. When the last scattering of gas molecules occured, it occurred everywhere at the same time, just that at any one time, we see just a portion of it.
consider instead a box filled with flashbulbs. At the same time, they all flash on for an instant. So, at t=1, we see the sphere of bulbs at c distance. At t=2, the light from the bulbs at 2c reaches us, and the d=c bulbs we no longer see -- we saw them at t=1, and in effect watched them go out, to be replaced by the light from the bulbs at d=c plus a little bit. So, we see light continually, even though all the bulbs flashed at once for an instant. Just that as time goes on, the light we see is older and older, from bulbs further and further away.
Add in expansion, and the light getting red-shifted, and we go from phenomenally bright flash right next to us at t=0, to flashed from further and further awaym getting redder and redder as time goes on, until now, the flashes are right down at a few degrees above absolute zero.
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Post by Progenitor A on Nov 8, 2010 14:03:05 GMT 1
Who said the universe was expanding INTO anything? That is a commoin misconception, as I keep saying, not helped by all those pictures of explosions and expanding balloons................... Infinite space CAN expand, as I've said many times before. Imagine the plane, with small squares drawn on it. An infinite number, all 1cm across. Now expand, so all squares 2cm across. The plane is as full as it was before, there is no space that was empty of small squares now filled with larger squares. What a silly analogy! If the plane holding the squares is infinite in extent it cannot, by definition, expand. And the primordial atom idea is just plain wrong Is it? And how do you know? if we have an infinite universe, because if infinite, it always was Sheer gibberish indicating lack of clarity of the thought process -- what becomes infinite as we roll the film backwards is the density, but that only means goes to a point if we have a finite universe, not an inifinite one. More gibberish! Your English is appalling. As regards Tong -- if you look at any timeline of the universe on any reputable cosmology website, we have the classical prediction for the big bang (infinite denisty at t=0), but usually with a hazy bit right near t=0, indicating quantum gravity, unknown physics etc. Right, as Tong said, we just do not know As I've said before, new physics may modify the infinite denisty prediction. But this doesn't invalidate the big bang per se, which is the overall picture of an expanding universe, and one where the bang is continuing, and still happening. It is not the BANG of an exploding universe, which is then picture some people seem to have, that the Big Bang was some initial explosion, and everything else is just stuff flying outwards from that explosion, hence if we invalidate classical theories at the instant of the bang, the whole big bang model is wrong. This is wrong. THe expansion continues, the universe is still banging, we're just not sure yet of the conditions at the very earliest times. More indication of lack of clear thinking What is expanding is not just matter within some larger empty space, but the whole of space itself. Hence the CMB fills the universe AND ALWAYS DID! Just that as it expands the CMB gets redshifted. So, the CMB that resulted from the matter that now makes up us and the earth has travelled away from us, which is why we don't see it. What we see are photons that have travelled from somewhere else. God you are so bloody inarticulate! Think of it like this. Suppose we had a box filled with gas molecules at speed v, banging into each other, so that all the box is filled with gas. They only travel a short way before collliding with another molecule. Now imagine that there is a change, so that the gas molecules no longer collide. So, sitting in the box, and having a gas molecule detector, after 1s, we detect molecules that have travelled v meters since their last collision. At time t=2s, we detect molecules that have travelled 2v since last collision. Yet as time unrolls, the box is still filled with molecules, they keep travelling, and we keep detecting them. In effect, what we see in terms of the molecules is the last-scattering surface, which at t=1s, is a surface v away. At t=2, sphere 2v in radius, and so on,. When the last scattering of gas molecules occured, it occurred everywhere at the same time, just that at any one time, we see just a portion of it. Bollocks absolute inarticulate bollocks consider instead a box filled with flashbulbs. At the same time, they all flash on for an instant. So, at t=1, we see the sphere of bulbs at c distance. At t=2, the light from the bulbs at 2c reaches us, and the d=c bulbs we no longer see -- we saw them at t=1, and in effect watched them go out, to be replaced by the light from the bulbs at d=c plus a little bit. So, we see light continually, even though all the bulbs flashed at once for an instant. Just that as time goes on, the light we see is older and older, from bulbs further and further away. Add in expansion, and the light getting red-shifted, and we go from phenomenally bright flash right next to us at t=0, to flashed from further and further awaym getting redder and redder as time goes on, until now, the flashes are right down at a few degrees above absolute zero. You are here demonstrating exactly the same confusion of ideas and inability of expression that you exhibited in the Path Losses thread - and that thread t indicated to me that you are not clever and basically do not know what you are speaking about - I too am not clever, but I do not waffle, and I do recognise cleverness when I see it.
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Post by abacus9900 on Nov 8, 2010 15:42:41 GMT 1
Who said the universe was expanding INTO anything? That is a commoin misconception, as I keep saying, not helped by all those pictures of explosions and expanding balloons................... You see, this is highly problematical from a philosophical perspective because the idea seems to be saying the BB and the subsequent expansion of the universe has 'created' something out of nothing, which is illogical. If the universe is expanding into quite literally absolutely nothing then the universe has somehow magically managed to bootstrap itself without some prior cause being necessary, which is no better than asserting the God did it! But it's worse than that because the BB model effectively invalidates any scientific analysis since it relies on an irrational approach to the question of how reality began. If space and time are not in fact expanding into anything whatsoever then the BB has arrived at a cul-de-sac in that no possible new ideas can be applied to it. Now this, in the strictest scientific sense, is directly opposed to Popper's view that any scientific theory must at least be open to falsification. This is not the case with the inflationary model due to the insistence that it is purely a self-referential system, i.e. it does not rely on anything else for its existence but itself. It's really equivalent to saying that the BB idea has put a limit on scientific enquiry because anything 'outside' of it is not testable (even in theory) because there was nothing that could have possibly existed apart from it. Does this sound a bit like the kind of religious orthodoxy found in the early Catholic Church when Galileo proposed his revolutionary ideas? I think it rather does.
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Post by abacus9900 on Nov 8, 2010 15:49:51 GMT 1
I fail to understand why anybody would worry about infinity because such a concept is simply untestable and will be untestable forever. Why? Because you could go on and on and on and you would still not know for certain whether the universe was infinite or not because it is impossible to measure infinity, at least for physical things like the universe. You could, on the other hand, assert quite correctly that, say, the number line for integers was infinite because we know that no matter how huge an integer you can always add 1, but this is purely mathematical and the fact is mathematics and physics are not precisely the same thing.
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