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CMB
Jul 20, 2016 15:01:08 GMT 1
Post by mrsonde on Jul 20, 2016 15:01:08 GMT 1
This has been discussed before on this board - notably by a lady called Speak like a Wild Animal - but years ago and without achieving any satisfactory conclusion as far as I'm concerned, and since then it's supposed theoretical explanation has been used to elaborate several new theories, including the Nobel-prize winning theory the universe is accelerating in its expansion, in the latest mapping of the universe, and hence as foundational evidence for dark energy and dark matter.
The CBR is allegedly thermal radiation that originates in the Big Bang. Its existence is in fact the primary evidence for that theory. That is, it's light arriving at our detectors - on top of a New York skyscraper or Princeton laboratory originally, if I remember aright - from all directions, but supposedly all from the same source, the initial photon decoupling a short instance after our universe came into existence.
The head-scratching puzzle about this theory is: how come this light is only arriving, here, now? Clearly, space must be expanding at infinitesimally close to the speed of light for this to be possible, right? What sense then in the claim that it's accelerating in that expansion? Also - it is axiomatic in SR that c is an invariable constant: we'll always measure it as c, whatever the dilation of space or time. Also, that space would allegedly have been of a comparatively tiny size at the beginning of the universe - or shortly after the photon decoupling. If c was the same then as now, as all theories contend, the photons emitted would have traversed its entire extent within microseconds. So - is it their re-emittance, or reflection, that we're detecting? What sense then the "map we've constructed? But I know this isn't the supposed explanation - I just can't make head or tail of the proposed real one. Personally, I strongly suspect no one else can either - I've looked hard enough to find one that makes sense.
So - someone have a go, please. Why hasn't the light of the CBR long passed us by?
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CMB
Jul 23, 2016 22:51:10 GMT 1
Post by mrsonde on Jul 23, 2016 22:51:10 GMT 1
What, no response? None from all these world-renowned "physicists" we have on this board? Not even from our resident fast-draw wiki consultant, the one who knows all about dark matter and Ceiphed variables?
Well, that tells me something.
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CMB
Jul 26, 2016 7:38:38 GMT 1
Post by fascinating on Jul 26, 2016 7:38:38 GMT 1
What, no response? None from all these world-renowned "physicists" we have on this board? Not even from our resident fast-draw wiki consultant, the one who knows all about dark matter and Ceiphed variables? Well, that tells me something. There's an example of how mrsonde's snarky remarks can close down a discussion.
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CMB
Aug 1, 2016 22:57:45 GMT 1
Post by mrsonde on Aug 1, 2016 22:57:45 GMT 1
What "discussion"? There's yet another example of how Fascinating prefers to throw out insults rather than make any worthwhile contribution.
7-0, is it?
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CMB
Aug 1, 2016 23:55:56 GMT 1
Post by alancalverd on Aug 1, 2016 23:55:56 GMT 1
One hesitates to cast too many pearls before swine, partly for the reasons enumerated in Matthew 7:6 and partly because any mention of black bodies in this forum is likely to cause outrage.
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CMB
Aug 4, 2016 16:20:38 GMT 1
Post by mrsonde on Aug 4, 2016 16:20:38 GMT 1
You haven't got the first clue, in other words.
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CMB
Aug 4, 2016 19:28:03 GMT 1
Post by mrsonde on Aug 4, 2016 19:28:03 GMT 1
Look, as far as my understanding of current Physics theory goes, this is the best case that can be made for the CMB being evidence for the Big Bang. Since that alleged event, the universe has been expanding such that we are now moving, in relation to that point event, at very close to the speed of light. And so, we are now able to detect all around us, from every direction, the radiation emitted at that event. This is the claim - made by at least three authoritative authors, from my shelves, and a presumably well-edited account on Wiki.
Now, I've tried very hard to find a statement from these alleged authorities that specify how long this photon-decoupling flash lasted. It's a very brief event, as far as they're willing to stipulate. We first detected the CMB in the 1960s. Not a single one of these authorities claim that this "very brief" period lasted for 50 years!
You might be inclined to say, well, it's something to do with time dilation or what-not. A micro-second then, at the beginning of time, might stretch out for centuries. So, 13-14 billion years later, allegedly, we just happen to be at the right time to detect this event? I don't believe that's the claim at all, and I've never read anyone so stupid as to claim it. Also, it doesn't make sense, according to SR. If we're detecting the CMB now as passing us at the speed of light - as we must do, axiomatically - then why are we able to do this at just this particluar period of history, 13-14 billion years later? We wouldn't have done so in the Stone Age, or won't do sometime in the future, when it's all passed us by? Where are the calculations for this time period? Nowhere to be found.Where is the reasoning expounding the explanation routinely given to explain this bizarre coincidence? Nowhere to be found. It just so happens that we're moving at a speed that guarantees that we'll find this radiation from an event at the beginning of the universe, and the idea is we always will do and always would have done. We're moving at very very close to the speed of light, apparently, like a balloon being blown up (what a tiresome metaphor, how many times have you heard it?), and so of course we'll find it all around us. Forget Einstein, he was an idiot: absorb the populist metaphor.
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CMB
Aug 7, 2016 13:25:50 GMT 1
Post by alancalverd on Aug 7, 2016 13:25:50 GMT 1
I see nothing in the literature to suggest that the "recombination event" was a singular,universal, isotropic flash. Indeed it is difficult to see how it could have been, unless you believe in a god with powers that extend beyond physics.
Why could we not detect the CMB in the stone age? I suspect the absence of microwave spectrometers may have something to do with it, though even with such things, you need mavericks like Penzias and Wilson to waste Company time and money scraping pigeon shit out of the antenna.
You see, dear boy, that the universe was formed a very, very long time ago, and homo sapiens, even if he had been around since the year dot, has spent most of his pitiful existence just trying to exist.
And it isn't a onetime event. The universe seems to be cooling as it expands (there's classical physics for you!)and has just reached a mean intergalactic temperature of about 3 K. Next year it will be a tiny bit less and the CMB spectrum will have shifted appropriately (though not enough to measure). If it doesn't pass 2.5K in a few zillion years, we'll abandon the Big Bang theory and you can have your money back.
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CMB
Aug 11, 2016 19:16:51 GMT 1
Post by mrsonde on Aug 11, 2016 19:16:51 GMT 1
I see nothing in the literature to suggest that the "recombination event" was a singular,universal, isotropic flash. Indeed it is difficult to see how it could have been, unless you believe in a god with powers that extend beyond physics. It's usually called "the Big Bang". I too can find no one going on the line to claim how long this decoupling event was supposed to last. Hawking mentions a "dozen microseconds", but I suspect, as you clearly do, that he's making it up. I agree with you though, this has little to do with physics. Or God. The theory is we could have done, if we'd had the knowledge and equipment. It was there to detect - slightly warmer, that's all. Yes, well, get to the point please. That's the whole theory. "Seems" to whom? Who the f#@k is able to measure the temperature of the universe, ffs?! Give me a break. No, it isn't. No one from the time of classical physics would have had the nerve to make any such outlandish claim. No. That is not what the CBR is supposed to represent. No one makes any such claim. The claim is in the name. If it's not enough to measure, there's plainly no scientific sense in what you're claiming. It's unverifiable. Look - I posed a simple question, and you haven't even attempted to answer it. That tells me you don;t know where to begin. I'll repeat: why hasn't the light from the Big Bang long long ago passed us by? When at its emittance (I don't care how long it's supposed to have lasted - it sure as hell isn;t going on now!) the theory states that the universe was at little more than point-sized, and the speed of light was what it is now. Let's take the Stone Age, or whatever. Let's consider the light we're receiving now from then - some nearby galaxy or star, say. No, let's say a supernova - a new light source, produced sometime in the Stone Age, but only now being detected here, now. The CBR would have been detectable there, then, when this light was emitted, says the theory, just a little bit warmer. What we're detecting now when we look at this supernova is the light that it emitted, all those thousands of years ago, plus the light from the Big Bang, having passed that supernova star, arriving here at the same time. Right? Now, to repeat, my question is: why did that CBR light take so long to catch up with that star that went supernova in the Stone Age, thus arriving here at the same time? Please answer the question. Just science and reason, please - save the supercilious sarcasm for the friendly chatroom.
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CMB
Aug 11, 2016 20:50:58 GMT 1
Post by nickrr on Aug 11, 2016 20:50:58 GMT 1
I think that where you're going wrong is assuming that the light from the big bang originated from one point. Firstly, the CMB originated from a time about 380,000 years after the big bang when electrons combined with protons, helium nuclei etc to form atoms. As atoms are electrically neutral this allowed light to travel freely hence giving the CMB. This means that the CMB originated from every point in the universe. The radiation from the CMB we are now seeing is simply the radiation that was was emitted from points in space (actually a sphere in 3 dimensional space) that is just the right distance away from us such that that the radiation took around 13.3 billion years to reach us. The radiation that we see next year will have been emitted at points in space that form a sphere just slightly larger than this and so on.
Of course when the radiation was emitted the point in space we currently occupy was much closer to the points of emission than we are now because the universe was far smaller. It's taken so long to reach us because the expansion of the universe has created a lot of extra space for the radiation to travel through.
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CMB
Aug 12, 2016 10:44:20 GMT 1
Post by fascinating on Aug 12, 2016 10:44:20 GMT 1
I'm trying to think this through. In the past, when the CMB was emitted, the Universe was not 13.3 billion light years radius but, say, only a billion light years radius. If some radiaton was emitted a billion light years from us then, are you saying that, because the Universe added another 12.3 billion light years to its size, then that radiation had to cover that much more space? That implies that the Universe has been expanding close to the speed of light for all of that period (or it expanded for a while at much faster than the speed of light for maybe a short while, and more slowly for the rest of the time).
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CMB
Aug 12, 2016 18:32:41 GMT 1
Post by nickrr on Aug 12, 2016 18:32:41 GMT 1
You're quite correct that the universe as a whole was much smaller than it is now when the CMB was emitted and also that therefore this radiation has had to travel through more space as the universe has expanded. The points in space from which the CMB we are now seeing was emitted will indeed be travelling away from us at close to the speed of light. Actually, because it also appears that the expansion of the universe is accelerating it's possible that these areas might be moving away from us at greater than the speed of light (that's a guess on my part).
How fast a particular point in the universe is expanding away from us is directly proportional to how far away from us it is. So somewhere a certain distance from us will be receding at a certain speed, so something twice as far away will be receding at twice the speed, something half as far away will be travelling from us at half the speed etc. This means that there will be some parts of the universe that are moving away from us at faster than the speed of light. This means that we will never receive any radiation from these regions. In fact I believe that the prevailing view among cosmologists is that the vast majority of the universe is beyond this horizon so we will only ever be able to see a tiny proportion of the whole universe.
One point to note is that parts of the universe moving away at faster than the speed of light doesn't violate Einstein's "nothing can travel faster than light" principle because this only restricts travel of something through space, it doesn't limit the rate at which space itself can expand.
Hope this makes some sense!
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CMB
Aug 13, 2016 9:19:11 GMT 1
Post by alancalverd on Aug 13, 2016 9:19:11 GMT 1
I refer the honorable gentleman to the answer I gave on 1 August.
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CMB
Aug 13, 2016 19:04:45 GMT 1
Post by mrsonde on Aug 13, 2016 19:04:45 GMT 1
I think that where you're going wrong is assuming that the light from the big bang originated from one point. Firstly, the CMB originated from a time about 380,000 years after the big bang Hi again Nick. Thanks for your imput. I've never come across this figure before - it seems impressively precise, I must say. But okay, if that's what the theory says, let's take it at face value. Yes - a few microseconds or 380,000 years, amounts to the same thing doesn't it? Why is it only arriving here now? For how long was this continual emitting process supposed to have lasted? And are you saying that were we or some alien race able to detect the CBR at, say, 400,000 years ago, they wouldn;t have detected any such radiation? Yes - that's what I said the theory must imply. That we are travelling away from that origin at very very close to the speed of light. But, unfortunately, that is not the theory.
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CMB
Aug 14, 2016 12:23:15 GMT 1
Post by fascinating on Aug 14, 2016 12:23:15 GMT 1
So maybe the CMB is simply the radiation from the edge of the observable Universe, that is light from objects that are moving away from us, at just less than the speed of light, with the wavelength stretched out by the relative speed. There again, maybe not.
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