Get a clue. You don't know what you're talking about and are trying to act like you do. Who does that remind me of? You haven't read the 'actual' literature on this subject. It's obvious to me. Guth's Inflation [Eternal Inflation] has been replaced by a new hypothesis? Really? A host of assumptions? You're just making up bullshit. Your desire to be right exceeds your interest in the subject matter. So how do experiments based on a host of assumptions win awards?
At Rest with our Hubble view
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Get a clue. You don't know what you're talking about and are trying to act like you do. Who does that remind me of? You haven't read the 'actual' literature on this subject. It's obvious to me. Guth's Inflation [Eternal Inflation] has been replaced by a new hypothesis? Really? A host of assumptions? You're just making up bullshit. Your desire to be right exceeds your interest in the subject matter. So how do experiments based on a host of assumptions win awards?
Though About.com is not always a scholarly source for cut and paste, this comment does take us back to the problems that cosmologists had reconciling BBT before and after the discovery of inflation. General Relativity accommodates an eternal steady state universe just as well as it accommodates and expanding or a contracting universe.:
http://space.about.com/od/astronomybasics/a/Origin-Of-The-Universe.htm
Alternatives to the Big Bang Theory
"While the Big Bang theory is the most widely accepted theory about the origins of the Universe, and is supported by all the observational evidence, there are other models that explain the evidence equally well.
Some of the other theories argue that the Big Bang theory is based on a false premise -- that the Universe is built on an ever expanding space-time. Some, instead, prefer to build theories on a static Universe, which is what was originally predicted by Einstein’s theory of general relativity. Einstein’s theory was only later modified to accommodate the way the Universe appears to be expanding."
From a layman perspective I'm just trying to get my arms around a physical picture of the expanse of the universe when the CMB was released and transparency began. Am I correct to understand that the size of the big bang "arena" at that point in time was like some say, 40 billion light years across?
If that is correct, and if the radiation that was released and that makes up the CMB has expanded at the speed of light for 13 billion years, then at a minimum the size of the "arena" has increased by 26 billion light years, making it at least 66 billion light years across. Is that generally accepted or is there a link to a source that gets at what the size might be today?
http://space.about.com/od/astronomybasics/a/Origin-Of-The-Universe.htm
Alternatives to the Big Bang Theory
"While the Big Bang theory is the most widely accepted theory about the origins of the Universe, and is supported by all the observational evidence, there are other models that explain the evidence equally well.
Some of the other theories argue that the Big Bang theory is based on a false premise -- that the Universe is built on an ever expanding space-time. Some, instead, prefer to build theories on a static Universe, which is what was originally predicted by Einstein’s theory of general relativity. Einstein’s theory was only later modified to accommodate the way the Universe appears to be expanding."
From a layman perspective I'm just trying to get my arms around a physical picture of the expanse of the universe when the CMB was released and transparency began. Am I correct to understand that the size of the big bang "arena" at that point in time was like some say, 40 billion light years across?
If that is correct, and if the radiation that was released and that makes up the CMB has expanded at the speed of light for 13 billion years, then at a minimum the size of the "arena" has increased by 26 billion light years, making it at least 66 billion light years across. Is that generally accepted or is there a link to a source that gets at what the size might be today?
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Do you really think that Guth was the last word on inflationary theory?
The WMAP 5th year cosmological results cite two Guth papers; they are from 1981 and from 1982.
Why are you telling me to read the WMAP papers?
I'm something of an Einstein fan, but when I read him talking cosmology I find myself saying "Come on Albert! Believe in your own theory!" I think when you "get" general relativity and all the stuff about stress-energy and pressure, you come to the conclusion that the universe just has to expand. It can't do anything other than expand, and it can't contract,quantum-wave said:
I don't think so. That sounds way too big. But can you point me to something that backs that up?quantum-wave said:
No, that isn't generally accepted. What is, is that the CMB has been redshifted a thousandfold. That would mean the universe is a thousand times bigger than it was. The space that the light is travelling through is expanding.quantum-wave said:
Perhaps you should spend more time learning the mathematics of GR rather than ignoring it in favor of your imagined version? What Einstein meant with this theory, including stress-energy and its influence on geometry, is carefully expressed in that mathematics.
Of course, Einstein was well aware that his theory allowed for the contraction of space and one can find this not only in the details of his scientific theory but in his correspondence with other scientists.
You mean based on current observations of the redshift and the CMBR. But when Einstein published in 1915, he didn't know about the expansion as indicated by the redshift or about the CMBR. General Relativity accommodated a steady state as well as expansion and contraction, because Einstein did include a cosmological constant, and the value of that constant would determine the "shape" of the universe, i.e. "open", "flat", or "closed" as I understand it. We now think the universe is very slightly "open" because of the observations and data that show accelerating separation of the galaxies and galaxy groups.
The 40 billion light years was a discussion on a forum thread on the topic. No link right now but it isn't absurd is it? The discussion was about the size of the universe and the size of the visible horizon. Both are theory dependent but the 40 billion light years was supposed to be current theory. I am hoping to get some good source but what I do have is a link that mentions the size of the visible horizon http://www.pbs.org/wgbh/nova/space/how-big-universe.html
"This horizon describes the visible universe—a region some 28 billion light years in diameter. But what are the horizons of a civilization that inhabits the most distant galaxies we see? And what about galaxies at the limits of their vision? There is every reason to think that the universe extends a long way beyond the part of the universe we can see. In fact, a variety of observations suggest that our visible patch may be a small fraction—maybe an infinitely small fraction—of the whole universe."
My understanding from that is this: across that entire 28 billion light year expanse, the CMB has been inflowing for over 13 billion years. If we were about to reach the moment when the CMB radiation stopped flowing at the outer reaches, and it is certainly not likely, that would mean the current size of the big bang connected universe was 28 billion LY plus the distance that the light had traveled, excluding any stretching of space. That is then a minimum of the 28 billion plus an increase in the radius of more than 13 billion LY which makes the size a minimum of 54 billion light years.
If you are referring to the inflation which occurred in a fraction of the first second, it was not the source of the red-shifting of the CMB after the point it was "released" which wasn't for another 380,000 years after that.
Instead, the microsecond of inflation is necessary to get us to the point where the size of the big bang universe can accommodate the background that we observe. We have to acknowledge that at the point of recombination, the universe had to be large enough for the blackbody radiation to continue to come from all directions for as long as it seems to have been coming, i.e. more than 13 billion years, which equated to the minimum diameter of 54 billion years today, and you can add stretching to that.
No, I mean based on the energy-pressure diagonal in the stress-energy-momentum tensor along with "the energy of a gravitational field shall act gravitatively in the same way as any other kind of energy". It's like a gravitational field is a pressure-gradient in space. It alters the motion of light and bodies through space, it doesn't suck space in. So space doesn't contract, and when you smooth away pressure variations, it's still got its innate pressure, so it has to expand.
It was a kludge to balance a "dusty" universe against collapse because Einstein had a conviction that the universe was static.
The evidence from WMAP and the Planck mission indicates that the universe is flat. I think it's flat, and it's always been flat. Take a look at the FLRW metric which "starts with the assumption of homogeneity and isotropy of space". Now read Einstein's Leyden Address where he refers to a gravitational field as inhomogeneous space. If you have homogeneous space you have no gravitational fields at all. So light goes straight. It doesn't end up coming back round on itself.
The particle horizon is thought to be 46 billion light years away, see wiki, which means the observable universe is circa 93 billion light years across. However that isn't necessarily the size of the universe. We don't know how much of it we can see.
That's wrong. It's doubled up on the "light-travel distance". Whilst light has been travelling for circa 14 billion years the universe has been expanding.quantum_wave said:
We have no observations that suggest that our visible patch might be an infinitely small fraction of the whole universe.quantum_wave said:
The minimum diameter is 93 billion light years! I think you need to backtrack a bit on all this.quantum_wave said:
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This is one of Farsight's fantasies. He has been corrected about this on many, many message boards. He is not able to actually provide any mathematical details to defend his particular strange interpretation of Einstein, against as he admits Einstein's own interpretation, because he has admitted to never working through the mathematics of general relativity.
Again, another fantasy. Einstein's own cosmological models were homogeneous models.
It seems impossible that there would never be any CMB, unless we were to reach a point when it was so redshifted that it would be undetectable. Even in a finite universe, there will always be a light path through the CMB surface to any position in space.
Earlier in the thread I asked if everything in BBT before the opacity was lifted was theory and math. Your response is an example of why I asked. Einstein didn't know anything about the opacity or the lifting of it at the point of recombination. His equations were not based on any physical observations related to redshift or CMB. Correct me if I'm wrong, but you are interpreting the math as if it had to be explaining an expanding universe, and I am saying that though the equations accommodate expansion, they did not require it. The expansion factor comes in when you insert a positive cosmological constant.
True, and he considered it one of his biggest mistakes, but it proved to be ingenious
.Sometimes these threads get confused because we each offer what we think BBT with Inflation is telling us, and sometimes we offer what we think the so called real universe is doing based on new science and independent thinking.
I am trying to say what I think BBT with Inflation is saying. It is about the history of the universe as we know it now, including the measurements of the redshift and the CMBR. Prior to that new knowledge, there was what the 1915 General Relativity as published said. In that document there are the possibilities as defined by the EFEs back before redshift and CMB were known, which could have been applicable depending of if the unverse was expanding, contracting or steady state.
If I understand correctly, at the point in time that recombination occurred, the universe was a finite "oven" to use Eram's phrase. The oven door opened ~380 thousand years after the Big Bang according to current BBT with Inflation. Do you agree or not?
If that is what the theory says, then at that point in time the "oven" was of some physical size. The size would have be the measure of the amount of exponential Inflation at faster than the speed of light that occurred in the first second, plus the amount of expansion that occurred after the first microsecond of time. That would equate to the physical size of particle horizon when recombination occurred. The stars and galaxies formed after that point and when they formed they were all inside the particle horizon, looking out toward it so to speak, agreed?
Yes, if you refer to "expanding" as the physical motion of the galaxies and galaxy groups relative to each other. In BBT that includes the stretching of space, and so if recombination occurred at 380,000 years, the last 13 or so billion years featured space being added between galaxies plus any actual relative motion of the galaxies that formed in an expanding environment. Particles were all moving away from each other right from the point of recombination if I understand that piece of BBT.
True, the link I quoted added that but there is no evidence as to what portion our observable universe is of the whole.
Well, I can live with 93 billion LY, but I hope we can get on the same page in regard to what the standard cosmology now says, and what General Relativity as published by Einstein said. The time line of events since 1915 has brought changes which have been reflected in the current cosmological model.
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We don't seem to agree on this part. Maybe you would agree that the "oven" that Eram mentioned earlier was finite in size, and at the point of recombination, the opacity was lifted and the photon energy remnant from the Big Bang was released.
My understanding of that release was that it didn't matter where you were within the whole universe at the moment of release, photon energy of the CMB would have been observed to be coming at you from all directions because you were inside the dimensions of the "oven". But it was coming from somewhere within that finite space that the universe occupied at the moment of recombination. Do you agree with that?
If not, then we are not on the same page, but if so, then there was a source of inflowing radiation that would run out someday unless the "stretching of space" was occurring at the speed of light to offset the CMBR that passed your given point.
Perhaps we have different physical pictures of the BBT universe at the various points in time, and I could stand to be corrected.
The cosmological constant has an effect on expansion or collapse, but GR can include either without a cosmological constant. That's just how it works. Einstein introduced it for the purposes of having a model with no expansion or contraction.Earlier in the thread I asked if everything in BBT before the opacity was lifted was theory and math. Your response is an example of why I asked. Einstein didn't know anything about the opacity or the lifting of it at the point of recombination. His equations were not based on any physical observations related to redshift or CMB. Correct me if I'm wrong, but you are interpreting the math as if it had to be explaining an expanding universe, and I am saying that though the equations accommodate expansion, they did not require it. The expansion factor comes in when you insert a positive cosmological constant.
True, and he considered it one of his biggest mistakes, but it proved to be ingenious
The visible universe was finite. Whether or not the universe is infinite or not is unknown. From the attempts to determine whether or not there is any overlap in the CMB as we see it, it looks like the universe is big enough that whether or not it is finite is not currently relevant to the details of the CMB. I don't remember the papers, but I bet they're in the reference list of one of the WMAP papers.
Even in a finite GR universe, you cannot escape the universe. If you look in a direction, you look back in time and the light from the past came from the surface of recombination, as you're calling it.
The oven was, literally, everywhere. So, yes, the position that we occupy now was within that oven. But so is every position; there is nowhere to possibly be outside of it.
No, he didn't. But to be honest, I don't think they alter much. The opacity is a "mere detail".
I disagree. The cosmological constant was there to balance the gravitational collapse of dust within the universe. But space itself doesn't collapse due to this gravity. And yet Einstein inserted a cosmological constant. It's like huh?
It would have been more ingenious if Einstein had predicted the expanding universe.True, and he considered it one of his biggest mistakes, but it proved to be ingenious
No problem.
You've missed the trick. A gravitational field is like a pressure gradient in space. It affects the motion of light but it doesn't make space get smaller. The universe can't contract due to gravity.
I agree that the universe was finite, but not that it was some kind of oven with a door that opened.
Meh, I agree with some of it. Enough. Let's push on.
IMHO recombination is another "mere detail".
It's not easy, because it's all a bit of a mess. Einstein got stuck on his static universe, FLRW got stuck on open/closed/flat universes, many cosmologists claim the universe must be infinite because it's flat, others ignore conservation of energy when it comes to dark energy, others think lambda is absolutely constant, and so on. And then there's the Goldilocks multiverse guys and the holographic universe guys. It's chaos out there.
It's funny that you find that disturbing, but you still don't actually believe it when people tell you that you are wrong and you still don't bother to learn the physics.
It's funny that you know that you are disagreeing with your hero Einstein here, but you still don't actually believe it when people tell you that you are wrong and you still don't bother to learn the physics.
Yes, exactly. I've heard that the steady state was referred to as balancing a pencil on its end.
If you speak of the universe from the perspective of BBT, it started as a singularity which I equate to an infinitely dense zero volume point in space, and even after all of the expansion, it is still finite. Literally, we don't know that to be true, and if you consider other cosmological models, certainly there are those that can feature infinite space.
I would agree, and would also make a small point here. In BBT it is not a matter of whether or not it is finite; it is finite in BBT. Do you agree? Modifications that are not yet generally accepted into BBT might bring in the "infinite" as a possibility.
I'm not doubting it. Many possibilities have been and are being explored, and the current model evolves as science unfolds. But I think that the consensus is still the singularity and a finite universe.
True, but what I am doing is advancing the surface in a way that I think theory says it changes. It is of course not a fixed surface stuck as it was ~13 billion years ago. It has expanded and cooled to about 2.7K, and everything within the surface back then has experienced 13 billion years of history. Sure, when we look out, we are looking back in time, but we don't see anything but the most distant galaxies moving away from us and the CMB coming toward us. We cannot see the surface of the particle horizon yet, but I consider it to be where the last of the most distant galaxies are. Beyond that, but still within the big bang universe, I agree we can't see beyond that particle horizon, which means we can't see to the CMB horizon which has been expanding at the speed of light plus any stretching of space since the time when stars and galaxies were just forming. And we believe that it doesn't matter where you are today, it will look the same, i.e. the cosmological principle is in effect on a grand scale.
If there is an outlook edge to where galaxies cease to exist, there is still CMB out beyond that "sphere of galaxies", out to some finite distance, assuming the CMB has been expanding since the recombination.
True, but when the stars and galaxies were forming and separating, they were not separating at the speed of light, while the CMB that was released at that same time was expanding at the speed of light. Add stretching to that. There should be a "sphere of galaxies", and space free of galaxies beyond that, filled with both the original photon energy fromt he Big Bang, i.e. the CMB, and with the light emitted by that "sphere of galaxies", I would think.
Lol, mostly true when you put all of the science together. But the international scientific community has to have a consensus, and it has to keep advancing that consensus. It is a jumble of versions of what is the consensus and what is being considered as the new consensus, but we layman have the privilege of going by the popular media, and they are hesitant to call a change in consensus on their own.
I read a lot of papers, quantum_wave. I read a lot of popular media too, but I'm afraid a lot of that is woo. Have a read of Woit's blog.
Thanks for the blog link. I'm sure I will find a lot of interesting reading there. And yes to the popular media being a lot of Woo. I guess if we are going by the popular media to get our cosmology, we have to be able to cover a lot of ground and make a lot of decisions as to what is woo and what isn't. That is the fun of it to some degree. The rest of the layman fun is the discussions of our various takes on what the consensus is and isn't, and what we individually think of the consensus that we arrive at.
Agreed. I think the more ground you cover the better you get at spotting woo.
It's good to talk. And if we all agreed about everything life would be so dull. But talking of arriving at a consensus, take a look at that stress-energy tensor again. See that shear stress? Have you ever thought to ask: what's that doing there?quantum_wave said:
Lol, I'm not embarrassed to say I hadn't singled that out for contemplation. I think you are finding some of the fine points that I would certainly miss when looking at the field equations. What I get out of it is that classical equations focused on matter density (the mass), and the spacetime equations focus on energy density of both matter and space.
My layman view is that the difference is GR attributes energy density to the space occupied by matter and the space surrounding matter. If that is anywhere near correct, then spacetime is curved relative to all of the energy density in it. Further, any volume of space has spacetime curvature relative to the energy density in that particular volume. Therefore, the curvature that affects any point in space is the net of all of the energy density surrounding it as metred by the EFEs for that particular point in space. That is why the EFEs are difficult to work with and the classical equations are pretty sufficient for non-relativistic circumstances.