|
|
Thread Tools | Display Modes |
#11
|
|||
|
|||
A quasar, too heavy to be true
[[Mod. note -- I apologise for the delay in processing this article.
It arrived in my moderation queue on 2017-12-18, just before an extended power/internet outage at my location. -- jt]] Le 17/12/2017 eM- 21:18, Phillip Helbig (undress to reply) a ecrit: In article , jacob navia writes: 1) At z = 1000 we have a temperature of 2,728 degrees... Completely new and unknown processes must have been at work to form structures like a black hole at those temperatures. Perhaps different than for stellar-mass black holes, but not necessarily completely new and unknown. Not necessarily, those mysterious processes created "out of some random fluctuation" made those seeds and that quasar comes into being just a few hundred million years later. OK. Note that quasars come in huge galaxies. A survey based on on the SDSS, was done by Matsuoka et al (https://arxiv.org/abs/1312.2417). He looked at stripe 82 and all quasars inside it were in galaxies more than 10E10 sun masses. [[Mod. note -- I think there's an observational selection effect he The very first paragraph of that abstract refers to "optically luminous" quasars. We believe that fainter quasars exist, but if (as we expect) these are hosted in smaller/fainter galaxies, they will be hard(er) to observe. -- jt]] All that in about 450 My. And nothing less than a black hole of 1E4 solar masses. It seems (to me) impossible that gravity can condense something at those temperatures. Then read up on your physics. Yes, let's do that. Primordial black holes were a speculation within big bang theory that was never observed. I would like to remember your own words in this discussion group when discussing with Mr Oldershaw when you argued against the black holes he proposed. Observations rule out the existence of many small black holes because they would bend light and that wasn't observed. That is what you said. Now you propose that big black holes were created somehow from the "start". They would become the nucleous of future galaxies. Of course "some random fluctuation" could create anything, including a very convenient "seed" to grow up a huge galaxy in no time. I just find that unlikely. 2) At z = 40 we have a temperature of 112 K. Star formation happens in clouds with temperatures between 10 to 20 K. Yes, 112 K is not "searing hot", but hot enough to make star formation impossible. Not all black holes must form from stars. Yes, they could form by accretion. So just 40 million black holes of 20 solar masses each in average would create that monster one in around 500 My. And those weren't created out of stars any more, (there is no time nor conditions to do that) but they just existed somehow. It makes one of those (20 solar masses each!) accretting to the black hole each month for 500 million years. Black hole mergers release an incredibly amount of energy, so how anything could survive in an environment where those events happen every month is a mystery. A consequence of that is that there isn't any host galaxy, blown away by those explosions each month... [[Mod. note -- 1. The standard scenario is that the first generation of stars to form ("population III" is the somewhat-confusing standard term) tended to be fairly massive, so their lives were perhaps 1-3 million years before producing supernovae and ~10 solar-mass black holes. These are the "seeds black holes" under discussion (which could then grow by accretion and/or mergers). 2. BH mergers do indeed release a lot of energy... but they release it as gravitational waves, which propagate outwards and have only a minute effect on the host galaxy. -- jt]] To me, all that sounds very unlikely. 3) If we assume that star formation could happen at 50 K, i.e. at z = 17, approx 228 My after the bang, that leaves 690 - 228 --462 My to form a black hole that has an 800 Msun mass... Not all black holes must form from stars. I am not saying that BB theory is impossible. I am just saying that explaining observations within that framework becomes more and more difficult, requiring more and more "ad hoc" hypothesis (now we have primordial black holes) Primordial black holes are neither an ad-hoc hypothesis nor were they thought of first to explain this observation. Do a literature search for "primordial black holes". Yes, it is instructive. A literature search confirms that quasars live in big galaxies. and requiring explanations that look less and less probable. By which measure? Look at this discussion. You add hypothesis after hypothesis. These black holes, the acceleration of black hole condensation, the acceleration of galaxy formation... And observations that contradict the bang start coming almost daily now. ALMA has seen a galactic collision at 780 My and the two galaxies are very dusty and huge... I will post another article about that. You have been claiming this for years, but have never come up with anything which convincingly contradicts the big bang. True, this was clear to me several years ago. And now those ideas are being confirmed. The more time passes, the more unlikely the whole bb theory becomes. Now, if we follow bare observations. We have a galaxy, at least 1E10 solar masses and ours is 1E12 solar masses, a factor of 100. Our galaxy is around 14 billion years old (the age of its oldest star, just around the corner, a few dozen light years away), so 14E9 / 100 -- that galaxy could by around 1400 Mys old. So, the universe must be *AT LEAST* 15Gy old. Host galaxies of quasars are very difficult to see. The survey mentioned above has around 1000 points, somehow a good sample, but still not very precise. Also, there is no reason to suppose a linear relationship between time and size... Old galaxies could be small also, but if they host a quasar, I suppose they should be big. And to build big things you need time. A test of your hypothesis would be to observe that galaxy for a month to see if it emits a GRB... |
#12
|
|||
|
|||
A quasar, too heavy to be true
In article , Gary
Harnagel writes: Well, maybe no outright contradicting the BB, but it doesn't agree with the experimental evidence without inflation: The Big Bang means that the universe is expanding from a hotter, denser state. Don't move the goalposts by redefining "big bang". Even so, one can have both the big bang and inflation, which is what most cosmologists believe. "Inflation isn't falsifiable, it's falsified -- BICEP did a wonderful service by bringing all the Inflationists out of their shell, and giving them a black eye." - Roger Penrose Despite his substantial contributions, Penrose is now an outsider. "Even from the beginning, inflation looked like a kluge to me-- I rapidly formed the opinion that these guys were just making it up as they went along" -- Neil Turok Turok has his own axe to grind, with Steinhardt. Check it out. Do you think that it is more believable? And a "singularity" is certainly unphysical. It means the physics has broken down. It would seem that alternatives might exist: No-one believes that singularities actually exist. https://www.edge.org/conversation/pa...aul-steinhardt http://clearlyexplained.com/answers/membranetheory.html Where are the testable, falsifiable predictions which differ from other theories? |
#13
|
|||
|
|||
A quasar, too heavy to be true
In article , jacobnavia
writes: Not necessarily, those mysterious processes created "out of some random fluctuation" made those seeds and that quasar comes into being just a few hundred million years later. What is mysterious? Why the scare quotes? Both are indications that you are not convinced of your own arguments, otherwise such rhetorical devices would not be necessary. And nothing less than a black hole of 1E4 solar masses. It seems (to me) impossible that gravity can condense something at those temperatures. Then read up on your physics. Yes, let's do that. Primordial black holes were a speculation within big bang theory that was never observed. What is the difference between a speculation, a hypothesis, and a theory? One reason people don't take your arguments seriously is that you argue rhetorically, not scientifically. I would like to remember your own words in this discussion group when discussing with Mr Oldershaw when you argued against the black holes he proposed. In a completely different mass range. Observations rule out the existence of many small black holes because they would bend light and that wasn't observed. That is what you said. Yes, in the mass range Oldershaw proposed (within a couple of orders of magnitude of a solar mass. Now you propose that big black holes were created somehow from the "start". They would become the nucleous of future galaxies. It is not my proposal, but an idea with a long history in the literature, and is not an ad-hoc hypothesis. Of course "some random fluctuation" could create anything, including a very convenient "seed" to grow up a huge galaxy in no time. I just find that unlikely. "Just finding" is not science. |
#14
|
|||
|
|||
A quasar, too heavy to be true
On Thursday, December 21, 2017 at 5:18:17 PM UTC-7, Phillip Helbig (undress to reply) wrote:
In article , Gary Harnagel writes: Well, maybe no outright contradicting the BB, but it doesn't agree with the experimental evidence without inflation: The Big Bang means that the universe is expanding from a hotter, denser state. Don't move the goalposts by redefining "big bang". Even so, one can have both the big bang and inflation, which is what most cosmologists believe. "Inflation isn't falsifiable, it's falsified -- BICEP did a wonderful service by bringing all the Inflationists out of their shell, and giving them a black eye." - Roger Penrose Despite his substantial contributions, Penrose is now an outsider. So the inflationists voted on physics? "Even from the beginning, inflation looked like a kluge to me-- I rapidly formed the opinion that these guys were just making it up as they went along" -- Neil Turok Turok has his own axe to grind, with Steinhardt. Check it out. Do you think that it is more believable? Sure they have their own ax to grind. So did Lemaitre. So does Hawking. Is there anything to the claim made at the end of "Theory of Everything" that Hawking is now trying to refute that time had a beginning? And a "singularity" is certainly unphysical. It means the physics has broken down. It would seem that alternatives might exist: No-one believes that singularities actually exist. Of course not, but they still exist in the mathematics used to describe the BB and are still discussed glibly. https://www.edge.org/conversation/pa...aul-steinhardt http://clearlyexplained.com/answers/membranetheory.html Where are the testable, falsifiable predictions which differ from other theories? It will come. And it's funny that mathematics with singularities is used to validate predictions, no? |
#15
|
|||
|
|||
A quasar, too heavy to be true
In article , Gary
Harnagel writes: "Inflation isn't falsifiable, it's falsified -- BICEP did a wonderful service by bringing all the Inflationists out of their shell, and giving them a black eye." - Roger Penrose Despite his substantial contributions, Penrose is now an outsider. So the inflationists voted on physics? I'm not sure what you mean here. Of course, science is not a democracy; the majority can be wrong. However, there is a consensus that inflation probably happened and that Penrose is probably wrong on this point. In any case, there is debate, and the issue is not solved by quoting arguments from only one side (especially the minority). "Even from the beginning, inflation looked like a kluge to me-- I rapidly formed the opinion that these guys were just making it up as they went along" -- Neil Turok Turok has his own axe to grind, with Steinhardt. Check it out. Do you think that it is more believable? Sure they have their own ax to grind. So did Lemaitre. So does Hawking. The point is that the quote makes it sound like they have some independent evidence against inflation, whereas in fact they are touting their own alternative theory. As for Lemaitre, he had a hypothesis which went beyond what was known at the time; it was not a rival to another hypothesis attempting to explain the same thing. Is there anything to the claim made at the end of "Theory of Everything" that Hawking is now trying to refute that time had a beginning? Whether or not time had a beginning does not alter the fact that we can trace the evolution of the universe back to a time when it was very hot and very dense. By convention, the time at which it had infinite density according to a naive extrapolation (which no-one believes accurately describes the very early universe) is known as the big bang. And it's funny that mathematics with singularities is used to validate predictions, no? No, because they are not used to validate predictions in the regime with singularities. I can navigate fine with latitude and longitude as long as I am not at the north or south pole. |
#16
|
|||
|
|||
A quasar, too heavy to be true
On Saturday, December 23, 2017 at 8:30:10 AM UTC-7, Phillip Helbig (undress to reply) wrote:
In article , Gary Harnagel writes: "Inflation isn't falsifiable, it's falsified -- BICEP did a wonderful service by bringing all the Inflationists out of their shell, and giving them a black eye." - Roger Penrose Despite his substantial contributions, Penrose is now an outsider. So the inflationists voted on physics? I'm not sure what you mean here. Of course, science is not a democracy; the majority can be wrong. However, there is a consensus that inflation probably happened and that Penrose is probably wrong on this point. In any case, there is debate, and the issue is not solved by quoting arguments from only one side (especially the minority). The "arguments" from the "other side" are taken as FACT: https://www.space.com/52-the-expandi...-to-today.html "The universe was born with the Big Bang as an unimaginably hot, dense point. When the universe was just 10-34 of a second or so old -- that is, a hundredth of a billionth of a trillionth of a trillionth of a second in age -- it experienced an incredible burst of expansion known as inflation, in which space itself expanded faster than the speed of light." The only argument I see FOR inflation is the uniformity of the CMBR. Steinhardt has another take on it. "Even from the beginning, inflation looked like a kluge to me-- I rapidly formed the opinion that these guys were just making it up as they went along" -- Neil Turok Turok has his own axe to grind, with Steinhardt. Check it out. Do you think that it is more believable? Sure they have their own ax to grind. So did Lemaitre. So does Hawking. The point is that the quote makes it sound like they have some independent evidence against inflation, whereas in fact they are touting their own alternative theory. Sure. It's another way to explain a conundrum: How the heck did the CMBR get so uniform? I think it's a good thing to have alternate theories. It keeps one's mind loosened up and not moribund. As for Lemaitre, he had a hypothesis which went beyond what was known at the time; it was not a rival to another hypothesis attempting to explain the same thing. So he was a smart guy and found a way to propose a theory consistent with both GR and his religion. Is there anything to the claim made at the end of "Theory of Everything" that Hawking is now trying to refute that time had a beginning? Whether or not time had a beginning does not alter the fact that we can trace the evolution of the universe back to a time when it was very hot and very dense. Sure, but not so dense that collapse is inevitable. And it doesn't matter that quantum effects "may" prevent a singularity. It's unlikely that they can be responsible for an expansion. It seems to me that expansion is possible only if the initial size/mass is great enough (i.e., greater than the Schwarzschild radius. Note that a mass with density only that of water and with a radius out to the asteroid belt would form a black hole from which nothing could escape. There are various estimates for the mass of the universe: http://hypertextbook.com/facts/2006/...cPherson.shtml varying from 1e50 to 1e60 kg (I'm ignoring the entry that proposes infinity). For the mass range indicated, the Schw. radius varies from 16000 to 160 trillion light-years, it being 1.6 billion light-years for M = 1e55 kg. By convention, the time at which it had infinite density according to a naive extrapolation (which no-one believes accurately describes the very early universe) is known as the big bang. So what do you think obviates infinite density? More importantly, what prevents all the initial matter from being inside the Schw. radius? And it's funny that mathematics with singularities is used to validate predictions, no? No, because they are not used to validate predictions in the regime with singularities. I can navigate fine with latitude and longitude as long as I am not at the north or south pole. There is no new physics at the poles. You just need a different math. In the case of cosmology, are you hoping for a new mathematics or a new physics? Steinhardt's theory proposes a new physics, but he needs a new mathematics to make predictions to validate his theory. A question I've had: How can the CMBR be light from the BB? Shouldn't that light have passed us long, long ago? [[Mod. note -- That's a FAQ. See, for example http://www.askamathematician.com/201...ady-passed-us/ https://www.quora.com/Why-is-the-cos...d-still-around -- jt]] |
#17
|
|||
|
|||
A quasar, too heavy to be true
In article , Gary
Harnagel writes: The "arguments" from the "other side" are taken as FACT: https://www.space.com/52-the-expandi...-bang-to-toda= y.html space.com is hardly the best place to see what scientists really believe. "The universe was born with the Big Bang as an unimaginably hot, dense po= int. When the universe was just 10-34 of a second or so old -- that is, a hund= redth of a billionth of a trillionth of a trillionth of a second in age -- it experienced an incredible burst of expansion known as inflation, in which space itself expanded faster than the speed of light." Yes, this is the standard idea. The only argument I see FOR inflation is the uniformity of the CMBR. The fact that the CMB power spectrum looks like what one would predict from amplified quantum fluctuations is another good argument. ANY good theory has to explain the uniformity of the CMB. Steinhardt has another take on it. That's fine. The way forward is to propose experiments which will distinguish between hypotheses. As for Lemaitre, he had a hypothesis which went beyond what was known at the time; it was not a rival to another hypothesis attempting to explain the same thing. So he was a smart guy and found a way to propose a theory consistent with both GR and his religion. Yes, Lema=EEtre was a priest, but the idea that he favoured the big bang since it is consistent with his theology goes against all we know about him. Sure, but not so dense that collapse is inevitable. And it doesn't matte= r that quantum effects "may" prevent a singularity. It's unlikely that the= y can be responsible for an expansion. Who said that they are? It seems to me that expansion is possible only if the initial size/mass is great enough (i.e., greater tha= n the Schwarzschild radius. The Schwarzschild radius is not applicable here; it is applicable in static asymptotically flat space-times. Note that a mass with density only that of water and with a radius out to the asteroid belt would form a black hole from which nothing could escape= .. There are various estimates for the mass of the universe: http://hypertextbook.com/facts/2006/...cPherson.shtml varying from 1e50 to 1e60 kg (I'm ignoring the entry that proposes infini= ty). For the mass range indicated, the Schw. radius varies from 16000 to 160 trillion light-years, it being 1.6 billion light-years for M = 1e55 kg. Don't be confused by dimensional analysis; the universe is not a black hole, even if it is dense enough. So what do you think obviates infinite density? The answer will be given by a theory of quantum gravity. Do you have one? There is no new physics at the poles. You just need a different math. In the case of cosmology, are you hoping for a new mathematics or a new physics? Steinhardt's theory proposes a new physics, but he needs a new mathematics to make predictions to validate his theory. He needs falsifiable predictions to which can differentiate his theory from others. |
#18
|
|||
|
|||
A quasar, too heavy to be true
On Monday, December 25, 2017 at 1:20:57 PM UTC-7, Phillip Helbig (undress to reply) wrote:
In article , Gary Harnagel writes: The "arguments" from the "other side" are taken as FACT: https://www.space.com/52-the-expandi...-to-today.html space.com is hardly the best place to see what scientists really believe. "The universe was born with the Big Bang as an unimaginably hot, dense point. When the universe was just 10-34 of a second or so old -- that is, a hundredth of a billionth of a trillionth of a trillionth of a second in age -- it experienced an incredible burst of expansion known as inflation, in which space itself expanded faster than the speed of light." Yes, this is the standard idea. Which came from space.com, so I don't understand your snide comment. The only argument I see FOR inflation is the uniformity of the CMBR. The fact that the CMB power spectrum looks like what one would predict from amplified quantum fluctuations is another good argument. ANY good theory has to explain the uniformity of the CMB. Steinhardt's idea is one BIG quantum fluctuation. Steinhardt has another take on it. That's fine. The way forward is to propose experiments which will distinguish between hypotheses. It's hard to propose experiments for something SO big. What Steinhardt needs are some little predictions, though. As for Lemaitre, he had a hypothesis which went beyond what was known at the time; it was not a rival to another hypothesis attempting to explain the same thing. So he was a smart guy and found a way to propose a theory consistent with both GR and his religion. Yes, Lema=EEtre was a priest, but the idea that he favoured the big bang since it is consistent with his theology goes against all we know about him. You think his belief system had NOTHING to do with it? Each of us has our own model of the universe that we have developed over our lives. I have mine and you have yours ... and Lemaitre had his. Sure, but not so dense that collapse is inevitable. And it doesn't matter that quantum effects "may" prevent a singularity. It's unlikely that they can be responsible for an expansion. Who said that they are? I think we'll have to look outside our universe for the that, but it COULD be quantum effects (brane theory is a quantum theory). It seems to me that expansion is possible only if the initial size/mass is great enough (i.e., greater than the Schwarzschild radius. The Schwarzschild radius is not applicable here; it is applicable in static asymptotically flat space-times. It seems to be quite close to that now. Why propose that it was different in a past that we can't detect? Note that a mass with density only that of water and with a radius out to the asteroid belt would form a black hole from which nothing could escape. There are various estimates for the mass of the universe: http://hypertextbook.com/facts/2006/...cPherson.shtml varying from 1e50 to 1e60 kg (I'm ignoring the entry that proposes infinity). For the mass range indicated, the Schw. radius varies from 16000 to 160 trillion light-years, it being 1.6 billion light-years for M = 1e55 kg. Don't be confused by dimensional analysis; That's NOT "dimensional analysis." You might repeat your claim that the Schwarzschild model doesn't apply. the universe is not a black hole, even if it is dense enough. How do you know this? So what do you think obviates infinite density? The answer will be given by a theory of quantum gravity. Do you have one? Not me! :-) There is no new physics at the poles. You just need a different math. In the case of cosmology, are you hoping for a new mathematics or a new physics? Steinhardt's theory proposes a new physics, but he needs a new mathematics to make predictions to validate his theory. He needs falsifiable predictions to which can differentiate his theory from others. Indeed. There are quantum gravity theories that equate to GR in the weak field. String theory is one of them. But perhaps they'll only get differentiation under conditions we can never find without our own black hole to play with. |
#19
|
|||
|
|||
A quasar, too heavy to be true
In article , Gary
Harnagel writes: The "arguments" from the "other side" are taken as FACT: https://www.space.com/52-the-expandi...-big-bang-to-= today.html space.com is hardly the best place to see what scientists really believe. "The universe was born with the Big Bang as an unimaginably hot, dens= e point. When the universe was just 10-34 of a second or so old -- tha= t is, a hundredth of a billionth of a trillionth of a trillionth of a second in age -- it experienced an incredible burst of expansion know= n as inflation, in which space itself expanded faster than the speed of light." Yes, this is the standard idea. Which came from space.com, so I don't understand your snide comment. space.com is basically an internet newspaper. Some things they write are formally correct, some are not. At best, you could argue that space.com takes the standard scenario as "fact" instead of "hypothesis". It's hard to propose experiments for something SO big. What Steinhardt needs are some little predictions, though. Indeed. As for Lemaitre, he had a hypothesis which went beyond what was known at the time; it was not a rival to= another hypothesis attempting to explain the same thing. So he was a smart guy and found a way to propose a theory consistent = with both GR and his religion. Yes, Lema=EEtre was a priest, but the idea that he favoured the big ban= g since it is consistent with his theology goes against all we know about= him. You think his belief system had NOTHING to do with it? Each of us has ou= r own model of the universe that we have developed over our lives. I have mine and you have yours ... and Lemaitre had his. Yes, he was a priest, but, unlike some other scientists who are Christian (i.e., Christian scientists, not necessarily Christian Scientists), such as Don Page, he managed to keep the two areas separate. The Big Bang really has little to do with the biblical creation story, apart from the fact that in both the universe is not infinitely old. This is a superficial similarity. Sure, but not so dense that collapse is inevitable. And it doesn't matter that quantum effects "may" prevent a singularity. It's unlike= ly that they can be responsible for an expansion. Who said that they are? I think we'll have to look outside our universe for the that, but it COUL= D be quantum effects (brane theory is a quantum theory). I meant "Who said that they are responsible for expansion?" It seems to me that expansion is possible only if the initial size/ma= ss is great enough (i.e., greater than the Schwarzschild radius. The Schwarzschild radius is not applicable here; it is applicable in static asymptotically flat space-times. It seems to be quite close to that now. Why propose that it was differen= t in a past that we can't detect? Because the Schwarzschild radius, as I already mentioned, applies in an asymptotically flat spacetime. That does not describe the universe. Note that a mass with density only that of water and with a radius ou= t to the asteroid belt would form a black hole from which nothing could escape. There are various estimates for the mass of the universe: http://hypertextbook.com/facts/2006/...cPherson.shtml varying from 1e50 to 1e60 kg (I'm ignoring the entry that proposes infinity). For the mass range indicated, the Schw. radius varies from 16000 to 1= 60 trillion light-years, it being 1.6 billion light-years for M = 1e55= kg. Don't be confused by dimensional analysis; That's NOT "dimensional analysis." You might repeat your claim that the Schwarzschild model doesn't apply. The mass and radius of a spatially closed universe correspond to those of a black hole, basically because of "dimensional analysis", not because the universe is a black hole. the universe is not a black hole, even if it is dense enough. How do you know this? Maybe the moderator can insert some standard text here. Basically, a black hole is a region WITHIN space(time). [[Mod. note -- Ok. This is basically a question of what we mean by the phrase "black hole". The standard definition is that it's a region from which light rays can't escape to "far away" (from the black hole region). Among other things, this definition relies on their being a set of events (points in spacetime) that we're willing to call "far away" (from the black hole(s)). But there's no meaningful way to say that some points in spacetime are "far away" from the entire universe. So, there's no meaningful way to even ask the question "is the universe a black hole". -- jt]] Indeed. There are quantum gravity theories that equate to GR in the weak field. String theory is one of them. Also a problem of a lack of testable predictions. |
#20
|
|||
|
|||
A quasar, too heavy to be true
On Tuesday, December 26, 2017 at 11:40:23 AM UTC-7, Phillip Helbig (undress to reply) wrote:
In article , Gary Harnagel writes: Which came from space.com, so I don't understand your snide comment. space.com is basically an internet newspaper. Some things they write are formally correct, some are not. At best, you could argue that space.com takes the standard scenario as "fact" instead of "hypothesis". It's hard to propose experiments for something SO big. What Steinhardt needs are some little predictions, though. Indeed. You think his belief system had NOTHING to do with it? Each of us has our own model of the universe that we have developed over our lives. I have mine and you have yours ... and Lemaitre had his. Yes, he was a priest, but, unlike some other scientists who are Christian (i.e., Christian scientists, not necessarily Christian Scientists), such as Don Page, he managed to keep the two areas separate. I didn't realize that about Don Page, or much about him at all. From this little treatise: http://www.preposterousuniverse.com/...and-cosmology/ One Bob Zannelli responded, "Don Page is a first rate cosmologist, and a very nice guy to boot. He is scrupulously honest and while I reject his evangelical Christianity I have great respect for him." I don't understand your denigration of him. [[Mod. note -- For an overview of Don Page's work, see http://arxiv.org:443/find/astro-ph/1.../0/1/0/all/0/1 Note that just searching on "Page_D" produces a mixture of Don Page's work and those of a different person, Dany Page. -- jt]] The Big Bang really has little to do with the biblical creation story, apart from the fact that in both the universe is not infinitely old. Well, we can argue THAT sometime :-) I mean, it all depends upon the nature of God and the definition of the universe. This is a superficial similarity. I agree. Either can have a previous genesis depending .... I think we'll have to look outside our universe for the that, but it COULD be quantum effects (brane theory is a quantum theory). I meant "Who said that they are responsible for expansion?" If one posits extreme temperatures at the "beginning" then it seems that you're dealing with photons (or perhaps other relativistic particles), so expansion is inevitable. It seems to me that expansion is possible only if the initial size/mass is great enough (i.e., greater than the Schwarzschild radius. The Schwarzschild radius is not applicable here; it is applicable in static asymptotically flat space-times. It seems to be quite close to that now. Why propose that it was different in a past that we can't detect? Because the Schwarzschild radius, as I already mentioned, applies in an asymptotically flat spacetime. That does not describe the universe. Well, that flat claim of yours doesn't agree with observation: https://en.wikipedia.org/wiki/Flatness_problem Note that a mass with density only that of water and with a radius out to the asteroid belt would form a black hole from which nothing could escape. There are various estimates for the mass of the universe: http://hypertextbook.com/facts/2006/...cPherson.shtml varying from 1e50 to 1e60 kg (I'm ignoring the entry that proposes infinity). For the mass range indicated, the Schw. radius varies from 16000 to 160 trillion light-years, it being 1.6 billion light-years for M = 1e55 kg. Don't be confused by dimensional analysis; That's NOT "dimensional analysis." You might repeat your claim that the Schwarzschild model doesn't apply. The mass and radius of a spatially closed universe correspond to those of a black hole, basically because of "dimensional analysis", not because the universe is a black hole. You'll have to explain that in much more detail. I don't see (1 - 2*G*M/rc^2) as "dimensional analysis." the universe is not a black hole, even if it is dense enough. How do you know this? Maybe the moderator can insert some standard text here. Basically, a black hole is a region WITHIN space(time). [[Mod. note -- Ok. This is basically a question of what we mean by the phrase "black hole". The standard definition is that it's a region from which light rays can't escape to "far away" (from the black hole region). Among other things, this definition relies on their being a set of events (points in spacetime) that we're willing to call "far away" (from the black hole(s)). But there's no meaningful way to say that some points in spacetime are "far away" from the entire universe. So, there's no meaningful way to even ask the question "is the universe a black hole". -- jt]] Of course, this ASSUMES that the FLRW metric describes our universe. Since, as Don Page pointed out in the link given above, "We simply do not know whether or not our universe had a beginning." My belief system says that it didn't. And I reject the "bounce" model, too. IOW, "big bangs" happen repeatedly without bouncing. In such a universe (multiverse?) curvature is only a "local" phenomenon. Indeed. There are quantum gravity theories that equate to GR in the weak field. String theory is one of them. Also a problem of a lack of testable predictions. Sure, but there are hints that may lead to testable predictions. One is that gravity "leaks." Another is the possibility of "Alice" matter: https://en.wikipedia.org/wiki/Mirror_matter The weak interaction breaks parity. Why? Is it possible that not only does gravity leak, but parity does, too? Are dark matter and Alice matter the same thing? Beta decay is due to the weak interaction, and anomalies in the beta decay of several isotope species have been noted: https://arxiv.org/abs/0808.3283 Is dark matter in an adjacent brane? Is the weak interaction another way to probe adjacent branes? Perhaps the assertion that string theory can make no predictions is itself a belief system. |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Could Delta IV Heavy use the same technique as Falcon Heavy | Alan Erskine[_3_] | Space Shuttle | 1 | May 20th 11 07:56 AM |
Whoa, it can't be true, it can't be true, William Shatner knows,he'll protect us | LIBERATOR[_3_] | History | 2 | March 24th 09 05:28 PM |
Heavy H = Lots of Heavy Compounds | G=EMC^2 Glazier | Misc | 3 | November 12th 05 06:12 PM |
Since Boeing and LM are partnering 50/50 and Boeing already has Delta IV Heavy does that mean we'll never see the Atlas V Heavy? | D. Scott Ferrin | History | 5 | May 6th 05 05:34 PM |
Delta IV Heavy: Heavy Enough for Mars | Damon Hill | Policy | 1 | December 22nd 04 07:39 PM |