> If we're convinced it's finite in age, then it can't be infinite in spatial extent. AG
John K Clark
--
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Le lun. 13 janv. 2020 à 10:28, Alan Grayson <agrays...@gmail.com> a écrit :
On Monday, January 13, 2020 at 1:33:01 AM UTC-7, stathisp wrote:--On Mon, 13 Jan 2020 at 13:48, Alan Grayson <agrays...@gmail.com> wrote:
On Sunday, January 12, 2020 at 8:58:06 AM UTC-7, John Clark wrote:On Thu, Jan 2, 2020 at 2:30 AM Alan Grayson <agrays...@gmail.com> wrote:
> If we're convinced it's finite in age, then it can't be infinite in spatial extent. AGWe don't know for sure our universe is infinite in size and we'll never know for sure because we'll never be able to measure precisely zero curvature with no error at all, but we do know it's pretty damn flat, if it's curved it's so slight that a light beam would have to go at least 500 times as far as our telescopes can see for it to return where it started. So if you respect the empirical evidence for the Big Bang but the idea of a beginning of a infinitely sized universe makes you unhappy then the Multiverse idea offers you an obvious solution, you get an infinitely large infinitely old Multiverse but with the observable universe having a beginning and being only finitely large. However I understand the Multiverse makes you unhappy too. I fear you may be destined to be unhappy.By the way ... does the inverse also make you unhappy, something infinitely old but finite in spatial extent?John K ClarkAll the models pictorially represented, have the Universe beginning very small, and inflation is claimed to increase its size from, say, much smaller than a proton, to about the size of the Earth or Solar System in a few Planck intervals. If it begins small, or if you run the clock backward it becomes progressively smaller, how could it have started with infinite spatial extent? Don't you see something wrong with the model? AGThe model says that a subset of the universe starts small and gets bigger. This is not inconsistent with the whole universe starting and remaining infinite in spatial extent.Stathis PapaioannouI thought I made that clear; what I am calling "the universe" is precisely the SUBSET you refer to, which starts small and gets bigger. It is THAT SUBSET which cosmologists claim has infinite spatial extent, based on measurements. What you're calling "the whole universe" includes the underlying entity on which the BB started, and on which measurements CANNOT be made. It could be infinite in spatial extent, or is possibly an entity for which the concept of spatial extent might not exist. AGAs the bigbang is a singularity at the start... what prevents it to contain an infinite content in a zero/small volume, after all it's a singularity and we know only things after the big bang started ? and after inflation (which I understand is only space metric which inflate), there is still an infinite content.
--
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On Monday, January 13, 2020 at 2:38:57 AM UTC-7, Quentin Anciaux wrote:Le lun. 13 janv. 2020 à 10:28, Alan Grayson <agrays...@gmail.com> a écrit :
On Monday, January 13, 2020 at 1:33:01 AM UTC-7, stathisp wrote:--On Mon, 13 Jan 2020 at 13:48, Alan Grayson <agrays...@gmail.com> wrote:
On Sunday, January 12, 2020 at 8:58:06 AM UTC-7, John Clark wrote:On Thu, Jan 2, 2020 at 2:30 AM Alan Grayson <agrays...@gmail.com> wrote:
> If we're convinced it's finite in age, then it can't be infinite in spatial extent. AGWe don't know for sure our universe is infinite in size and we'll never know for sure because we'll never be able to measure precisely zero curvature with no error at all, but we do know it's pretty damn flat, if it's curved it's so slight that a light beam would have to go at least 500 times as far as our telescopes can see for it to return where it started. So if you respect the empirical evidence for the Big Bang but the idea of a beginning of a infinitely sized universe makes you unhappy then the Multiverse idea offers you an obvious solution, you get an infinitely large infinitely old Multiverse but with the observable universe having a beginning and being only finitely large. However I understand the Multiverse makes you unhappy too. I fear you may be destined to be unhappy.By the way ... does the inverse also make you unhappy, something infinitely old but finite in spatial extent?John K ClarkAll the models pictorially represented, have the Universe beginning very small, and inflation is claimed to increase its size from, say, much smaller than a proton, to about the size of the Earth or Solar System in a few Planck intervals. If it begins small, or if you run the clock backward it becomes progressively smaller, how could it have started with infinite spatial extent? Don't you see something wrong with the model? AGThe model says that a subset of the universe starts small and gets bigger. This is not inconsistent with the whole universe starting and remaining infinite in spatial extent.Stathis PapaioannouI thought I made that clear; what I am calling "the universe" is precisely the SUBSET you refer to, which starts small and gets bigger. It is THAT SUBSET which cosmologists claim has infinite spatial extent, based on measurements. What you're calling "the whole universe" includes the underlying entity on which the BB started, and on which measurements CANNOT be made. It could be infinite in spatial extent, or is possibly an entity for which the concept of spatial extent might not exist. AG
--As the bigbang is a singularity at the start... what prevents it to contain an infinite content in a zero/small volume, after all it's a singularity and we know only things after the big bang started ? and after inflation (which I understand is only space metric which inflate), there is still an infinite content.The BB is only a singularity as far as GR is concerned, because GR fails at that point in time. When we have a better theory, the alleged singularity at T = 0 will go away. What you call "infinite content in zero/ small volume" makes no sense, which is why we call this condition is called a singularity! How could the content be space, if you've have zero or small volume. This idea is immediately, and obviously, self contradictory. AG--
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Le lun. 13 janv. 2020 à 10:50, Alan Grayson <agrays...@gmail.com> a écrit :
On Monday, January 13, 2020 at 2:38:57 AM UTC-7, Quentin Anciaux wrote:Le lun. 13 janv. 2020 à 10:28, Alan Grayson <agrays...@gmail.com> a écrit :
On Monday, January 13, 2020 at 1:33:01 AM UTC-7, stathisp wrote:--On Mon, 13 Jan 2020 at 13:48, Alan Grayson <agrays...@gmail.com> wrote:
On Sunday, January 12, 2020 at 8:58:06 AM UTC-7, John Clark wrote:On Thu, Jan 2, 2020 at 2:30 AM Alan Grayson <agrays...@gmail.com> wrote:
> If we're convinced it's finite in age, then it can't be infinite in spatial extent. AGWe don't know for sure our universe is infinite in size and we'll never know for sure because we'll never be able to measure precisely zero curvature with no error at all, but we do know it's pretty damn flat, if it's curved it's so slight that a light beam would have to go at least 500 times as far as our telescopes can see for it to return where it started. So if you respect the empirical evidence for the Big Bang but the idea of a beginning of a infinitely sized universe makes you unhappy then the Multiverse idea offers you an obvious solution, you get an infinitely large infinitely old Multiverse but with the observable universe having a beginning and being only finitely large. However I understand the Multiverse makes you unhappy too. I fear you may be destined to be unhappy.By the way ... does the inverse also make you unhappy, something infinitely old but finite in spatial extent?John K ClarkAll the models pictorially represented, have the Universe beginning very small, and inflation is claimed to increase its size from, say, much smaller than a proton, to about the size of the Earth or Solar System in a few Planck intervals. If it begins small, or if you run the clock backward it becomes progressively smaller, how could it have started with infinite spatial extent? Don't you see something wrong with the model? AGThe model says that a subset of the universe starts small and gets bigger. This is not inconsistent with the whole universe starting and remaining infinite in spatial extent.Stathis PapaioannouI thought I made that clear; what I am calling "the universe" is precisely the SUBSET you refer to, which starts small and gets bigger. It is THAT SUBSET which cosmologists claim has infinite spatial extent, based on measurements. What you're calling "the whole universe" includes the underlying entity on which the BB started, and on which measurements CANNOT be made. It could be infinite in spatial extent, or is possibly an entity for which the concept of spatial extent might not exist. AGAnd so what do you see not contradictory in the existence of the universe itself ? Either it has always been, or not, and if not, that makes no sense. I see nothing contradictory to have something infinite, so it could always has been infinite in content, seeing it as zero volume is a mistake because that presuppose a volume in another space. What I'm saying is that there was infinite content (and still is) but all metrics (space) was of zero extends, and inflation extended the "space" not the content.
Anyway, in the end, there can't be an explanation which make sense. The fact we're here in the first place being able to ask question is magical.Quentin
--As the bigbang is a singularity at the start... what prevents it to contain an infinite content in a zero/small volume, after all it's a singularity and we know only things after the big bang started ? and after inflation (which I understand is only space metric which inflate), there is still an infinite content.The BB is only a singularity as far as GR is concerned, because GR fails at that point in time. When we have a better theory, the alleged singularity at T = 0 will go away. What you call "infinite content in zero/ small volume" makes no sense, which is why we call this condition is called a singularity! How could the content be space, if you've have zero or small volume. This idea is immediately, and obviously, self contradictory. AG--
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--All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)
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On Monday, January 13, 2020 at 2:54:48 AM UTC-7, Quentin Anciaux wrote:Le lun. 13 janv. 2020 à 10:50, Alan Grayson <agrays...@gmail.com> a écrit :
On Monday, January 13, 2020 at 2:38:57 AM UTC-7, Quentin Anciaux wrote:Le lun. 13 janv. 2020 à 10:28, Alan Grayson <agrays...@gmail.com> a écrit :
On Monday, January 13, 2020 at 1:33:01 AM UTC-7, stathisp wrote:--On Mon, 13 Jan 2020 at 13:48, Alan Grayson <agrays...@gmail.com> wrote:
On Sunday, January 12, 2020 at 8:58:06 AM UTC-7, John Clark wrote:On Thu, Jan 2, 2020 at 2:30 AM Alan Grayson <agrays...@gmail.com> wrote:
> If we're convinced it's finite in age, then it can't be infinite in spatial extent. AGWe don't know for sure our universe is infinite in size and we'll never know for sure because we'll never be able to measure precisely zero curvature with no error at all, but we do know it's pretty damn flat, if it's curved it's so slight that a light beam would have to go at least 500 times as far as our telescopes can see for it to return where it started. So if you respect the empirical evidence for the Big Bang but the idea of a beginning of a infinitely sized universe makes you unhappy then the Multiverse idea offers you an obvious solution, you get an infinitely large infinitely old Multiverse but with the observable universe having a beginning and being only finitely large. However I understand the Multiverse makes you unhappy too. I fear you may be destined to be unhappy.By the way ... does the inverse also make you unhappy, something infinitely old but finite in spatial extent?John K ClarkAll the models pictorially represented, have the Universe beginning very small, and inflation is claimed to increase its size from, say, much smaller than a proton, to about the size of the Earth or Solar System in a few Planck intervals. If it begins small, or if you run the clock backward it becomes progressively smaller, how could it have started with infinite spatial extent? Don't you see something wrong with the model? AGThe model says that a subset of the universe starts small and gets bigger. This is not inconsistent with the whole universe starting and remaining infinite in spatial extent.Stathis PapaioannouI thought I made that clear; what I am calling "the universe" is precisely the SUBSET you refer to, which starts small and gets bigger. It is THAT SUBSET which cosmologists claim has infinite spatial extent, based on measurements. What you're calling "the whole universe" includes the underlying entity on which the BB started, and on which measurements CANNOT be made. It could be infinite in spatial extent, or is possibly an entity for which the concept of spatial extent might not exist. AGAnd so what do you see not contradictory in the existence of the universe itself ? Either it has always been, or not, and if not, that makes no sense. I see nothing contradictory to have something infinite, so it could always has been infinite in content, seeing it as zero volume is a mistake because that presuppose a volume in another space. What I'm saying is that there was infinite content (and still is) but all metrics (space) was of zero extends, and inflation extended the "space" not the content.I don't think you understand the issue I've raised; namely, if our bubble has a finite age and is expanding, it must be finite in spatial extent since the expansion rate is finite. But a flat universe, claimed by most, maybe all cosmologists, is infinite in spatial extent. How could it start infinite in spatial extent, yet be tiny in the beginning? I conclude that our universe, that is, our bubble (which doesn't include the substratum from which it arose), must be spherical and closed. AG
--Anyway, in the end, there can't be an explanation which make sense. The fact we're here in the first place being able to ask question is magical.Quentin--As the bigbang is a singularity at the start... what prevents it to contain an infinite content in a zero/small volume, after all it's a singularity and we know only things after the big bang started ? and after inflation (which I understand is only space metric which inflate), there is still an infinite content.The BB is only a singularity as far as GR is concerned, because GR fails at that point in time. When we have a better theory, the alleged singularity at T = 0 will go away. What you call "infinite content in zero/ small volume" makes no sense, which is why we call this condition is called a singularity! How could the content be space, if you've have zero or small volume. This idea is immediately, and obviously, self contradictory. AG--
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Le lun. 13 janv. 2020 à 11:10, Alan Grayson <agrays...@gmail.com> a écrit :
On Monday, January 13, 2020 at 2:54:48 AM UTC-7, Quentin Anciaux wrote:Le lun. 13 janv. 2020 à 10:50, Alan Grayson <agrays...@gmail.com> a écrit :
On Monday, January 13, 2020 at 2:38:57 AM UTC-7, Quentin Anciaux wrote:Le lun. 13 janv. 2020 à 10:28, Alan Grayson <agrays...@gmail.com> a écrit :
On Monday, January 13, 2020 at 1:33:01 AM UTC-7, stathisp wrote:--On Mon, 13 Jan 2020 at 13:48, Alan Grayson <agrays...@gmail.com> wrote:
On Sunday, January 12, 2020 at 8:58:06 AM UTC-7, John Clark wrote:On Thu, Jan 2, 2020 at 2:30 AM Alan Grayson <agrays...@gmail.com> wrote:
> If we're convinced it's finite in age, then it can't be infinite in spatial extent. AGWe don't know for sure our universe is infinite in size and we'll never know for sure because we'll never be able to measure precisely zero curvature with no error at all, but we do know it's pretty damn flat, if it's curved it's so slight that a light beam would have to go at least 500 times as far as our telescopes can see for it to return where it started. So if you respect the empirical evidence for the Big Bang but the idea of a beginning of a infinitely sized universe makes you unhappy then the Multiverse idea offers you an obvious solution, you get an infinitely large infinitely old Multiverse but with the observable universe having a beginning and being only finitely large. However I understand the Multiverse makes you unhappy too. I fear you may be destined to be unhappy.By the way ... does the inverse also make you unhappy, something infinitely old but finite in spatial extent?John K ClarkAll the models pictorially represented, have the Universe beginning very small, and inflation is claimed to increase its size from, say, much smaller than a proton, to about the size of the Earth or Solar System in a few Planck intervals. If it begins small, or if you run the clock backward it becomes progressively smaller, how could it have started with infinite spatial extent? Don't you see something wrong with the model? AGThe model says that a subset of the universe starts small and gets bigger. This is not inconsistent with the whole universe starting and remaining infinite in spatial extent.Stathis PapaioannouI thought I made that clear; what I am calling "the universe" is precisely the SUBSET you refer to, which starts small and gets bigger. It is THAT SUBSET which cosmologists claim has infinite spatial extent, based on measurements. What you're calling "the whole universe" includes the underlying entity on which the BB started, and on which measurements CANNOT be made. It could be infinite in spatial extent, or is possibly an entity for which the concept of spatial extent might not exist. AGAnd so what do you see not contradictory in the existence of the universe itself ? Either it has always been, or not, and if not, that makes no sense. I see nothing contradictory to have something infinite, so it could always has been infinite in content, seeing it as zero volume is a mistake because that presuppose a volume in another space. What I'm saying is that there was infinite content (and still is) but all metrics (space) was of zero extends, and inflation extended the "space" not the content.I don't think you understand the issue I've raised; namely, if our bubble has a finite age and is expanding, it must be finite in spatial extent since the expansion rate is finite. But a flat universe, claimed by most, maybe all cosmologists, is infinite in spatial extent. How could it start infinite in spatial extent, yet be tiny in the beginning? I conclude that our universe, that is, our bubble (which doesn't include the substratum from which it arose), must be spherical and closed. AGIf the content was infinite, but space metric inflated from zero to something, the result is still infinite and space arise, as there was an infinity of space whose metric got bigger, there is still infinity after inflation, just more empty space in between matter.
--Anyway, in the end, there can't be an explanation which make sense. The fact we're here in the first place being able to ask question is magical.Quentin--As the bigbang is a singularity at the start... what prevents it to contain an infinite content in a zero/small volume, after all it's a singularity and we know only things after the big bang started ? and after inflation (which I understand is only space metric which inflate), there is still an infinite content.The BB is only a singularity as far as GR is concerned, because GR fails at that point in time. When we have a better theory, the alleged singularity at T = 0 will go away. What you call "infinite content in zero/ small volume" makes no sense, which is why we call this condition is called a singularity! How could the content be space, if you've have zero or small volume. This idea is immediately, and obviously, self contradictory. AG--
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On Monday, January 13, 2020 at 3:13:57 AM UTC-7, Quentin Anciaux wrote:Le lun. 13 janv. 2020 à 11:10, Alan Grayson <agrays...@gmail.com> a écrit :
On Monday, January 13, 2020 at 2:54:48 AM UTC-7, Quentin Anciaux wrote:Le lun. 13 janv. 2020 à 10:50, Alan Grayson <agrays...@gmail.com> a écrit :
On Monday, January 13, 2020 at 2:38:57 AM UTC-7, Quentin Anciaux wrote:Le lun. 13 janv. 2020 à 10:28, Alan Grayson <agrays...@gmail.com> a écrit :
On Monday, January 13, 2020 at 1:33:01 AM UTC-7, stathisp wrote:--On Mon, 13 Jan 2020 at 13:48, Alan Grayson <agrays...@gmail.com> wrote:
On Sunday, January 12, 2020 at 8:58:06 AM UTC-7, John Clark wrote:On Thu, Jan 2, 2020 at 2:30 AM Alan Grayson <agrays...@gmail.com> wrote:
> If we're convinced it's finite in age, then it can't be infinite in spatial extent. AGWe don't know for sure our universe is infinite in size and we'll never know for sure because we'll never be able to measure precisely zero curvature with no error at all, but we do know it's pretty damn flat, if it's curved it's so slight that a light beam would have to go at least 500 times as far as our telescopes can see for it to return where it started. So if you respect the empirical evidence for the Big Bang but the idea of a beginning of a infinitely sized universe makes you unhappy then the Multiverse idea offers you an obvious solution, you get an infinitely large infinitely old Multiverse but with the observable universe having a beginning and being only finitely large. However I understand the Multiverse makes you unhappy too. I fear you may be destined to be unhappy.By the way ... does the inverse also make you unhappy, something infinitely old but finite in spatial extent?John K ClarkAll the models pictorially represented, have the Universe beginning very small, and inflation is claimed to increase its size from, say, much smaller than a proton, to about the size of the Earth or Solar System in a few Planck intervals. If it begins small, or if you run the clock backward it becomes progressively smaller, how could it have started with infinite spatial extent? Don't you see something wrong with the model? AGThe model says that a subset of the universe starts small and gets bigger. This is not inconsistent with the whole universe starting and remaining infinite in spatial extent.Stathis PapaioannouI thought I made that clear; what I am calling "the universe" is precisely the SUBSET you refer to, which starts small and gets bigger. It is THAT SUBSET which cosmologists claim has infinite spatial extent, based on measurements. What you're calling "the whole universe" includes the underlying entity on which the BB started, and on which measurements CANNOT be made. It could be infinite in spatial extent, or is possibly an entity for which the concept of spatial extent might not exist. AGAnd so what do you see not contradictory in the existence of the universe itself ? Either it has always been, or not, and if not, that makes no sense. I see nothing contradictory to have something infinite, so it could always has been infinite in content, seeing it as zero volume is a mistake because that presuppose a volume in another space. What I'm saying is that there was infinite content (and still is) but all metrics (space) was of zero extends, and inflation extended the "space" not the content.I don't think you understand the issue I've raised; namely, if our bubble has a finite age and is expanding, it must be finite in spatial extent since the expansion rate is finite. But a flat universe, claimed by most, maybe all cosmologists, is infinite in spatial extent. How could it start infinite in spatial extent, yet be tiny in the beginning? I conclude that our universe, that is, our bubble (which doesn't include the substratum from which it arose), must be spherical and closed. AGIf the content was infinite, but space metric inflated from zero to something, the result is still infinite and space arise, as there was an infinity of space whose metric got bigger, there is still infinity after inflation, just more empty space in between matter.Forget about matter. I am discussing spatial extent. If it starts small, and expands at any rate less than infinite, its spatial extent cannot be infinite. AG
----Anyway, in the end, there can't be an explanation which make sense. The fact we're here in the first place being able to ask question is magical.Quentin--As the bigbang is a singularity at the start... what prevents it to contain an infinite content in a zero/small volume, after all it's a singularity and we know only things after the big bang started ? and after inflation (which I understand is only space metric which inflate), there is still an infinite content.The BB is only a singularity as far as GR is concerned, because GR fails at that point in time. When we have a better theory, the alleged singularity at T = 0 will go away. What you call "infinite content in zero/ small volume" makes no sense, which is why we call this condition is called a singularity! How could the content be space, if you've have zero or small volume. This idea is immediately, and obviously, self contradictory. AG--
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> My hunch, and that's all it is, is that "the substratum" from which the BB emerged, is infinitely old, and the concept of spatial extent probably doesn't apply to it. There could be many BB's, possibly an infinite number, but all finite in spatial extent if they had beginnings. AG
> The BB is only a singularity as far as GR is concerned, because GR fails at that point in time.
> if our bubble has a finite age and is expanding, it must be finite in spatial extent since the expansion rate is finite.
> infinite spatial extent means that a beam of light will never return to its starting point, as it would for a spherical surface. For a flat surface, a beam in any direction never returns to its starting point. THIS is what infinite spatial extent MEANS.
> the winking out is purely a geometric effect of the expansion.
--Stathis Papaioannou
>> If, as this one does, all the Big Bang's have a finite number of particles and are all of finite spatial extent then there is only a finite number of ways those particles can be arranged. But if there are a infinite number of those Big Bang's then in one of them (actually in a infinite number of them) there must be an arrangement of particles that are identical to you in every way except he spells his last name "Greyson" not "Grayson". So I guess both Mr. Greyson and Mr. Grayson have changed their minds and now believe in the existence of the Multiverse.
> I think you're making the assumption that the possible arrangement of a finite set of particles of finite extent corresponds to a countable set. But if space is continuous, that assumption fails, and with it your entire thesis.
> There is only ONE Grayson, thankfully.
>> if inflation is correct and in the very early universe the distance between any 2 points expanded faster than light then they've moved beyond their observable horizon and once you've done that you can't go back, so even today a beam of light sent from one of those points can never reach the other.
> Right, and that's how the non-observable region is created during inflation, but it would occur independent of the rate of expansion, provided the expansion continues. Like I said, it's a purely geometric effect of expansion. AG
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> Suppose you're sitting at the origin of a one-dimension space. A line 100 meters long will increase 1 meter per unit time if the rate of expansion is 1% per unit time. If the line is a 1000 meters long, the end point moves away 10 meters per unit time, and so forth. So if the line is long enough, the length will eventually increase more than 300,000 km, for any rate of expansion per unit time. 300,000 km is the distance light travels in one second. Thus, the end point will eventually increase in distance more than can be overcome by light traveling at c. This is what I mean by a purely geometric effect. Brent showed me this awhile back, and it was an A-HA moment! Winking out of distant galaxies does NOT depend on the rate of expansion; only that it continues. AG
On 13 Jan 2020, at 10:54, Quentin Anciaux <allc...@gmail.com> wrote:Le lun. 13 janv. 2020 à 10:50, Alan Grayson <agrays...@gmail.com> a écrit :
On Monday, January 13, 2020 at 2:38:57 AM UTC-7, Quentin Anciaux wrote:Le lun. 13 janv. 2020 à 10:28, Alan Grayson <agrays...@gmail.com> a écrit :
On Monday, January 13, 2020 at 1:33:01 AM UTC-7, stathisp wrote:--On Mon, 13 Jan 2020 at 13:48, Alan Grayson <agrays...@gmail.com> wrote:
On Sunday, January 12, 2020 at 8:58:06 AM UTC-7, John Clark wrote:On Thu, Jan 2, 2020 at 2:30 AM Alan Grayson <agrays...@gmail.com> wrote:
> If we're convinced it's finite in age, then it can't be infinite in spatial extent. AGWe don't know for sure our universe is infinite in size and we'll never know for sure because we'll never be able to measure precisely zero curvature with no error at all, but we do know it's pretty damn flat, if it's curved it's so slight that a light beam would have to go at least 500 times as far as our telescopes can see for it to return where it started. So if you respect the empirical evidence for the Big Bang but the idea of a beginning of a infinitely sized universe makes you unhappy then the Multiverse idea offers you an obvious solution, you get an infinitely large infinitely old Multiverse but with the observable universe having a beginning and being only finitely large. However I understand the Multiverse makes you unhappy too. I fear you may be destined to be unhappy.By the way ... does the inverse also make you unhappy, something infinitely old but finite in spatial extent?John K ClarkAll the models pictorially represented, have the Universe beginning very small, and inflation is claimed to increase its size from, say, much smaller than a proton, to about the size of the Earth or Solar System in a few Planck intervals. If it begins small, or if you run the clock backward it becomes progressively smaller, how could it have started with infinite spatial extent? Don't you see something wrong with the model? AGThe model says that a subset of the universe starts small and gets bigger. This is not inconsistent with the whole universe starting and remaining infinite in spatial extent.Stathis PapaioannouI thought I made that clear; what I am calling "the universe" is precisely the SUBSET you refer to, which starts small and gets bigger. It is THAT SUBSET which cosmologists claim has infinite spatial extent, based on measurements. What you're calling "the whole universe" includes the underlying entity on which the BB started, and on which measurements CANNOT be made. It could be infinite in spatial extent, or is possibly an entity for which the concept of spatial extent might not exist. AGAnd so what do you see not contradictory in the existence of the universe itself ? Either it has always been, or not, and if not, that makes no sense. I see nothing contradictory to have something infinite, so it could always has been infinite in content, seeing it as zero volume is a mistake because that presuppose a volume in another space. What I'm saying is that there was infinite content (and still is) but all metrics (space) was of zero extends, and inflation extended the "space" not the content.Anyway, in the end, there can't be an explanation which make sense. The fact we're here in the first place being able to ask question is magical.
QuentinAs the bigbang is a singularity at the start... what prevents it to contain an infinite content in a zero/small volume, after all it's a singularity and we know only things after the big bang started ? and after inflation (which I understand is only space metric which inflate), there is still an infinite content.The BB is only a singularity as far as GR is concerned, because GR fails at that point in time. When we have a better theory, the alleged singularity at T = 0 will go away. What you call "infinite content in zero/ small volume" makes no sense, which is why we call this condition is called a singularity! How could the content be space, if you've have zero or small volume. This idea is immediately, and obviously, self contradictory. AG--
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--All those moments will be lost in time, like tears in rain. (Roy Batty/Rutger Hauer)--
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> Personally, I don't believe in repeats, and I think the proof, if there is one, has to do with continuity or uncountability.
What I am claiming is that the universe beyond what is observable is NOT infinite in spatial extent. It's finite because it starts out small and has been expanding for finite time. AG
On Mon, Jan 13, 2020 at 8:49 AM Alan Grayson <agrays...@gmail.com> wrote:> Personally, I don't believe in repeats, and I think the proof, if there is one, has to do with continuity or uncountability.General Relativity says there are an infinite number of states in spacetime that something can be in, but Quantum Mechanics says the number is only astronomically large.
--The model says that a subset of the universe starts small and gets bigger. This is not inconsistent with the whole universe starting and remaining infinite in spatial extent.
Stathis Papaioannou
I thought I made that clear; what I am calling "the universe" is precisely the SUBSET you refer to, which starts small and gets bigger. It is THAT SUBSET which cosmologists claim has infinite spatial extent, based on measurements.
Forget about matter. I am discussing spatial extent. If it starts small, and expands at any rate less than infinite, its spatial extent cannot be infinite. AG
On 1/13/2020 2:10 AM, Alan Grayson wrote:
--The model says that a subset of the universe starts small and gets bigger. This is not inconsistent with the whole universe starting and remaining infinite in spatial extent.
Stathis Papaioannou
I thought I made that clear; what I am calling "the universe" is precisely the SUBSET you refer to, which starts small and gets bigger. It is THAT SUBSET which cosmologists claim has infinite spatial extent, based on measurements.
First, a proper subset of an infinite set can also be infinite (in fact that's one definition of "infinite").
Second, nobody measures an infinite portion of the universe.
We can only measure the curvature of the part we can see.
Third, it is not clear what is THAT SUBSET to which you refer.
Cosmologists are aware that only an initially infinite subset of space can be infinite after a finite expansion.
On 1/13/2020 2:21 AM, Alan Grayson wrote:
Forget about matter. I am discussing spatial extent. If it starts small, and expands at any rate less than infinite, its spatial extent cannot be infinite. AG
But so what? What is "it"? and what are you worried about? If "it" is some portion of the universe we can see, it's finite. The inference that the universe is infinite is based on curvature measure in the part we can see.
> There are systems for which the eigen spectrum of possible experimental outcomes is continuous, thus infinite. AG
The inference that the universe is infinite is based on curvature measure in the part we can see.
Brent
On Monday, January 13, 2020 at 11:12:36 AM UTC-7, Brent wrote:
On 1/13/2020 2:10 AM, Alan Grayson wrote:
--The model says that a subset of the universe starts small and gets bigger. This is not inconsistent with the whole universe starting and remaining infinite in spatial extent.
Stathis Papaioannou
I thought I made that clear; what I am calling "the universe" is precisely the SUBSET you refer to, which starts small and gets bigger. It is THAT SUBSET which cosmologists claim has infinite spatial extent, based on measurements.
First, a proper subset of an infinite set can also be infinite (in fact that's one definition of "infinite").
True. AGSecond, nobody measures an infinite portion of the universe.
I never made that claim. AGWe can only measure the curvature of the part we can see.
I never claimed otherwise. How could we measure what we can't (in some sense) see? Impossible! AGThird, it is not clear what is THAT SUBSET to which you refer.
I'm referring to the observable and non-observable regions. When cosmologists claim the universe is flat, they're referring to these regions and nothing else. It does NOT include the underlying entity from which our bubble emerged. Thus, a subset of a possibly larger totality. AGCosmologists are aware that only an initially infinite subset of space can be infinite after a finite expansion.
So, at the instant of the BB, that is"initially", there's a process which creates an infinity of space having zero time duration?
How is this different from a singularity? This is where I have a problem. There is no process that can create anything, let alone a spatial infinity, with no time passing. AGThey refer to a part of the universe that is beyond observation as being within the "particle horizon" because it consists of the evolved locations of things which are seen now as they were 14 billion years ago. Those things are now 49 billion light years away due to the expansion...which is sometimes referred to as the present diameter of the observable universe.https://en.wikipedia.org/wiki/Particle_horizon
Brent
What you're calling "the whole universe" includes the underlying entity on which the BB started, and on which measurements CANNOT be made. It could be infinite in spatial extent, or is possibly an entity for which the concept of spatial extent might not exist. AG
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On Monday, January 13, 2020 at 11:20:41 AM UTC-7, Brent wrote:
On 1/13/2020 2:21 AM, Alan Grayson wrote:
Forget about matter. I am discussing spatial extent. If it starts small, and expands at any rate less than infinite, its spatial extent cannot be infinite. AG
But so what? What is "it"? and what are you worried about? If "it" is some portion of the universe we can see, it's finite. The inference that the universe is infinite is based on curvature measure in the part we can see.
IT, the universe, has (IMO) a very small but positive curvature, which is what we measure. Since we can't precisely measure zero curvature, as JC earlier stated, there's no way to distinguish the two cases -- flat and infinite in spatial extent versus spherical and finite in spatial extent -- on measurements. But since flat and infinite at the instant of the BB implies a singularity, I reject that model. AG
They think it's infinite at the beginning but always represent it as very small at the beginning. That's a great way to communicate. Would you buy a used car from one of those guys? AG
That's a great way to communicate. Would you buy a used car from one of those guys? AG
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On 1/13/2020 12:59 PM, Alan Grayson wrote:
On Monday, January 13, 2020 at 1:22:05 PM UTC-7, Brent wrote:
On 1/13/2020 11:02 AM, Alan Grayson wrote:
On Monday, January 13, 2020 at 11:20:41 AM UTC-7, Brent wrote:
On 1/13/2020 2:21 AM, Alan Grayson wrote:
Forget about matter. I am discussing spatial extent. If it starts small, and expands at any rate less than infinite, its spatial extent cannot be infinite. AG
But so what? What is "it"? and what are you worried about? If "it" is some portion of the universe we can see, it's finite. The inference that the universe is infinite is based on curvature measure in the part we can see.
IT, the universe, has (IMO) a very small but positive curvature, which is what we measure. Since we can't precisely measure zero curvature, as JC earlier stated, there's no way to distinguish the two cases -- flat and infinite in spatial extent versus spherical and finite in spatial extent -- on measurements. But since flat and infinite at the instant of the BB implies a singularity, I reject that model. AG
Fine. Nobody thinks there was a singularity.
Brent
They think it's infinite at the beginning but always represent it as very small at the beginning.
No they represent all the universe we can interact with as small then. If you have something to question, how about quoting it explicitly; instead of your interpretation.
Brent
--That's a great way to communicate. Would you buy a used car from one of those guys? AG
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On Monday, January 13, 2020 at 5:12:33 PM UTC-7, Brent wrote:
On 1/13/2020 12:59 PM, Alan Grayson wrote:
On Monday, January 13, 2020 at 1:22:05 PM UTC-7, Brent wrote:
On 1/13/2020 11:02 AM, Alan Grayson wrote:
On Monday, January 13, 2020 at 11:20:41 AM UTC-7, Brent wrote:
On 1/13/2020 2:21 AM, Alan Grayson wrote:
Forget about matter. I am discussing spatial extent. If it starts small, and expands at any rate less than infinite, its spatial extent cannot be infinite. AG
But so what? What is "it"? and what are you worried about? If "it" is some portion of the universe we can see, it's finite. The inference that the universe is infinite is based on curvature measure in the part we can see.
IT, the universe, has (IMO) a very small but positive curvature, which is what we measure. Since we can't precisely measure zero curvature, as JC earlier stated, there's no way to distinguish the two cases -- flat and infinite in spatial extent versus spherical and finite in spatial extent -- on measurements. But since flat and infinite at the instant of the BB implies a singularity, I reject that model. AG
Fine. Nobody thinks there was a singularity.
Brent
They think it's infinite at the beginning but always represent it as very small at the beginning.
No they represent all the universe we can interact with as small then. If you have something to question, how about quoting it explicitly; instead of your interpretation.
Brent
How about if I quote you? You wrote earlier it could be infinite "at the start", "initially". This suggests at the instant of the BB, it became infinite.
--I interpret this to mean a process resulting in infinite extent. which took zero time; hence a singularity. Your other alternative is that it inflated hugely in a finite time interval. I can see this, but then it couldn't be infinite in spatial extent. AG
--That's a great way to communicate. Would you buy a used car from one of those guys? AG
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On 1/13/2020 5:52 PM, Alan Grayson wrote:
On Monday, January 13, 2020 at 5:12:33 PM UTC-7, Brent wrote:
On 1/13/2020 12:59 PM, Alan Grayson wrote:
On Monday, January 13, 2020 at 1:22:05 PM UTC-7, Brent wrote:
On 1/13/2020 11:02 AM, Alan Grayson wrote:
On Monday, January 13, 2020 at 11:20:41 AM UTC-7, Brent wrote:
On 1/13/2020 2:21 AM, Alan Grayson wrote:
Forget about matter. I am discussing spatial extent. If it starts small, and expands at any rate less than infinite, its spatial extent cannot be infinite. AG
But so what? What is "it"? and what are you worried about? If "it" is some portion of the universe we can see, it's finite. The inference that the universe is infinite is based on curvature measure in the part we can see.
IT, the universe, has (IMO) a very small but positive curvature, which is what we measure. Since we can't precisely measure zero curvature, as JC earlier stated, there's no way to distinguish the two cases -- flat and infinite in spatial extent versus spherical and finite in spatial extent -- on measurements. But since flat and infinite at the instant of the BB implies a singularity, I reject that model. AG
Fine. Nobody thinks there was a singularity.
Brent
They think it's infinite at the beginning but always represent it as very small at the beginning.
No they represent all the universe we can interact with as small then. If you have something to question, how about quoting it explicitly; instead of your interpretation.
Brent
How about if I quote you? You wrote earlier it could be infinite "at the start", "initially". This suggests at the instant of the BB, it became infinite.
No. "Became" would not be "at the start". That's why I want see what you quoting. You ability to interpret seems inventive to say the least.
Brent
--I interpret this to mean a process resulting in infinite extent. which took zero time; hence a singularity. Your other alternative is that it inflated hugely in a finite time interval. I can see this, but then it couldn't be infinite in spatial extent. AG
--That's a great way to communicate. Would you buy a used car from one of those guys? AG
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On Monday, January 13, 2020 at 7:48:01 PM UTC-7, Brent wrote:
On 1/13/2020 5:52 PM, Alan Grayson wrote:
On Monday, January 13, 2020 at 5:12:33 PM UTC-7, Brent wrote:
On 1/13/2020 12:59 PM, Alan Grayson wrote:
On Monday, January 13, 2020 at 1:22:05 PM UTC-7, Brent wrote:
On 1/13/2020 11:02 AM, Alan Grayson wrote:
On Monday, January 13, 2020 at 11:20:41 AM UTC-7, Brent wrote:
On 1/13/2020 2:21 AM, Alan Grayson wrote:
Forget about matter. I am discussing spatial extent. If it starts small, and expands at any rate less than infinite, its spatial extent cannot be infinite. AG
But so what? What is "it"? and what are you worried about? If "it" is some portion of the universe we can see, it's finite. The inference that the universe is infinite is based on curvature measure in the part we can see.
IT, the universe, has (IMO) a very small but positive curvature, which is what we measure. Since we can't precisely measure zero curvature, as JC earlier stated, there's no way to distinguish the two cases -- flat and infinite in spatial extent versus spherical and finite in spatial extent -- on measurements. But since flat and infinite at the instant of the BB implies a singularity, I reject that model. AG
Fine. Nobody thinks there was a singularity.
Brent
They think it's infinite at the beginning but always represent it as very small at the beginning.
No they represent all the universe we can interact with as small then. If you have something to question, how about quoting it explicitly; instead of your interpretation.
Brent
How about if I quote you? You wrote earlier it could be infinite "at the start", "initially". This suggests at the instant of the BB, it became infinite.
No. "Became" would not be "at the start". That's why I want see what you quoting. You ability to interpret seems inventive to say the least.
Brent
Why do I have to quote anyone?
I am just using basic logic and trying to resolve an apparent inconsistency. So, if not at the start, then during inflation. How could inflation produce infinite spatial extent? The rate of expansion might be incredibly huge, but not infinite. AG
--Stathis Papaioannou
>> If infinite distances makes you squeamish I don't see how you can consistently embrace infinite outcomes. And besides this is not mathematics, in physics nothing is provably infinite, nobody has ever found an infinite number of anything.
> It's not a matter of, or a case of being squeamish with infinite outcomes. I just don't see how cosmologists can claim the universe is flat -- which means infinite in spatial extent -- if it starts small and expands for a finite time.
On Mon, Jan 13, 2020 at 9:03 PM Alan Grayson <agrays...@gmail.com> wrote:>> If infinite distances makes you squeamish I don't see how you can consistently embrace infinite outcomes. And besides this is not mathematics, in physics nothing is provably infinite, nobody has ever found an infinite number of anything.> It's not a matter of, or a case of being squeamish with infinite outcomes. I just don't see how cosmologists can claim the universe is flat -- which means infinite in spatial extent -- if it starts small and expands for a finite time.Infinity is not a number, infinity is a process that evolves in time. If a cosmologists says the universe is infinite he means that a pulse of light will keep getting more distant from its starting point and never return.
On Tuesday, January 14, 2020 at 3:06:48 AM UTC-7, John Clark wrote:On Mon, Jan 13, 2020 at 9:03 PM Alan Grayson <agrays...@gmail.com> wrote:>> If infinite distances makes you squeamish I don't see how you can consistently embrace infinite outcomes. And besides this is not mathematics, in physics nothing is provably infinite, nobody has ever found an infinite number of anything.> It's not a matter of, or a case of being squeamish with infinite outcomes. I just don't see how cosmologists can claim the universe is flat -- which means infinite in spatial extent -- if it starts small and expands for a finite time.Infinity is not a number, infinity is a process that evolves in time. If a cosmologists says the universe is infinite he means that a pulse of light will keep getting more distant from its starting point and never return.That's what I mean! Only it's not true if the universe is spherical.
Let's forget it. These discussions are worthless. AG
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> >It is true for a de Sitter universe as a solution of the Einstein equations. If the universe is spherical, it will eventually recontract, and light cannot get right round and back to its starting point before the universe recontracts to a point. If the universe is expanding via dark energy, even if spherical, light still cannot get round because of the expansion. In other words, you can never see the back of your own head no matter what the geometry of the universe!!!!!Bruce
> Since it's not a perfect sphere [...]
> light never exactly returns to its starting point. That's just an approximation
> Let's forget it. These discussions are worthless.
On Tue, Jan 14, 2020 at 6:47 AM Alan Grayson <agrays...@gmail.com> wrote:> >It is true for a de Sitter universe as a solution of the Einstein equations. If the universe is spherical, it will eventually recontract, and light cannot get right round and back to its starting point before the universe recontracts to a point. If the universe is expanding via dark energy, even if spherical, light still cannot get round because of the expansion. In other words, you can never see the back of your own head no matter what the geometry of the universe!!!!!Bruce> Since it's not a perfect sphere [...]Because we're talking about curved Spacetime and not curved space and because non-Euclidean geometry must be used (due to that minus sign that sneaks into Pythagoras formula if time is one of the dimensions) it's misleading to call it a "sphere", it's even misleading to call it the surface of a 4D sphere. What we really want to know is it the geometry of the universe is open or closed.
> light never exactly returns to its starting point. That's just an approximationThat's what happens in a de Sitter universe, its flat and open and you get a de Sitter universe if the universe is not dominated by matter but by the Cosmological Constant, which is probably Dark Energy.
On Tuesday, January 14, 2020 at 10:27:27 AM UTC-7, John Clark wrote:On Tue, Jan 14, 2020 at 6:47 AM Alan Grayson <agrays...@gmail.com> wrote:> >It is true for a de Sitter universe as a solution of the Einstein equations. If the universe is spherical, it will eventually recontract, and light cannot get right round and back to its starting point before the universe recontracts to a point. If the universe is expanding via dark energy, even if spherical, light still cannot get round because of the expansion. In other words, you can never see the back of your own head no matter what the geometry of the universe!!!!!Bruce> Since it's not a perfect sphere [...]Because we're talking about curved Spacetime and not curved space and because non-Euclidean geometry must be used (due to that minus sign that sneaks into Pythagoras formula if time is one of the dimensions) it's misleading to call it a "sphere", it's even misleading to call it the surface of a 4D sphere. What we really want to know is it the geometry of the universe is open or closed.Hypersphere; closed; if you believe it's age is finite. AG> light never exactly returns to its starting point. That's just an approximationThat's what happens in a de Sitter universe, its flat and open and you get a de Sitter universe if the universe is not dominated by matter but by the Cosmological Constant, which is probably Dark Energy.Since it's not perfectly homogeneous, a beam of light can be bent, this way and that way, so it's unlikely to return exactly to its point of origin. You know, what we OBSERVE and MEASURE is an expanding universe, so an ad hoc insertion of an infinite spatial extent is suspect. AG
On 14 Jan 2020, at 11:06, John Clark <johnk...@gmail.com> wrote:On Mon, Jan 13, 2020 at 9:03 PM Alan Grayson <agrays...@gmail.com> wrote:>> If infinite distances makes you squeamish I don't see how you can consistently embrace infinite outcomes. And besides this is not mathematics, in physics nothing is provably infinite, nobody has ever found an infinite number of anything.> It's not a matter of, or a case of being squeamish with infinite outcomes. I just don't see how cosmologists can claim the universe is flat -- which means infinite in spatial extent -- if it starts small and expands for a finite time.Infinity is not a number, infinity is a process that evolves in time.
If a cosmologists says the universe is infinite he means that a pulse of light will keep getting more distant from its starting point and never return. I don't know if the universe is infinite or not but I see nothing obviously absurd with the idea.
And when cosmologists say the universe started at a singularity what they mean is it started at a place they don't understand, they never claimed to know everything. In physics "singularity" doesn't mean infinite density or zero volume, it means "our theories break down here and produce ridiculous results”.
John K Clark
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On Tuesday, January 14, 2020 at 11:56:51 AM UTC-7, Alan Grayson wrote:
On Tuesday, January 14, 2020 at 10:27:27 AM UTC-7, John Clark wrote:On Tue, Jan 14, 2020 at 6:47 AM Alan Grayson <agrays...@gmail.com> wrote:> >It is true for a de Sitter universe as a solution of the Einstein equations. If the universe is spherical, it will eventually recontract, and light cannot get right round and back to its starting point before the universe recontracts to a point. If the universe is expanding via dark energy, even if spherical, light still cannot get round because of the expansion. In other words, you can never see the back of your own head no matter what the geometry of the universe!!!!!Bruce> Since it's not a perfect sphere [...]Because we're talking about curved Spacetime and not curved space and because non-Euclidean geometry must be used (due to that minus sign that sneaks into Pythagoras formula if time is one of the dimensions) it's misleading to call it a "sphere", it's even misleading to call it the surface of a 4D sphere. What we really want to know is it the geometry of the universe is open or closed.Hypersphere; closed; if you believe it's age is finite. AG> light never exactly returns to its starting point. That's just an approximationThat's what happens in a de Sitter universe, its flat and open and you get a de Sitter universe if the universe is not dominated by matter but by the Cosmological Constant, which is probably Dark Energy.Since it's not perfectly homogeneous, a beam of light can be bent, this way and that way, so it's unlikely to return exactly to its point of origin. You know, what we OBSERVE and MEASURE is an expanding universe, so an ad hoc insertion of an infinite spatial extent is suspect. AGIt's like a leaf on a tree. The leaf is our universe, closed and finite in spatial extent. It's attached to what I've called "the substratum", analogous to a tree, possibly infinite in spatial extent and having an infinite past. Let's call it "the Tree of Life". Our universe is connected to it, has been since the BB, which is why it's expanding, like a leaf growing. AG
On 14 Jan 2020, at 11:06, John Clark <johnk...@gmail.com> wrote:On Mon, Jan 13, 2020 at 9:03 PM Alan Grayson <agrays...@gmail.com> wrote:>> If infinite distances makes you squeamish I don't see how you can consistently embrace infinite outcomes. And besides this is not mathematics, in physics nothing is provably infinite, nobody has ever found an infinite number of anything.> It's not a matter of, or a case of being squeamish with infinite outcomes. I just don't see how cosmologists can claim the universe is flat -- which means infinite in spatial extent -- if it starts small and expands for a finite time.Infinity is not a number, infinity is a process that evolves in time.That is Aristotle potential infinite. Cantorial actual infinities are treated by sets in set theory, and behave like numbers (we can add them, but it is not commutative, we can multiply them, exponentiate them, etc.It is doubtful that there are actual infinities in the observable realm, and if we are machines, that is a priori undecidable. Now, with a non mechanist theory of mind, all notions are open.If a cosmologists says the universe is infinite he means that a pulse of light will keep getting more distant from its starting point and never return. I don't know if the universe is infinite or not but I see nothing obviously absurd with the idea.It is easy to prove that the physical (observable) universe has to be infinite, and contains non computable elements once we bet on Mechanism in the cognitive science. And without mechanism, also, but for very different reason.And when cosmologists say the universe started at a singularity what they mean is it started at a place they don't understand, they never claimed to know everything. In physics "singularity" doesn't mean infinite density or zero volume, it means "our theories break down here and produce ridiculous results”.Yes, and to invoke a singularity in an explanation is not much different than invoking a god or a primary universe. That explains nothing and such terms designates our ignorance.
Bruno
John K Clark--
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On Tuesday, January 14, 2020 at 3:37:22 PM UTC-7, Alan Grayson wrote:
On Tuesday, January 14, 2020 at 11:56:51 AM UTC-7, Alan Grayson wrote:
On Tuesday, January 14, 2020 at 10:27:27 AM UTC-7, John Clark wrote:On Tue, Jan 14, 2020 at 6:47 AM Alan Grayson <agrays...@gmail.com> wrote:> >It is true for a de Sitter universe as a solution of the Einstein equations. If the universe is spherical, it will eventually recontract, and light cannot get right round and back to its starting point before the universe recontracts to a point. If the universe is expanding via dark energy, even if spherical, light still cannot get round because of the expansion. In other words, you can never see the back of your own head no matter what the geometry of the universe!!!!!Bruce> Since it's not a perfect sphere [...]Because we're talking about curved Spacetime and not curved space and because non-Euclidean geometry must be used (due to that minus sign that sneaks into Pythagoras formula if time is one of the dimensions) it's misleading to call it a "sphere", it's even misleading to call it the surface of a 4D sphere. What we really want to know is it the geometry of the universe is open or closed.Hypersphere; closed; if you believe it's age is finite. AG> light never exactly returns to its starting point. That's just an approximationThat's what happens in a de Sitter universe, its flat and open and you get a de Sitter universe if the universe is not dominated by matter but by the Cosmological Constant, which is probably Dark Energy.Since it's not perfectly homogeneous, a beam of light can be bent, this way and that way, so it's unlikely to return exactly to its point of origin. You know, what we OBSERVE and MEASURE is an expanding universe, so an ad hoc insertion of an infinite spatial extent is suspect. AGIt's like a leaf on a tree. The leaf is our universe, closed and finite in spatial extent. It's attached to what I've called "the substratum", analogous to a tree, possibly infinite in spatial extent and having an infinite past. Let's call it "the Tree of Life". Our universe is connected to it, has been since the BB, which is why it's expanding, like a leaf growing. AGA fruit tree is a better analogy, since most fruits are approximately spherical, as is our universe (hyper-spherical); observable and non-observable regions. It must be somehow connected to its source or origin, but how that connection manifests is currently above my pay grade. The problem with current models of a flat universe is that the infinity of spatial extent implied, seems like an ad hoc hypothesis, not organically connected with the rest of the theory. AG
Already about 74% of the matter/energy in our universe is in the form of Dark Energy, and as time progresses that percentage can only increase and we'll get closer and closer to a pure de Sitter universe. That's because the Cosmological Constant is a property of empty space, so as the accelerating universe creates more space it also creates more Dark Energy, however the total amount of matter (both regular and dark) remains fixed.
>> Already about 74% of the matter/energy in our universe is in the form of Dark Energy, and as time progresses that percentage can only increase and we'll get closer and closer to a pure de Sitter universe. That's because the Cosmological Constant is a property of empty space, so as the accelerating universe creates more space it also creates more Dark Energy, however the total amount of matter (both regular and dark) remains fixed.
> Why does the total amount of matter, both regular and dark, remain fixed as the universe expands? AG
On Wed, Jan 15, 2020 at 6:54 PM Alan Grayson <agrays...@gmail.com> wrote:>> Already about 74% of the matter/energy in our universe is in the form of Dark Energy, and as time progresses that percentage can only increase and we'll get closer and closer to a pure de Sitter universe. That's because the Cosmological Constant is a property of empty space, so as the accelerating universe creates more space it also creates more Dark Energy, however the total amount of matter (both regular and dark) remains fixed.> Why does the total amount of matter, both regular and dark, remain fixed as the universe expands? AGThe simple answer is in General Relativity there is a mechanism for creating new space but not for creating new matter.
The Cosmological Constant is the energy that is always inherent in space even when it has no matter in it. General Relativity says that this vacuum energy will cause space to accelerate, that is to say more space will be created, so unlike the matter in it vacuum energy will not become diluted as the universe expands but will remain constant in both space and time. According to General Relativity the curvature of Spacetime (NOT the curvature of space) is determined by the energy and momentum in it, and as Sean Carroll says "the manifestation of spacetime curvature is simply the fact that space is expanding".
>> as Sean Carroll says "the manifestation of spacetime curvature is simply the fact that space is expanding".
> If curvature is caused by energy and momentum in space-time, Carroll's statement doesn't make sense. AG
I f
John K Clark
On Wed, Jan 15, 2020 at 6:54 PM Alan Grayson <agrays...@gmail.com> wrote:>> Already about 74% of the matter/energy in our universe is in the form of Dark Energy, and as time progresses that percentage can only increase and we'll get closer and closer to a pure de Sitter universe. That's because the Cosmological Constant is a property of empty space, so as the accelerating universe creates more space it also creates more Dark Energy, however the total amount of matter (both regular and dark) remains fixed.> Why does the total amount of matter, both regular and dark, remain fixed as the universe expands? AGThe simple answer is in General Relativity there is a mechanism for creating new space but not for creating new matter.
On Thursday, January 16, 2020 at 2:02:22 PM UTC-7, John Clark wrote:On Thu, Jan 16, 2020 at 1:25 PM Alan Grayson <agrays...@gmail.com> wrote:
>> as Sean Carroll says "the manifestation of spacetime curvature is simply the fact that space is expanding".
> If curvature is caused by energy and momentum in space-time, Carroll's statement doesn't make sense. AGHas it ever occured to you that if a professor of physics at one of the best universities in the world makes a statement about physics that makes no sense to you it might not be because he is talking nonsense but because you don't understand something? It makes no sense to you because you assume spatial curvature and spacetime curvature mean the same thing. But you're wrong, they don't. And they don't because the time dimension behaves in a fundamentally different way than any of the 3 spatial dimensions do; more specifically if you want to use Pythagoras theorem in spaceTIME (not to be confused with space) to calculate a distance in spaceTIME then you have to stick in a minus sign that Euclid and Pythagoras knew nothing about.
I f
John K Clark
You're referring, of course, to the Lorentz metric with the minus sign. Yeah, I've heard of it -- used in pseudo Riemannian manifolds, and without it those space-time causal cones wouldn't make sense. But I read again and again that "curvature" of space-time is caused by the presence of mass/energy, so I find Carroll's comment puzzling. He seems to be saying that expansion is caused by curvature, when it's generally thought to be caused by dark energy.
Also, as you know, I am not an enthusiast (to put it mildly) of the Many Worlds theory of Everett, but Carroll is. So I don't pray at the feet of physicists, even those from prestigious universities. AG
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On 1/16/2020 3:17 PM, Alan Grayson wrote:
On Thursday, January 16, 2020 at 2:02:22 PM UTC-7, John Clark wrote:On Thu, Jan 16, 2020 at 1:25 PM Alan Grayson <agrays...@gmail.com> wrote:
>> as Sean Carroll says "the manifestation of spacetime curvature is simply the fact that space is expanding".
> If curvature is caused by energy and momentum in space-time, Carroll's statement doesn't make sense. AGHas it ever occured to you that if a professor of physics at one of the best universities in the world makes a statement about physics that makes no sense to you it might not be because he is talking nonsense but because you don't understand something? It makes no sense to you because you assume spatial curvature and spacetime curvature mean the same thing. But you're wrong, they don't. And they don't because the time dimension behaves in a fundamentally different way than any of the 3 spatial dimensions do; more specifically if you want to use Pythagoras theorem in spaceTIME (not to be confused with space) to calculate a distance in spaceTIME then you have to stick in a minus sign that Euclid and Pythagoras knew nothing about.
I f
John K Clark
You're referring, of course, to the Lorentz metric with the minus sign. Yeah, I've heard of it -- used in pseudo Riemannian manifolds, and without it those space-time causal cones wouldn't make sense. But I read again and again that "curvature" of space-time is caused by the presence of mass/energy, so I find Carroll's comment puzzling. He seems to be saying that expansion is caused by curvature, when it's generally thought to be caused by dark energy.
"Dark energy" is a place-holder name for whatever is responsible for the accelerating expansion of the universe. So it could be curvature (i.e. just an intrinsic constant of spacetime) or it could be a quantum field that would have a corresponding particle that we could look for. And what would be puzzling about Carroll having a different opinion than what is "generally thought" when it is a completely unsettled empirical question on which experts may be expected to have different theories. In fact there isn't any "generally thought" consensus, and science doesn't go by consensus anyway. What puzzles me is that you spend so much time writing to these email lists when your level of understanding would be improved a lot more by reading a book, e.g. David Mahon's "Relativity Demystified" or Robert Wald's "General Relativity" or "Gravity" by Jim Hartle or even Vic's "Comprehensible Cosmos".
Brent
--Also, as you know, I am not an enthusiast (to put it mildly) of the Many Worlds theory of Everett, but Carroll is. So I don't pray at the feet of physicists, even those from prestigious universities. AG
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> Carroll seems to be an outlier
> I don't pray at the feet of physicists, even those from prestigious universities
John K Clark
John K Clark
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> IF at T = 0, the universe began as ...[Blah Blah]... I sent an email to a noted cosmologist about this (whose name slips my mind), someone Brent referenced, but never received a reply.
> I'll give you the benefit of the doubt, and assume you also have the IQ of boiling water, in centigrade. AG
>> the time dimension behaves in a fundamentally different way than any of the 3 spatial dimensions do; more specifically if you want to use Pythagoras theorem in spaceTIME (not to be confused with space) to calculate a distance in spaceTIME then you have to stick in a minus sign that Euclid and Pythagoras knew nothing about.> Of course, as I guess you now, by using an imaginary time (defining t’ = it), we can come back to the Pythagorean theorem, without the minus sign, and restore Euclideanity. That leads to something called Euclidian Relativity. I do often that for pedagogical purpose. Not sure if this is really fundamental.
John K Clark
>> Yes, you can use that to represent a curved path in 4D (one of time 3 of space) Minkowski Space where Special Relativity lives, but as you say that doesn't really get to the fundamental issue because Minkowski Space is flat and Special Relativity says nothing about gravity, for that you need General Relativity and GR doesn't live in Minkowski Space.In General Relativity curved Spacetime is what gravity is, and in GR if there is any curvature in the Spacetime of the universe, and we know there is because we know that gravity exists, then, unless vacuum energy also exists and is fine tuned to one very precise value, the universe can not be stable, it must be either expanding or contracting. There are thermodynamic reasons to think it can't be contracting so it must be expanding.And that is why no physicist would say that Carroll's statement "the manifestation of spacetime curvature is simply the fact that space is expanding" was controversial .> The question is, what does he mean? Is space expanding BECAUSE of curvature? If so it's expanding because of gravity, since you wrote that gravity and curvature are equivalent. But since gravity is attractive (as far as we know), how could it be responsible for expansion (as distinguished from contraction)? AG
Can you elaborate further? Not clear what this diagram demonstrates. AG
We learn from observation that it's expanding which is consistent with thermodynamic reasoning.
John K Clark
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