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#1
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how big is the universe?
I'm having trouble understanding just how big the universe is.
Many people I talk to seem to think (assuming, for example, that the universe is 13 billion years old)- that it's 13 billion light years in radius- that we can almost see back to the edge- of course there is no edge and that's all about lookback time and the "observable universe", not current reality and distances. Assuming that Guth's theory of inflation is more or less true- I vaguely remember reading in some "popular" astronomy book that the universe inflated to a size much bigger than the observable universe- so that the O.U. is a tiny little part of the total universe. If this is the case, how could we know how big it is? And, I've seen some recent cosmology writing implying that it is infinite. I can understand the suggestion that if space will continue to get bigger forever- that it is "open"- but I can't equate open with infinite. I think when some astronomers say infinite, they don't mean to imply infinite as we non scientists think of it. Anyways, I find this all very fascinating. It's tough enough to imagine that the universe may be 10-15 billion light years to the "edge"- but to ponder that this observable universe may only be a tiny part of a much bigger inflated universe really pushes me over the edge. G But, I'm rambling- if the universe is much bigger than the observable universe- how could we ever know how big it is? And, when astronomers try to determine the total mass- do they mean the total mass of the observable universe or the total universe, and does it make a difference? One last bit of rambling- I have this crazy idea that if we can ever figure out what dark matter and dark energy is- not only will all of that contain a vast amount of information- similar to the way that electromagnetic energy contains info- but that such discoveries will cause a quantum level advance in the physical sciences- so important that it will be a milestone in human evolution. JZ |
#2
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how big is the universe?
There was a nice piece of work that hit the news recently (I don't
have a link to the paper right now) that analyzed the scale of background fluctuations in the CMB to try to set a limit on the size of the universe. The reasoning was that if we see fluctuations at all scales, the universe should be infinite or very, very large. The fluctuations were caused by what were essentially sound waves echoing back and forth across the early universe before it inflated (I think that is right) when all regions were communicating with all others. Like sound in an organ pipe, if the universe had a particular size then some vibration modes would be preferred over others, leaving a characteristic fingerprint. On the other hand, if the univers was infinite there would be no preferred mode and all frequencies would be present. The answer they got was surprising to me. The fluctuations cut off above a certain scale, which they calculated implied a current size of around 70 billion light years. So according to their results the full universe is bigger than the observable universe, but not a whole lot bigger. The observable universe is a sizable fraction of the whole, which I find surprising. This is new work and it may not hold up, but it was nicely done and if it stands it will have deep implications for inflation and a host of other theories that want the universe to be orders of magnitude larger than the observable universe. Ed Gibbs |
#3
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how big is the universe?
There was a nice piece of work that hit the news recently (I don't
have a link to the paper right now) that analyzed the scale of background fluctuations in the CMB to try to set a limit on the size of the universe. The reasoning was that if we see fluctuations at all scales, the universe should be infinite or very, very large. The fluctuations were caused by what were essentially sound waves echoing back and forth across the early universe before it inflated (I think that is right) when all regions were communicating with all others. Like sound in an organ pipe, if the universe had a particular size then some vibration modes would be preferred over others, leaving a characteristic fingerprint. On the other hand, if the univers was infinite there would be no preferred mode and all frequencies would be present. The answer they got was surprising to me. The fluctuations cut off above a certain scale, which they calculated implied a current size of around 70 billion light years. So according to their results the full universe is bigger than the observable universe, but not a whole lot bigger. The observable universe is a sizable fraction of the whole, which I find surprising. This is new work and it may not hold up, but it was nicely done and if it stands it will have deep implications for inflation and a host of other theories that want the universe to be orders of magnitude larger than the observable universe. Ed Gibbs |
#4
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how big is the universe?
"Ed Gibbs" wrote in message
... There was a nice piece of work that hit the news recently (I don't have a link to the paper right now) that analyzed the scale of background fluctuations in the CMB to try to set a limit on the size of the universe. The reasoning was that if we see fluctuations at all scales, the universe should be infinite or very, very large. When astronomers use the term "infinite" in this context, what do they mean? |
#5
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how big is the universe?
"Ed Gibbs" wrote in message
... There was a nice piece of work that hit the news recently (I don't have a link to the paper right now) that analyzed the scale of background fluctuations in the CMB to try to set a limit on the size of the universe. The reasoning was that if we see fluctuations at all scales, the universe should be infinite or very, very large. When astronomers use the term "infinite" in this context, what do they mean? |
#6
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how big is the universe?
I think when they say "infinite" they mean just that - goes on forever
and ever without end. That is distinctly different from very, very large - which implies that it is finite, though possibly so large that it appears for all intents and purposes to be infinite. There are also finite but unbounded - a universe that could be very, very large (not infinite) but has no edge - say a 4 dimensional sphere that you can go around to come back to where you started, as you can on the surface of the earth. Then there are things like perpetual inflation, which posits that our very, very large big bang universe is one of an enormous and constantly growing (though quite possibly finite) number of big bang universes. And then there are the really crazy theories...;-) Ed Gibbs Joe Zorzin wrote in message ... When astronomers use the term "infinite" in this context, what do they mean? |
#7
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how big is the universe?
I think when they say "infinite" they mean just that - goes on forever
and ever without end. That is distinctly different from very, very large - which implies that it is finite, though possibly so large that it appears for all intents and purposes to be infinite. There are also finite but unbounded - a universe that could be very, very large (not infinite) but has no edge - say a 4 dimensional sphere that you can go around to come back to where you started, as you can on the surface of the earth. Then there are things like perpetual inflation, which posits that our very, very large big bang universe is one of an enormous and constantly growing (though quite possibly finite) number of big bang universes. And then there are the really crazy theories...;-) Ed Gibbs Joe Zorzin wrote in message ... When astronomers use the term "infinite" in this context, what do they mean? |
#8
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how big is the universe?
http://www.forestmeister.com
"Ed Gibbs" wrote in message ... I think when they say "infinite" they mean just that - goes on forever and ever without end. And there is actually some logic to this, that the universe may be infinite in the common sense? I can see it as a philosophical speculation, but can it be derived from a scientific model? I'm non scientist, so I'm not arguing against- actually, I find the idea fascinating- but I'm trying to get a grasp on what it means, scientifically. Since the universe was once very small, and as it grew, it must have been finite- how does something go from being finite to infinite? Or, does the model say that it was infinite from the beginning, and what does that really mean? I've read some speculation that our big bang was something that occured withing some bigger framework, which perhaps is infinite, so in that sense, I can sort of "get it". That is distinctly different from very, very large - which implies that it is finite, though possibly so large that it appears for all intents and purposes to be infinite. Either way, it's mind blowing- to think of all the stuff out there, that if knew about it we'd be shocked. We need to somehow, eventually, learn about what's out there, otherwise we are very provincial indeed. (I don't like the word "indeed", but sometimes I use it when I'm in awe. G) There are also finite but unbounded - a universe that could be very, very large (not infinite) but has no edge - say a 4 dimensional sphere that you can go around to come back to where you started, as you can on the surface of the earth. OK, I can get that one- that's easy by comparison. Then there are things like perpetual inflation, which posits that our very, very large big bang universe is one of an enormous and constantly growing (though quite possibly finite) number of big bang universes. And then there are the really crazy theories...;-) No doubt if our civilization continues for centuries, each generation will push the envelope, each discovering more amazing stuff than the last. I find this to be wonderful, the bigger and more outrageous the better- from a philosophical point of view. Now, if only somewhere out there is some civilization that has been around for millions of years, which has done a "Comparative Study of Evolution on a Galactic Scale" and the follow up "Compartive Study of Civilizations on a Galactic Scale". Then of course, an even more advanced civilization will do a compartive study across galaxies. And, somewhere out there is the most advanced, the smartest, of all that may have a deep understanding of the universe on a scale larger than their respective "visible universe". My theory, from a dummy's point of view, is that when we have a better understanding of dark matter and dark energy, somehow there is a lot of infomation contained therein, that could tell us a lot about a big chunk of the universe, maybe beyond "the edge" of the visible universe- such as the "large scale structure" too big for us to see- structures so big that from within any given "visible universe" you could see only a small part of it. Ed Gibbs Joe Zorzin wrote in message ... When astronomers use the term "infinite" in this context, what do they mean? |
#9
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how big is the universe?
http://www.forestmeister.com
"Ed Gibbs" wrote in message ... I think when they say "infinite" they mean just that - goes on forever and ever without end. And there is actually some logic to this, that the universe may be infinite in the common sense? I can see it as a philosophical speculation, but can it be derived from a scientific model? I'm non scientist, so I'm not arguing against- actually, I find the idea fascinating- but I'm trying to get a grasp on what it means, scientifically. Since the universe was once very small, and as it grew, it must have been finite- how does something go from being finite to infinite? Or, does the model say that it was infinite from the beginning, and what does that really mean? I've read some speculation that our big bang was something that occured withing some bigger framework, which perhaps is infinite, so in that sense, I can sort of "get it". That is distinctly different from very, very large - which implies that it is finite, though possibly so large that it appears for all intents and purposes to be infinite. Either way, it's mind blowing- to think of all the stuff out there, that if knew about it we'd be shocked. We need to somehow, eventually, learn about what's out there, otherwise we are very provincial indeed. (I don't like the word "indeed", but sometimes I use it when I'm in awe. G) There are also finite but unbounded - a universe that could be very, very large (not infinite) but has no edge - say a 4 dimensional sphere that you can go around to come back to where you started, as you can on the surface of the earth. OK, I can get that one- that's easy by comparison. Then there are things like perpetual inflation, which posits that our very, very large big bang universe is one of an enormous and constantly growing (though quite possibly finite) number of big bang universes. And then there are the really crazy theories...;-) No doubt if our civilization continues for centuries, each generation will push the envelope, each discovering more amazing stuff than the last. I find this to be wonderful, the bigger and more outrageous the better- from a philosophical point of view. Now, if only somewhere out there is some civilization that has been around for millions of years, which has done a "Comparative Study of Evolution on a Galactic Scale" and the follow up "Compartive Study of Civilizations on a Galactic Scale". Then of course, an even more advanced civilization will do a compartive study across galaxies. And, somewhere out there is the most advanced, the smartest, of all that may have a deep understanding of the universe on a scale larger than their respective "visible universe". My theory, from a dummy's point of view, is that when we have a better understanding of dark matter and dark energy, somehow there is a lot of infomation contained therein, that could tell us a lot about a big chunk of the universe, maybe beyond "the edge" of the visible universe- such as the "large scale structure" too big for us to see- structures so big that from within any given "visible universe" you could see only a small part of it. Ed Gibbs Joe Zorzin wrote in message ... When astronomers use the term "infinite" in this context, what do they mean? |
#10
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how big is the universe?
Joe Zorzin writes:
http://www.forestmeister.com "Ed Gibbs" wrote in message ... I think when they say "infinite" they mean just that - goes on forever and ever without end. [...] Since the universe was once very small, and as it grew, it must have been finite- how does something go from being finite to infinite? It can't, and it doesn't. Or, does the model say that it was infinite from the beginning, and what does that really mean? See http://www.astro.ucla.edu/~wright/infpoint.html. -- Gordon D. Pusch perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;' |
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