Strange Posted March 11, 2016 Share Posted March 11, 2016 (edited) While the following one is incorrect: if we add infinite observable points, than we should get an infinite Universe It is not necessarily incorrect. But it may be incorrect. Or it may be correct. If the universe is infinite then it is correct. If the universe is not infinite then you cannot add infinite "observable points" and so it is not correct. If there is no limitation, than why the Universe can't be infinite? It may be. Or it may not. I know you find this impossible to deal with but ... [scary music, flashes of lightning, weird sound effects] ... WE DON'T KNOW !!!! Possibly we will never know. It might be impossible to know. Edited March 11, 2016 by Strange Link to comment Share on other sites More sharing options...
David Levy Posted March 11, 2016 Author Share Posted March 11, 2016 (edited) David: "Today, that same spot is 46 billion light-years away, making the diameter of the observable universe a sphere around 92 billion light-years." So, the radius of the whole Universe is 46 BLY." Why does your argument bait and switch from "observable" to "whole" universe? That is a logical error. Thanks Well, in the following article: http://www.space.com/24073-how-big-is-the-universe.html It is stated: "Like a ship in the empty ocean, astronomers on Earth can turn their telescopes to peer 13.8 billion light-years in every direction, which puts Earth inside of an observable sphere with a radius of 13.8 billion light-years. The word "observable" is key; the sphere limits what scientists can see but not what is there. But though the sphere appears almost 28 billion light-years in diameter, it is far larger." Hence, the observable sphere of the Universe is 28 Gly. That is clear. "Scientists know that the universe is expanding. Thus, while scientists might see a spot that lay 13.8 billion light-years from Earth at the time of the Big Bang, the universe has continued to expand over its lifetime. Today, that same spot is 46 billion light-years away, making the diameter of the observable universe a sphere around 92 billion light-years" Threfore, the observable Universe is based on the expansion from the Big Bang. This is now clear to me. Never the less: "According to NASA, scientists know that the universe is flat with only about a 0.4 percent margin of error (as of 2013). A flat universe is an infinite universe; thus the size of the universe is infinite" Hence, if the universe is flat than it should be infinite. The chance that the Universe is flat is - 99.6%. So, the chance that the universe is infinite is 99.6%. Do you agree? Edited March 11, 2016 by David Levy Link to comment Share on other sites More sharing options...
Klaynos Posted March 11, 2016 Share Posted March 11, 2016 It's not a "chance". 0.4% is a comment on the error of the measurements, they are up to 0.4% different to what is measured. So no, I don't agree. Link to comment Share on other sites More sharing options...
Strange Posted March 11, 2016 Share Posted March 11, 2016 Hence, the observable sphere of the Universe is 28 Gly. Oh good grief. Again? Really? Are you related to goldfish? Observable universe: Misconceptions on its size The (current) radius is about 46 billion light years. Do you want to write that down so you don't forget it again. Hence, if the universe is flat than it should be infinite. This is not necessarily true. It depends on the topology. There is a good discussion of that here: http://physics.stackexchange.com/questions/123674/why-does-a-flat-universe-imply-an-infinite-universe Read from "This claim is simply wrong" (a familiar phrase to you by now.) Link to comment Share on other sites More sharing options...
MigL Posted March 11, 2016 Share Posted March 11, 2016 Do you not see that this depends on the size of the observational universe compared to the 'total universe ? If your observable Earth was the size of a parking lot, and you couldn't see or be affected by any other parts of it, But you could measure the curvature of that parking lot, and it was flat with a 0.4 % margin of error, would you conclude that the Earth was flat and infinite in extent ? Or would you say you don't have enough information and refrain from jumping to conclusion ? Link to comment Share on other sites More sharing options...
David Levy Posted March 12, 2016 Author Share Posted March 12, 2016 Do you not see that this depends on the size of the observational universe compared to the 'total universe ? O.K. What is the size of our "total Universe"? If I understand it correctly, it depends on the location of the observer. So, for example, if we can place a virtual observer at the radius end our observable universe, than by definition the updated Observable Universe radius should be twice the size. therefore, in this case, the updated observable Universe radius should be 92 Gly and its diameter is 184 Gly. So, would you kindly advice how far can we set this virtual observer? and what is the real size of our total universe? Link to comment Share on other sites More sharing options...
ACG52 Posted March 12, 2016 Share Posted March 12, 2016 If I understand it correctly You don't. Link to comment Share on other sites More sharing options...
Strange Posted March 12, 2016 Share Posted March 12, 2016 What is the size of our "total Universe"? Nobody knows. As the article you says, it may well be infinite because it appears t be flat. If I understand it correctly, it depends on the location of the observer. As we can take it as an axiom that you don't understand, we can be fairly confident that the size of the universe has nothing to do with where you are. Is the world a different size for people in Paris or New York? So, for example, if we can place a virtual observer at the radius end our observable universe, than by definition the updated Observable Universe radius should be twice the size. No. The observable universe is the universe that an observer can observe. From any point it is 46 billion light years radius. So, would you kindly advice how far can we set this virtual observer? and what is the real size of our total universe? The observer can be anywhere. No one knows the size of the universe. Oh, and before you ask: No one knows the size of the universe. And to answer your next question: No one knows the size of the universe. OK? Is the world a different size for people in Paris or New York? There may a be a useful analogy here. On the Earth, when you look around, there is a maximum distance you can see, called the horizon. Of the top of my head, I don't remember the distance (and it depends on your altitude) but let's say it is 30 miles. So you can see a maximum of 30 miles in each direction. That is your "observable Earth". Someone 30 miles from you can see 30 miles in each direction, that is their observable Earth. Someone in China can see 30 miles in each direction, that is their observable Earth. So the "observable Earth" is a fixed size but different for each observer. The earth is of finite size (but unbounded, remember) so you can consider it to be made up of a finite number of "observable Earths". That may or may not be true of the Universe. (Because, and you may not know this, we don't know how big the universe is or if it infinite. Bet that's a surprise to you.) 1 Link to comment Share on other sites More sharing options...
swansont Posted March 12, 2016 Share Posted March 12, 2016 If I understand it correctly, it depends on the location of the observer. So, for example, if we can place a virtual observer at the radius end our observable universe, than by definition the updated Observable Universe radius should be twice the size. therefore, in this case, the updated observable Universe radius should be 92 Gly and its diameter is 184 Gly. An observer any distance away is not in the same sphere. You don't get to arbitrarily redefine this. How would you get 46 billion ly away in the first place? How would you communicate what you see? What is a virtual observer, anyway? Link to comment Share on other sites More sharing options...
David Levy Posted March 12, 2016 Author Share Posted March 12, 2016 (edited) There may a be a useful analogy here. On the Earth, when you look around, there is a maximum distance you can see, called the horizon. Of the top of my head, I don't remember the distance (and it depends on your altitude) but let's say it is 30 miles. So you can see a maximum of 30 miles in each direction. That is your "observable Earth". Someone 30 miles from you can see 30 miles in each direction, that is their observable Earth. Someone in China can see 30 miles in each direction, that is their observable Earth. Excellent example. Now, let's assume that you are in the ocean. The 30 Miles will be called - "observable view". About 20 Miles away from you, one of your best friend is located (me of course). We can see each other and we can communicate. The question: Do you agree that as good friends who are willing to share their observable view, can we cover more ocean view than each one of us individually? If so, what is our maximal shared observable view? Edited March 12, 2016 by David Levy Link to comment Share on other sites More sharing options...
Endy0816 Posted March 12, 2016 Share Posted March 12, 2016 Based on c. You can't cheat it. The light that reached him will be reaching you at the same time as his message does. Link to comment Share on other sites More sharing options...
swansont Posted March 12, 2016 Share Posted March 12, 2016 We can see each other and we can communicate. Which makes this a really poor example. "Shared observable view" is a nonsensical phrase in the context of the observable universe. Link to comment Share on other sites More sharing options...
imatfaal Posted March 12, 2016 Share Posted March 12, 2016 ! Moderator Note David Levy This thread will go nowhere till you stop immediately responding to posts and instead start trying to understand the ideas before typing. If the thread continues in this current direction - ie if you continue with your lack of real engagement - I will lock the thread. And for crying out loud stop with the patronising lecturing tone and the idiotic use of the rhetorical. It would be annoying and insulting from a Professor of Astrophysics - from a forum poster who started the thread not understanding the concept of the observable universe it is infuriating and trollish. If you post "do you agree" before totally misrepresenting/misunderstanding someone's idea then I would not be at all surprised if the post just gets trash-canned. Do not respond to this moderation within the thread Link to comment Share on other sites More sharing options...
Endy0816 Posted March 12, 2016 Share Posted March 12, 2016 (edited) I think the issue is that OP is thinking that it is only a matter of optics, rather than a limit imposed by the finite speed of light. Note other factors involved as well. Redshift, expansion. Edited March 12, 2016 by Endy0816 Link to comment Share on other sites More sharing options...
David Levy Posted March 12, 2016 Author Share Posted March 12, 2016 (edited) I think the issue is that OP is thinking that it is only a matter of optics, rather than a limit imposed by the finite speed of light. Note other factors involved as well. Redshift, expansion. No. The only problem is that I have no idea what is the total size of the Universe. It seems that none of us really knows the answer. As it is stated by Strange: It is not necessarily incorrect. But it may be incorrect. Or it may be correct. If the universe is infinite then it is correct. If the universe is not infinite then you cannot add infinite "observable points" and so it is not correct. It may be. Or it may not. I know you find this impossible to deal with but ... [scary music, flashes of lightning, weird sound effects] ... WE DON'T KNOW !!!! Possibly we will never know. It might be impossible to know. It's quite difficult for me to accept "don't know" as an answer. Therefore, I have asked several questions from different perspectives in order to get better understanding on this issue. Just as an example Let's assume that there is no "shared" observable Universe. What shall we understand from this answer? One possibility is that this could be an indication that our observable universe is perfectly match with the observable Universe of someone which is located 1Gly or even 10Gly away from us. Therefore, we could understand that our observable Universe should perfectly match the size of the Total universe. However – we know that this is incorrect The second possibility is that the total universe is smaller than the observable Universe. - That for sure is incorrect. The last possibility is that the total universe is bigger than the observable Universe. – And that no one really knows. We could continue the discussion without any real progress. Therefore, thanks for the support Edited March 12, 2016 by David Levy Link to comment Share on other sites More sharing options...
Phi for All Posted March 12, 2016 Share Posted March 12, 2016 The only problem is that I have no idea what is the total size of the Universe. It seems that none of us really knows the answer. ! Moderator Note Ta-da! And we're done here. No more threads like this, PLEASE. This was 5 pages of people telling you what you finally posted here. Link to comment Share on other sites More sharing options...
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