Strange Posted January 20, 2016 Posted January 20, 2016 By the way: you keep talking about the importance of evidence and theory. This is one of those cases where the theory came first (with its prediction of what we should expect to find). When Hubble's law was discovered it was consistent with the theory, but not convincing by itself. Then various other bits of evidence were found, all consistent with the theory, so it got stronger. Then the CMB was found with exactly the properties predicted. That was the death of the steady state and alternative models.
swansont Posted January 20, 2016 Posted January 20, 2016 No no no. A billion light years is a unit of distance. Not years. During this time the universe has been expanding so the distance of the light path will be GREATER than 13 billion years (emphasis added) light years
David Levy Posted January 20, 2016 Author Posted January 20, 2016 Correct. It took 13 billion YEARS. At the time it was emitted, it was much less than 13 billion light years away. It is now much more than 13 billion light years away. You should find out how to calculate these distances and then you will gain a better understanding. Thanks So you agree that the light of this galaxy had been emitted 13 billion years ago. In other ward - it took the light 13 Billion years to get mother Earth. If we ignore the expantion (just for one moment) - it is correct to assume that this light had been emitted from a distance of 13 Billion Ly? -1
Strange Posted January 20, 2016 Posted January 20, 2016 If we ignore the expantion (just for one moment) - it is correct to assume that this light had been emitted from a distance of 13 Billion Ly? If you live in a different universe, then that might be true. But in this universe it is not true(*). You can't ignore expansion. You might as well say, "if we ignore the speed of light" or "if we ignore the fact we are humans" or "if we ignore the fact that this is a science forum". (*) as far as we know ... current best theories ... evidence ... consistent ... within margins of error ... further evidence ... yada yada
Mordred Posted January 20, 2016 Posted January 20, 2016 Thanks So you agree that the light of this galaxy had been emitted 13 billion years ago. In other ward - it took the light 13 Billion years to get mother Earth. If we ignore the expantion (just for one moment) - it is correct to assume that this light had been emitted from a distance of 13 Billion Ly? This would be true only if there is no expansion/contraction. However at no point in the Universe history has it not been expanding. Different rates of expansion but expansion nonetheless.
David Levy Posted January 20, 2016 Author Posted January 20, 2016 (edited) If you live in a different universe, then that might be true. But in this universe it is not true(*). You can't ignore expansion. You might as well say, "if we ignore the speed of light" or "if we ignore the fact we are humans" or "if we ignore the fact that this is a science forum". Thanks!!! So, in a different universe it is correct. Let's call it Alfa Universe. In that Alfa Universe they didn't heard about the BBT or expansion theories. But they see all the features that we get. In that Alfa universe, they do not ignore the speed of light - as light which travels 13 B ly, means a distance of 13 Bly. So, can we agree that in Alfa universe - a redshift of 12 represents a distance of 13 B ly? Can we also agree that a redshift of 1100 represents a distance of about 1,300 Billion Ly? Edited January 20, 2016 by David Levy
Strange Posted January 20, 2016 Posted January 20, 2016 Thanks!!! So, in a different universe it is correct. Let's call it Alfa Universe. In that Alfa Universe they didn't heard about the BBT or expansion theories. But they see all the features that we get. In that Alfa universe, they do not ignore the speed of light - as light which travels 13 B ly, means a distance of 13 Bly. So, can we agree that in Alfa universe - a redshift of 12 represents a distance of 13 B ly? Can we also agree that a redshift of 1100 represents a distance of about 1,300 Billion Ly? In your fantasy universe, there is no expansion therefore no changing scale factor and therefore no redshift. How about this: in Alfa universe magic exists and all unicorns are pink (because they are redshifted).
pzkpfw Posted January 20, 2016 Posted January 20, 2016 So, can we agree that in Alfa universe - a redshift of 12 represents a distance of 13 B ly? Please explain what causes redshift in Universe Alfa. 1
David Levy Posted January 20, 2016 Author Posted January 20, 2016 (edited) In your fantasy universe, there is no expansion therefore no changing scale factor and therefore no redshift. No, as I have stated, in that fantasy alfa universe they see the same redshift as we do. So, can we agree that in that in Alfa universe - a redshift of 12 represents a distance of 13 B ly? Can we also agree that a redshift of 1100 represents a distance of about 1,300 Billion Ly? Edited January 20, 2016 by David Levy
Strange Posted January 20, 2016 Posted January 20, 2016 No, as I have stated, in that fantasy alfa universe they see the same redshift as we do. Why? What causes it?
David Levy Posted January 20, 2016 Author Posted January 20, 2016 Why? What causes it? If light travels 13 Bly in Alfa universe, than the distance is 13 Bly. We have already agreed on that. However, a galaxy that its light travels 13 Bly, had a redshift of 12. Therefore, can we agree that in that Alfa universe - a redshift of 12 represents a light travels of 13 B ly? In this case, a redshift of 12 represents a distance of 13 B ly. In the same toke - a redshift of 1100 should represent a distance of about 1,300 Billion Ly.
pzkpfw Posted January 20, 2016 Posted January 20, 2016 That doesn't answer the question. Without a mechanism for what causes redshift in your Universe, then you're having to make yet another unfounded assumption in making the ~ if 12-->13, then 1100-->1300 ~ claim.
Strange Posted January 20, 2016 Posted January 20, 2016 If light travels 13 Bly in Alfa universe, than the distance is 13 Bly. We have already agreed on that. However, a galaxy that its light travels 13 Bly, had a redshift of 12. Therefore, can we agree that in that Alfa universe - a redshift of 12 represents a light travels of 13 B ly? In this case, a redshift of 12 represents a distance of 13 B ly. In the same toke - a redshift of 1100 should represent a distance of about 1,300 Billion Ly. What is the cause of the redshift in this? If you are just going to invent random redshifts with no cause and random distance with no basis in reality, then you are not doing science. It is just The Game of Thrones. (But less interesting.)
David Levy Posted January 20, 2016 Author Posted January 20, 2016 That doesn't answer the question. Without a mechanism for what causes redshift in your Universe, then you're having to make yet another unfounded assumption in making the ~ if 12-->13, then 1100-->1300 ~ claim. That is a severe mistake! In any real world problem, we are supposed to set all the evidences on the table. It doesn't matter if we like it or not. All the evidences must be clear and open. Just after understanding the meaning of each evidence, we can go ahead and try to look for a correct solution. No one can give us a confirmation that we will be able to find solution. We might even find that our current theory is the correct one. However, in our universe - we first set the solution, and then try to fix it to the evidences. About 50 years ago we had a brilliant idea of the BBT. It was great theory for its time. However, after 50 years, and after so many discoveries, it’s the time to open the meaning of those discoveries/evidences without covering it with BBT/Expansion sheet. In Alfa universe, they insist to understand the meaning of those evidences. Please – let's help them. Let's discover the real meaning of each and every evidence, without covering it by any kind of sheet.
Strange Posted January 20, 2016 Posted January 20, 2016 But you are just making things up. That isn't evidence, it is fantasy. Also, in our universe we knew the cause of the redshift before it was found. So, what is the cause of the redshift in your universe? But, if they see all the same things that we do, then they probably live in a similar universe described by GR and the explanation for everything they see is that their universe is expanding. However, in our universe - we first set the solution, and then try to fix it to the evidences. Nonsense. You are seriously in a fantasy world now.
swansont Posted January 20, 2016 Posted January 20, 2016 No, as I have stated, in that fantasy alfa universe they see the same redshift as we do. So, can we agree that in that in Alfa universe - a redshift of 12 represents a distance of 13 B ly? Can we also agree that a redshift of 1100 represents a distance of about 1,300 Billion Ly? So now we're discussing science fiction? Is there a point to this? This is a science forum. However, in our universe - we first set the solution, and then try to fix it to the evidences. Bollocks. What evidence is "fixed"?
Strange Posted January 20, 2016 Posted January 20, 2016 So, can we agree that in that in Alfa universe - a redshift of 12 represents a distance of 13 B ly? Can we also agree that a redshift of 1100 represents a distance of about 1,300 Billion Ly? I would rather discuss the Beta universe where a redshift of 1100 represents a distance of 13 B ly. And a redshift of 12 represents a distance of about 1,300 Billion Ly. Except on Tuesdays.
David Levy Posted January 20, 2016 Author Posted January 20, 2016 (edited) What is the cause of the redshift in this? Why it is so important to understand the cause of the redshift before understanding the real meaning of redshift? We actually know exactly the meaning of redshift http://cosmology101.wikidot.com/redshift-and-expansion "The further away an object is the greater the amount of redshift." For example - If we have some sort of disease, does it mean that we should start by understanding the cause of it? No. First we go the doctor. We let him know all the illness evidences which we have. We open it one by one. Just after getting all the evidences about our disease, the doctor might find the main cause for it. However, in our Universe - it seems that it works differently. We have to start by the cause. So, sorry Alfa Universe - you won't get help today. Edited January 20, 2016 by David Levy
Strange Posted January 20, 2016 Posted January 20, 2016 Why it is so important to understand the cause of the redshift before understanding the real meaning of redshift? Because that is the only way we can draw any conclusions. Otherwise you can just make up any "facts" you like. We have to start by the cause. Yep. That is what happened in our universe. Without knowing the cause we wouldn't have had an explanation for redshift, the CMB or any of the other evidence for the big bang model. In this case, it was theory (cause) first and then the evidence to confirm it.
swansont Posted January 21, 2016 Posted January 21, 2016 Why it is so important to understand the cause of the redshift before understanding the real meaning of redshift? Because we're doing science, not science fiction. Or magic. 1
MigL Posted January 21, 2016 Posted January 21, 2016 Are we just enabling him now ? David has no clue what red-shift is, nor what causes it. If he did he wouldn't be asking such non-sensical questions. Is it really that difficult to type it into your browser and go to the Wiki explanation David ? Please ! Everybody's head is really starting to hurt from banging it against the proverbial wall.
ajb Posted January 21, 2016 Posted January 21, 2016 Why it is so important to understand the cause of the redshift before understanding the real meaning of redshift? So in this other universe the occupants are amazed to see that they are bathing in a near perfect thermal bath of about 2.725K. In our Universe we know that this came from the recombination epoch when the temperature of the Universe was about 3000K. It is the expansion of the Universe that has cooled this background temperature. The occupants of your other universe will need some way of explaining the origin of this radiation, presumably they will come to a non-static universe model.
Phi for All Posted January 21, 2016 Posted January 21, 2016 ! Moderator Note David, you're certainly not stupid, but you're ignorant in this area, and you're refusing the very help you need by not learning basics. Arguing from incredulity, waving hands with no evidence to support you but your own insistence is NOT what science is about. Closing the thread. Don't open another on the same topic, unless you're willing to show more rigor. 2
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