David Levy
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Where Does Space End? It Must End Somewhere!
David Levy replied to Edisonian's topic in Astronomy and Cosmology
I'm quite confused. You have stated that: So, if it is infinite, then 13.8 Bly ago it was also infinite? Hence, why do we need to set it (13.8 Bly ago) to finite hot dense state? -
Where Does Space End? It Must End Somewhere!
David Levy replied to Edisonian's topic in Astronomy and Cosmology
So, if it is infinite, why do we need the BBT? -
Where Does Space End? It Must End Somewhere!
David Levy replied to Edisonian's topic in Astronomy and Cosmology
Yes, that is excelant explanation. If 13.8 Bly ago the Universe had started as finite than it can't be infinite today. Fully agree. Somehow, we must offer better explanation for infinite Universe. -
Where Does Space End? It Must End Somewhere!
David Levy replied to Edisonian's topic in Astronomy and Cosmology
So, as the Universe is many times larger than 46 Bly, and especially if it is infinite: How can we explain that size of Universe by the BBT? -
Lambda-CDM (supposition vs. evidence)
David Levy replied to shmengie's topic in Astronomy and Cosmology
Can you please elaborate about those problems? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
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'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 -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
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? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
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? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
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? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
So, the following statement is correct: technically, we can add more and more observable points. For each point, the observable universe will be 46Bl While the following one is incorrect: if we add infinite observable points, than we should get an infinite Universe Why can't we add infinite number of observer points? Is there any limitation for that? If there is no limitation, than why the Universe can't be infinite? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
Thanks Do you mean that our observable universe is 46Gly while someone which is located 10Gly away will also have the same size of observable universe? Therefore, each observer should be at the center of his visible Universe, regardless from its location. Is it correct? If so, than technically, we can add more and more observable points. For each point, the observable universe will be 46Bly. Hence, if we add infinite observable points, than we should get an infinite Universe. Is it correct? If so, then why don't we say that the size of the universe in infinite? Did I miss something? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
O.K. There is no edge. However: What shall we see at the end of the 46 Gly radius? I assume that in the direction of Earth we should see galaxies. But, what shall we see at the opposite direction? What shall we see at a distance (radius) of 50 Gly or even 100 Gly? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
Please, If you claim that there is a curvature - than I fully agree. If you claim that there is no edge - than I fully agree. You set the frame for the curvature. However, as agree, there must be one frame for all. So, under the same frame, how could it be that the expansion can work (expand), while light must stay in the loop??? Don't you see the paradox? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
Thanks So you agree that curvature affects the expansion as it affects the light. Both should move in the same pattern due to the influence of the curvature. However, when we have started the discussion it was stated that the Universe has no edge as the light travels in some sort of a loop (as on the surface of a basketball). Hence, if the light moves in a loop, than the expansion should also move in a loop. However, that contradicts the main idea of the expansion. How could it be that there is any expansion if it moves in a loop (as on the surface of a basketball)? So, how did we calculate that the radius of the current observable Universe is 46 Bly? Did we assume a straight forward expansion? If so, than it is a severe mistake. The curvature must force almost a zero expansion. How can we explain this new paradox? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
What about expansion - How could it be that the curvature affects the light but it doesn't affect the expansion? Sorry, but we can't add the curvature just when it can help us. If we add it, we must consider its impact from the first moment of the Universe. Hence, we have to consider how the expansion should be under the impact of the curvature. -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
I didn't claim that we are living in a 2D Universe. It is very clear to me that the curvature should add one more dimension. So, with the following explanation about the curvature, they speak clearly about the radius of curvature. http://mathworld.wolfram.com/Curvature.html "The curvature of a two-dimensional curve is related to the radius of curvature of the curve's osculating circle. Consider a circle specified parametrically by…" So, in a flat paper, there is no radius. In a ball there is a radius. Therefore, although they are discussing about the surface (which is only 2D) this surface is part of a three dimensions shape - which has a radius. As you can see, the calculation is similar to a surface of a ball. We can't set a real calculation of the surface of a ball without knowing its radius. So there in one more dimension. Can we set a calculation of the surface of a ball without knowing its radius? Hence, in principal, the radius of curvature is like added spatial to the 2D. Why do you disagree about it? In the same token, if we have to add a curvature to a universe, than somehow we must add the radius of curvature factor to our formulas about the Universe. I will call it one more spatial. You can call it at any name which you like. However, without information about that radius of curvature of the Universe, our calculations aren't accurate. Therefore, as usual we must take a decision: If we believe that the Universe has no curvature, than all our current formulas are perfectly O.K.If we believe that the universe has a curvature, than we must add the impact of the radius of curvature to our formulas and calculations. Why that message is incorrect? With regards to the expantion - I didn't get you answer about the impact of the curvature on the expansion. How could it be that the curvature affects the light but it doesn't affect the expansion? Sorry, but we can't add the curvature just when it can help us. If we add it, we must consider its impact from the first moment of the Universe. Hence, we have to consider how the expansion should be under the impact of the curvature. -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
Sorry, it is stated clearly: "The curvature of a two-dimensional curve is related to the radius of curvature of the curve's osculating circle. Consider a circle specified parametrically by…" So, actually, as I have already stated, a two dimension had been converted to three dimensions radius of curvature. So why you disagree? Please also look at the mathematics. It is totally different than a simple formulas for two dimension flat paper. How can you explain it? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
Sorry, that is totally incorrect. Think about paper and a surface of basketball. is it the same? Can you use the same mathematics formulas to both cases (even if both represent only a surface)? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
Well, please look at the picture when Ω = 1 (Flat) Instead of universe we can think about a flat paper with only two spatial. However, If Ω is different than 1, then it is like we band this paper. Therefore, instead of two spatial we actually get three spatial. (So, instead of a flat shape we get a volume – or some sort of a ball) Even if you think about the surface of that paper, it is not the same. We have got totally different shape as we add one more spatial. Hence, If Ω is different than 1, by definition we add one more spatial. So, if the Universe has three spatial, this banding activity should add one more spatial. Please advice why you disagree? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
Thanks for the articles. With regards to the curvature; http://cosmology101.wikidot.com/universe-geometry It is stated: "In a flat curvature the three angles of a equilateral triangle will add up to 1800. A positive curvature will add up to greater than 1800, a negative curvature will add up to less than 1800" Please advice if you agree with the following: In a flat curvature - The Universe has only three dimensions. In a positive/negative curvature - The Universe has more than three dimensions. Now, on what kind of curvature our mathematics had been developed for. In other words, could it be that Einstein' and Friedman' equations had been developed only for a flat curvature Universe? If so, does it mean that new/updated formulas should be used for any type of curvature which is not flat (positive/negative curvature)? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
As I have already stated, it is perfectly O.K. to use the analogy of the surface of a sphere. Therefore, yes - we can assume that the universe acts as as surface of a sphere. However, if it is a surface of a sphere then everything should react on the same basis. Hence, If the light goes as in a surface of a sphere, then also the expansion should work under the same conditions. So, how could it be that we assume that the light goes in some sort of loop, while the expansion goes straight on? Isn't it the same universe? Thanks Mordred. I will read the article. Yes, fully agree. We can choose any point of view. However, it must work for all. - Light and Expansion. Hence, if there is a curvature in light, then there must be a curvature in the expansion. Therefore, if this is correct, than we need to adjust all our calculations about the expansion. Do you agree? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
Yes, I fully understand. But we can't say again - "sorry we don't know, however, based on what we don't know, it is clear that what you say is incorrect". So, if the Universe is flat, then what does it means? How that might affect the idea that a finite Universe has no edge? If it has a curvature time - then what does it mean? How this kind of phenomenon could affect the Universe from the first moment. Is it a constant phenomenon? Why we didn't add it in our formulas and calculations? Does it mean that Einstein and Friedman have missed something? If that is correct, than could it be that the expansion is also in a the positive curvature case? Why the light can go in loop, while the expansion is not in the loop? So, could it be that we are living in some sort of a close loop universe? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
Thanks Mordred Well, I'm not sure that I fully understand the meaning of 3 torus or a sphere. However, if you claim that the Universe is a 3 torus or a sphere then, yes it could be that it is finite with no edge. But you have to prove that the Universe is 3 torus or a sphere and also explain what is it. Do you mean that there is a chance that eventually, the light will come back to the starting point? If yes, than it is a close loop - similar to the surface of the basketball. Then this is perfectly O.K. to assume that there is no end. However, if the light will travel with the curvature. to the infinite (in a finite universe), then at some point it must hit the end of the finite universe I assume that this is a pure theory. Is it correct? If so, please try to distinguish between theory and evidence. Is it also a theory or we have a clear evidence for that? So, do we have measurements results (evidences) which support a flat universe? If so, why do we consider about "positive curvature case"? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
Well I agree that an observer outside the Universe might see it differently from us. But, a 46 billion LY radius sphere is a 92 billion Ly diameter sphere. However - 92 billion Ly diameter sphere is a limited number. So, what the observer might see at the end of those 92 billion Ly? In the same token- Hence, do you agree about the following? "The Universe has only three dimensions, it is finite but it has no edge" So, what is the meaning of finite? Do you agree that if we go at one direction all the way, then at some point we will get to an end? If so, what shall we see? However, if there is no end – then why do we claim that it is finite? -
Are we located at the core of the Universe?
David Levy replied to David Levy's topic in Speculations
What physical laws? So, Do you agree that the Universe has only three dimensions? If so - in any three dimensions there must be an edge. Why are you all against it? I'm not sure that I fully understand this explanation. Would you kindly elaborate? In the following 2D example - If we go over the surface of the basketball, then, there will be no end as it is a close loop. Therefore, there is no edge. Actually, if we start at one point and walk in one direction, then we might get back to the same point. So, do you mean that the Universe is some sort of a close loop in three dimensions? Hence, can we assume that if we go in one direction, eventually we might get back to the same spot?