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Bjoern Feuerbacher wrote in message ...
Marcel Luttgens wrote: Bjoern Feuerbacher wrote in message ... Marcel Luttgens wrote: [snip] Evasion noted. Answer my questions above. Do you claim that this formula is wrong? Or that applying it to a homogeneous universe would not give zero? Let's make some "reverse engineering": O.k. Let's consider an imaginary stable spherical universe of mean density rho and radius R. Let's consider an imaginary stable homogeneous universe of density rho, with the shape of a cuboid which extends infinitely in two directionsand has the thickness D in the third direction. At the surface of the sphere, the acceleration A of gravity is given by the formula A = GM/R^2, where G is the gravitational constant. At both surfaces of the cuboid, the acceleration A of gravity is given by the formula A = G D rho / 2, where G is the gravitational constant. The acceleration is everywhere parallel to the direction in which the cuboid has the thickness D. At a distance d R from the center of the sphere, the acceleration of gravity becomes a = A*d/R = (GM/R^3)*d At a height d D above the middle plane of the cuboid, the acceleration of gravity becomes a = A*d/D = G d rho / 2. As rho = M/V and V = (4/3)*pi*R^3, M/R^3 = (4/3)*pi*rho, hence a = [(4/3)*G*pi*rho]*d I do not need this step, since my formula above expresses a already in terms of rho, not in terms of M. In this formula, a is independant from R, thus R can take any value. Hence, the formula should apply to a stable infinite universe of mean density rho. In this formula, a is independent of D, thus D can take on any value. Hence, the formula should apply to a stable infinite homogeneous universe of density rho. I.e. in an infinitely extended homogeneous universe, the gravitational field is parallel everywhere and points to a certain plane. Not the result you wanted to achieve, eh? Will you now *finally* admit that there is something wrong with your approach? Your approach is nice, but doesn't lead to H or formulae applicable to our universe. Mine does. For instance, d = 13.7 * z/(z+1) Gly leads to about the same results as those obtained by Ned Wright with his calculator for a flat universe with H0=71 and Omega M = 0.27. The only difference lies in the choice of Omega M = 0.42 instead of 0.27. As I said, the proof of the pudding is in the eating. [snip] Bye, Bjoern Marcel Luttgens |
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In message , Marcel
Luttgens writes Your approach is nice, but doesn't lead to H or formulae applicable to our universe. Mine does. For instance, d = 13.7 * z/(z+1) Gly leads to about the same results as those obtained by Ned Wright with his calculator for a flat universe with H0=71 and Omega M = 0.27. The only difference lies in the choice of Omega M = 0.42 instead of 0.27. As I said, the proof of the pudding is in the eating. I may have missed it, but have you explained how H0 applies to your universe ? (which is static) -- What have they got to hide? Release the ESA Beagle 2 report. Remove spam and invalid from address to reply. |
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#464
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On Fri, 03 Sep 2004 14:22:48 +0200, Bjoern Feuerbacher
wrote: BTW, how *could* such a universe be stable? You yourself say that there is a gravitational acceleration, so it can't be stable!!! gravitational acceleration? Does anyone deny that a gravitational acceleration is a constant for any given mass? I thought at least that was agreed on. |
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Jonathan Silverlight wrote in message ...
In message , Marcel Luttgens writes Bjoern Feuerbacher wrote in message ... Well, the result you get for the gravitational field of the universe then is obviously wrong, as my argument above shows. Your argument implies that gravity can be felt at distances greater than c/H. You keep talking about c/H and cH, but if H has its usual meaning surely it doesn't apply to a static universe? At a distance d R from the center of the sphere, the acceleration of gravity becomes a = A*d/R = (GM/R^3)*d As rho = M/V and V = (4/3)*pi*R^3, M/R^3 = (4/3)*pi*rho, hence a = [(4/3)*G*pi*rho]*d In this formula, a is independant from R, thus R can take any value. Hence, the formula should apply to a stable infinite universe of mean density rho. As the dimension of a is L/T^2, the dimension of (4/3)*G*pi*rho is 1/T^2, and the square root of this expression corresponds to the inverse of a time. The formula a = [(4/3)*G*pi*rho]*d can thus be written a = K^2 * d Or the Hubble constant also corresponds to 1/T, and is given, according to Steven Weinberg (see Gravitation and Cosmology, 1972, p. 476) by the formula H^2 = (8/3)*G*pi*rho(c), where rho(c) is the critical density of the universe. As the ratio of the present density rho to the critical density rho / rho(c) = 2*q0, and q0 is likely 1, rho(c) = rho/2. Then H^2 = (4/3)*G*pi*rho(c) = K^2, or K = H. The formula giving the acceleration of gravity at a distance d from a point P situated in a stable and even infinite (as R can take any value) universe can thus also be written a = H^2 * d Marcel Luttgens |
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Marcel Luttgens wrote:
Will you also answer my other post? Bjoern Feuerbacher wrote in message ... Marcel Luttgens wrote: Bjoern Feuerbacher wrote in message ... Marcel Luttgens wrote: [snip] Evasion noted. Answer my questions above. Do you claim that this formula is wrong? Or that applying it to a homogeneous universe would not give zero? Let's make some "reverse engineering": O.k. Let's consider an imaginary stable spherical universe of mean density rho and radius R. Let's consider an imaginary stable homogeneous universe of density rho, with the shape of a cuboid which extends infinitely in two directionsand has the thickness D in the third direction. At the surface of the sphere, the acceleration A of gravity is given by the formula A = GM/R^2, where G is the gravitational constant. At both surfaces of the cuboid, the acceleration A of gravity is given by the formula A = G D rho / 2, where G is the gravitational constant. The acceleration is everywhere parallel to the direction in which the cuboid has the thickness D. At a distance d R from the center of the sphere, the acceleration of gravity becomes a = A*d/R = (GM/R^3)*d At a height d D above the middle plane of the cuboid, the acceleration of gravity becomes a = A*d/D = G d rho / 2. As rho = M/V and V = (4/3)*pi*R^3, M/R^3 = (4/3)*pi*rho, hence a = [(4/3)*G*pi*rho]*d I do not need this step, since my formula above expresses a already in terms of rho, not in terms of M. In this formula, a is independant from R, thus R can take any value. Hence, the formula should apply to a stable infinite universe of mean density rho. In this formula, a is independent of D, thus D can take on any value. Hence, the formula should apply to a stable infinite homogeneous universe of density rho. I.e. in an infinitely extended homogeneous universe, the gravitational field is parallel everywhere and points to a certain plane. Not the result you wanted to achieve, eh? Will you now *finally* admit that there is something wrong with your approach? Your approach is nice, but doesn't lead to H or formulae applicable to our universe. Mine does. *sigh* You failed to get the point. With your approach, one gets the result that there is a spherical symmetric gravitational field in a universe with a homogeneous density. With my approach, one gets the result that in such a universe, there exists a homogeneous gravitational field pointing to a plane. Obviously not both results can be right at once, hence at least one of them *has* to be wrong. But both approaches are *equally* valid. Conclusion: *both* approaches are *not* valid. What's your problem with understanding this *very simple* logic? For instance, d = 13.7 * z/(z+1) Gly leads to about the same results as those obtained by Ned Wright with his calculator for a flat universe with H0=71 and Omega M = 0.27. Which results do you mean, specifically? And what does "about the same" mean? How big are the deviations? The only difference lies in the choice of Omega M = 0.42 instead of 0.27. As I said, the proof of the pudding is in the eating. Right. Please note that the BBT explains all the stuff below. I wonder how you explain it... * Where does the Cosmic Microwave Background Radiation come from in your model? Why is it so marvelously homogeneous? How do you explain the power spectrum of the fluctuations in it, e.g. the acoustic peak? How do you explain that when one takes these fluctations as representing density fluctuations, and does computer simulations to see how these density fluctuations grow with time, one gets the present-day large scale structure of the universe? How do you explain that the temperature of the CMBR changes with time? * How do you explain that the universe is static and does not collapse under the influence of gravity? * How do you explain that there is evidence that in the early universe, the expansion of the universe was decelerating, and only some billion years ago started accelerating? * How do you explain that the oldest stars we can see are only about 13 billion years old, although small stars can live for hundreds of billions of years? If there was no Big Bang, but the universe is static, why don't we see such stars? * How do you explain that galaxies far away from us look very different from the ones close to us? (see e.g. quasars, or the Hubble Ultra Deep Field) * How do you explain the abundance of elements in the universe? If it existed for an infinite time in the past, why are not all elements fused to iron now? * What about the second law of thermodynamics? If the universe is infinitely old, entropy should be at a maximum now. Bye, Bjoern |
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Bjoern Feuerbacher wrote in message ...
Marcel Luttgens wrote: Will you also answer my other post? *** Sure. Bjoern Feuerbacher wrote in message ... Marcel Luttgens wrote: Let's consider an imaginary stable spherical universe of mean density rho and radius R. Let's consider an imaginary stable homogeneous universe of density rho, with the shape of a cuboid which extends infinitely in two directionsand has the thickness D in the third direction. At the surface of the sphere, the acceleration A of gravity is given by the formula A = GM/R^2, where G is the gravitational constant. At both surfaces of the cuboid, the acceleration A of gravity is given by the formula A = G D rho / 2, where G is the gravitational constant. The acceleration is everywhere parallel to the direction in which the cuboid has the thickness D. At a distance d R from the center of the sphere, the acceleration of gravity becomes a = A*d/R = (GM/R^3)*d At a height d D above the middle plane of the cuboid, the acceleration of gravity becomes a = A*d/D = G d rho / 2. As rho = M/V and V = (4/3)*pi*R^3, M/R^3 = (4/3)*pi*rho, hence a = [(4/3)*G*pi*rho]*d I do not need this step, since my formula above expresses a already in terms of rho, not in terms of M. In this formula, a is independant from R, thus R can take any value. Hence, the formula should apply to a stable infinite universe of mean density rho. In this formula, a is independent of D, thus D can take on any value. Hence, the formula should apply to a stable infinite homogeneous universe of density rho. I.e. in an infinitely extended homogeneous universe, the gravitational field is parallel everywhere and points to a certain plane. Not the result you wanted to achieve, eh? Will you now *finally* admit that there is something wrong with your approach? Your approach is nice, but doesn't lead to H or formulae applicable to our universe. Mine does. *sigh* You failed to get the point. With your approach, one gets the result that there is a spherical symmetric gravitational field in a universe with a homogeneous density. With my approach, one gets the result that in such a universe, there exists a homogeneous gravitational field pointing to a plane. Obviously not both results can be right at once, hence at least one of them *has* to be wrong. But both approaches are *equally* valid. Conclusion: *both* approaches are *not* valid. What's your problem with understanding this *very simple* logic? *** Some humans are hairy, other not. Are you implying that for instance Chineses are not human? For instance, d = 13.7 * z/(z+1) Gly leads to about the same results as those obtained by Ned Wright with his calculator for a flat universe with H0=71 and Omega M = 0.27. Which results do you mean, specifically? And what does "about the same" mean? How big are the deviations? *** The deviations are small. Here are some results (light travel time in Gy): z Ted Wright (Omega M = 0.27) Luttgens (d = 13.7 * z/(z+1)) 0.1 1.29 1.25 0.5 5.02 4.57 1 7.73 6.85 3 11.48 10.28 6 12.72 11.74 z Ted Wright (Omega M = 0.42) 0.1 1.27 0.5 4.79 1 7.18 3 10.29 6 11.21 As you implied, all results can be wrong. The only difference lies in the choice of Omega M = 0.42 instead of 0.27. As I said, the proof of the pudding is in the eating. Right. Please note that the BBT explains all the stuff below. I wonder how you explain it... *** If cosmologists were not BBT biased, they could perhaps explain the stuff below by hypothetizing a stable univere. * Where does the Cosmic Microwave Background Radiation come from in your model? Why is it so marvelously homogeneous? How do you explain the power spectrum of the fluctuations in it, e.g. the acoustic peak? How do you explain that when one takes these fluctations as representing density fluctuations, and does computer simulations to see how these density fluctuations grow with time, one gets the present-day large scale structure of the universe? How do you explain that the temperature of the CMBR changes with time? *** It is not marvelously homogeneous. This is the biggest problem for BBT proponents. * How do you explain that the universe is static and does not collapse under the influence of gravity? *** Einstein had a solution, the cosmological constant. * How do you explain that there is evidence that in the early universe, the expansion of the universe was decelerating, and only some billion years ago started accelerating? *** First inflation, then deceleration, followed by acceleration. How can one believe in such ad hoc cosmological calisthenics? * How do you explain that the oldest stars we can see are only about 13 billion years old, although small stars can live for hundreds of billions of years? If there was no Big Bang, but the universe is static, why don't we see such stars? *** Did you ask youself about the fate of those small stars? (helium white dwarf, etc., far cooler than the current minimum mass main sequence stars. The luminosity of these frugal objects would be more than a thousand times smaller than the dimmest stars of today, with commensurate increases in longevity, see arXiv: astro- ph/ 9701131 v1 18/01/1997, A DYING UNIVERSE: The Long Term Fate and Evolution of Astrophysical Objects). * How do you explain that galaxies far away from us look very different from the ones close to us? (see e.g. quasars, or the Hubble Ultra Deep Field) *** What you get is what you see. * How do you explain the abundance of elements in the universe? If it existed for an infinite time in the past, why are not all elements fused to iron now? *** Because of recycling. * What about the second law of thermodynamics? If the universe is infinitely old, entropy should be at a maximum now. *** Should? Instead of trying at any price to save the BBT, cosmologists should look for alternative theories. Marcel Luttgens Bye, Bjoern |
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Marcel Luttgens wrote:
Bjoern Feuerbacher wrote in message ... Marcel Luttgens wrote: [snip] *sigh* You failed to get the point. With your approach, one gets the result that there is a spherical symmetric gravitational field in a universe with a homogeneous density. With my approach, one gets the result that in such a universe, there exists a homogeneous gravitational field pointing to a plane. Obviously not both results can be right at once, hence at least one of them *has* to be wrong. But both approaches are *equally* valid. Conclusion: *both* approaches are *not* valid. What's your problem with understanding this *very simple* logic? *** Some humans are hairy, other not. Are you implying that for instance Chineses are not human? No. But what on earth has that to do with my argument above? For instance, d = 13.7 * z/(z+1) Gly leads to about the same results as those obtained by Ned Wright with his calculator for a flat universe with H0=71 and Omega M = 0.27. Which results do you mean, specifically? And what does "about the same" mean? How big are the deviations? *** The deviations are small. Here are some results (light travel time in Gy): Taken from where, specifically? z Ted Wright (Omega M = 0.27) Luttgens (d = 13.7 * z/(z+1)) 0.1 1.29 1.25 0.5 5.02 4.57 1 7.73 6.85 3 11.48 10.28 6 12.72 11.74 Deviations of up to about 8%. z Ted Wright (Omega M = 0.42) 0.1 1.27 0.5 4.79 1 7.18 3 10.29 6 11.21 Deviations of up to 9%. I would not call that "small". As you implied, all results can be wrong. Huh? What are you talking about? The only difference lies in the choice of Omega M = 0.42 instead of 0.27. So you also use a cosmological constant? As I said, the proof of the pudding is in the eating. Right. Please note that the BBT explains all the stuff below. I wonder how you explain it... *** If cosmologists were not BBT biased, they could perhaps explain the stuff below by hypothetizing a stable univere. Perhaps. That is a total wild speculation. Could you please explain how the present model is able to describe the universe so well if it is wrong? There *are* are were always some cosmologists who tried to model a stable universe (Hoyle, Narlikar, etc.). However, they failed to explain all the stuff below, although they worked for decades on that - and at least Hoyle is obviously a rather bright man (you know that he got the Nobel prize?). * Where does the Cosmic Microwave Background Radiation come from in your model? Why is it so marvelously homogeneous? How do you explain the power spectrum of the fluctuations in it, e.g. the acoustic peak? How do you explain that when one takes these fluctations as representing density fluctuations, and does computer simulations to see how these density fluctuations grow with time, one gets the present-day large scale structure of the universe? How do you explain that the temperature of the CMBR changes with time? *** It is not marvelously homogeneous. Let's see. Five questions, and you answered only one of them, and that only by asserting something which is completely wrong. The CMBR *is* marvelously homogeneous. The fluctuations are on the order of 10^(-5)! This is the biggest problem for BBT proponents. Next false assertion. As I pointed out above, when one takes these fluctations as representing density fluctuations, and does computer simulations to see how these density fluctuations grow with time, one gets the present-day large scale structure of the universe. So the inhomogenities are not a problem, but they are exactly of the size needed for our models to work! * How do you explain that the universe is static and does not collapse under the influence of gravity? *** Einstein had a solution, the cosmological constant. The cosmological constant is a parameter in the equations of General Relativity. Please tell me how you derive your model from these equations. * How do you explain that there is evidence that in the early universe, the expansion of the universe was decelerating, and only some billion years ago started accelerating? *** First inflation, then deceleration, followed by acceleration. Yes. How can one believe in such ad hoc cosmological calisthenics? There is nothing ad hoc about the deceleration and acceleration. Both are supported by solid evidence. Inflation is partly ad hoc, but also makes predictions which can be tested - and *were* tested, with confirming results. Who was it who said just above "the proof of the pudding is in the eating"? And who is OTOH who keeps ignoring about 95% of the available positive evidence for the BBT, and inflates every small problem with the theory to huge proportions? * How do you explain that the oldest stars we can see are only about 13 billion years old, although small stars can live for hundreds of billions of years? If there was no Big Bang, but the universe is static, why don't we see such stars? *** Did you ask youself about the fate of those small stars? Yes. (helium white dwarf, etc., far cooler than the current minimum mass main sequence stars. The luminosity of these frugal objects would be more than a thousand times smaller than the dimmest stars of today, with commensurate increases in longevity, see arXiv: astro- ph/ 9701131 v1 18/01/1997, A DYING UNIVERSE: The Long Term Fate and Evolution of Astrophysical Objects). Totally irrelevant here, since I was *not* talking about white dwarfs. I meant the remains of K and M stars. If the universe were much older than 13.7 billion years, quite a lot of K and M stars should have left the main sequence already. But we don't see any such stars. * How do you explain that galaxies far away from us look very different from the ones close to us? (see e.g. quasars, or the Hubble Ultra Deep Field) *** What you get is what you see. Evasion noted. * How do you explain the abundance of elements in the universe? If it existed for an infinite time in the past, why are not all elements fused to iron now? *** Because of recycling. How? Evasion noted. * What about the second law of thermodynamics? If the universe is infinitely old, entropy should be at a maximum now. *** Should? Yes. Evasion noted. Instead of trying at any price to save the BBT, cosmologists should look for alternative theories. Marcel Luttgens Bye, Bjoern |
#470
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In message , Marcel
Luttgens writes I presume that you will disagree with the following quote. I don't disclose the name of its author, because some mainstreamers could label him as a crank. Trouble is, there are no secrets from Google :-) and if you champion ideas such as a face on Mars and the EPH as the origin of the asteroids the label begins to look right. -- What have they got to hide? Release the ESA Beagle 2 report. Remove spam and invalid from address to reply. |
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