εllipse
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If space is flat or open, does that make it infinite? Is a closed universe the only type that would be finite, or would a flat or open universe also somehow be finite?
Welcome to these Forums ellipse! A good question even if it seems obvious at first.εllipse said:If space is flat or open, does that make it infinite? Is a closed universe the only type that would be finite, or would a flat or open universe also somehow be finite?
Generally speaking if space is flat ... then it would be open and infinite and unbounded.
εllipse said:Thanks, so if space is infinite then would the amount of matter in the universe be infinite? .
And everything that is not forbidden is compulsory!In an infinite Universe, all things would be repeated an infinite number of times
There is a 4th necessary property upon which Olber's Paradox depends.Garth said:Olber's Paradox is dependent on three necessary properties of the universe that were all thought true in pre-GR days since Newton.
1. The universe is infinitely old.
2. The universe is infinitely large.
3. The universe is static.
If anyone of these three conditions do not hold the paradox is resolved.
The standard model breaks the first and third of these conditions and it may also break the second if the density parameter Omegatotal > 1.
Absolutely right. The energy level can be extreme, but when is is redshifted to the point that we can no longer even measure its frequency relative to the ground state, it has essentially joined the ground state of the vacuum. We have no reference to a perfectly empty vacuum from our universe, so we cannot measure the difference between the ground state of our universe and a "perfect" vacuum.Hurkyl said:You still get infinite energy, it's just redshifted to the lower end of the spectrum.
If we move relative to this ground state (lets call it the CMB just for grins) we might expect to see some anisotropies in the observed temperatures.Hurkyl said:The doppler effect worries me greatly, though. Suppose in one frame we have this infinite, "undetectable" bath of radiation. If something moves at high velocity with respect to this frame, it would blueshift the radiation. By moving closer and closer to the speed of light, we can blueshift an arbitrarily large magnitude of radiation into, say, the visible range. (and it would all be going in one direction)
There is a fourth condition. The distribution of light sources is homogeneous and isotropic, or at least, with a fractal dimension greater than two. Otherwise (fractal dimension less than two), the paradox is resolved in a static, spatially infinite and enternal universe.Garth said:Olber's Paradox is dependent on three necessary properties of the universe that were all thought true in pre-GR days since Newton.
1. The universe is infinitely old.
2. The universe is infinitely large.
3. The universe is static.
If anyone of these three conditions do not hold the paradox is resolved.
Homogeneity and isotropy are assumed; however, as the darkness of the whole night sky is taken to be isotropic (more or less) could it be otherwise?hellfire said:There is a fourth condition. The distribution of light sources is homogeneous and isotropic, or at least, with a fractal dimension greater than two. Otherwise (fractal dimension less than two), the paradox is resolved in a static, spatially infinite and enternal universe.
The energy is not lost, but transferred to the aether (the virtual particle field of the quantum vacuum).Chronos said:I object to your fourth condition on Olbers paradox, turbo. Energy is simply lost in that scenario, which rewrites the laws of thermodynamics. If it is absorbed by some sort of background state, the background temperature should increase over time, not decrease - which is what is observed.
In an universe with a distribution of light sources with fractal dimension less than two (isotropic or not) you do have a dark sky, and so I guess you can have "isotropic darkness". I am not sure I properly understood your question…Garth said:Homogeneity and isotropy are assumed; however, as the darkness of the whole night sky is taken to be isotropic (more or less) could it be otherwise?
Dodging the question is not an answer. If the 'aether' absorbs the missing energy, should it not be heating up instead of cooling down - as observational evidence indicates? The Eddington story is irrelevant. His reasoning in arriving at the 'correct' answer was ... flawed. He was just as fallible as anyone else, as Chandrasekhar learned. Anectdotal evidence is amusing, but not substantive.turbo-1 said:The energy is not lost, but transferred to the aether (the virtual particle field of the quantum vacuum).
Eddington calculated in 1926 that the contribution of all the radiating sources in the universe would cause the temperature of the vacuum in empty space to be about 3 degrees K (he later refined it to 2.8 K). About 40 years later, this was found to be correct. Somehow, Wilson and Penzias' discovery has come to be acclaimed as the most resounding success of Gamow's Big Bang model, which predicted a background temperature of 50 degrees K.
Dodging the question? Let's look at the situation. If you radiate an object and increase its energy, it will re-radiate that energy (like a piece of metal sitting in sunlight will absorb UV and optical and IR and radiate heat away in IR). The object will come to an equilibrium temperature and will NOT continue to get hotter and hotter until it is as hot as the Sun. That is a pretty silly concept. The aether is reradiating impinging EM at a very low temperature, and it is in equilibrium.Chronos said:Dodging the question is not an answer. If the 'aether' absorbs the missing energy, should it not be heating up instead of cooling down - as observational evidence indicates? The Eddington story is irrelevant. His reasoning in arriving at the 'correct' answer was ... flawed. He was just as fallible as anyone else, as Chandrasekhar learned. Anectdotal evidence is amusing, but not substantive.
Can you demonstrate this effect in a laboratory?turbo-1 said:. The aether is reradiating impinging EM at a very low temperature, and it is in equilibrium.
Well, first you might want to read this overview of the history of calculations of the temperature of "empty" space. These fellows (with the exception of Gamow) mostly modeled a static universe that was in dynamical equilibrium and "empty" space or aether in thermal equilibrium. See especially section 13 re: the work of Finlay-Freundlich and Max Born.Garth said:Can you demonstrate this effect in a laboratory?
Garth
http://www.astro.ucla.edu/~wright/Eddington-T0.htmlturbo-1 said:...The Eddington "story" (as you put it) is not only relevant, it is quite telling. If you can show how his reasoning was "flawed" please do. I'll be quite interested.
Okay, I have found this: Laboratory-Scale Test of de Broglie’s Tired-Photon ModelGarth said:Can you demonstrate this effect in a laboratory?
Garth
Thank you. Eddington nailed the magnitude (summing the energy contributions of all radiative sources in the Universe), as did a number of other people before and after him. The fact that he did not successfully predict the frequency distribution (due to absorption and re-radiation at lower and lower frequencies) does not diminish the acheivement of accurately predicting the magnitude of the signal. Heck, Gamow was boldly predicting 50 degrees absolute in the 1950s. I think it's safe to say that he had heard of Guillaume, Eddington, Nernst, Herzberg, Finlay-Freundlich and Max Born, and chose to disagree with them. He was wrong, yet claimed the Wilson-Penzias observation as confirmation of his BB ideas.Chronos said:
Producing the 'right' answer for the wrong reasons is more often called astrology than science.turbo-1 said:...The fact that he did not successfully predict the frequency distribution (due to absorption and re-radiation at lower and lower frequencies) does not diminish the acheivement of accurately predicting the magnitude of the signal.