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Thread: Relativity

  1. #31
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    Re: Relativity

    Quote Originally Posted by Andreas
    Um, we wouldn't be able to see a galaxy that recedes at superluminal speed because its light never reaches us. Thus we can't "see them glowing."
    This was a common belief among some astronomers before Davis and Lineweaver wrote their famous paper three years ago. But they provided an explanation of the physical mechanism of how a photon from a superluminal galaxy can reach us. From their point of view, the light speeds up while on the way to the earth, as it passes through different areas of “comoving space” that are closer to the earth and that are not moving away from the earth as fast as the “comoving space” of the galaxy that emitted the light.

    Using the basic 1911 Einstein theory, I say the “comoving space” of galaxies are merely the “local gravitational fields” of the galaxies, and those fields regulate the speed of light locally, at and near those galaxies. Our collective gravitational fields within our galaxy regulate the speed of light inside our galaxy. Our fields are what modern cosmologists tend to call our local “comoving space”. Here is the Davis-Lineweaver paper. This is new, but it is mainstream astronomy and cosmology now:

    LINK TO PAPER

  2. #32
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    Re: Relativity

    Milli, what do you think about what I have said about Einstein changing the reason for the 1905 clock slow-down from “relative motion” to a physical force caused by a “gravitational field” in 1918?

  3. #33
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    Re: Relativity

    Quote Originally Posted by Sam5
    Milli, what do you think about what I have said about Einstein changing the reason for the 1905 clock slow-down from “relative motion” to a physical force caused by a “gravitational field” in 1918?
    As near I as I can tell, you have misinterpreted it. It's not "physical force," that is the culprit. As we've discussed, two clocks can experience the same force, but be at different rates, according to GR.

    At a certain point, our intuition fails us, and we have to resort to the original formulation of the theory.

  4. #34
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    Re: Relativity

    Quote Originally Posted by milli360
    As near I as I can tell, you have misinterpreted it. It's not "physical force," that is the culprit. As we've discussed, two clocks can experience the same force, but be at different rates, according to GR.
    Could you point out that claim in any of the original GR theorys? give me the exact wording in the original papers, and then we can discuss it.

  5. #35
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    Re: Relativity

    Quote Originally Posted by Sam5
    Could you point out that claim in any of the original GR theorys? give me the exact wording in the original papers, and then we can discuss it.
    I thought you agreed that clocks on the equipotential surface of the Earth were at the same rate, according to GR?

  6. #36
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    Re: Relativity

    Quote Originally Posted by milli360
    It's not "physical force," that is the culprit. As we've discussed, two clocks can experience the same force, but be at different rates, according to GR.
    Please show us a reference from the original GR theory papers.

  7. #37
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    Re: Relativity

    Quote Originally Posted by Sam5
    Please show us a reference from the original GR theory papers.
    I don't have them. My copies are at the library.

    Do you disagree with that then?

  8. #38
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    Re: Relativity

    For reference:

    Copy of Einstein's 1905 "Theory of Special Relativity" in the original edition and language: "Zur Elektrodynamik bewegter Körper." (Some of the posters here are from Germany - and some other folks read German. Perhaps for reference, it would be nice to have access to the original paper in German from 1905.) (Note that in 1905 "v" stood for the speed of light.)

    http://www.wiley-vch.de/berlin/journals/adp/890_921.pdf

    Here is the 1923 English translation: (Note that "c" is now used for the speed of light by the translator. See also the "Editor's Notes" at the end of the paper which describe corrections of erroneous incorrect translations and errors found in the 1923 translation.)

    http://www.fourmilab.ch/etexts/einstein/specrel/www/

    Einstein's follow-up paper also from 1905:

    http://www.fourmilab.ch/etexts/einstein/E_mc2/www/

  9. #39
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    Quote Originally Posted by Sam5
    There is no such thing as “expanding space”.

    I’ve got a 1959 University astronomy book that has the galaxies moving through space.

    The “expansion of space” idea only started being promoted when the high-z galaxies were discovered in the 1960s-‘90s, and that indicated they were moving faster than “c” relative to the earth. So, in the continuing effort to try to salvage Einstein’s 1905 “speed limit” prediction, all of a sudden we started hearing about “the expansion of space”, with the galaxies “not moving” at all! But nobody can give any scientific explanation of it, because it’s nonsense. It’s one of the greatest con-jobs of modern cosmology.
    So your view is that galaxies are moving away from each other but space itself is not expanding? Ok - so you're saying that there is a finite number of galaxies and an infinite empty space into which they are moving? Am I understanding your position correctly?

    The question then becomes: why can't we see a variation in the density of galaxies (or the CMBR) which shows us where the edge is? Why can't we determine the direction to the center by observing the motion of the galaxies around us?

    Data, Sam, does not support your position.

  10. #40
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    Quote Originally Posted by russ_watters
    Quote Originally Posted by Sam5
    There is no such thing as “expanding space”.

    I’ve got a 1959 University astronomy book that has the galaxies moving through space.

    The “expansion of space” idea only started being promoted when the high-z galaxies were discovered in the 1960s-‘90s, and that indicated they were moving faster than “c” relative to the earth. So, in the continuing effort to try to salvage Einstein’s 1905 “speed limit” prediction, all of a sudden we started hearing about “the expansion of space”, with the galaxies “not moving” at all! But nobody can give any scientific explanation of it, because it’s nonsense. It’s one of the greatest con-jobs of modern cosmology.
    So your view is that galaxies are moving away from each other but space itself is not expanding? Ok - so you're saying that there is a finite number of galaxies and an infinite empty space into which they are moving? Am I understanding your position correctly?
    Yes. But, that “finite” number is super large. Maybe many times more than what we can currently see. Every time we build a bigger telescope, we see more distant galaxies. But just because there are a whole lot of them, that doesn’t mean there are an infinite number of them.

    Quote Originally Posted by russ_watters
    The question then becomes: why can't we see a variation in the density of galaxies (or the CMBR) which shows us where the edge is? Why can't we determine the direction to the center by observing the motion of the galaxies around us?
    If you are on a particle inside a spherical explosion, and if the center and the outer edge are far enough away, you won’t be able to see either. You’ll see the other particles separating all around you, but you won’t know where you are within the expanding sphere.

    If the universe is large enough, we’ll never see the “outer edge”, and we might not ever know if there is one.

    We’re still stuck in the same situation we’ve always been stuck in. The further we look, there are galaxies all around us, so we don’t know where the “edge” is or even if there is one. The universe is pretty big, and about all we know is that we’re somewhere inside it. But that’s the same as what we knew 5,000 years ago.

  11. #41
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    Quote Originally Posted by russ_watters
    Data, Sam,

    I watched this thing about “expanding space” come about in the science media during the ‘80s and ‘90s. It was talked about more and more, the more superluminal galaxies were discovered. It is used only to try to keep nature from violating Einstein’s “c speed limit” rule. That’s all it is used for. I’ve seen some astronomers say, “the galaxies are stationary and not moving, but they are being carried along by expanding space.” This is just plain nuts.

    There are no physics papers that explain how “space expands” or how it could “expand”. This is just a slogan, a nonsense slogan designed to keep nature from “violating” one of “Einstein’s Laws”. This is just plain nuts too. It’s as if some astronomers think of Einstein as “God”, and they claim nature “can not violate God’s laws”, which “God” wrote in the form of science papers in 1905 and 1916. This is crazy.

  12. #42
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    Quote Originally Posted by Sam5
    Quote Originally Posted by russ_watters
    Data, Sam,

    I watched this thing about “expanding space” come about in the science media during the ‘80s and ‘90s. It was talked about more and more, the more superluminal galaxies were discovered. It is used only to try to keep nature from violating Einstein’s “c speed limit” rule. That’s all it is used for. I’ve seen some astronomers say, “the galaxies are stationary and not moving, but they are being carried along by expanding space.” This is just plain nuts.
    Why is it nuts? It's a perfectly good explanation for the fact that almost every observed galaxy is moving away from us and for why those that aren't (Andromeda and the Magellanic Clouds, for instance) are gravitationally bound to us. That would mean that either our galaxy is at the center of the universe, which is impossible, or that spacetime is expanding.

    Incidentally, would you care to actually cite a specific, *current* reference that argues for superluminal galaxies? Twenty-year old documentaries aren't exactly great sources, espescially for a field like cosmology that's changed a lot over the last six years.

    There are no physics papers that explain how “space expands” or how it could “expand”.
    You mean besides the fact that it pops right out of Einstein's General Theory of Relativity? Einstein himself realised this possibility. Granted he thought it was wrong and introduced the Cosmological Constant to eliminate it, but, like a good scientist, changed his mind when Hubble proved that the universe was in fact expanding.

    This is just a slogan, a nonsense slogan designed to keep nature from “violating” one of “Einstein’s Laws”. This is just plain nuts too. It’s as if some astronomers think of Einstein as “God”, and they claim nature “can not violate God’s laws”, which “God” wrote in the form of science papers in 1905 and 1916. This is crazy.
    You need to brush up on both your science and your history here. Like I mentioned, Einstein's original theory argued for a static universe and *that* was proved wrong very quickly. Moreover, as any physicist will tell you General Relativity is flawed simply because it's incompatible with quantum mechanics. Not that Heisenberg and Plank were gods either, since quantum needs refinement to accomidate gravitation. Einstein's theories will eventually be replaced, just like Newton's were.

    As for it being a slogan, let's look at the evidence:

    In general, every galaxy in the universe is moving away from us. Those that aren't are gravitationally bound to the Milky Way.

    If galaxies drifted aimlessly, we should see roughly equal numbers of galaxies moving towards us as away from us. We don't.

    We can see the light from supposedly 'superluminal' galaxies, implying that they are travelling slower than the speed of light.

    The Earth is not the center of the universe. Otherwise, we would only see young objects as we look deeper into space, not the oldest objects known to man.

    To date, repeated experiments have shown that it is impossible to get *electrons* to travel at the speed of light without expending an *infinite* amount of energy. Thus, it should take a *lot* more energy to get even a small *galaxy* close to the speed of light.


    Put these all together. The Earth can't be at the center of the universe, which means that we can't be at the source of the Big Bang. Therefore, there's no special reason why galaxies should be moving away from us and there's no evidence that galaxies move randomly. Also, experiments in particle accelerators have, for decades, all seem to say that it's impossible to accelerate even a low-mass object, like an electron, to the speed of light, simply because the acceleration decreases as the particle's speed approaches the speed of light. If you think about it, the basic laws of momentum make it equally impossible for a galaxies, which are much more massive than electrons, to acheive speeds even close to the speed of light from a simple explosion like you argue the Big Bang was.

    The only possibilities that I can see here are that either the laws of inertia don't apply to galaxies *or* that space itself is expanding. Since I can't think of any good reason why large masses should behave differently than small masses, it must be space expanding.

    Perhaps continental drift would provide a good analogy. Instead of galaxies, think about Eurasia and the Americas. They're not randomly drifting away from each other. The *Atlantic* is expanding, pushing them away from each other. Why can't something analogous be happening in space? Why can't the Big Bang be the beginning of that expansion rather than a literal explosion?

  13. #43
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    Quote Originally Posted by Taibak
    Why is it nuts? It's a perfectly good explanation for the fact that almost every observed galaxy is moving away from us and for why those that aren't (Andromeda and the Magellanic Clouds, for instance) are gravitationally bound to us.
    That's fine. What you just said is NOT "nuts".

    What is “nuts” about it is this is, one theoretical physicist told me what the galaxies are doing is “a change in distance without movement.”, and I think that is nuts.

    Some of these guys claim “the galaxies aren’t moving, it is space that is expanding.”

    Well, even if “space expands”, the galaxies are “moving”.

    What you just said is NOT nuts, because you said, “almost every observed galaxy is moving away from us”, and that IS correct. But “a change in distance without motion” is NOT correct.

  14. #44
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    Quote Originally Posted by Sam5
    Quote Originally Posted by Taibak
    Why is it nuts? It's a perfectly good explanation for the fact that almost every observed galaxy is moving away from us and for why those that aren't (Andromeda and the Magellanic Clouds, for instance) are gravitationally bound to us.
    That's fine. What you just said is NOT "nuts".

    What is “nuts” about it is this is, one theoretical physicist told me what the galaxies are doing is “a change in distance without movement.”, and I think that is nuts.

    Some of these guys claim “the galaxies aren’t moving, it is space that is expanding.”

    Well, even if “space expands”, the galaxies are “moving”.

    What you just said is NOT nuts, because you said, “almost every observed galaxy is moving away from us”, and that IS correct. But “a change in distance without motion” is NOT correct.
    Well actually it all depends on how you define 'movement.' If you define it as a change in position relative to another source, then yes galaxies are moving away from us and you're right that the expansion of space drives this movement. That's certainly one way of looking at it, but not the only way.

    The catch is that observers in any galaxy will get the same result we will - that galaxies are generally moving away from them. That can't happen without spacetime expanding. As such, it's not wrong to say that the galaxies aren't 'moving' - that they are not and were not being propelled by some force in the same sense that a kick propells a soccer ball or rockets propel the space shuttle. They're just being dragged along by space and time. It's the difference between saying that an object is changing its distance from another object and saying that the distance between two objects is changing itself and, consequently, the relative positions of the two objects. This is why the raisins-in-bread analgy or the spots-on-a-balloon analogy work fine.


    On a related note, anyone know if it's theoretically possible for two galaxies to be at rest relative to each other? If I understand this right, they'd have to be gravitationally bound to compensate for the effects of spacetime expansion. However, that seems like it would in practice require them to either be orbiting each other, like binary stars, or gradually pull them towards each other. It seems like, in theory, that it should be possible for two galaxies to be travelling in the same direction relative to some distant object, but have their gravities pulling on each other with *exactly* the force needed to keep their relative distance constant as the intervening spacetime tried to expand.

    Even so, I can't shake the feeling that the acceleration due to gravity should be much greater than the acceleration of spacetime at close distances and at long distances the effects of exansion would be much more pronounced than the effects of gravity. It would seem prohibitively difficult to get even a metastable relationship here. Am I totally off base here?

  15. #45
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    Quote Originally Posted by Taibak
    As such, it's not wrong to say that the galaxies aren't 'moving' - that they are not and were not being propelled by some force in the same sense that a kick propells a soccer ball....
    You can’t say that. You’ve got absolutely no idea what started them to move in the first place, and no one does. We just built a big telescope one day and there they were already moving. No one knows why.

  16. #46
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    Quote Originally Posted by Sam5
    Quote Originally Posted by Taibak
    As such, it's not wrong to say that the galaxies aren't 'moving' - that they are not and were not being propelled by some force in the same sense that a kick propells a soccer ball....
    You can’t say that. You’ve got absolutely no idea what started them to move in the first place, and no one does. We just built a big telescope one day and there they were already moving. No one knows why.
    So now you dispute the conclusions of our observations. We know more than you think Sam5...

  17. #47
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    Quote Originally Posted by Taibak
    This is why the raisins-in-bread analgy or the spots-on-a-balloon analogy work fine.
    The center raisin doesn’t move and it’s at the center of the “expansion” of all the other raisins. That is a good analogy. So is Lamaitre’s “fireworks” analogy and Newton’s “projectile force” idea.

  18. #48
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    Quote Originally Posted by freddo
    Quote Originally Posted by Sam5
    Quote Originally Posted by Taibak
    As such, it's not wrong to say that the galaxies aren't 'moving' - that they are not and were not being propelled by some force in the same sense that a kick propells a soccer ball....
    You can’t say that. You’ve got absolutely no idea what started them to move in the first place, and no one does. We just built a big telescope one day and there they were already moving. No one knows why.
    So now you dispute the conclusions of our observations. We know more than you think Sam5...
    Ok, if you know why they are moving, then you tell us why. Is it some kind of secret?


    added:


    The last book I read about it said it was due to some kind of “big bang”, with the universe expanding from a “dot” or a “point”. Has that idea changed? This is essentially Lamaitre’s 1927 “fireworks” theory and Newton’s “projectile force”.

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    Ok, if you know why they are moving, then you tell us why. Is it some kind of secret?
    Irellevant.. You said it was wrong to claim they're "not and were not being propelled by some force in the same sense that a kick propells a soccer ball...." In the absence of knowing whether a force existed or not - how can you possibly assert that this is wrong to say?

  20. #50
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    Quote Originally Posted by freddo
    Ok, if you know why they are moving, then you tell us why. Is it some kind of secret?
    Irellevant.. You said it was wrong to claim they're "not and were not being propelled by some force in the same sense that a kick propells a soccer ball...." In the absence of knowing whether a force existed or not - how can you possibly assert that this is wrong to say?
    You said, “So now you dispute the conclusions of our observations. We know more than you think Sam5...”

    So I asked you what are your conclusions. What do you know about it?

    Or were you just making that up?

    I suspect, just like everyone else, you don't know why they are moving.

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    I suspect, just like everyone else, you don't know why they are moving.
    As I said, the why is beside the point. We have a pretty good idea on the how..

  22. #52
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    Quote Originally Posted by Sam5
    Quote Originally Posted by Taibak
    This is why the raisins-in-bread analgy or the spots-on-a-balloon analogy work fine.
    The center raisin doesn’t move and it’s at the center of the “expansion” of all the other raisins. That is a good analogy. So is Lamaitre’s “fireworks” analogy and Newton’s “projectile force” idea.
    Fair point about there being a raisin at the center of the loaf. I admit that's where the analogy breaks down. Still, it's salvageable simply because it's a good way to get one's brain around the idea of intervening space (the bread) expanding. However, the other two simply do not work with the Big Bang. The Big Bang was not an explosion, no matter what its name implies, so there is no projectile force. It was just the beginning of spacetime expansion.

    The fireworks analogy doesn't work well because it uses different geometry than the universe. If you use the *entire* sphere, you have yourself a finite, three-dimensional object with a center. Tthat's a problem since the universe has neither a finite edge nor a center - it uses a very different method of expansion. Moreover, with a firework it's quite clear that an explosive force is pushing the sparks outward - there seems to be no such force driving the expansion of the universe. If you restrict yourself to the *surface* of the sphere, well, you're better off using the balloon for the sake of clarity. You're still dealing with what's clearly an explosive force rather than an expanding intervening distance. More importantly, you don't have a clearly defined surface. That's a problem because if GR is right, the universe *is* an infinite four-dimensional surface. Why model it with something that lacks such an important feature of the theory?

  23. #53
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    Quote Originally Posted by Taibak
    On a related note, anyone know if it's theoretically possible for two galaxies to be at rest relative to each other? If I understand this right,

    ...

    relative to some distant object, but have their gravities pulling on each other with *exactly* the force needed to keep their relative distance constant as the intervening spacetime tried to expand.
    I don't see any theoretical reason why the expansion can't be balanced by gravity.

    Quote Originally Posted by Taibak
    Even so, I can't shake the feeling that the acceleration due to gravity should be much greater than the acceleration of spacetime at close distances and at long distances the effects of exansion would be much more pronounced than the effects of gravity.
    Relative to whom? If your looking out very far, yes, spacetime expansion would appear much greater. But, remember, if the galaxies are close enough, the galaxie's movement due to expansion, from our point of view, would be about the same. It doesn't matter if the galaxies are close to us or at z=5, the expansion is still increasing at 50-100 kp/s/Mpc. Move out Andromeda another million light years and it would be about 1 Mpc away. It should be moving away at 50-100 km/s/Mpc due to expansion, but it would still probably be moving toward us, due to gravity (since is currently is moving toward us at 100 kps). I can see the distance between us and Andromeda, if moved a bit farther out, being at some point equal to the expansion value and therefore at rest to us.

    Quote Originally Posted by Taibak
    It would seem prohibitively difficult to get even a metastable relationship here. Am I totally off base here?
    I wouldn't guarentee how long it would stay that way, but I don't think you're off base here. It just don't think it would be a stable, long term, type relationship, IMHO.

  24. #54
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    Quote Originally Posted by Taibak
    Quote Originally Posted by Sam5
    Quote Originally Posted by Taibak
    This is why the raisins-in-bread analgy or the spots-on-a-balloon analogy work fine.
    The center raisin doesn’t move and it’s at the center of the “expansion” of all the other raisins. That is a good analogy. So is Lamaitre’s “fireworks” analogy and Newton’s “projectile force” idea.
    Fair point about there being a raisin at the center of the loaf. I admit that's where the analogy breaks down. Still, it's salvageable simply because it's a good way to get one's brain around the idea of intervening space (the bread) expanding. However, the other two simply do not work with the Big Bang. The Big Bang was not an explosion, no matter what its name implies, so there is no projectile force. It was just the beginning of spacetime expansion.

    I think the bread expands because of some kind of gas, maybe CO2. Are you suggesting that there is some kind of yeast in space that is releasing CO2 gas that is causing the galaxies to move apart?

    What happened to the “big bang” theory and the big explosion from that little point? That theory was taught for about 65 years.

    Have they changed it to the "big poof"?

    I think Astronomy magazine had a big contest a few years ago, wanting people to give it a new name. I guess astronomy theory is now up to holding contests about it in Astronomy magazine.

  25. #55
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    Quote Originally Posted by Sam5
    I think the bread expands because of some kind of gas, maybe CO2. Are you suggesting that there is some kind of yeast in space that is releasing CO2 gas that is causing the galaxies to move apart?
    Sam, you need to look up the word "analogy" in the dictionary.

    By the way - the way it applies to the theory isn't that just the center rasin isn't moving: none of the rasins are moving. The bread is expanding between the rasins, which makes it appear to every rasin that every other rasin is moving away from it.

    Also - The Sam5 Model of the Universe has a pretty big flaw: even in your model, we can calculate an age. And when we start looking at objects that are far enough away that they are close to that age, we should start seeing the structure you propose. But we don't.

  26. #56
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    Quote Originally Posted by Sam5
    The last book I read about it said it was due to some kind of “big bang”, with the universe expanding from a “dot” or a “point”. Has that idea changed? This is essentially Lamaitre’s 1927 “fireworks” theory and Newton’s “projectile force”.
    No, the idea is still that the universe still expanded out of a point-like singularity. What has changed, however, is the idea that the singularity just contained matter and energy which became unstable and exploded. I think it's more accurate to say that over the past seven or so decades, physicists have realised that GR allows for spacetime itself to expand and that this expansion would have had to have started with the Big Bang. As such, that original point-like singularity contained space and time as well as matter and energy.

    We don't know what started the expansion or what was outside that singularity. There are a lot of theories that seek to explain these things, but so far none of them have been proven. None of them include any kind of explosive force or 'projectile force' though.

  27. #57
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    Quote Originally Posted by russ_watters
    Quote Originally Posted by Sam5
    I think the bread expands because of some kind of gas, maybe CO2. Are you suggesting that there is some kind of yeast in space that is releasing CO2 gas that is causing the galaxies to move apart?
    Sam, you need to look up the word "analogy" in the dictionary.

    I think Lemaitre’s fireworks analogy, which lasted for 65 years, is much better than the cosmic muffin analogy.

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    I think the bread expands because of some kind of gas, maybe CO2. Are you suggesting that there is some kind of yeast in space that is releasing CO2 gas that is causing the galaxies to move apart?
    http://dictionary.reference.com/search?q=analogy

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    Quote Originally Posted by Taibak
    Quote Originally Posted by Sam5
    The last book I read about it said it was due to some kind of “big bang”, with the universe expanding from a “dot” or a “point”. Has that idea changed? This is essentially Lamaitre’s 1927 “fireworks” theory and Newton’s “projectile force”.
    No, the idea is still that the universe still expanded out of a point-like singularity. What has changed, however, is the idea that the singularity just contained matter and energy which became unstable and exploded. I think it's more accurate to say that over the past seven or so decades, physicists have realised that GR allows for spacetime itself to expand and that this expansion would have had to have started with the Big Bang.
    What do you mean “GR allows”? You mean GR didn’t allow it 10 and 20 years ago? Does GR change with time?

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    Quote Originally Posted by Sam5
    Quote Originally Posted by freddo
    Quote Originally Posted by Sam5
    Quote Originally Posted by Taibak
    As such, it's not wrong to say that the galaxies aren't 'moving' - that they are not and were not being propelled by some force in the same sense that a kick propells a soccer ball....
    You can’t say that. You’ve got absolutely no idea what started them to move in the first place, and no one does. We just built a big telescope one day and there they were already moving. No one knows why.
    So now you dispute the conclusions of our observations. We know more than you think Sam5...
    Ok, if you know why they are moving, then you tell us why. Is it some kind of secret?

    added:

    The last book I read about it said it was due to some kind of “big bang”, with the universe expanding from a “dot” or a “point”. Has that idea changed? This is essentially Lamaitre’s 1927 “fireworks” theory and Newton’s “projectile force”.
    You believe in the steady state universe? :rollseyes: Figures.

    How do you explain CMB radiation?

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