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#31
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Looking into the past with a telescope
On Jan 28, 8:37 pm, Greg Crinklaw wrote: Starboard wrote: First I'd like to state that what I am going to describe will be described from a perspective that did not exist. I state the obvious only because earlier, Greg shot me down for my metaphor about a guy watching the big bang expand. He quickly stated that such a condition was impossible. Of course I knew that I was only trying to conduct a little thought experiment. Much the same, the analogy of the balloon. After all, people cannot exist as 2D creatures right? That's the equivalent of starting a metaphor with, "assume a cow is spherical."I think you need to stop being so stuck on your own view and instead try to understand the one people are presenting you with. Please try to let go of your preconceptions. A good popular book on cosmology might help a lot. As you read it, come back here and ask questions to clarify things. To answer your question above, the 2D world is an analogy. Don't confuse this with a model of the universe--it isn't. It's just an analogy meant to explain a concept. It is *not* the same as your cow assumption! As a 3D being you understand the world in 3 dimensions. But what if there are more dimensions than you can perceive? What would that look like? The answer is that you'd observe some odd things about the universe--things that don't easily fit into your 3D view, like a universe that expands away from any point within it, and has no center. The guy can enjoy Albert's orginal 1920 explanation for 'warped space' at a time before galaxies were observationally observed, - http://www.bartleby.com/173/31.html Now Albert's idea for 'bending space' was the lament that light leaving stars would go to waste hence if you bend space....,in any case you can read the hilaroius reasons in the preceding chapter - "This view is not in harmony with the theory of Newton. The latter theory rather requires that the universe should have a kind of centre in which the density of the stars is a maximum, and that as we proceed outwards from this centre the group-density of the stars should diminish, until finally, at great distances, it is succeeded by an infinite region of emptiness. The stellar universe ought to be a finite island in the infinite ocean of space. This conception is in itself not very satisfactory. It is still less satisfactory because it leads to the result that the light emitted by the stars and also individual stars of the stellar system are perpetually passing out into infinite space, never to return, and without ever again coming into interaction with other objects of nature. Such a finite material universe would be destined to become gradually but systematically impoverished. " So you get to see Albert reject the possibility of stellar galactic islands,you get to see his reasons for 'bending' a non geometric term called 'space' and you get to see a bunch of people reach conclusions that match a 1898 science diction novel by H.G. Well's 'Scientific people,' proceeded the Time Traveller, after the pause required for the proper assimilation of this, 'know very well that Time is only a kind of Space." 1898 WELLS http://www.bartleby.com/1000/1.html As for Newton who started the mess,at least he never called for or used an idea of a 'universal center',that was not his style and he is actually explicit about things - "Cor. 2. And since these stars are liable to no sensible parallax from the annual motion of the earth, they can have no force, because of their immense distance, to produce any sensible effect in our system. Not to mention that the fixed stars, every where promiscuously dispersed in the heavens, by their contrary actions destroy their mutual actions, by Prop. LXX, Book I." Newton If you can find a place in Newton's agenda,and he was an opportunist,that states he requires a universal center then good luck to you,the one thing about Newton that he was far cleverer than you or any of those early 20th century fopes. The 2D analogy is there merely as a means of investigating how more dimensions than can be sensed can produce a universe with some of these odd characteristics. You have to imagine a 2D being who knows nothing beyond the surface of the balloon. The entire universe is the surface only. So when the balloon is blown up, where is the center? The answer is twofold: for the 2D being it has no center. But for you as a 3D being you can see that the center lies in a dimension beyond that of the surface of the balloon. What is obvious to the 3D being is not apparent at all to the 2D being. Her only hope is to note some odd things about her universe and postulate more dimensions to explain them. Try to imagine this analogy from the point of view of the 2D being. Think about questions like, what would they observe if someone from outside blew up the balloon? If they started out in one direction and traveled far enough, they would come back to where they started. That would seem like magic. So how would they explain that scientifically? But please keep in mind that the universe is NOT the surface of a balloon. Again, it is the concept of what more dimensions than can be perceived might look like that is important. Once that concept is understood, then understand that in our own universe there are some weird things that can't easily be explained in 3D. But postulating more dimensions explains them neatly. Greg -- Greg Crinklaw Astronomical Software Developer Cloudcroft, New Mexico, USA (33N, 106W, 2700m) SkyTools: http://www.skyhound.com/cs.html Observing:http://www.skyhound.com/sh/skyhound.html Comets: http://www.skyhound.com/sh/comets.html To reply take out your eye |
#32
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Looking into the past with a telescope
On Jan 28, 8:44 pm, "Greg Neill" wrote: "Davoud" wrote in ... I can think of no reason why the Universe can't have a central region in three-dimensional space if the Big Bang theory is correct.If the BB is correct, then every place in the 3D universe was once co-located with the center. So there is no unique place that one can call The Center, since every place equally fulfills the role. I love all this fuss. "If we ponder over the question as to how the universe, considered as a whole, is to be regarded, the first answer that suggests itself to us is surely this: As regards space (and time) the universe is infinite. There are stars everywhere, so that the density of matter, although very variable in detail, is nevertheless on the average everywhere the same. In other words: However far we might travel through space, we should find everywhere an attenuated swarm of fixed stars of approximately the same kind and density." http://www.bartleby.com/173/30.html Does anybody realise that when that was written in 1920, the observational /magnification guys still had to discover stellar galactic islands. The next paragraph makes the whole thing hilarious,as least for this astronomer - "This view is not in harmony with the theory of Newton. The latter theory rather requires that the universe should have a kind of centre in which the density of the stars is a maximum, and that as we proceed outwards from this centre the group-density of the stars should diminish, until finally, at great distances, it is succeeded by an infinite region of emptiness. The stellar universe ought to be a finite island in the infinite ocean of space." Even now it is still just too funny and that all this fuss about expanding balloons and whatnot,the theoretical freaks and the magnification guys just turned swarm of stars to swarm of galaxies and kept right on going as if nothing happened. Keep on talking,I love this stuff |
#33
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Looking into the past with a telescope
On Jan 28, 7:04 pm, (Brian Tung) wrote: Steve Paul wrote: Uh oh... I'm getting in way over my head here.. What is "stuff", if not matter and energy?Space-time. "There are really four dimensions, three which we call the three planes of Space, and a fourth, Time. There is, however, a tendency to draw an unreal distinction between the former three dimensions and the latter, " http://www.bartleby.com/1000/1.html That statement could be found in any science fiction section of a bookstore in 1898. This following statement is found on a Nasa website and a billion dollar satellite sent to prove it - "What does the word 'spacetime' mean? (Question 42) - It means that in our universe, 3-dimensional space and time form a single indivisible new physical object which has 4 dimensions. All physical laws and phenomena seem to require thinking about space and time as this blended object. That's what Einstein's relativity theories were all about. " http://einstein.stanford.edu/ Now how a science fiction novel morphed into a cheerfully believable concept promoted as a 'supreme human achievement should frighten the life out of genuine people into taking action but unfortunately that has not happened yet. If you really want to believe that if you travel real fast that the universe will change for you then go for it but does there really need to be so many people who believe this exotic fantasy. -- Brian Tung The Astronomy Corner athttp://astro.isi.edu/ Unofficial C5+ Home Page athttp://astro.isi.edu/c5plus/ The PleiadAtlas Home Page athttp://astro.isi.edu/pleiadatlas/ My Own Personal FAQ (SAA) athttp://astro.isi.edu/reference/faq.html |
#34
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Looking into the past with a telescope
Davoud:
I can think of no reason why the Universe can't have a central region in three-dimensional space if the Big Bang theory is correct. Greg Neill: If the BB is correct, then every place in the 3D universe was once co-located with the center. So there is no unique place that one can call The Center, since every place equally fulfills the role. I have seen this argument in various guises. In /my/ /mind/ it breaks down because of mixed verb tenses. "Every place /was/ /once/ co-located in the center." OK, but "every place" departed the center when space-time expanded, leaving the center behind. These "places" did not all carry the center with them so that each one is now a center of its own. Such a place -- a region that was denser than average due to a quantum fluctuation and later became the core of a galaxy -- may be a local center, but it is not the Universal center -- in /my/ /mind/ . Simple common sense says that the two-dimensional surface of a sphere has no center -- I figured that out for myself while playing with a solid-color, featureless rubber ball as a child -- but if you look beyond the surface, inside the sphere, you will find a center. Davoud -- usenet *at* davidillig dawt com |
#35
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Looking into the past with a telescope
"Davoud" wrote in message ...
Davoud: I can think of no reason why the Universe can't have a central region in three-dimensional space if the Big Bang theory is correct. Greg Neill: If the BB is correct, then every place in the 3D universe was once co-located with the center. So there is no unique place that one can call The Center, since every place equally fulfills the role. I have seen this argument in various guises. In /my/ /mind/ it breaks down because of mixed verb tenses. "Every place /was/ /once/ co-located in the center." OK, but "every place" departed the center when space-time expanded, leaving the center behind. These "places" did not all carry the center with them so that each one is now a center of its own. Such a place -- a region that was denser than average due to a quantum fluctuation and later became the core of a galaxy -- may be a local center, but it is not the Universal center -- in /my/ /mind/ . Your difficulty with this seems to stem from your adhering to a model where things exploded out from a center into a pre-existing space or void. This is not the case in the BB model where space itself expanded. There was nothing at all (not even space) "outside". Simple common sense says that the two-dimensional surface of a sphere has no center -- I figured that out for myself while playing with a solid-color, featureless rubber ball as a child -- but if you look beyond the surface, inside the sphere, you will find a center. That's fine if you have the ability to look beyond the surface. If you can't, then you're confined to looking on the surface. The same thing holds for us, who can only point to things inside the universe. There is no direction in all of space that we can point to that is in the direction of a unique center in 3D space, yet every direction points to the Big Bang (since we look back in time as we look further out). |
#36
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Looking into the past with a telescope
On Jan 28, 9:51 pm, "Greg Neill" wrote: "Davoud" wrote in ... Davoud: I can think of no reason why the Universe can't have a central region in three-dimensional space if the Big Bang theory is correct. Greg Neill: If the BB is correct, then every place in the 3D universe was once co-located with the center. So there is no unique place that one can call The Center, since every place equally fulfills the role. I have seen this argument in various guises. In /my/ /mind/ it breaks down because of mixed verb tenses. "Every place /was/ /once/ co-located in the center." OK, but "every place" departed the center when space-time expanded, leaving the center behind. These "places" did not all carry the center with them so that each one is now a center of its own. Such a place -- a region that was denser than average due to a quantum fluctuation and later became the core of a galaxy -- may be a local center, but it is not the Universal center -- in /my/ /mind/ .Your difficulty with this seems to stem from your adhering to a model where things exploded out from a center into a pre-existing space or void. This is not the case in the BB model where space itself expanded. There was nothing at all (not even space) "outside". Simple common sense says that the two-dimensional surface of a sphere has no center -- I figured that out for myself while playing with a solid-color, featureless rubber ball as a child -- but if you look beyond the surface, inside the sphere, you will find a center.That's fine if you have the ability to look beyond the surface. If you can't, then you're confined to looking on the surface. The same thing holds for us, who can only point to things inside the universe. There is no direction in all of space that we can point to that is in the direction of a unique center in 3D space, yet every direction points to the Big Bang (since we look back in time as we look further out).- Hide quoted text -- Show quoted text - Here is the answer you are looking for - " 'Now, it is very remarkable that this is so extensively overlooked,' continued the Time Traveller, with a slight accession of cheerfulness. 'Really this is what is meant by the Fourth Dimension, though some people who talk about the Fourth Dimension do not know they mean it. It is only another way of looking at Time. There is no difference between time and any of the three dimensions of space except that our consciousness moves along it. But some foolish people have got hold of the wrong side of that idea. You have all heard what they have to say about this Fourth Dimension?'" http://www.bartleby.com/1000/1.html This is what you get when axial rotation to celestial sphere geometry morphs into orbital motion to an aether,remove the aether and bingo - you get bare celestial sphere geometry. I think the fiction which created the early 20th century concepts far surpasses the narrative neccessities which Wells used to create a wonderful science fiction story. Want to know what Newton thought of aether - "The fictitious matter which is imagined as filling the whole of space is of no use for explaining the phenomena of Nature, since the motions of the planets and comets are better explained without it, by means of gravity; and it has never yet been explained how this matter accounts for gravity. The only thing which matter of this sort could do, would be to interfere with and slow down the motions of those large celestial bodies, and weaken the order of Nature; and in the microscopic pores of bodies, it would put a stop to the vibrations of their parts which their heat and all their active force consists in. Further, since matter of this sort is not only completely useless, but would actually interfere with the operations of Nature, and weaken them, there is no solid reason why we should believe in any such matter at all. Consequently, it is to be utterly rejected." NEWTON The fiction of the early 20th century was to dump 'aether' on Newton as 'absolute space' and then reject it all over again. I love this fiction stuff,carry on and we will take the whole thing apart and expose where you are getting the anti-astronomical every- point-is-the-center-of-an-expanding- universe. |
#37
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Looking into the past with a telescope
Davoud:
I can think of no reason why the Universe can't have a central region in three-dimensional space if the Big Bang theory is correct. Greg Neill: If the BB is correct, then every place in the 3D universe was once co-located with the center. So there is no unique place that one can call The Center, since every place equally fulfills the role. David: I have seen this argument in various guises. In /my/ /mind/ it breaks down because of mixed verb tenses. "Every place /was/ /once/ co-located in the center." OK, but "every place" departed the center when space-time expanded, leaving the center behind. These "places" did not all carry the center with them so that each one is now a center of its own. Such a place -- a region that was denser than average due to a quantum fluctuation and later became the core of a galaxy -- may be a local center, but it is not the Universal center -- in /my/ /mind/ . Greg Neill: Your difficulty with this seems to stem from your adhering to a model where things exploded out from a center into a pre-existing space or void. This is not the case in the BB model where space itself expanded. There was nothing at all (not even space) "outside". Ah, well, you didn't read my post in its entirety. I adhere to no such model. I conceded that the standard model is difficult for me to grasp, as I wrote "But I can't get my mind around an immaterial edge beyond which is nothing whatsoever, not even empty space. One cosmologist, half joking, said 'It could be a brick wall, for all we know.' " The latter statement eases my frustration a bit; I've heard plenty of learned scientists say that they can't make sense out of it, either. Simple common sense says that the two-dimensional surface of a sphere has no center -- I figured that out for myself while playing with a solid-color, featureless rubber ball as a child -- but if you look beyond the surface, inside the sphere, you will find a center. That's fine if you have the ability to look beyond the surface. If you can't, then you're confined to looking on the surface. The same thing holds for us, who can only point to things inside the universe. There is no direction in all of space that we can point to that is in the direction of a unique center in 3D space, yet every direction points to the Big Bang (since we look back in time as we look further out). Perhaps we have not yet seen far enough? I understand that what you raise is a possibility, even if it flies in the face of reason. Reason says that, unless the Universe is infinite in time and extent it has a center. Among other possibilities are that the expanding Universe left in place a point from which that expansion began, and that the Universe (also) has a center of mass. In addition to the balloon analogy, I envision the similar raisin bread analogy; the raisin bread begins as a ball of dough unaffected by any outside influence (because there is no outside.) As it expands due to internal forces (because there is no outside) it remains a ball, and what was the center remains the center as every single place in the bread down to the smallest possible place (is that called the Planck distance?) moves away from the center. Davoud -- usenet *at* davidillig dawt com |
#38
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Looking into the past with a telescope
On Sun, 28 Jan 2007 15:28:41 -0500, Davoud wrote:
I can think of no reason why the Universe can't have a central region in three-dimensional space if the Big Bang theory is correct. If the Universe exhibits perfect radial symmetry, then the center is a simple point in three-dimensional space... No reason except that this is inconsistent with GR, the concept of space-time, and just about everything else theory tells us about the Universe (much of which has held up very well to experimental verification). _________________________________________________ Chris L Peterson Cloudbait Observatory http://www.cloudbait.com |
#39
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Looking into the past with a telescope
"Davoud" wrote in message ...
Greg Neill: Your difficulty with this seems to stem from your adhering to a model where things exploded out from a center into a pre-existing space or void. This is not the case in the BB model where space itself expanded. There was nothing at all (not even space) "outside". Ah, well, you didn't read my post in its entirety. I adhere to no such model. I conceded that the standard model is difficult for me to grasp, as I wrote "But I can't get my mind around an immaterial edge beyond which is nothing whatsoever, not even empty space. One cosmologist, half joking, said 'It could be a brick wall, for all we know.' " The latter statement eases my frustration a bit; I've heard plenty of learned scientists say that they can't make sense out of it, either. No, I read your post. It still appears to me that your model includes some outside that we can point to. The BB model does not have any edge or boundary that is reachable from within our universe by travelling in any direction in space. Simple common sense says that the two-dimensional surface of a sphere has no center -- I figured that out for myself while playing with a solid-color, featureless rubber ball as a child -- but if you look beyond the surface, inside the sphere, you will find a center. That's fine if you have the ability to look beyond the surface. If you can't, then you're confined to looking on the surface. The same thing holds for us, who can only point to things inside the universe. There is no direction in all of space that we can point to that is in the direction of a unique center in 3D space, yet every direction points to the Big Bang (since we look back in time as we look further out). Perhaps we have not yet seen far enough? The BB model says that there is no "far enough", as there is no boundary in 3D space. I understand that what you raise is a possibility, even if it flies in the face of reason. Reason says that, unless the Universe is infinite in time and extent it has a center. There is no center just as there is no center on the surface of a balloon. The center of expansion of a balloon lies outside of the surface, and is not accessible in any way to a 2D being living on it -- he couldn't even point to it. Among other possibilities are that the expanding Universe left in place a point from which that expansion began, and that the Universe (also) has a center of mass. For the balloon analogy, that center would lie outside of space and time. There would be no place on the surface of the balloon that would correspond to a center of mass. In addition to the balloon analogy, I envision the similar raisin bread analogy; the raisin bread begins as a ball of dough unaffected by any outside influence (because there is no outside.) As it expands due to internal forces (because there is no outside) it remains a ball, and what was the center remains the center as every single place in the bread down to the smallest possible place (is that called the Planck distance?) moves away from the center. The raisin bread analogy fails to capture the essence of the BB geometry precisely because of the fact that it presupposes that the bread is expanding into an existing 3D space. The balloon analogy (although itslef rather limited) does a slightly better job here, although it requires one to extrapolate the situation from 2D to 3D. |
#40
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Looking into the past with a telescope
Davoud wrote:
I can think of no reason why the Universe can't have a central region in three-dimensional space if the Big Bang theory is correct. If the Universe exhibits perfect radial symmetry, then the center is a simple point in three-dimensional space; if, due to quantum fluctuations, the Universe has minor bumps at its edge, like the surface of a rocky planet, then the center in three-dimensional space would need to be spread out; a central /region/ rather than a point. I think you have a notion of the universe's expansion which is at variance with the actual Big Bang theory. In the simplest case, the universe is a 3-sphere--what you might think of geometrically as the usual four-dimensional hypersphere. (The '3' refers to the dimension of the hypersphere's "surface," not its interior.) By referring to the "center" of the universe, we assume the existence of a "metric"--a consistent ruler by which distances *not* within the actual universe may be measured. Even so, that center is not on the hypersurface of the hypersphere--it is in the interior. Its location cannot therefore be specified by the three coordinates that span the universe; a fourth is needed. There are more complex cases, but they all involve the center not lying on the universe itself, but somewhere else, and invariably requiring a fourth coordinate (if in fact it exists and it is possible to specify its location in such a way). The problem is the edge. I can at least grasp the /concept/ of a center. In my version of the balloon analogy the balloon is perfectly spherical (or very nearly so, considering the above-mentioned quantum fluctuations it doesn't need a stem because it is self-inflating. Every point is moving away from a common center, which is where those points started out (wrapped in a single dimension?) when the balloon was infinitely small. But the /edge/ of the Universe? From inside the balloon I can move to the edge and encounter a material substance that I cannot penetrate. My balloon is transparent, and I can see what is outside that object. But I can't get my mind around an immaterial edge beyond which is nothing whatsoever, not even empty space. One cosmologist, half joking, said "It could be a brick wall, for all we know." In the case of the balloon, the edge *is* the two-dimensional universe. Beings in that universe cannot see "through" their universe the way you or I can; that is a benefit conferred by our three-dimensional nature. They are confined to looking at objects on the surface. In the same way, we don't see a boundary to our universe, because the things we can see are confined to the three-dimensional surface of the four-dimensional hypersphere (in the simplest case). Our eyes don't work perpendicular to all three familiar spatial directions, so we can't see through our universe the way that four-dimensional beings could. Physicists used to say that, ultimately, the Universe could and would be explained by a few simple laws that everyone could understand at least in a rudimentary way. I think that all hope for such an explanation has been abandoned. I don't think any *physicist* has seriously believed this in the last century or so. Quantum theory pretty much defies intuitive understanding; the best that most can hope for is to be able to perform the mathematical manipulations well enough to get the right answer at the end. So I suspect physicists abandoned this idea a long time ago; probably by the time of Poincare. String theory, Inflation, the notion that gravity is so weak because it is Not of This World, but is just leaking in from another dimension; the Universe may be a hologram; the Universe may not exist at all except in our minds; the physicists themselves don't agree on or understand this stuff. They don't agree on the speculative stuff. The basic tenets of the Big Bang are agreed upon by nearly all practicing cosmologists. There is rather strong consensus on it. There are interesting phenomena that people are trying to explain in a number of different ways, but this divergence shouldn't be taken for fundamental disagreement on the basic physics underlying the evolution of the universe. Here is my one prediction, however: There will not be a Theory of Everything that unifies gravity with the other forces. Gravity, it will be decided, is distinct, and must be understood on its own terms. What is the physical basis for your prediction? The reason I ask is that it is not as though there is *no* unification between gravity and the other three forces. There are incomplete unifications that make some successful non-trivial predictions about high-energy particle behavior. (These theories can be found through an assiduous Web search.) What is lacking is a *comprehensive* unification. But the fact that incomplete theories exist is encouraging, in my opinion. |
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