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Philosophy 101
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The Universe
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The Universe |
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fractal007 Senior Member
since 2000-06-01
Posts 1958 |
I don't know if this is EXACTLY a philosophical question par se[sp], but it's something that's nevertheless been bugging me for quite some time. So here goes: Why is it that no matter where we look in space, we see quasars, and the big bang? This is described in Terence Dickinson's book The Universe...And Beyond. Why don't we only see quasars and stuff in one direction-that of the big bang itself? |
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Not A Poet Member Elite
since 1999-11-03
Posts 3885Oklahoma, USA |
Well, that one's fairly simple, at least from a simple viewpoint. We actually exist somewhere in the midst of the result of that big bang. Imagine yourself at some great distance outside the universe viewing it. You would see something like a big and expanding ball of fire. This is like looking at a smaller explosion of any kind, again from a distance of course. Now keep that image in mind and try to imagine that you are somewhere inside that explosion or big bang. Any direction you look, you see part of that fireball. It all looks pretty much the same, except at the outer edge. That is the point at which the explosion first began. That is the exact situation in which you actually reside. Theory says that the quasars were some of the first object emitted by the big bang so they are at the outside edge of the universe, the point at which the explosion began. Since you are on the inside looking out, you see quasars in all directions. In short, since you are on the inside, the beginning of the big bang surrounds you and lies in all directions and is continuously expanding. Well, that's my opinion anyway Pete Imagination is more important than knowledge Albert Einstein |
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fractal007 Senior Member
since 2000-06-01
Posts 1958 |
Not a Poet: THat's an ok explanation of it, except for one thing. Most astronomers figure that quasars were more common at the beginning of the universe. So, therefore, the further back we look into the universe[IE the further away we look] the younger the galaxies look. So, unless I've read your reply wrong, you haven't explained why we see the universe as it was at an earlier stage in its life, no matter where we look. THe idea of looking at the inside of an explosion is good, except for the fact that this explosion is over 20 billion lightyears in diameter. I still don't understand why we see young galaxies no matter where we look. It was my understanding that nothing can travel faster than light, so there seem to me to be no logical explanation of why we see objects as they were closer to the beginning of the universe, no matter where we look. |
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Not A Poet Member Elite
since 1999-11-03
Posts 3885Oklahoma, USA |
Well, you almost got it. To add a bit more, think of the universe as finite (an assumption I know but one consistent with most current scientific theory). It started out as an infinitesimal dot then the big bang and it began to expand and continues to do so today. The oldest part of that expanding universe is the outer boundary or the skin of the ball. If you are somewhere on the inside of that ball then no matter what direction you look, if you look far enough, you will see that outer skin. Just like being inside a room, no matter your specific location as long as you are inside, any direction you look you will see its walls (or ceiling or floor). That outer skin is where those quasars reside so you likewise see quasars in any direction. Since the universe is not expanding as fast as the speed of light, the light from anywhere on that outer skin will eventually reach your eyes. Since it is so far away is why it takes so long to get here and is why they can estimate its age. Hope this is a little clearer. Pete Imagination is more important than knowledge Albert Einstein |
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fractal007 Senior Member
since 2000-06-01
Posts 1958 |
OK, now I see where you're going with this. So the universe is mostly an expanding shell. Although, as you've said, this is just an opinion. I guess we'll have to wait until they do actually see the Big Bang, itself. However, the astronomer's findings seem to indicate that the "era of Quasars" is at an equal distance away, no matter where we look. As, according to them, is the Big Bang. |
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Craig Member
since 1999-06-10
Posts 444 |
Pete Good explanation, well put. Your interpretation coincides almost exactly with my understanding of the known universe, the only difference is your finite versus my infinite universe (or multiverse as Brad once called it), but I can live with that.  Fractal007 The thing that seems to be the stumbling block with regard to quasars is the ‘redshift’ effect noted by astronomers. The effect is based upon spectrographic images of quasars, which seem to show that all quasars are moving away from us and that they all lie a specified distance in space (and so time) away. Pete has explained the first part but the second part has caused problems for a long time. The answer may be found in the fact that using the same images some scientists have formulated strong evidence that these radio stars are travelling in excess of the speed of light. This goes against our present knowledge of physics, which states that speeds in excess of light cannot be attained. If the calculation of speed is incorrect it casts doubts on the ‘redshift’ effect in relation to distance. This is a contentious point at the moment, made even more so by the discovery of quasars that seem to be a lot nearer than any observed before, Cygnus A (3C405) is a good example. Dr. Halton Arp the originator of ejection and redshift theory in quasars wasn’t a popular chap when he formulated his theories, he was denied telescope time and forced to move to Germany. Our understanding of quasars has moved on since then, but the whole question of the ‘redshift’ phenomenon still seems to split the scientific community. I think the only thing we can say for certain is that, at present, we aren’t certain. Thanks for the chance to read and reply |
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Not A Poet Member Elite
since 1999-11-03
Posts 3885Oklahoma, USA |
Fractal, First, the following argument is based on the acceptance of the big bang theory, which may or may not be factual. In reality, I don't think of the universe as just an expanding shell. I used that analogy for descriptive purposes. I see an expanding outer shell but each individual point inside that shell is moving outward also. Thus the whole is expanding, not just the shell. So think of it as an expanding solid ball rather than a shell. BTW, this was an excellent and challenging question which seems to be leading to a very interesting discussion. Thanks for submitting. Craig, Thanks for the compliment. Note though that I didn't claim the universe to be finite. I only asked to assume that for the purpose of the discussion. It is not a requirement for the explanation to work but does make things much easier to visualize. After all, how could we observe an infinite universe from a distance? At lease, how could we with our finite minds conceptualize such an observation? Now I must compliment you on the discussion of the redshift and its relation to quasar theory. Well done! I think it is entirely proper to be a bit skeptical of the tendency to blindly accept these theories. There is a partial explanation of the second part, or at least a contributing factor. As I understand, quasars are calculated to be moving at very near the speed of light so minor errors in observations or calculations could make a major difference in the results. If we were observing from the exact center of the universe, then the quasars would, of course, all appear the same distance away. Now we most likely are not at the exact center but we may well be very close to it, at least in comparison to the quasars. Thus by our indirect measurement method (estimating distance from the apparent redshift without knowing the makeup of the source) we may just be failing to notice or observe our own distance from the center. Well, I seem to be rambling too much to make any sense. Maybe someone else can pick up from this point and cary on for a while. BTW, my own speculation is that the universe is finite. I guess the big bang presupposes that. Of course, we'll never know the answer in our lifetimes, if ever. It probably doesn't make any difference in the overall grand scheme of things either. Pete Imagination is more important than knowledge Albert Einstein |
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fractal007 Senior Member
since 2000-06-01
Posts 1958 |
Craig: What would the wavelength of something receeding faster than the speed of light look like? I was just reading about dark matter in Michael Rowan-Robinson's Our Universe. Do you think that dark matter itself may effect the physical properties of the universe. If there are objects of mass and substance in the universe which are capable of moving faster than light, then does that mean that there may be problems with relativity on an extremely large scale as well as on the extremely small scale? I assume that we are all in agreement about an inflationary model of the universe. The book says: "One of the requirements of the inflationary morel is that the universe contain a very high proportion, perhaps ninety-nine percent, of dark matter." -P. 171 Robinson goes on to say that we do not know what exactly this dark matter is. Not a Poet: Your idea holds, but how did the expanding ball start expanding in the first place? Of course, this is based on the assumption that there is a finite amount of matter in the universe. But let's assume that we've got an infinite amount of matter in the universe. It would still have to have started off somewhere. I mean, there is a finite distance between us and the other galaxies. This leads me to another question: is the rate of expansion of the universe constant? Hubble found that the rate of expansion is proportional to distance. But why is that? |
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Not A Poet Member Elite
since 1999-11-03
Posts 3885Oklahoma, USA |
Since I got here first, I want to address your questions to Craig. Don't mean to step on your toes Craig and I still want to hear your thoughts. Interesting question on the wavelength thing. My best guess is that it would be infinite. I believe calculus and the limit axiom would predict just that. I think an infinite wavelength would not be a wave at all. Interesting. By inflationary model of the universe, I assume you mean expanding. I think the dark matter determines whether the universe continues to expand forever or eventually reverses and collapses back on itself. This is a problem which has been discussed for years. I don't remember now what the original theory was but at some time astronomers estimated the total mass in the universe (who knows how they might have done that). The bottom line was that without dark matter (which was not included in the estimate) there was not enough mass to cause the reversal. In other words, at the current rate of expansion, all the bodies have reached and exceeded escape velocity from the gravitational field produced by the estimated mass. Therefore, it will continue to expand and never collapse. If there is enough dark matter, however, the the gravitational field would be such that escape velocity has not been reached. Since there seems to be nothing pushing the matter apart and only gravity pulling it back together, then it must eventually collapse. This all, of course, is dependent on the big bang as the reason for the current expansion. Now for the questions addressed to me. BTW, please don't assume that I am an expert in this field. I did study a little astronomy and astrophysics in college but that was quite a few years ago. Not only have I forgotten a lot but a lot has probably been learned that I haven't kept up with. quote: Simple. The big bang. All that matter was concentrated in a small region and the giant explosion simply threw it out in all directions. It is still expanding due to the momentum gained from that original expulsion. If you are really asking what was the cause of the explosion, I don't know the answer. Probably the most likely theory is something along the lines of a "critical mass", much like the trigger of an atomic bomb. And, I think you are right. It seems to me that the big bang theory probably assumes a finite amount of matter and probably even a finite universe. Or maybe that really is the same thing. I can't say it isn't possible but I have a hard time accepting an infinite amount of matter. It seem to me that regardless of the distance over which it was spread that an infinite mass would produce an infinite gravitational field. I should be able to feel that. I think the question of whether the expansion rate is constant is as yet unresolved. If it is constant then that would first seem to indicate that there is not sufficient matter to cause the eventual collapse. I am reaching a bit here so don't take this too seriously. But I think I can address the idea of expansion rate being proportional to distance. Again go back to my expanding ball of exastic material. If the ball is expanding overall a some rate and you pick any point inside the ball, then every other point inside or on the ball will appear to be moving away from your selected point. Furthermore, the farther a point is from your selected point then the faster it will appear to be receeding. This is just the nature of the geometry of the ball. I think you can prove this to yourself mathematically with a little calculus and analytic geometry. That is, unless I am wrong here. Well, got to get back to work for a while now but I look forward to the next chapter. Pete |
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fractal007 Senior Member
since 2000-06-01
Posts 1958 |
As far as the receeding galaxies going faster, I think I may have a few questions that might shed some light on it. 1> Is there such a phenomenon as gravitational lensing? 2> If so, do scientists take it into account when judging distances of other galaxies?[Quasars are thought to contain massive black holes. Such objects would likely create some pretty nasty problems in the wavelengths of light] 3> With respect to your idea of an expanding sphere, Not A Poet, could it be that the distance is affecting the impulse on the galaxies' momentum? We know that gravitational force is proportional to distance. Finally, about that question of why it's expanding in the first place, I posed that to challenge the idea of infinite mass. If the universe was infinitely massive then it would not be able to expand much, because there would likely be a uniform distribution of galaxies throughout infinity. Either that, or else there would be a few places[namely black holes] in which the mass was infinite, and so they would be sucking the rest of the universe into themselves. It can be argued, however, that the cosmic singularity[I think that's the name for the "seed" that started the big bang] was finitely small, but infinitely massive. However, this would still result in infinite gravity, as you've said, Not a Poet. That's why I stick to the idea of a seed that has incredible mass, and that explodes with enough force to send this mass careening in every direction. There is also another problem: The galaxies in the known universe all seem to be uniformly distributed. In my opinion[although it's not really backed by much] it is due to a uniform distribution of mass throughout the universe. But if what I've said is true, then why does the universe's mass happen to be so well distributed? THis leads many to think that there is dark matter. This is because we often see rings of galaxies surrounding regions of complete darkness. But these rings all seem to be well distributed. So, Not a Poet, I'm with you as far as a finite universe is concerned. This is probably due to the fact that I always see the universe as having a beginning, or else at least continuing to cycle in Big Crunches and Bangs, at regular intervals. The idea that "the universe was just always here" doesn't sit well with me. |
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Not A Poet Member Elite
since 1999-11-03
Posts 3885Oklahoma, USA |
1> If by "gravitational lensing" you mean gravity bending light rays, that has been proven in recent years beyond doubt. I don't have the reference right off but can get it if you need (I think). 2> That's a good question. Surely they do but I can't say for sure. Even if they do, how do they know how much gravity effect to include. Kind of makes you wonder about the whole thing doesn't it? I would think you are right about the nasty effects on light and wavelengths, etc. 3> Not sure what you mean by "impulse on galaxy momentum." Technically though gravity is inversely proportional to the square of the distance. But that's probably what you meant. quote: This pretty much describes how I see it also. I don't seem to have an opinion regarding the distribution of matter but I understand it is thought to be rather uniform on a macro sense, if that makes any sense at all when discussing something so large, but that it is locally not so. Just don't know. quote: Again I essentially agree. Keep in mind though that a finite universe still does not imply it is cyclical. It is still possible for a finite universe to expand forever. That all depends on that postulated dark matter. Pete |
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Craig Member
since 1999-06-10
Posts 444 |
As far as the wavelength question goes, your guess is as good as mine, present popular theory suggests that speeds above that of light aren’t possible, until they’re proved wrong I’ll bow to Petes guess. The redshift calculations that predicted speeds in excess of light were based upon the phenomena of the Doppler effect, the light only seems to have a higher frequency in the same way that sound seems to change pitch relative to speed. You've got me thinking of what they saw to prompt their assertions, I'll see if I can find out more information. The dark matter question is as I understand it dependant on whether you believe the universe to be open, closed or flat . A flat universe is one that is neither expanding nor contracting, a closed universe would produce an expansion slowed and then reversed by gravitational force, back into a big crunch. The open would not contain sufficient mass to halt the expansion, recent calculations and observations point towards the later of these three, but to be fair all three seem to take turns at being the flavour of the day. The reason dark matter is reliant on which is correct is that each relies on the mass-density of the universe and it’s gravitational pull to effect the necessary results. Estimates predict that the universe hasn’t the mass to support two of these theories, dark matter is the suggested missing mass. W.I.M.Ps, MA.C.H.O.s brown dwarfs, heavy hydrogen, twin big bangs based on bubble theory have all been offered as potential answers, so far none has been proved any more plausible than any other. Gravitational lensing was predicted by Einstein and proved during an eclipse in 1919 by studies of light from distant stars passing near the sun. As far as I understand it the lensing effect bends light and was used to as a basis in an attempt to prove the existence of M.A.C.H.Os (Massive Astrophysical Compact Halo Objects). The theory was that M.A.C.H.Os orbiting a galaxy would produce a ‘flash’ from stellar bodies every 50,000 years, some success was achieved but not enough evidence was collected to prove their existence. A Black hole - An entity that has a gravitational force so great that light can’t escape from it (consequently we can’t see them, which is helpful). They are one possible explanation for rotational galaxies and if they do exist light could theoretically be slowed if it passed close enough. At the end of the day I'm drawn more and more to the certainty of uncertainty |
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fractal007 Senior Member
since 2000-06-01
Posts 1958 |
Craig: Whoa. I didn't know that there are still theorists who believe in a flat universe. I thought that was a thing of the past due to Hubble's observations. All: Our recent discussion over the uniform distribution of mass on a large scale throughout the universe has led me to the following question: Does anyone think that we may need a new branch of physics to deal with HUGE things. I mean, we've already got Newtonian physics which explains the motion of planets and the such. We've got quantum physics to examine the behaviour of subatomic particles. Do you think that we now need a new branch to discuss the behaviour of masses of galaxies? Not A Poet: By impulse I meant the change in momentum due to gravitational force counteracting the expansion of the galaxies. I was posing that as a possible explanation for the galaxies appearing to be receding at a rate directly proportional to their distance from us. However, if that was the explanation, then it would mean that we are at the center of the universe. All: Do you think that some of our observations of the expanding universe may be hampered by some unseen factors? Sorry for not having as long a response, lol. Not thinking at my best today I guess. Perhaps later on today. |
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Craig Member
since 1999-06-10
Posts 444 |
I still haven’t discounted the flat earth theory yet! Hubbles constant doesn’t seem all that constant, new data and ideas seem to crop up and rotate the flat, open, closed state of the universe. An interesting example is Einstein’s theories on the universe, he originally constructed a thesis that was based on an expanding universe that would contract when gravity kicked in. Astronomers at the time assured him that the universe was neither expanding nor contracting, he then added a whole section proposing a force that would suit the model suggested – anti-gravity was born. Unfortunately soon after the astronomers decided that Einstein’s first assumption was correct, so anti-gravity was dropped to match the new model. Recent data suggests that the universe is expanding and will continue to do so, if calculations of the mass/density of the universe are correct this opens up the possibility that another force other than gravity is at work. Guess what - Einstein’s anti-gravity theory has been dusted off and offered as an explanation. “Do you think that some of our observations of the expanding universe may be hampered by some unseen factors? “ I think anti-gravity falls into that category, personally I think that what we’ll find is that it’s plain old gravity when the light from the universes surrounding our own eventually reach us.  All hell will break lose at that time, the cause of the big bang itself will be questioned, the singularity didn’t contract but was ripped apart by gravity, I can see the headlines now |
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rad802 Member
since 2008-04-19
Posts 279KY U.S.A. |
The lastest theory being tossed around is that the universe is really a multiverse. And that the big bang may have ocurred when two undulating membranes touched at a point. The universe has been expanding ever since. Either it has enough mass to eventually stop expanding and collapse again (a closed universe) or it will expand forever (an open universe) as it turns out the the universe appears to be balanced right between these and has been said to be flat. This explanation is of a closed universe. An open universe cannot be visualised because every point in space is saddle shaped. Einstein did not know when he penned his famous theories, that space was stretching. In fact the universe is stretching or expanding from the three dimensions we know, into a higher dimension. We can not visualise this but we can visualise two dimensions expanding into three. It would look like the skin of a balloon. The skin of the balloon is just like a sheet of paper and has been called flatland, a two dimensional universe. If you put little dots all over it to represent the galaxies and you blow this balloon up, you will see the dots are moving away from each other just like the galaxies are doing. No matter which direction you look, you are looking into the past at a time when the universe was smaller. Now lets say this balloon has a north and south pole. If you are standing at the north pole and you look out across this two dimensional surface you will notice that the universe has no edge. If light were infinitely fast and you had a powerful enough telescope you could see the back of your head. But light takes time to travel. And so as we look out across space we don't see the serface of a sphere but a sight line spiraling in tword the center like the shell of a nautilus. Let's imagine that the universe is 5 billion light years around and the light leaving a star at the south pole travels two and a half billion years to reach us if the universe were not expanding. But because it is expanding, by the time the light reaches us six and three eighths billion light years later the universe is now twenty billion light years around. If you graph this out on a sheet of paper, you will notice that space was stretching out so fast that it exceeded the speed of light. There is also another scenario in which space swirls faster than light. The space around a spinning black hole is being spun by the immense gravity at a rate faster than light. A worthy legacy is the irrevocable consequence of dreaming. Rick A. Delmonico [This message has been edited by rad802 (08-15-2009 09:51 PM).] |
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rad802 Member
since 2008-04-19
Posts 279KY U.S.A. |
Not a poet said: "Now keep that image in mind and try to imagine that you are somewhere inside that explosion or big bang. Any direction you look, you see part of that fireball. It all looks pretty much the same, except at the outer edge. That is the point at which the explosion first began. That is the exact situation in which you actually reside." But the universe has no edge. Every direction you look in, you are looking back in time at an older, smaller universe. If you look far enough across space you will see the very first stars in the very first galaxies that formed in the early universe. this is true no matter which direction you look in. If you don't understand this, see my previous post. The last theory I read about the universe expanding stated that the rate of expansion was actually increasing. This is not completely understood by scientist at this time. |
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