SciForums.com > Science > Physics & Math > beyond the universe PDA View Full Version : beyond the universe Post ReplyCreate New Thread stef 73003-09-02, 04:00 PMWhat could possibly lie beyond the visible universe? What if the universe is like a drop of water in the ocean and there are other domains much bigger than are own? I know that is impossible to look past the cosmological horizon, but if it weren't, what might we see? For me it is hard to comprehend and I was wondering what others had to say. Tyler03-09-02, 05:41 PMWhat do we mean by outside the Universe? I can't even comprehend that idea. Like there's some barrier between the Universe and then further matter. But then how d we define Universe? Pollux V03-09-02, 06:15 PMCouldn't we just say that the universe is infinite, that it always has been and always will be? That no matter how far you go that you will never reach an end, that there is an infinite amount of combinations of everything to continuously regenerate new things. Welcome to sciforums, stef, since it may be overwhelming, I find it helps to close one eye:D Enjoy. Hoth03-09-02, 06:49 PMHe said "beyond the visible universe", not beyond the absolute universe, which makes the question harder. Maybe before the big bang there was another universe that was an opposite of ours, like a reversed time version of ours... one that started out infinitely large and thin and slowly coalessed to eventually become the big crunch that led to our big bang. That'd be nicely symmetric, and fun, even if it doesn't make too much sense from our perspecitve. If there's something which we can't observe the effects of, we'll never be able to understand it. Pollux V03-09-02, 06:58 PMIf it's not infinite my theory is that something sometime went faster than the speed of light, and we are inside that unlucky bloke right now. Tyler03-09-02, 07:16 PMIf something is infinitely big, as far as I know my math, there is no way for it too shrink below infinte. Infinite - 1 = infinite; does it not? kmguru03-09-02, 07:47 PMCan anyone tell me the following: The size of the visible Universe in light years (x,y,z) The average size of a galaxy in LY (x,y,z) The average distance between galaxies in LY Xelios03-09-02, 10:43 PMThe size of the visible universe is the time since the Big Bang (about 15-18 billion ly) in all directions. I believe our galaxy is no more than 100,000 ly across (50 kiloparsecs) but only about 100 parsecs "thick" at its thickest point. The average seperation of galaxies in a cluster is several megaparsecs. The distance between clusters of galaxies is usually about 10 megaparsecs. Not sure what that is in ly though. Adam03-10-02, 12:20 AMI was thinking that either the universe is EVERYWHERE, infinite, eternal, and there was no Big Bang at all... Or, maybe we have Big Bangs followed by Big Crunch/new Big Bang, et cetera, always expanding and contracting, like a big pulsating mess of matter and energy. But what if that is the case, and sometimes some matter escapes beyond the reach of that final contraction, keeps drifting outward where matter is more and more rare? What is there are "universes", big pulsating collections of matter/energy, spread out all over, like we consider galaxies in the universe? What if throughout some broader medium there are multiple clumps of matter? Just as there are galaxies here and there, what about entire "universes" expanding and collapsing here and there, separated by mostly empty space, with matter occasionally drifting between? kmguru03-10-02, 05:18 PMXelios: Based on your data, I roughly calculate the distance between two Universes (assuming there is more) to be about 10,000 billion Light Years. If that is the case, the photon coming from another universe might lose all or major part of its energy by the time it gets to our universe. Besides we have no idea what may lie at the edge of our universe. It could be a fluidic medium that can not pass light.... Just some thoughts to chew on.....(for hamster that is, btw, where is hamster?) On the big bang thing, I am not too convinced that is what happened. We may get a better explanation one of these days.... stef 73003-10-02, 08:09 PMAdam's thinking like i am. Collections of universes outside our own like galaxies in our universe. Or there might be infinite nothingness in all directions. Boris203-11-02, 04:50 AMStef >>Collections of universes outside our own like galaxies in our universe. Or there might be infinite nothingness in all directions. Yes either of these is a possibility. There is no "outside" to this universe. This universe is "made" of spacetime. So if this Universe is spacetime how can you have something that exist without space to exist in or time to exist? There are multiverse theories, do a Google, but there is probably no way for us to ever find out. This is because we would, or our probes etc, have to cross a region of no spacetime to find them. ismu03-11-02, 06:13 AMIt may seem hard to believe that space can be anything BUT infinite! If space ends at some boundary, what could lie beyond the boundary, if not more space? But in the 1850s, the German mathematician Bernhard Riemann discovered an alternative -- a new geometrical shape that has a finite volume, yet has no boundaries at all. This new three-dimensional shape is called a "hypersphere." Although a hypersphere cannot be visualized from the outside, it CAN be visualized and drawn from the inside. One catch: the geometry inside this new shape is different from the Euclidean geometry we learn in school. Today we know that there are actually several alternatives to infinite space. That's good, because the concept of infinite space is a difficult one: If there are infinitely many galaxies like ours, would there be other creatures out there who looked just like you? We know of no other infinities in nature. Astronomers have not been able to directly detect a "curvature" to the universe, and have not been able to find enough matter in the universe that would cause space to curve around on itself. Therefore, we can not say with confidence that the universe is finite. But it is still possible for the universe to be finite and extremely large: If the entire universe were large enough, then measurements in the part we can observe wouldn't let us distinguish the shape of the universe as a whole -- anymore than we could tell if the Earth were flat or round based on observations in our own backyard. For the time being, we don't know what kind of universe we inhabit: an infinite one we can't quite conceive of, or a finite one whose size we can't quite determine! Dinosaur03-13-04, 10:35 PMIt seems strange, but I think that our universe is about 90-100 billion light years in diameter. A recent article in Scientific American stated that photons from the Cosmic Microwavve Background have traveled about 45 billion light years, but only took about 13 billion years to make the trip. The expansion of the universe elongated the path they took to get to us. The above suggests that we are at the center of an observable universe which is 45-50 light years in diameter. MacM03-14-04, 10:42 AMI personally see the universe as being finite. That is there is "Nothinness" as our Domain . Nothingness being defined as absence of time space. As Dinoasur has stated I too see the universe being much larger than what we observe. I see time-space as an ongoing expansion from the initial Big Bang with time-space expanding faster than the material expansion within it. So galaxies are moving out into newly created universal volumes. ddovala04-16-04, 04:23 PMWhat if to an outside observer our universe expands and contracts incredibly fast, almost infinately, and radiates energy as such. Then expanding outward our universe could be some kind of subatomic partical to a higher world, persay. And likewise all of our matter, (if we could zoom in that far, which, i know, is impossible) were other universes expanding and contracting almost infinately fast (making a spherical shape?). Etc. etc. If this were true there would be no "elementary" particle right? jellyca04-26-07, 01:14 PMthis hurts my head. i want the answers. i feel that when i am older i will accept that we are not ready or meant to know and will leave it be but for now i like to think about my different ideas. I always used to imagine that the universe was like a bubble and when you came up to the edge, it was like a force holding it all together. the wall would be trasparent and you could just pass through it like fog....even my imagination wont let me see what is beyond the 'bubble' though. P.S more life must be out there! just us in the whole universe, yeah right... and let me guess, it revolves around us too! :D Billy T04-26-07, 01:47 PM"Beyond the Universe" is located the region "the inside of the outside." Zen anyone? :D To MacM: Glad to see you active here again. Your and my, (when it comes to how mind works) quality of crackpots are rare. ;) Dinosaur04-26-07, 09:22 PMIf the observable recession velocities are correct (they probably are at least reasonable), then there are galaxies moving away from us at velocities greater than the speed of light. This is independent of the validity of the current Big Bang Cosmology: It only depends on the validity of the observed recession velocities and the derived relation between recession velocity and distance. On the basis of the above, the regions beyond the observable universe are not very different from the observable universe. There are clusters of galaxies separated by large volumes of space which are empty or close to being a vacuum. Perhaps the density of that region is less than the density of the observable universe (I do not know about this issue). Since the observable universe is a sphere centered on our solar system, I suppose that the region beyond it is best thought of as a spherical shell. Note: That region is not only not observable, it can have no cause/effect relationship with us. Note: From the point of view of Alpha Centauri, the observable universe is a sphere whose center is offset from our observable universe by about 4 light years. Similarly, the observable universe from the point of view of the Andromeda Galaxy, the center of the observable universe is offset from our observable universe by about 2.5 million light years. In my mind, I think of the entire universe as a 3D sphere. That view is not consistent with the above. If the entire universe is a 3D sphere, the observable universe could not be a sphere with a center offset from our observable universe from the point of view of every galaxy, including those receding from at velocities way beyond the speed of light. The above suggests either an infinite universe or some 4D or higher dimensional geometry.If Bang cosmology is correct, an infinite universe does not seem reasonable, since it has only been expanding for about 13 billion years. Note again: This is not dependent on the validity of Big Bang Cosmology. It is only dependent on the validity of the observed recession velocities, which seem to be at least close to correct. If the recession velocities are incorrect by a large amount, the data still indicates an expanding universe with a finite age, not an infinite universe. This leaves us with a finite universe conforming to some higher dimensional geometry rather than its being a 3D sphere. A 4D geometric shape with time as the fourth dimension? A 4D geometric shape of some sort with the fourth dimension being spatial rather than being time? Some 4D shape embedded in a much higher dimensional space, allowing for very counterintuitive geometric properties?Note that objects like Klein bottles (a 2D surface) cannot be embedded in a 3D space. With our 3D intuition, we cannot visualize such geometric objects. Note that a cone or a cylinder and many other 2D surfaces have the same intrinsic geometry as a Euclidean Plane. In higher dimensional spaces, there can be some weirdly curved 2D & 3D spaces which conform to ordinary geometry. Once you accept the notion of our universe being finite (which it might be), you can speculate that there are other universes external to ours, although we or our descendants are unlikely to ever be able to interact with or observe such universes. I obviously do not acept the notion of colliding branes (My intuition has been wrong on simpler issues so I will not try to defend this opinion). BTW: Cantor showed the logical consistency of the concept of orders of infinity. The real numbers are an example of an infiinty beyond that of the infinite set of integers. I suppose our universe could be infinite without negating the possibility of universses external to it. This boggles my mind too much for me to try to think deeply about the concept. nietzschefan04-26-07, 09:31 PMBig bang = just a really big Quasar? One of many? We really would not see anything coming at us from and equivalent "bang" 1 trillion LY away... We accept that other galaxies exhist, because we can see them. So far we have not detected another ummmm "universe-bigbang", so we don't know. It could be we would never know right? As the masses start to pull back on each other again and we go back to the "big crunch", we get pulled away from other bang-crunches. One would think perhaps that eventually all of these would also be pulled together... Pete04-26-07, 09:41 PMWhat could possibly lie beyond the visible universe? What if the universe is like a drop of water in the ocean and there are other domains much bigger than are own? I know that is impossible to look past the cosmological horizon, but if it weren't, what might we see? For me it is hard to comprehend and I was wondering what others had to say. I think that the Universe beyond the observable Universe probably looks a lot like our Observable Universe for a long way out, like for trillions of light years. Beyond that... here be dragons :shrug: Dinosaur04-26-07, 10:29 PMI always preferred the Steady State and/or Bang/Crunch cosmologies over the Big Bang. Unfortunately, the Steady State or Continous Creation Cosmologies (my favorites) are fatally flawed by observable data. I think the Bang/Crunch Cosmologies are also flawed, although perhaps not as fatally as the Steady State cosomologies. In the absence of some serious supporting arguments, I think that Bang/Crunch Cosmologies should not be presented as possibilites. Leave them to threads dedicated to advocating such notions unless you are willing to provide some justification for considering them. draqon04-26-07, 10:41 PMOur universe expands from itself and descends into itself. Beyond the universe is nothing, vacuum. Our universe never was created or destroyed, it is a harmonic motion of self recycling. Beyond the visible universe is that which holds this universe matrix, it is theoretically impossible for us to imagine the other universe which our universe is part of. However I can give a relation, our universe is like a quark and the universe we are part of is like social interaction between species in relation to that quark. The other universe is not physical in our sense, it has its own perception of reality that when transcribed to our own terms related to chaos. nietzschefan04-26-07, 11:08 PMI always preferred the Steady State and/or Bang/Crunch cosmologies over the Big Bang. Unfortunately, the Steady State or Continous Creation Cosmologies (my favorites) are fatally flawed by observable data. I think the Bang/Crunch Cosmologies are also flawed, although perhaps not as fatally as the Steady State cosomologies. In the absence of some serious supporting arguments, I think that Bang/Crunch Cosmologies should not be presented as possibilites. Leave them to threads dedicated to advocating such notions unless you are willing to provide some justification for considering them. hmm I don't think that's fair - I was on-topic. Bang/Crunch has been observed just as much as "big bang". Dinosaur04-26-07, 11:56 PMNietzschefan: A citation or some supporting discussion for the following? Bang/Crunch has been observed just as much as "big bangI am unaware of anything other than speculation relating to Bang/Crunch. When/how was this observed? Dragon: The syntax, vocabulary, and sentence structure of your last post are all understandable. I find the semantics unclear. Could you elaborate? Does anybody else have a problem with that post? Pete04-27-07, 12:15 AMNo more than usual. draqon adds a surprising flavour of poetry to the subforum, I think. Even though he's clearly out of place, he's part of the scenery like a preschooler at a po-mo cocktail party. bsemak04-27-07, 12:58 AMThe universe is by definition everything. Really, everything. I mean it, absolutly everything. Talking about what is beyond it would actually make no sense. Dinosaur04-27-07, 03:06 AMBsemak: Without context, the following might be reasonable from the point of view of a dictionary definition. The universe is by definition everything. Really, everything. I mean it, absolutly everything. Talking about what is beyond it would actually make no sense.Note that dictionaries are most reliable when defining simple words and often are lacking when defining words related to more complex subject matter. The term observable universe refers to only a part of a concept called our universe. Note that there are many different observable universes, assuming that our universe is expanding. Our observable universe is not the same as the observable universe from a point of view in the Andromeda Galaxy. It is reasonable to say that both of these observable universes belong to the same universe, which I choose to call our universe. Perhaps we could get around the above bit of semantics by coining new terms: obverse and maybe ourverse. Then universe could have the meaning you assign to it. We would still have to talk about our obverse amd the Andromeda obverse, so we would not have gained much by the new vocabulary. The following would require still another term: othverse. I do not think there is any evidence for the existence of universes other than ours. However, there are those who speculate about the possibility of our universe being one of many unverses existing in some higher dimensional space. Perhaps we might find evidence that such speculations have validity. Even in the absence of such evidence, it would be sad to ban speculation about such an interesting concept because somebody insists that there is only one such thing as a universe and it includes all that there is. Your view is analogous to the view of those who say: "Infinity is infinity. There is no such concept as larger and smaller infinities." Yet Cantor developed the concept of many different infinite sets. It is definitely known that the set of all real numbers has more members than the set of all integers. Yet both sets are infinite. Infinity is not the biggest number there is, and universe is not all there is. bsemak04-27-07, 04:50 AMMy point was that there is actually no definition (in my mind) on what we mean by "the Universe" not semantics or what the dictionary says. Human langueage is in many cases inadequate to describe physics, just think of QM. With regard to Cantor, infinities are not well defined (or have I forgotten some math from all these eons ago?). My point was that the term Universe is not defined. If the definition is "everything" (whatever that means can also be discussed) then it makes no sense to talk what is on the other side. You cannot even say "nothing" the question it self is meaningless. Zephyr04-27-07, 05:09 AMMaybe the universe is like a Klein bottle - no outside. Farsight04-27-07, 08:11 AMThe word universe is of Latin origin, being comprised of two parts: Uni as in unicycle meaning "one", and verse, as in vice versa meaning "turned into". It means "turned into one". It means, as besmak said: "everything". Hence if you hear people talking about parallel universes they're basically talking about multiple everythings. It doesn't parse. Ditto for beyond the universe. BenTheMan04-27-07, 09:32 AMThe intent of the question was obviously to ask "what is beyond our hubble volume", i.e. "what is beyond the observable universe?" It's pretty easy to answer, I think. The universe is flat, which we know from doing experiments. Because it is flat, it is infinite. So Pete is right. Before inflation, our observable universe fit in a box of about 10^-33 cm on a side. That's what inflation does---it takes a little volume of space and blows it up. So if you imagine the early universe being "smooth" in some sense---that is, not too different from one place to another---it is still smooth. All of the little bubbles that were close to each other before inflation are still close together. The only difference is that the little bubble is 14 billion light years across. The implication of all of this is, of course, that everything happens. So when creationists bitch about how unlikely life spontaneously appearing is, this is my favorite argument. Because the universe is infinite, not only do all things occur, they all occur infinitely many times! http://map.gsfc.nasa.gov/m_uni/uni_101shape.html Zephyr04-27-07, 09:57 AMBecause the universe is infinite, not only do all things occur, they all occur infinitely many times! Even impossible things? Even if our universe is infinite in space, it may only be finite in usable energy due to thermodynamics II. Wouldn't that make it finite in terms of interesting events? A bit off topic, but that kind of thing makes me wonder - what if there is another earth, surrounded by identical stars, with identical people on it? Except that at this very moment, the you over there does something different to the you over here. Reality splits. Which one is then you? draqon04-27-07, 10:28 AMuniverse cannot have shape because its shape depends on time. Billy T04-27-07, 10:41 AM...It is definitely known that the set of all real numbers has more members than the set of all integers. Yet both sets are infinite. Infinity is not the biggest number there is, and universe is not all there is.Are you sure of this? I am not a mathematician, but believe that when one has to sets each with an infinite number of elements (members) then the only way to determine if one is larger (has more members) is to try to establish a "one to one" corespondence between them. I think that set of real numbers is not larger than seto of integers or even only the real numbers between 0 and 1! counter intutive as this may seem. For example, you give me real number: abc....xyz... and I say that uniquely, one-to-one, correspondes to interger abc....xyz... or squezing it into the line segment 0to1, the 1-to-1 correspondence is to point: 0.abc....xyz... You can never find any real number that I can not give a unique 1-to-1 corresponding number to, so your set is no bigger than mine. Even all the points in the plane (X,y) are that same size infinity as the points between 0 and 1 on the x-axis. For example you give me point (ABC...XYZ... , abc....xyz...) and I tell you the 1-to-1 uniquely corresponding point is in the range 0 to 1 is: 0.AaBbCc...XxYyZz... For every point you have, even using the entire XY plane, I have a 1-to-1 uniquely corresponding point. - How can you then claim you have more points than me? BenTheMan04-27-07, 11:41 AMEven impossible things? Impossible in what sense? Even if our universe is infinite in space, it may only be finite in usable energy due to thermodynamics II. Wouldn't that make it finite in terms of interesting events? This is a good quesiton. The second law says that the maximum entropy should scale as the surface area of our hubble volume, in planck units. Hmmm. I must be missing something simple? What do you mean that it is finite? A bit off topic, but that kind of thing makes me wonder - what if there is another earth, surrounded by identical stars, with identical people on it? Except that at this very moment, the you over there does something different to the you over here. Reality splits. Which one is then you? This is an obvious question:) There was an article in scientific american a few years to this effect. The answer is, of course, there are (in principle) an infinite number of copies of me! universe cannot have shape because its shape depends on time. Stick to buddhism dude, because you don't know shit about physics. BenTheMan04-27-07, 11:44 AMIt is definitely known that the set of all real numbers has more members than the set of all integers. Yet both sets are infinite. There is another way to see this---take the following two integrals: \int_{a>0}^{\infty}dx \frac{1}{x} \int_{a>0}^{\infty}dx x One is a logarithmic divergence, and one is a quadratic divergence. The first integral is infinite, but it grows very slowly at large values. In terms of physics, these types of integrals pop up all the time, when doing things like simple particle scattering problems. draqon04-27-07, 11:49 AMStick to buddhism dude, because you don't know shit about physics. no, I want to learn about physics, so do tell me. What did I say wrong? Its just an assumption as yours is, one experiment with the balloon in the Earth atmosphere, and you base it as a fact? http://news.bbc.co.uk/1/hi/sci/tech/727073.stm And Einstein did not believe that universe was flat, so what he is a fool too? And what did I say wrong? This universe spans for millions of parsecs, different locations of universe are in different time zones. And how do you account for universe expanding? just some antimatter energy and particles? will not do, give proof for that. darksidZz04-27-07, 12:00 PMU suspect the universe does end, it would be funny to see your expressions when I'm proved right! LMAO draqon04-27-07, 12:03 PMU suspect the universe does end, it would be funny to see your expressions when I'm proved right! LMAO I just as Mr. Pete make assumptions here. He thinks however that if he applies known math equations to the world it can be explained just like that, whereas my motto is that such cannot be done since we dont know about universe enough at all. Example: dark matter , go observe it Mr. pete wilgory04-27-07, 12:12 PMIn our observable area of the universe, we find planets, stars, galaxies, clusters of galaxies, etc. Due to the uniformity of what we see, it is reasonable to infer, that this is what we would find beyond what we observe. What is commonly called our universe is what I call a space-time continuum. According to the standard model, the diameter of this continuum is thought to be 130 billion lightyears. Beyond this is the unknown and will never be known by those in our continuum. I see no reason to dought the existence of more. Therefore I consider the universe to be, the continuum we are in, and whatever else there may be. draqon04-27-07, 12:17 PMBeyond this is the unknown and will never be known by those in our continuum. I see no reason to dought the existence of more. Therefore I consider the universe to be, the continuum we are in, and whatever else there may be. Thats like saying " In a school beyond this classroom is another classroom"...really means nothing wilgory04-27-07, 12:54 PMDragon, How do you suppose mainstream cosmologist arrived at the 130 billion LY figure for the diameter of the "universe". Do you believe that what is observable is all there is? Chatha04-27-07, 01:55 PMI don't know what lays beyond the universe, but people of such calibre that live in such realms are nothing but Gods. Dinosaur04-27-07, 04:45 PMBenTheMan: I am pretty sure that both your integrals represent infinite volumes, with one larger than the other. However, I do not remember enough of any pertinent math course to be certain on this issue. Billy T: The set of all real numbers between 0 and 1 has more members that the set of all integers. Cantor had a proof which was similar to the following. The digits associated with all the real number can be associated with an array:A11, A12, A13 . . . . A21, A22, A23 . . . . A31, A32, A33 . . . . . . . . . . .Each row of the above array corresponds to a real number: A1x is the first row, A2x, the second, and so forth. Now, if the number of memeber in the two sets are the same, then each row (a real numbers between 0 & 1) can be paired with an integerb]:[/b] 1 with Row A1x, 2 with A2x, 3 with A3x, et cetera. Now suppose we create a real number with digits B1, B2, B3 . . . . . . . as follows.Choose B1 different from A11 Choose B2 different from A22 Choose B3 different from A33 . . . . . . .I vaguely remember some requirement that the choices made for digits Bx, not allow all the digits beyond some point to be the same (or perhaps they cannot all be zeros or nines). The real number represent by B1B2B3 . . . . . . . differs from every real number in the above list, proving that the one-to-one pairing cannot be done. There will always be at least one real number unpaired. BenTheMan04-27-07, 05:30 PMAnd Einstein did not believe that universe was flat, so what he is a fool too? No, but Einstein died about 45 years before there was any experimental evidence to the contrary. If he was alive today, he'd have to be a fool not to believe that the universe was flat. So, if you're comfortable talking out of your ass about physics that's irrelevant in light of new experimental results, have fun. BenTheMan04-27-07, 05:32 PMExample: dark matter , go observe it Mr. pete http://home.slac.stanford.edu/pressreleases/2006/20060821.htm This google search took 10 seconds. BenTheMan04-27-07, 05:43 PMIts just an assumption as yours is, one experiment with the balloon in the Earth atmosphere, and you base it as a fact? Why don't you look at the links I've posted. Thats like saying " In a school beyond this classroom is another classroom"...really means nothing But if you are confined to the classroom, and have no way of ever leaving, or ever seeing outside of the classroom, and all of your theories tell you that there's another classroom, how can you say anything else? What is commonly called our universe is what I call a space-time continuum. According to the standard model, the diameter of this continuum is thought to be 130 billion lightyears. Ok... This is confusing. I had to do a bit of research, but the idea is this... The universe is 13.7 billion years old, but due to the periods of inflation, the actual distance is 78 billion light years. Which means diameter = 156 Gly. It's like adjusting the cost of something for inflation (in the economic sense). For example, a new car cost $4000 brand new in 1950, and$20,000 today. BenTheMan04-27-07, 05:44 PMI don't know what lays beyond the universe, but people of such calibre that live in such realms are nothing but Gods. They probably think the same things about us... monadnock04-27-07, 06:25 PMMAX TEGMARK ON MULTIVERSES: Q: You state in your paper "the key question is not whether parallel universes exist (Level I is the uncontroversial cosmological concordance model), but how many levels there are." Are you suggesting that the existence of level I parallel universes is not a key question? In other words, do you argue that the number of universes is larger than n=1 (the lowest number we can obtain from observation)? Indeed. Although it's far from obvious that n=oo, I think the astronomical evidence is very compelling that n > 1. The curvature of space measured by the cosmic microwave background is so small that if space is a (finite) hypersphere, then it is large enough to contain at least n=1000 other Hubble volumes. If space is finite by connecting back on itself like a donut, the cosmic microwave background measurements again require the donut to be large enough to contain n > 1 Hubble volumes. Of course you can always postulate that space ends abruptly right outside the cosmic horizon with a big warning sign said "MIND THE GAP", but you'll have a hard time providing an elegant mathematical formulation of that theory, let alone convincing other people of its virtues. http://space.mit.edu/home/tegmark/multiverse.html wilgory04-27-07, 08:32 PMWhy don't you look at the links I've posted. But if you are confined to the classroom, and have no way of ever leaving, or ever seeing outside of the classroom, and all of your theories tell you that there's another classroom, how can you say anything else? Ok... This is confusing. I had to do a bit of research, but the idea is this... The universe is 13.7 billion years old, but due to the periods of inflation, the actual distance is 78 billion light years. Which means diameter = 156 Gly. It's like adjusting the cost of something for inflation (in the economic sense). For example, a new car cost $4000 brand new in 1950, and$20,000 today. BenTheMan, My figure for the diameter of the space-time continuum may be outdated. My point was that we know much about what is beyond our observable area of the universe. I've read recently that some of the galaxies we are receiving light from are actually as far away as 47 billion lightyears. Don't ask me to explain how we know (I'm not a cosmologist). I understand it has to do with a couple of different types of redshift along with accelerated expansion. While we can not tell what these galaxies look like today, they have been observed. I consider this the limit of our observation. Beyond this we have to use reason and inference to deduce what the rest of the universe "looks" like. BenTheMan04-27-07, 08:34 PMMy figure for the diameter of the space-time continuum may be outdated. My point was that we know much about what is beyond our observable area of the universe. No, your figure was close. You said 130, I said 156. The universe is 13.7 billion light years old, but the diameter of the observable universe is 156 billion light years. 2inquisitive04-27-07, 09:26 PMThe 156 billion light-year diameter was due to a mistake made by a science writer for Space.com, an incorrect figure which has been widely quoted by other popular press outlets. Neil Carnish et all's 2004 paper calculated a minimum diameter of 78 a billion light-year diameter now, but most likely about 92-94 billion light-years in diameter for the observable universe. A pretty good explanation of how the diameter was calculated is available on a wiki page: http://en.wikipedia.org/wiki/Observable_Universe wilgory04-27-07, 10:36 PMThis is from Physics Help and Math Help - Physics Forums. It gives the "best fit" for the size of the universe. Wikipedia isn't always the best source. George Smoot has sometimes taught Physics 139 at Berkeley, an advance undergrad course in Spesh-and-Gen Relativity with supplemental Cosmology. You can get his notes if you google "smoot notes geometry universe" The notes give a simple formula for the radius of curvature. It is incredibly simple but let's try it. At least this will give a first approximation. You just take the HUBBLE LENGTH which we usually say is 13.8 gly, and you divide it by a factor which is sqrt(Omega - 1). that is all. If we use the best fit Omega of 1.011, then Omega - 1 is 0.011 and the square root is 0.105 and if you divide 13.8 billion lightyears by 0.105 you get 130 BILLION LIGHT YEARS. So if we live in a threesphere, and you want to picture it contained in boyscout fourspace, and as having a radius, this is a possible guess about the radius. If I have made a mistake in reading Smoot's notes or in calculating please let me know :smile: The Ned Wright paper that I am having fun with is mentioned here: physicsforums.com/showthread.php?p=1220828#post1220828 New Wright's new paper just came out arxiv.org/abs/astro-ph/0701584 discussion section page 14: "Using all the data together gives the plot shown in Figure 5. The best fit model is slightly closed with Omega_tot = 1.011 and M = 0.315. " Wright is an WMAP princ. investigator. Here is Wright's paper Constraints on Dark Energy from Supernovae, Gamma Ray Bursts, Acoustic Oscillations, Nucleosynthesis and Large Scale Structure and the Hubble constant Edward L. Wright (UCLA) 16 pages, 8 figure "The luminosity distance vs. redshift law is now measured using supernovae and gamma ray bursts, and the angular size distance is measured at the surface of last scattering by the CMB and at z = 0.35 by baryon acoustic oscillations. In this paper this data is fit to models for the equation of state with w = -1, w = const, and w(z) = w_0+w_a(1-a). The last model is poorly constrained by the distance data, leading to unphysical solutions where the dark energy dominates at early times unless the large scale structure and acoustic scale constraints are modified to allow for early time dark energy effects. A flat LambdaCDM model is consistent with all the data." the initial announcement of WMAP3 "implications for cosmology" paper by Spergel et al already contained hint of this. warning: it doesnt prove anything. the INFINITE FLAT universe is still consistent, it just is not the best fit. the best fit is with nearly spatially flat, slight positive spatial curvature and therefore the best fit is spatially finite. flat would be Omega = 1.00 exactly, the best fit is Omega = 1.011 However as Ned Wright is careful to say: a flat model is "consistent" with the data Billy T04-27-07, 10:49 PM...Billy T: The set of all real numbers between 0 and 1 has more members that the set of all integers. ... The digits associated with all the real number can be associated with an array:A11, A12, A13 . . . . A21, A22, A23 . . . . A31, A32, A33 . . . . . . . . . . .Each row of the above array corresponds to a real number: A1x is the first row, A2x, the second, and so forth. ...thanks - I see the proof, but if you give it again to someone, instead of your next paragraph, it would have been more clear to me if you said something like: "Each row of the "A matrix" corresponds to an interger, and conversely. I.e. there is no integer without a corrsponding row." Now here is how you can construct a real number that differs from all the rows in the A matrix .... I.e. there is no interger corresponding to it, the real so construced. I thought of much simpler proof that the reals are larger than the integers: For positive integers n > 2, let the 1-to-1 corresponding real be 1/n. For negative n < 2 let the 1-to-1 corresponding real be 1-1/n. For 2, 1, 0, -1, and -2 let the corresponding reals be 0.338, 0.337, 0.336, 0.335 and 0.334 respectively. Observer there is no interger corresponding to the infinite number of real between 0.339 and 0.666 May not be an especially pretty proof, but simple to understand and shows an infinte number of reals have no corresponding integer. This is more impressive than only showing one that does not have a 1-to-1 mate. To make this slightly thread related. - Volume of our universe is finite. There could be an infinite volume one so big that even an infinte number like ours could not fill it. BenTheMan04-28-07, 12:12 AMThe 156 billion light-year diameter was due to a mistake made by a science writer for Space.com, an incorrect figure which has been widely quoted by other popular press outlets. Neil Carnish et all's 2004 paper calculated a minimum diameter of 78 a billion light-year diameter now, but most likely about 92-94 billion light-years in diameter for the observable universe. We will have to iron this all out. I'll ask the astronomers on monday when I go in to work. I'll report back:) BenTheMan04-28-07, 12:19 AMIf we use the best fit Omega of 1.011, then Omega - 1 is 0.011 and the square root is 0.105 and if you divide 13.8 billion lightyears by 0.105 you get 130 BILLION LIGHT YEARS. Ok. I'll believe Smoot. He won the Nobel Prize. A couple of things to note... This is a first order approximation. Second, it is quite possible that the universe is flat, with omega ~ 1. A small change in the value that you use for omega means that there is a big change in the radius of curvature that you calculate. That is, the radius of curvature for omega = 1 is infinite, but the radius of curvature for omega = 1.011 is 130 billion light years. wilgory04-28-07, 12:49 AMBenTheMan, Of course I realize that the "size" depends on the model you use as well as the other variables that are not yet nailed down. That is why it's a best fit figure. Also did you notice that the 130 number was for the radius? That makes the diameter 260 billion LY. That is for the known universe (I prefer space-time continuum). For the observable area of the universe I would take the 47 billion LY figure (the furthest observed galaxies) as the radius. Making the diameter 94 billion LY. Lucas04-28-07, 02:30 AMMy personal opinion is that the Universe has a finite volume, but there's no exterior to it. It's geometry is such that you cannot get out of it, it's akin to those computer games (Space Invaders comes to mind) in which you reach the edge of the screen only to appear at the other end. Zephyr04-28-07, 09:35 AMFor positive integers n > 2, let the 1-to-1 corresponding real be 1/n. For negative n < 2 let the 1-to-1 corresponding real be 1-1/n. For 2, 1, 0, -1, and -2 let the corresponding reals be 0.338, 0.337, 0.336, 0.335 and 0.334 respectively. Observer there is no interger corresponding to the infinite number of real between 0.339 and 0.666 May not be an especially pretty proof, but simple to understand and shows an infinte number of reals have no corresponding integer. This is more impressive than only showing one that does not have a 1-to-1 mate. Unfortunately showing an injection from integers to reals doesn't prove |Z| < |R|, only |Z| \leq |R|. For example, there is an injection from naturals to integers (identity function), but both sets have the same cardinality as there is a bijection: f: N \rightarrow Z, f(x) = \left\{\begin{array}{ccc} \frac{x}{2} & \mbox{for} & x \mbox{even}\\ \frac{1-x}{2} & \mbox{for} & x \mbox{odd}\end{array}\right. So what you need to show is that an injection from reals to naturals (or integers) is not possible, not that an injection from naturals to reals is. Zephyr04-28-07, 09:50 AMImpossible in what sense? Against physical laws. E.g. reversals of entropy . . . The second law says that the maximum entropy should scale as the surface area of our hubble volume, in planck units. Hmmm. I must be missing something simple? What do you mean that it is finite? Doesn't that just mean that even if the energy is a homogeneous mush, as the universe expands it can become an even thinner homogeneous mush? But is it useful beyond a certain point? Gently Passing04-28-07, 12:12 PMPersonally I think our use of the word "Universe" to describe "that thing which occured as a result of the Big Bang that current data seems to support fairly well" is somewhat of a misnomer. At one point, the Milky Way Galaxy was considered "The Universe" until at some point (not sure when) it was discovered that our home galaxy is simply one of many such structures. Likewise it is possible, I suppose, that there are other "universes" as in other Big Bangs "somewhere else" - another concept eventually bound for the intellectual trash can - that may again redefine what "the universe" really is/means. It sounds hectic and mathematically foreboding, but actually it is just a matter of nomenclature. The existence of "others" would force us to come up with a name for the "local" collection of galaxies, of "all that is" - all that is known to be governed by the laws of Physics as we experience and measure them on planet Earth. The word "universe" would then be applied more appropriately to "everything that could possibly ever be, anywhere, anytime." It's sort of a cycle that has repeated as our ability to understand our surroundings has expanded. The dominating philosophy in our civilization from the time of Christ to perhaps 1000 ce was something like "the earth is a sort of planar island floating in some etherial universe governed by God (or gods)" - call it the Young, Flat Earth Theory Pretty ridiculous theory, but your average Joe Blacksmith from Whereverville really had no need for a more accurate conception of it - he needed his professional skill set, his ability to manage his resources and protect his home and family from outside forces that might threaten it. (of course a handful of intellectuals have conceived of much more accurate models throughout the course of human history - these were generally useless to everyday people more worried about something like the Black Plague, or invading people from other lands...) At some point in there we had a Solar Neighborhood model - the sun and the planets and a bunch of points of light of unknown nature. This was succeeded by the Bunch of Stars Like Our Own model, and that eventually led to the proposal that perhaps we were a part of some larger structure - this of course turned out to be a galaxy... The point is we have always seen to the very edge of technology and reason and declared, "THIS IS IT, WE NOW UNDERSTAND THE UNIVERSE!" And at each step we were wrong. I am simply proposing that we are (probably) still wrong. It will just take Physics another couple of decades to push the edge of our "universe" further out. We may never conceive of "all that is." BenTheMan04-28-07, 12:17 PMBenTheMan, Of course I realize that the "size" depends on the model you use as well as the other variables that are not yet nailed down. That is why it's a best fit figure. Also did you notice that the 130 number was for the radius? That makes the diameter 260 billion LY. That is for the known universe (I prefer space-time continuum). For the observable area of the universe I would take the 47 billion LY figure (the furthest observed galaxies) as the radius. Making the diameter 94 billion LY. Ok, now we're splititng hairs:) We'll say "really big". I think that using the furthest galaxies might be a bad idea, considering galaxy formation took maybe a billion years or so. Essentially, you're choosing an arbitrary event, i.e. first galaxy formation, to define what is the size of the universe. The natural event to define the size of the universe is the big bang. Against physical laws. E.g. reversals of entropy . . . Hmm. I am by no means an expert in the second law, but I know that one can phrase it in terms of a statistical argument. I have seen calculation estimating the time between second law violations to be on the order of 10^68 seconds, or something ridiculously long like that. The point is, if the universe is infinite, then the second law is violated somewhere! I am about to become in danger of talking out of my ass:) Doesn't that just mean that even if the energy is a homogeneous mush, as the universe expands it can become an even thinner homogeneous mush? But is it useful beyond a certain point? Could you clarify this a bit? Sorry if I'm slow. BenTheMan04-28-07, 12:34 PMOk. Zephyr has made me realize that I may be slightly mistaken, when he said his bit about physical laws. I said earlier that the universe should be homogeneous and everywhere outside of what we see should look surprisingly similar. There is another possibility. Namely, if we suppose that there is some grand unified theory immediately after the big bang, then there are no guarantees that the rest of the universe looks like our little patch. Explain this. Ok. What you should know is that it seems likely that the matter in our universe obeyed the symmetries generated by the group SO(10). What does this mean? In phyiscs, forces are manifestations of symmetries between partcles. A grand unified theory takes all of the forces and all of the matter, and embeds them in one description. So, for example, it is possible that immediately after the big bang, there were two forces---the grand unified force, described by SO(10), and gravity, which we're still unsure about . (GR doesn't work immediately after the big bang, so we really don't know what to do.) Today, we know of three forces, plus gravity (= four forces, really). The standard model, which has been tested to extreme accuracy, describes these forces as obeying the symmetry SU(3)xSU(2)xU(1). So, how does one get from SO(10) to SU(3)xSU(2)xU(1)? The answer is symmetry breaking. But now the kicker. The symmetry breaking doesn't have to occur in the same way everywhere in the early universe---just as there are more than one ways to skin a cat, there are more than one ways to break SO(10). And there's no gurantee that the symmetry breaking happened in the same way everywhere in the early universe. We know, at least, that the symmetry breaking happened the same everywhere in the OBSERVABLE universe, but untill we know more about the early universe, it's very hard to say that the universe is completely homogeneous. Assuming a flat (i.e. infinite) universe, the situation is: If we find no evidence for a grand unified theory, then the universe looks exactly the same everywhere, even outside what we can see. All of my arguments earlier still apply. If there is evidence for a grand unified theory, then it is likely that other parts of the universe look extremely different than our little patch. BenTheMan04-28-07, 12:40 PMhttp://cosmicvariance.com/2007/04/27/how-did-the-universe-start/ Here's a good blog post by Sean Carroll, a very brilliant scientist, about these ideas. You should listen to him before you listen to me:) Gently Passing04-28-07, 01:16 PMAs far as I know, the emotionally comforting "cyclic universe" has pretty much been superceded by the prevailing "Big Chill" idea - simply put, the Universe began as some phenomenon that appears to be a Big Bang, and will continue expanding and as particles continue to interact they will reach lower and lower energy states until eventually you have a diffuse field of "cold" particles with a temperature around (slightly higher than) absolute zero. It has always seemed to me that such cyclical ideas are born of the same thumb-sucking psychology that gave us a belief in Eternal Life, of a purpose beyond simply floating about in space consuming other life forms and eventually dying and so on... There are reputable theorists who have strong models to oppose a one-direction expansion, but there's no good reason to believe them. Chances are the narrow window in which life as we know it is possible will end up being a temporary state. Conclusion - our eternal fate at least as matter goes is cold and dead, expanding outward forever into nothingness. Avatar04-28-07, 01:23 PMI prefer the "we don't know yet" position in this, because we don't. About the names: we have the term "multiverse", don't we? ;) wilgory04-28-07, 02:32 PMSince I have finally reached the magic number and can now post links I have a couple that I found helpful in weeding out the various theories that abound on the web. http://www.math.ucr.edu/home/baez/RelWWW/ http://www.astro.ucla.edu/~wright/cosmolog.htm I also like to use NASA's website for answers to questions about the universe. As well as keeping up to date on the missions they are currently performing. It is a large site and to find a particular subject use the search function. http://www.nasa.gov/ Gently Passing04-28-07, 04:09 PMI guess what I was trying to say was as follows: As we proceed down the path of discovering our origins, we must be careful not to allow our assumptions, no matter how precious or comforting, to guide our conclusions. In other words, if it all turns out to be a big, cold, dead accident with absolutely no purpose whatsoever, and no God watching it all proudly from above, then we need to be honest with ourselves and accept the truth we have set out to discover. ...we may just find out we are not alone, that the universe is teeming with life and we are a part of a grand evolution - grander than any conceivable earth-bound process. It's like our cosmic scratch-off ticket. Those who aren't courageous enough to find out the truth need not pull out their quarters and pretend to be scientists. ShadmiDoron05-04-07, 04:26 PMBy using concepts like in,out we can find at least two logical connectives, which are XOR and NXOR. Let a thing be something OR nothing. XOR is the logical connective of locality, where a local thing is in XOR out. The truth table of locality is: in out 0 0 → F 0 1 → T (in , out are not the same) = { }_ 1 0 → T (in , out are not the same) = {_} 1 1 → F NXOR is the logical connective of non-locality, where a non-local thing is in NXOR out. The truth table of non-locality is: in out 0 0 → T (in , out are the same) = { } 0 1 → F 1 0 → F 1 1 → T (in , out are the same) = { } I think that what is called the universe is a complementation between locality and non-locality. So, the universe is both a non-finite collection of local things (where each one of them is in XOR out any given local thing) and a non-local thing that is in NXOR out any given local thing. From a non-local point of view, the question "What can be beyond the universe?" is meaningless, and from a local point of view any non-finite collection is incomplete if it is compared to non-locality (from this point of view, a non-finite collection is simply a mathematical entity that its final member does not exist (or in other words, it is a natural-open mathermatical entity)). HubertW03-20-11, 04:37 PMwell I heared that they have discovered that our galaxies are maintaining themselves because of the black matter, apart from gravitation. What can be bayond our universe (which is growing constantly after big bang) can be a balck matter and nothing more. when energy form big bang is spreading its changing the structure of black matter. just my theory Dywyddyr03-20-11, 04:52 PMResurrecting a four year old thread isn't very smart. Especially when: just my theory Isn't a theory at all but uninformed speculation. What evidence do you have for your "theory"? HubertW03-20-11, 06:58 PMof course its a speculation. in that matter its difficult to speak about any evidence. I base my speculation on that what I have heard recently about black matter and about that the universe has finish. what we know is that galaxies are placed among black matter, so if the univers as we know it is full of galaxies and black matter and if You think that where it ends there are no galaxies, so there has to be just black matter. simple Dywyddyr03-20-11, 07:05 PMwhere it ends there are no galaxies, so there has to be just black matter. simple Why should this be the case since you've already said that galaxies are placed among black matter I.e. the only place we find dark matter is intermingled with ordinary matter. This is like suggesting that since we find milk mixed in with coffee there should only be milk outside of the coffee cup. HubertW03-20-11, 07:10 PMok so what is that You think that there is beyond? Dywyddyr03-20-11, 07:20 PMok so what is that You think that there is beyond? It's one of those utterly meaningless questions. There's a thread somewhere discussing it.If you can find it it's worth a look. cosmictraveler03-20-11, 07:20 PMok so what is that You think that there is beyond? If I may give just one idea that might lie beyond our own , a multiverse could exist beyond. Here read about it. http://en.wikipedia.org/wiki/Multiverse HubertW03-20-11, 08:01 PMthnx HubertW03-20-11, 08:08 PMI have a question that maybe You can help me find an answer for. Why all the galaxies has a shape of circle and all the planets are round? does that depend on gravitation? Dywyddyr03-20-11, 08:09 PMPlanets are round because of gravity. HubertW03-20-11, 08:21 PMso following that, galaxies too and all the universe the same I suppose cause the center of univers is a black hole as I have read. correct me if Im wrong but as I understand the gravity exists because if the object has a weight bigger then the outside environment, its pulling the metter from outside? Dywyddyr03-20-11, 08:24 PMI'm not quite sure what you mean about "the object has a weight bigger then the outside environment", but gravity (as far we can tell) is an inherent property of matter (http://en.wikipedia.org/wiki/Gravitation). Anything that has matter exerts gravity. And the more matter the greater the gravity. HubertW03-20-11, 08:33 PMthats what I meant. sorry for not being clear but Im quite new in the subject. each thing that I find poses a lot of new questions. so if there is a big black hole in the center of universe, shouldnt all the matter be pulled inside? cause its opposite to what I hear about expanding of the universe? Dywyddyr03-20-11, 08:37 PMso if there is a big black hole in the center of universe, shouldnt all the matter be pulled inside? No, common misconception. Gravity is gravity. It's only "irresistible" if you cross the event horizon. If the Sun (our Sun) were replaced by a black hole of the same mass as the Sun then Earth would still remain in its current orbit. Although, of course, we'd be sat in the dark... ;) cosmictraveler03-21-11, 07:41 AMI have a question that maybe You can help me find an answer for. Why all the galaxies has a shape of circle and all the planets are round? does that depend on gravitation? Gravity is the key. You may be aware that Jupiter, our largest planetary neighbor in the solar system, is almost all gas (there is a small core of non-gaseous material). Understanding that Jupiter is a ball of gas, wouldn't it be bizzare if it had a shape other than a sphere? Think also of a bubble blown by a child (or your inner child) through a loop. Even very large ones (which are the most fun) seem to seek rest in a spherical shape, even if breezes batter and deform it from time to time. Matter seems to seek to balance internal forces. It would be scary to look up at Jupiter and discover that it had morphed into a doughnut shape or a large tube shape. When we are talking about collections of matter that are planet-sized, the same general idea holds. Taking a mass equal to that of the earth, and of similar materials, you could attempt in your mind to construct a pillar with a 1,000 kilometer diameter. But you wouldn't get too far before the pillar's mass would exert so much gravitational force that the whole thing would come crashing in. Even if you braced the pillar while building it, the inner sections would eventually crumble and/or melt long before you finished. Eventually, all the mass would find its way to balance out the gravitational forces. Read more: http://wiki.answers.com/Q/Why_are_planets_round#ixzz1HEn8UevO HubertW03-21-11, 09:18 PMhello, You seem quite well informed about all this things. thanx for answering so far. I have another thing that is bothering me. light and darkness. theyare like matter and ani matter? canceling one another or they coexist? drumbeat03-21-11, 09:20 PMIs darkness not just the absence of light though? HubertW03-21-11, 09:31 PMwell, what I have read is that darkness has a particles which creates it. the same as light which is made of photons. following Your way of thinking the absnce of mater should be emptiness and appeares that there is antimatter. I think the most difficult question of all it to describe what is nothing cause there is always something there. drumbeat03-21-11, 10:09 PMfollowing Your way of thinking the absnce of mater should be emptiness and appeares that there is antimatter. . No, hang on. My point was that darkness is the absence of light, where as anti-matter is NOT the absence of matter, but a separate entity in itself. Pete03-21-11, 11:46 PMwell, what I have read is that darkness has a particles which creates it. the same as light which is made of photons. Well, no. Darkons (http://wearcam.org/theory_of_darkness.html) were made up as an April Fool's joke. "Dark" just means "not much light". Usually, it specifically means "not enough light in the visible spectrum to see with human eyes." Like "quiet" means "not much sound". "Antimatter", on the other hand, doesn't mean "not much matter". It's something real, with mass, charge, and all other properties of regular matter. pywakit04-01-11, 03:50 PMIn response to the posters who believe we can never know what's beyond our Hubble volume ... IF space existed prior to our big bang, AND the laws of space are universal, AND our Hubble volume is a natural by-product of the laws of space, AND space is infinite without boundaries, AND other big bangs have occurred throughout eternity and infinity, THEN there is at least one way to potentially detect at least some of those big bangs. Per GR, those bangs should send out shock waves that would travel in all directions, gradually diminishing with distance. These shock waves, propogating out as ripples in space could be detected in the CMB of our own Hubble volume, or perhaps in other ways, especially as our ability to detect faint variations (patterns) increases. Roger Penrose et al. just published a paper a few months ago on CMB patterns he believes indicate major events prior to the big bang, which of course suggests space existing prior to the big bang. http://www.technologyreview.com/blog/arxiv/26132/ Steven Feeney et al. just published a paper on CMB patterns he believes indicate 'collisions' with universes outside the Hubble volume. http://arxiv.org/abs/1012.1995v1 And then there is Laura Mersini-Houghton of Chapal Hill ... http://quantumconfigurations.com/content/140-dark-flow-evidence-suggests-we-part-multiverse.html Was our universe once entangled with a neighbour? The observation of "dark flow" in galaxy clusters was predicted in 2006 by Laura Mersini-Houghton of the University of North Carolina at Chapel Hill and colleagues. She proposes that the effect occurs because our universe was once influenced by neighbouring domains (arxiv.org/abs/0810.5388). neighbouring domains (arxiv.org/abs/0810.5388). Mersini-Houghton reasoned that if a force exerted by other universes squeezed ours, it could generate a repulsive effect that would impede the shrinkage of matter into clusters but not leave an imprint on smaller scales. "This skews the distribution of lumps so they are not the same in all directions," she says. There is a preferred direction - the dark flow." She also predicted in 2006 that there should be two "holes" - regions with fewer galaxies than expected. Sure enough, there does appear to be a hole - the so-called "cold spot" identified by the WMAP probe. The hole is a very large region of space where the afterglow is cooler than average. However, its cause - and even existence - is disputed, and Mersini-Houghton's hypothesis remains controversial. I think it is premature to throw up our hands and state we can 'never know'. pywakit04-01-11, 04:02 PMNo, common misconception. Gravity is gravity. It's only "irresistible" if you cross the event horizon. If the Sun (our Sun) were replaced by a black hole of the same mass as the Sun then Earth would still remain in its current orbit. Although, of course, we'd be sat in the dark... ;) I think you forgot to include the word 'decaying'. Maybe I am wrong. Post ReplyCreate New Thread