I thought I'd make a separate post. In the math section, gerry explained if the space is finite then, like a balloon, it'll come back around. So what's beyond the area where it comes back around (beyond the balloon itself which would be our world here)? How can space not exist somewhere?
Could life live (somehow) outside the universe, without space and time dimensions if lets say they were sealed up in a spacecraft with oxygen and all. If no, could advanced technology make it work. If you went to where the 'balloon' ends and threw a rock out there, would it not exist or would it be space in an area of no space?
Posts: 6528 | Location: Grayson, Georgia, USA | Registered: 06-03-02
Take a look at the post on the shape of the universe, it may help a little. The thing to realize is that the balloon analogy is a simplification. To use it, we think of ourselves as two-dimensional beings, because we can picture how a two-dimensional surface can have shape. We can't picture three dimensional space having shape (or if you can, you have a better imagination than I do).
In the case of a closed universe (the balloon case) we would live on the surface of the balloon. We would only be able to travel on that surface. If we traveled far enough in any direction, we would end up back where we started (like traveling around the world. Up and down simply don't have a meaning. Could other balloons exist? It's possible. These would be separate universes (or more accurately, multiverses). Traveling in conventional ways (up-down, forward-backward, left-right), we could never reach these other universes. Perhaps they could be reached, but we would have to find a way to travel in a direction other than the three spatial dimensions that we can see. ************************************************* 04-03-03, 08:55 PM gerry Adding to Methos' excellently worded answer, if other "balloon" universes exist outside of our own, they could only be reached by travelling through other dimensions, which in all probability must be through a black hole, I don't see any other way. In the absence of higher dimensions, there is no way to get outside of our Universe, we are living on the "surface" of it just like a shadow lives on the surface of a balloon, and if that shadow shined a flashlight, the light would not move outside the balloon's surface, it would be destined to travel forever around and around the balloon's surface. However, the existence of a balloon's closed 2-dimensional surface can only be possible if a higher (3rd)dimension exists ....inside the balloon... or else you couldn't have a balloon in a 2D universe, only a circle. So the existence of higher order dimensions is most likely.
[This message was edited by gerry on 04-03-03 at 09:04 PM.]
04-03-03, 08:56 PM gatman I think some brilliant people get caught up in their own fantasy projections of possibilities. I readily admit I am ignorant in the sciences but sometimes a simple q can jolt things back to reality. Here is my q.
What is between atoms right here on say a pencil? What is between the electrons and nucleus. Why can "that" not exist beyound the edge of the universe ? And then is there in fact any such thing as the edge of the universe?
04-03-03, 09:29 PM gerry Gatman..
You ask a good question that only advances in quantum mechanics, M-theory, and quantum gravity will fully answer. There is a minimum distance that can never be penetrated, called the Planck Length, it is equal to about 10 -35 meters, and is about the size (length) of the building block of all matter called a "string", which is really a wave that vibrates through all dimensions of space-time. One cannot talk about the distance between an electron and the nucleus, because the electron also is a wave whose position can never be exactly known, due to the Heisenberg Uncertainty Principle (I think it was Hawking, or was it Einstein (?), who said thet not even God could determine its exact position!) Whether the Universe is infinite or finite, it has no edge, I refer you to the balloon analogies above. But it may have a "bound", in the form of other dimensions. These are not fantasy projections, they are scientific projections, that may, in fact, be reality.
04-04-03, 10:24 AM methos gatman - you're at the limits of my knowledge of cosmology (makes me wish I'd taken that course when I had the chance). There really isn't an edge of the universe in the typical sense (as in, traveling in 3 dimensions, you will never reach an edge - expansion of the universe doesn't mean that an edge is moving, it means that everything within the universe is getting farther apart without really moving).
As far as what exists between atoms - quantum mechanical fluctuations. Photons producing positron-electron pairs, which then collide, anhiliating each othe and producing a photon, for example. In fact, there is a theory that the entire universe is just a quantum mechanical fluctuation. For this to be the case, however, it would need to be a closed universe so that it would eventually collapse (and the current findings don't point to a closed universe).
You might be interested in reading a book on the subject. Brian Greene's "The Elegant Universe" is relatively easy to follow and detailed, but I think he fails to make it as exciting as he could, given the subject matter. John Gribbin is an excellent science writer and has written a few books that may be interesting. I haven't read his books on this subject, so I can only recommend them based on the assumption that they are as good as some of his other books.
04-04-03, 06:44 PM gatman Guess the word "fantasy" projects an unintended but dismisive attitude. I can understand that space, time, and mass all come in multiples of discrete units such as the plank length. While the wave theory makes it impossible to measure the distance accurately at any time I have heard no dispute that an atom is largely vacant space.
I would also argue that in the big bang theory that infinite space had to exist before the beginning of expansion otherwise there would be no space for the expansion. In essense I find it easier to imagine infinity than I do imagining a limiting balloon surface. I can see a boundry as in where the expansion has reached to.
If I remember correctly from a thread on the multiverse theory that is what Hawkings ascribes to. That with each choice you or I make there is a whole new and different universe created. If that is so then what difference does any decision make? And how di I end up in this universe? Given a choice of universes I think I would have chosen another. Guess that is as much a philosophical q as a physics q.
04-04-03, 07:08 PM methos gatman - Some guess that these other theoretical universes (if they exist) are the ones you refer to, but that's not a requirement for the existence of multiverses. If they exist, they may be nearly identical to ours or very different from ours.
The multiverse theory you speak of is an attempt to rationalize quantum mechanics. Experiments have never been done to verify it (because no one can figure out a way that this type of splitting universe would differ experimentally from other philosophical rationalizations of QM). Mathematically speaking, QM theory also doesn't support or refute it.
Physicists that ascribe to it or to other philosophical QM rationalizations are really just going with what makes the most sense to them, but there is no reason beyond that to believe one over another.
04-04-03, 09:31 PM jusork Ok I think I'm getting it. I think I can image the way our universe is kind of like a balloon. It's a very big balloon so it seems like it's really wide but really it's very flat and round. Since it's round it comes around. It's a little hard to imagine what is outside the bounds of this universe but I think it helps when I think about what coming back around when you walk around it actually means. It's just space that curves around. The only think that I don't really get is if the universe is expanding then what is it expanding into?
quote:Originally posted by gatman: If that is so then what difference does any decision make? And how di I end up in this universe? Given a choice of universes I think I would have chosen another. Guess that is as much a philosophical q as a physics q.
Your alternate self could ask the same question. I'm sure in one of the universes there's a perfect one and we'd all like to be in that one I guess.
04-06-03, 10:42 AM gerry
quote:Originally posted by jusork: The only think that I don't really get is if the universe is expanding then what is it expanding into?
It is expanding into NOTHING, nothing at all. By 'nothing', this does not mean 'vacuum'. A vacuum may have nothing in it, but it still occupies space. Nothing means no space at all, and no time. This is true whether the Universe is finite or infinite. It has no edge or bound. The Universe is ALL there is.
04-06-03, 12:55 PM jusork Ok I think I've got the idea and most of the understanding. Thanks.
04-13-03, 03:26 PM mattlynda so what happens if two of these 'balloons' hit each other? and go easy on me here. my brain has a hard time with science/math.
04-13-03, 04:59 PM gatman
quote:Originally posted by gerry: It is expanding into _NOTHING_, nothing at all. By 'nothing', this does not mean 'vacuum'. A vacuum may have nothing in it, but it still occupies space. Nothing means no space at all, and no time. This is true whether the Universe is finite or infinite. It has no edge or bound. The Universe is ALL there is.
Now you are beyond my comprehention with this concept of nothing Gerry. If such a nothing exists as oppossed to a complete vacumn then the universe would have to have a boundry. How else would you define the difference between the vacumn and the nothing?
If the universe is infinite then how could it have a boundry? If the universe is finite then how could it not have a boundry?
04-13-03, 08:48 PM Professor Please indulge me for jumping in so late in the thread.
The expanding universe arising from the big bang is usually described as "finite but unbounded." The balloon analogy, contrived so that we can make sense of 4-dimensional space-time, appears to be misunderstood in some of these posts.
Imagine a 2-dimensional "Flatland" universe in which the 2-dimensional inhabitants are embedded in their universe as bugs on the surface of a gigantic balloon. The balloon is so immense that locally it appears to be a flat Euclidean plane, though their individual worlds might be much smaller circular disks on this enormous surface. They are utterly unable to visualize the 3rd dimension and only in recent times have their physicists proposed that their universe is in reality a 3-dimensional sphere -- the balloon universe. Moreover their modern physicists have discovered that this balloon is expanding.
If you picture their galaxies as dots on the surface of the balloon, then as the balloon inflates the dots will all move further from one another. No matter which dot (galaxy) you stand on, it will appear that all the other dots are moving away from you, and the more distant galaxies appear to be receding at a faster rate (Hubble's Law).
Now -- and this is the essential point of my post -- this balloon analogy is commonly invoked because we humans can completely comprehend it, since it involves a 2-dimensional surface on a finite 3-dimensional sphere which is within our visual grasp.
The flatlanders traveling in their spaceships on this 2-dimensional surface, or peering through their telescopes (remember, their line of sight is always confined to this surface) will never encounter a wall or boundary. Their surface is unbounded, yet (as we 3-dimensional super-beings can clearly see) it is finite in size. In principle if they travel far enough they will return to their starting point -- having circumnavigated their spherical universe.
But this is merely an analogy of one less physical dimension than our actual universe, which appears to us humans to have three spatial dimensions but is thought to be the 3-dimensional "surface" of a four-dimensional hyper-spherical expanding "hyper-balloon." We are utterly incapable of visualizing this (I doubt even Einstein's brain was equipped to do so) so we have to use the Flatland & balloon analogy to make sense of the physical reality of a mathematical description of a higher-dimensional expanding universe.
When we say the universe is expanding, that doesn't mean that matter is expanding into pre-existing 3-dimensional empty space. Rather, it means that space itself is expanding, carrying the universe with it. Galaxies appear to be moving away from one another, again in accordance with Hubble's Law (the more distant, the faster they recede) and this observation is equally valid no matter which galaxy it is viewed from -- just because everything appears to flying away from us does not confer any special place for us in the universe. Again picture bugs on an inflating balloon surface.
That's what the balloon analogy is all about. Physical reality exists on the surface -- in this physical system it makes no sense to speak of what lies "beyond" this surface.
Of course it may be more complicated than that, where our universal "balloon" might be a hyper-torus (or even more exotic topology) rather than a hyper-sphere, or it might not be truly symmetrical, or it might even be a hyper-fractal multiverse, etc. -- many variations on the theme are possible with as yet too little evidence to sort it all out.
Any theory that incorporates more than three spatial dimensions (beginning with Special Relativity of 1905) can be understood mathematically but unfortunately cannot be directly visualized.
Hope this helps, and -- to paraphrase Mark Twain -- if I'd had more time I would have written less!
[This message was edited by Professor on 04-13-03 at 09:11 PM.]
04-13-03, 09:39 PM gerry
quote:Originally posted by mattlynda: so what happens if two of these 'balloons' hit each other? and go easy on me here. my brain has a hard time with science/math.
The balloon parallel universes theory is gaining momentum amongst scientists who have become believers in "M" theory. The M in M - theory may stand for 'membrane', shortened to the word 'brane'. Hawking says that such balloons (branes) may be only a few millimetrs apart, and that if the 2 balloons, or 'branes', were to collide, the results would be 'catastrophic', and that perhaps our universe started with a 'big bang' from such a collision. The brane does rack the brain of even the scientific geniuses.
Gatman..
You are correct in that an infinite universe can have no boundary. But as mentioned several times above, a finite universe can also be unbounded, visualization of such a universe can only be compared to visuallzing the unbounded surface of a balloon...a surface finite in size but with no end, and therfore no bound, unless you consider the boundary to be the 3rd dimension inside and outside of the 2 dimensional balloon surface. Did you ever dream of somehow transporting yourself to the most distant 'edge' of the universe, so that you can 'see' the 'nothing' that the universe is expanding into? Well, dream no more, we ARE on that most distant 'edge', sharing it with every planet and star and galaxy in the universe, onlty thing is, there's nothing to see, even if it could be seen.
This message has been edited. Last edited by: DorianGreyed,
Here is an excellent site that should answer all your questions. Browse around, clicking the links in green to the left. "Universe" has very good subtopics that address the issues
