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Topic: The Expanding Universe. (Read 1184 times) |
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Fox
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The Expanding Universe.
« on: 2007-06-26 21:40:11 » |
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Something here which I'm looking for a Virian perspective in. Scientists and astronomers claim today that the universe is expanding. Hubble's law expansion, cosmic microwave background radiation, galactic evolution and distribution and the abundance of primordial elements all go along way to strongly support the big bang theory and thus an expanding space/universal paradigm. But heres the bit which gets messy; what is the universe expanding in to? Is it even a valid question, or is it meaningless?
Based on what I've been taught the universe is expanding into nothingness, by our perspective. The universe is expanding into a fourth dimension of space that we cannot percieve. The only way to comprehend this is to use an analogy. Imagine a 2D universe in the shape of a balloon. Matter on this balloon can exist anywhere on the surface of the balloon but is unable to move below the surface or above it, for that spacial dimension, the 3D dimension, is impossible for the matter in that universe to exist in. Now imagine the balloon is being blown up and expanding into the 3rd dimension. Matter would not be able to notice the universe as being a bigger shape, it would simply be larger. Our universe is expanding into a 4th spacial dimension and is therefore getting larger in a way that we cannot percieve. One might notice that in the balloon analogy, the 2D matter that inhabits the dimension could essentially go around in a circle on the surface of the balloon and end up where it began. The same may or may not be true about our universe, it depends on the shape. Our universe may be a shape that has a barrier at the end, but chances are it would just loop as in the analogy. Also, imagine if someone were to pinch two parts of the balloon together with their finger. The 2D matter would not be able to notice this, but they would essentially be able to travel to the opposite side of their universe much quicker than by going around. This is the theory, or one of them, behind wormholes (and to some extent, hyper drives). And that's pretty much how most Scientists view the expanding universe. Other theories exist of course.
Personally I'm a little skeptical about all this and don't really know what to conclude (within reason; especially with the lack of evidence). As a result, I'm not to sure on how to question or evaluate this dilemma.
Thoughts, views and opinions welcomed respectively.
Fox
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Blunderov
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"We think in generalities, we live in details"
 
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Re:The Expanding Universe.
« Reply #1 on: 2007-06-27 02:44:59 » |
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[Blunderov] I recall asking the same question shortly after I came to Virus. The Hermit and Lucifer were kind enough to collaborate on a well considered reply which might perhaps reside in the archives somewhere.
It's not a very easy question to answer partly because our language fails us; how is it possible to speak of a time before time?
A concept which might be of assisstance is that of 'potential'; that is to say: the universe expands into potential space. Perhaps this does beg the question but I can't find another handle that works at all for me so I'm stuck with it.
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Blunderov
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Re:The Expanding Universe.
« Reply #2 on: 2007-06-27 13:00:10 » |
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[Blunderov]<belated postscript for Fox> A mindbendingly difficult (that's quantum mechanics for you) but very worthwhile book is " The Fabric of Reality" by David Deutsch. I warmly recommend it. In it the author gives a very interesting account, amongst other things, of the multiverse.
By relying on Deutsch' account it would be possible to argue that Fox's question is meaningless. The universe does not expand, Deutsch might argue; what happens is that we move from one universe into another; one that is slightly larger than the previous one. All possible universes exist already. Our perception of time is illusory. That we happen to experience the so called flow of time has nothing to do with the nature of the multiverse itself. Everything that it is (they are?), it already is.
Weird, no?
(Please feel free to question my interpretation of Deutsch. It is, as I said, mindbendingly difficult stuff and it all too possible that I have misunderstood something important. It seems possible though that the answer to your question is somewhere along these lines.)
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Konetzin
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Re:The Expanding Universe.
« Reply #3 on: 2007-06-27 16:09:57 » |
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The universe is actually expanding faster than the speed of light. Einstein's laws are not being violated, because the coordinate system used to model the universe takes the expansion into account - the universe does not follow the standard geometry you learned in school. The expansion of the universe is the same throughout the universe, and has little effect on local velocities, so the special coordinates are unnoticeable at everday distances and not figured into calculations unless the distances are huge. Same as if you have a 1000 km diameter balloon that is expanding at 1 m per second, you will hardly notice two dots move apart if they are just 1 cm apart. No paradox occurs because light still travels at the same speed locally, so information does not get transmitted faster than light.
The answer to your question has to do with the curvature of the universe, which depends on its mass. One of two things might happen if you try to get to the edge of the universe. If the universe keeps expanding faster than the speed of light (negative or zero curvature, analogous to a hyperbola or a parabola), you will not reach the edge of the universe because you will keep getting farther away from it even if you travel at the speed of light. If the universe slows down its expansion (positive curvature, analogous to an ellipse), you will experience the big crunch when you reach the edge of the universe, sooner than you would have if you just stayed in one spot (this is supported by the theory that time goes faster as you speed up). The big crunch is the opposite of the big bang, and will happen if the curvature is positive, since that will mean that the universe will down its expansion until it starts to actually get smaller.
Therefore the universe doesn't need to expand into anywhere, it just expands, since it is explained what will happen if you try to get to the edge. At least this is how I see it - you might want to look on some credible research institution websites.
You could look at these for example:
http://www.astro.ucla.edu/~wright/cosmology_faq.html#FTL
http://www.astro.ucla.edu/~wright/cosmology_faq.html#DN
http://www.astro.ucla.edu/~wright/cosmology_faq.html#RB
[edit: fixed links]
The actual problems with this theory are in a much more esoteric place - they have to do with the speed of expansion of the universe at its very early stages. Science is much more fun than magick. 
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Bass
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Re:The Expanding Universe.
« Reply #4 on: 2007-06-27 19:57:59 » |
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There is no way that our universe could be flat. Not unless the flatness had some sort of thickness. There are galaxies surrounding our own Milky Way, not just on the same planar level. Here is one scenario of flat universe theory: The galaxies are moving away from each other, implying that at one time they were occupying the same space. According to physics, as I understand it, the pull of gravity of all these galaxies will (very slowly)eventually slow them down untill the pull of gravity pulled them back. They would eventually have to come back to where they started at. Scenario 2: Now if the universe isn't flat but holds a definite shape then all galaxies would be moving outward from a central point within the center of the universe. The pull of gravity in this scenario would have to be much greater and therefore the galaxies would have to come back after a much shorter time. In either of the scenarios, two things I am certain of is that the universe has no definite end (because a galaxy cannot expand empty space) and all galaxies will come back to their original starting positions.
But what about Black Holes? I was making a small search on the internet trying to find a connection between Black Holes and the Expanding Universe: http://www.ingentaconnect.com/content/iop/cqg/2000/00000017/00000024/art00302
Quote:Black holes and a scalar field in an expanding universe
We consider a model of an inhomogeneous universe with the presence of a massless scalar field, where the inhomogeneity is assumed to consist of many black holes. This model can be constructed by following Lindquist and Wheeler, which has already been investigated without the presence of a scalar field to show that an averaged scale factor coincides with that of the Friedmann model in Einstein gravity. In this paper we construct the inhomogeneous universe with a massless scalar field, where it is assumed that the averaged scale factor and scalar field are given by those of the Friedmann model including the scalar field. All of our calculations are carried out within the framework of Brans-Dicke gravity. In constructing the model of an inhomogeneous universe, we define the mass of a black hole in the Brans-Dicke expanding universe which is equivalent to the ADM mass in the epoch of the adiabatic time evolution of the mass, and obtain an equation relating our mass with the averaged scalar field and scale factor. We find that the mass has an adiabatic time dependence in a sufficiently late stage of the expansion of the universe; that is our mass is equivalent to the ADM mass. The other result is that its time dependence is qualitatively different according to the sign of the curvature of the universe: the mass increases (decelerating) in the closed universe case, is constant in the flat case and decreases (decelerating) in the open case. It is also noted that the mass in the Einstein frame depends on time. Our results that the mass has a time dependence should be retained even in the general scalar-tensor gravities with a scalar field potential. Furthermore, we discuss the relation of our model of the inhomogeneous universe to the uniqueness theorem of black hole spacetime and the gravitational memory effect of black holes in scalar-tensor gravities. |
I think that black holes are only formed along with the formation of newborn galaxies. If I am not mistaken (I might be wrong on this) the only black holes in any galaxy are smack dab in the center of them. Spiral galaxies have sort of a flat plane where all the stars rotate around the center of gravity forming arms or spirals. In the center where all these arms connect are supermassive black holes. These small black holes are spinning so rapidly that everything around them can't help but to spin around the black hole. As the small black hole "eats" everything around them they shoot out ejecta that spews forth from the poles of the black hole. That is why spiral galaxies have the two "arms" coming from the top and bottom of the center. Some people like to think that black holes lead to an alternate dimension or some other place in the universe. I do not agree with this theory at all. I have a pretty good hunch that anyone or anything that gets sucked into a black hole will first be ripped apart by its gravity and then be crushed as it consumes matter. Then you will be ejected from the black hole in the ejecta that spews out.
Heres some philosophy to stir your braincells with. Lets look in the opposite direction for a moment. When we look at atoms and break them down we fins that they consist of smaller parts, protons, neutrons and electrons. Though protons and neutrons clump together there is still space between them. Break these parts down further and we get quarks. I'm sure that quarks also come in several varieties and can be broken down, as well. Now imagine that each galaxie in the universe is an atom or even a compound. Each solar system is a quark, so on an, so forth. Our air is made of many types of atoms and compounds. They flow freely around each other. Cool air down enough and they slow and can even become liquid. Allow it to warm and they expand and break away from eachothers 'gravity.' Maybe the same rules apply to our universe. Even though it seems to move much slower than atoms do, time is relative. Who knows? Maybe there are 'Life forms' of some sort that live in atoms. But their life span is so short their 'universe' appears to move slow as well. What if we are all living on a giant 'atom' and there are beings we can't even perceive that view us the same way we view atoms. The problem is we only imagine as far as we can 'see' and our period of recorded and studied history isn't even a microscopic blip in the grand theme of things.
Bass
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Cassidy McGurk
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Re:The Expanding Universe.
« Reply #5 on: 2007-06-28 12:21:12 » |
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I ilked this quote from Wikipedia
"Charles Goodwin has noted that if Deutsch is correct about the multiverse, he will win the Nobel prize. And also not win it."
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Fox
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Re:The Expanding Universe.
« Reply #6 on: 2007-07-04 17:34:56 » |
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Thanks for the recommendation Blunderov, I'll be adding it to my list!
Quote from: Bass on 2007-06-27 19:57:59 | There is no way that our universe could be flat. |
Actually according to the Wilkinson Microwave Anisotropy Probe (WMAP) the data hints at our universe being flat. Taking also into account here the metric expansion of space (particuarlly that the universe is homogeneous and isotropic in nature, and providing that these well supported views remain constant), the local geometry of our observable universe is determined on whether the density parameter, Omega, is greater then, equal to or less than 1. If it is greater than 1 we can conclude on a spherical universe using spherical geometry; if it is less than 1 we can conclude on a hyperbolic universe using hyperbolic geometry; but if it is equal to 1 we can conclude on a flat universe using Euclidean geometry. According to Astronomical measurements in matter-energy density (including spacetime intervals of supernovae events via Cepheid variables) the spacial curveture of local geometry is constrained very close to zero, giving us an approximated flat unierse; however, given that the curvature is not exactly zero (it’s actually somewhere between 1.00 and 1.04 according to the WMAP data, perhaps due to space-time being gravitationally warped) our universe may still prove to be somewhat spherical, or even hyperbolic (given the consistent horn topologies compatible with the data), at much greater observational distences then we can feasibly grasp today. If we can determine the local geometry of the universe, discover whether or not Hawking radiation exists and prove that the universe is finite (of which there is evidence to hint) then we may be able to place the “beyond” aspect of our universe on more scientifically supportable and stable grounds in stead of nonsensical ones.
However, my own conclusions at this time are that the closest and perhaps most reliable mathematical model we have to date concerning what might potentially exist “beyond” our observable universe, is probably M-theory; formed and developed by Edward Witten who is, in my opinion, one of the greatest mathematical physicists alive today, and is rivaled by few. The remarkable thing about M-theory is that the mathematics predict an eleventh dimension for an object to move in, on huge universal scales, in the form of an orbifold or manifold. To imagine the degree of freedom of this dimension try thinking of an elastic band shaped like a Torus stretching out uniformly at every point into a circular (R^2), or spherical (R^3) dimensional matrix; perhaps even with less or more degrees of freedom depending on the energy and holonomy of the string; thus forming a p-brane. Using this hypothetical model it’s possible that the universe (together with parallel universes (as predicted by string theory) in something known as a brane) is expanding into, or moving along this eleventh dimensional space in the same way as the elastic band/Torus would, being stretched outwards uniformly. Another great thing about M-theory is that, unlike most other views, it is not Ex nihilo but provides us with a potentual answer to the Big Bang with the instantiation of our universe being the ekpyrotic scenario. These video extracts, taken from The Elegant Universe (which I would recommend watching) should give you a better idea of what I mean:
Fox
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I've never expected a miracle. I will get things done myself. - Gatsu
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Rhysenn
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Re:The Expanding Universe.
« Reply #7 on: 2007-07-20 10:50:18 » |
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Quote from: Konetzin on 2007-06-27 16:09:57
The answer to your question has to do with the curvature of the universe, which depends on its mass. One of two things might happen if you try to get to the edge of the universe. If the universe keeps expanding faster than the speed of light (negative or zero curvature, analogous to a hyperbola or a parabola), you will not reach the edge of the universe because you will keep getting farther away from it even if you travel at the speed of light. If the universe slows down its expansion (positive curvature, analogous to an ellipse), you will experience the big crunch when you reach the edge of the universe, sooner than you would have if you just stayed in one spot (this is supported by the theory that time goes faster as you speed up). The big crunch is the opposite of the big bang, and will happen if the curvature is positive, since that will mean that the universe will down its expansion until it starts to actually get smaller.
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How exactly is the edge of the universe defined? I apologize if my understanding of astrophysics is not as deep as others here.
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Hermit
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Re:The Expanding Universe.
« Reply #8 on: 2007-07-20 17:48:18 » |
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[Rhysenn] How exactly is the edge of the universe defined? I apologize if my understanding of astrophysics is not as deep as others here.
[Hermit] It is where space time ends (actually where space time curls back upon itself). It might be easier to visualize when you conceive of spacetime (the Universe) as being defined by gravity (inertial fields) and when there is no mass, there is also no gravity (and thus no space and no time). As the Universe inflates (which is a much better term than expands, because the Universe is not expanding like the particles in a bomb where one can point to a certain center), but rather like the raisins in a bowl of dough that is rising), the "empty" space, including the space between atomic particles is expanding, and in fact, assuming that Omega is slightly over 1 - which is what I suspect will eventually prove to be the case (unless we find a whole lot more baryonic matter hiding somewhere (not impossible, but somewhat unlikely according to current comprehension)) - then at around 200 billion years post BB, as the last proton of the last Hydrogen atom in the Universe evaporates, its electron's orbit will be similar to that of Neptune around the Sun. (Sadly, there won't be anyone around to measure it.)
[Hermit] Hope that helped.
Regards (pleased to see you participating)
Hermit
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With or without religion, you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion. - Steven Weinberg, 1999
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