[dimmufan]

Scientists and astronomers all claim that the universe is expanding. The galaxies are moving farther away from each other. I have questions; what is the universe expanding in to? Is the universe just a vast expanse of nothingness or does it have a defined shape? What happens when we reach the end or is there even an end at all? Will the gravity of all the galaxies eventually pull themselves back together, or is the speed at which whole galaxies travel far greater than for gravity to take hold? Thoughts, comments, and answers are welcome.

[Momo Mastermind]

I've always wondered the same exact thing. I believe I once heard that scientists speculate that the universe is in a constant state of expansion/contraction, once it reaches the limits of its reach, it contracts into a single minute object, then again it expands. Perhaps, if this were true, then it gives even more notion to the beating heart, or the rhythme of all life. The universe is like a giant heart, obviously moving slower because of its sheer size, pulsating. Ugh, this is me getting intellectual

I use to lay at night thinking about this exact question, and it tormented me I really have no idea, the only thing I can go by is my own imagination and that which scientist disocover to be true. I really hope never to know, and there will be people on this forum who completely object to that statement. There will be people who claim that the purpose of life and the human mind is to learn all that can be learned, but I don't agree. There are just some things I personally wish never to know :/

It will be interesting to see what theories they come up with next, however ^_^

[Jin]

Here's what I've been told by 2 professors, who are, of course, falable, as is my memory of what they said, but here it is. The universe is expanding into nothingness, by our perspective, yes. 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.

Again, this is based on memory of a very short class session at university I attended about 3 years ago, so if anyone feels the need to correct me, feel free.

[Omega Weapon]

Expanding universe is the current understanding of the state of the universe. It states that the universe is not fixed. It is gradually expanding. It is based on the finding that all galaxies are moving away from each other. Application of general relativity to cosmology, along with the detection of red shifted light coming from galaxies outside the Milky Way Galaxy, led to the realization in the 1920s that all galaxies are receding . It is unknown whether the universe will expand indefinitely (open universe) or eventually collapse (closed universe) into an extremely dense, congested state, as it began, according to the big-bang model.

Friedman’s universe is the model of universe developed in 1922 by the Russian meteorologist and mathematician Aleksander Friedmann (1888–1925).

He believed that Albert Einstein's general theory of relativity required a theory of the universe in motion, as opposed to the static universe that scientists until then had proposed. He hypothesized a big bang followed by expansion, then contraction and an eventual big crunch. His model supposes a closed universe, but similar solutions involve an open universe (which expands infinitely) or a flat universe (in which expansion continues infinitely but gradually approaches a rate of zero).

Milky way is a large spiral galaxy (roughly 150,000 light-years in diameter) that contains Earth's solar system.

It includes the multitude of stars whose light is seen as the Milky Way, the irregular luminous band that encircles the sky defining the plane of the galactic disk. The Milky Way system contains hundreds of billions of stars and large amounts of interstellar gas and dust. Because the dust obscures astronomers' view of many of its stars, large areas could not be studied before the development of infrared astronomy and radio astronomy (see radio and radar astronomy). Its precise constituents, shape, and true size and mass are still not known; it is believed to contain large amounts of dark matter and a massive black hole at its core. The Sun lies in one of the Galaxy's spiral arms, about 27,000 light-years from the center.

Originally Posted by dimmufan

What happens when we reach the end or is there even an end at all ?

This is the only question I can answer now, In my opinion..Our universe is endless, there is no end to reach.......Thinking about these theories makes me crazy

[VidenTheColdOne]

lowl, your all asking questions that scientists have been asking for thousands of years. The truth is nobody really knows, and all they can do is guess, and even one scientists best guest could be so far from the truth as to be mind boggling. What do i think? The earth will die, and mankind will be extinct before we ever learn the answers to these questions, so its best not to think about it.

[dimmufan]

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. These are just my theories.

Jinjatsu and Omega Weapon raise some pretty interseting theories. Thanks for your input.

[Omega Weapon]

What about Black Holes? I was making a small search in the internet trying to find a connection between Black Holes and Expanding Universe:

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.

What do you think about this article?, I do believe that Black Holes "If they are exist" have an important part in all this but how...Not pretty sure

[Mike]

Here is an odd analogy to stir your braincells. Lets look in the opposite direction. 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.

[dimmufan]

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 SMBH are spinning so rapidly that everything around them can't help but to spin around the black hole. As the SMBH "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. As far as worm holes are concerned, I don't know what to think, as the only info we have on them is just speculation anyways.

[Omega Weapon]

The Expanding Universe Theory depends to a large degree upon the correctness of Hubble's Law; viz., the redshifts of distant objects are directly proportional to their distances from earth. Unfortunately for the Expanding Universe, some redshift measurements indicate a quadratic rather than linear relationship between redshift and distance. I.E. Segal's chronometric theory of the cosmos, however, does predict a quadratic relationship. In Segal's theory redshifts are due to the gravitational slowing of light rather than any gereral expansion of the universe.

Even if most astrophysicists are finally persuaded that the quadratic relationship is real, they will be loath to abandon the philosophically appealing Expanding Universe. Not only is the Expanding Universe consistent with Relativity but it states unequivocally that the earth (and man) does not occupy a preferred place in the universe.

Consider the universe. It has a size of about 15 billion light years or so. It also has a total amount of mass-energy. If we represent this mass-energy as quantum mechanical standing waves, just as we did for black holes, we can calculate the total entropy of the universe.

It turns out that the entropy of either a black hole or the universe is proportional to its size squared.

Thus for a given amount of total mass-energy, the larger the object the higher the entropy.

But the universe is expanding, so its size is increasing. Thus the total entropy of the universe is also increasing.

This leads us to the idea that the Second Law of Thermodynamics may be a consequence of the expanding universe. Thus cosmology explains this nineteenth century principle.

Put another way, recall that we have realised that the direction of time, "time's arrow," can come either from the fact that the universe is expanding or from the Second Law of Thermodynamics. We have now found a relationship between these two indicators of the direction of time.

It is amusing to speculate about what will happen to the Second Law of Thermodynamics if the universe is closed, so that at some point the expansion stops and reverses.

Even more wild is the idea that if the expansion of the universe determines the direction of time's arrow, then if the universe starts to contract the direction of time will also reverse.

Back to Black Holes now......

I made a search in the internet but unfortunately for me , I couldn't find anything important connection between the black holes and the expanding universe yet..However I will do my best trying to find something useful to share about it....

[Nin`]

For those interested in this kind of thinking, a mind-bendingly difficult (that's quantum mechanics for you) but very worthwhile book is "The Fabric of Reality" by David Deutsch. I would recommend it. In it the author gives a very interesting account, amongst other things, of the multiverse.

Some of the questions posed in this thread are not ones which are easily (or if at all possibly) answered, at lest with no fixed degree of certainly; I'll try and include some examples where I can. Our Universe is bounded by space-time, which is in turn dependent on the existence of matter-energy to define a reference frame. Areas not having space-time are not "outside the Universe" (which itself is meaningless for lack of a reference frame) but are simply undefined; though they maybe an extrinsic part of our universe (universii/parallel universes, or vacua for example). Space-time was instantiated some Planck-seconds after the quantum fluctuation, but it is incorrect to refer to a "before the Universe existed" type scenario, as that is, again, simply undefined as there was no space-time and thus no time (needed to make “before”, and thus “outside” meaningful). Although theoretically speaking, singularities within the Schwarzschild radius of a black hole are technically “beyond” (a logically correct term for “outside” here) our universe (like other possible dimensions and vacua) since anything, which is not subject to the laws of this Universe, cannot directly interact with our Universe (or the laws would not be laws).

Other universii (or vacua) may exist (highly probable according to quantum mechanics, string theory, M-theory as well as most of the consensus cosmological models) but need not resemble ours in any way whatever, and may be forever inaccessible to us except in thought experiments. Ask me once we’ve determined whether Hawking Radiation exists (it should) and whether Hawking Radiation conveys information (probably). If Hawking Radiation does exist (and it may, as in July 2004 Hawking suggested that he had derived a theorem permitting information to escape from a singularity - though it is still AFAIK unpublished) and can be validated, then it is possible that far from a mere 'hypothetical' concept, there may be an 'Ultimate ensemble' compatible multiverse with, at least, theoretical one way traps out of our Universe. But I wouldn't hold my breath. All 'modal reality' concepts, though endlessly fascinating to certain mathematicians, physicists and sci-fi authors are essentially mathematical masturbation which, while it apparently can provide as much pleasure to those playing with their surds, as most people get from the other kind, are nevertheless inherently unscientific in the absence of any visible necessity (Ockham).

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 (Ω), 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, conclude that 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.

In the mean time (from a philosophical perspective here), statements about the nature of truths are relative to a quasi-absolute (no matter how poorly defined) theoretical meta-construct (the map). Statements about observations (the terrain) are relative to the observer (from a particular perspective). Thus these two kinds of statements, while seemingly congruent, are members of completely different classes of objects, which are qualitatively different and attempting to compare them is utterly invalid. We should already know that no non-trivial system can be proven as being both complete and consistent (Goedel). The use of the term "everything" is being understood to establish a reference that includes all systems, including the complex, and including itself. Thus, neither "Everything is subjective", nor "Everything is objective" can be absolutely true. The statement, "Everything is some thing", is part of a formal system (of definitional statements) which is self-referring and purportedly complete - no matter what the "some thing" referred to may be. Thus, already being complete, it cannot be proved correct - irrespective of the thing, which everything is asserted to be. A statement about the nature of truth here thus falls into one of four categories:

• One which is relative to a formal system, where the formal system defines the thing, the truth-value of which, is being described.
• One that is relative to a perspective.
• One that combines aspects of both.
• Those which are invalid.

The truth-value of things in a formal system (i.e. Euclidean geometry) can only be determined in relation to that formal system (but need not be subjective as an absolute value for the comparisons may exist, the formal system itself establishing that absolute value). Here we establish a class of thing, which is indeed self-referentially absolute, a trivial formal system. Where the formal system is sufficiently well defined, and an external subject simple enough for all observers to perceive the things subject to the system from a sufficiently well defined perspective as being congruent within the limits of the formal system, then the formal system may serve as an absolute value for the evaluation of things perceived by those observers using that formal value as a referent. Even so, that imposed absolute value remains relative only to that formal system and so long as the observers perceive it as such.

So any question relating to what is “outside” our universe (although I find “beyond” to be a more definitive term) is a meaningless question from our relatively observable point in space-time. However, 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 in 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 gravitational flux, 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:

• The Elegant Universe: Welcome to the 11th Dimension (3/5)
  
• The Elegant Universe: Welcome to the 11th Dimension (4/5)

As a note of interest I say instantiation rather than creation, as the possibility that this Universe could exist made its eventual occurrence a near mathematical certainty, and our actual existence confirms this possibility. No "act of creation" (which would require intent) is necessary to explain this, and thus postulating it as a possibility is logically invalid (Ockhams Razor).

How the universe will “end” (if we can put it like that) on the other hand is a little easier to elucidate. Based on what we understand from gravity, the observation of nova events, and the energy density we are observing, our current consensus opinion is that if Omega is less than one (an “open” system), and therefore that our Universe is a hyperbolic Universe, consolidation is unlikely to occur before evaporation. The matter will eventually all evaporate, leaving an almost evenly distributed energy field which will only cease to exist once the last proton evaporates some 200 billion years from now, leaving the Universe without a reference framework, so ending space-time (without which our Universe cannot exist).

If Omega is greater than one (a “closed” system), and therefore our universe is a spherical universe, the gravitational force of all matter would eventually exceed and overwhelm the expansion rate. The universe would slow down and begin to contract its own sheer mass, resulting in a “Big Crunch” type scenario where the universe would once more become a single huge but tiny mass crammed into a naked gravitational singularity, around 42 billion years from now. However due to the strong negative pressure of dark matter, providing that it remains constant and which, theoretically, could well be accelerating the metric expansion, this scenario cannot happen.

However if Omega is equal to one (a “flat” system), then the universe would asymptotically reach an entropic equilibrium (a state of maximum homogeneity where expansion would reach a rate of zero) in which, eventually, all matter would be at a uniform temperature, density, composition and pressure; also known as heat death. This could theoretically last forever, or at lest indefinitely - providing that dark energy was absent. However, some cosmological models that include dark energy suggest, due to the predicted amounts of usable energy always being available, that a state of maximum entropy cannot feasibly occur. By including dark energy into a flat universe model the ultimate fate of the universe would be the same as an open universe, or (possibly) a "Big Rip".

Regards,

Nin`