Finite Universe is it possible?

[Ceritus]

What if the universe and its matter and energy was contained in a finite space and that this space does not grow or shrink. For example a huge cube and in the middle of it is where the big bang originated from. If this were true wouldn't it be possible that in a finite space with finite energy and matter interchanging bouncing around with stars exploding imploding excreting energy engulfing planets recreating dust etc etc... That everything would find its way into the exact same coposition in infinite time... meaning that our molecules were arranged in the same order an infinite amount of times and dispalced an infinite amount of times?
Then when there is an unbalacing of matter such as too many black holes absorbing to much matter and energy that they all gradually pull itself back together into a massive ball of matter and energy and explode again over and over being infinite big bangs.

I am aware of an horizon of a blackhole and not having any more gravitational pull than a normal star outside of this horizon but the constant gradual pull could combine everything in infinite time if the expanding stops because it hits the theoretical walls of the cube or sphere.

 

[Alkatran]

The big bang theory, the best one we have so far, states something similar. Except that it's an expanding 4-dimensional space-time (Think of a 2-dimensional universe on the surface of an expanding sphere)

According to that theory, there is no center to the universe. And don't worry about all matter ending up in the same spot in one massive black hole, it appears more likely that the universe is just going to keep expanding faster and faster.

 

[richardm]

it appears more likely that the universe is just going to keep expanding faster and faster.

Faster and faster? Why's that, then?

 

[tofu]

Oooh, cosmology questions! You should consider asking this question in the bad astronomy forums at badastronomy.com. This is right up their alley.

As to the original question, the universe is a finite volume, but that volume is unbounded. This means that there is no edge, and no place that you could go so that all the galaxies would be behind you, and nothing but darkness would be in front of you.

That volume does appear to be expanding at an ever increasing rate. As yet, no one knows exactly why. Maybe there is a force that works in opposition to gravity, but only over very large distances. Cosmologists have given this force the tentative name, "dark energy" but no theory predicted it, and no one knows why it should exist, it just seems to fit current observations.

 

[Ziggurat]

What if the universe and its matter and energy was contained in a finite space and that this space does not grow or shrink. For example a huge cube and in the middle of it is where the big bang originated from.

The most obvious problem with this idea is that it violates the idea of homgeneity - that is, that the universe is fairly uniform, and we're not special. If the universe is some finite volume with the big bang occuring at one point within that volume, then that point is special. The universe should appear different if you look towards that point than if you look away from it. But when we look around us in the universe, it all pretty much looks the same.

I also suspect you're misunderstanding the idea of the big bang. The idea isn't that there's this infinite space, within which you have a singularity which explodes, throwing matter outwards. Rather, it's that space itself is compressed into a singularity, and explodes outwards. All that matter is just along for the ride. The expansion isn't matter flying away from other matter so much as the space between them expanding - sort of like if you draw two dots on a balloon, inflate it, and watch the dots "move" away from each other.

 

[Ceritus]

Well the reason I bring up this theoretical wall is an idea I came up with while looking at a cumulonimbus. Such updraft of just moisture hits a cap where an inversion starts which is called the tropapause. This motion slows down and stops simply because of a difference in standard temperature. What if this entire universe is like a layer of atmosphere with ample space to expand in, but once you go past a certain point there is a different density or what not that will not allow the expanding to continue. Sure some storm updrafts are so strong they bust the tropapause but they eventually die down and stable itself out below it.

 

[Ziggurat]

What if this entire universe is like a layer of atmosphere with ample space to expand in, but once you go past a certain point there is a different density or what not that will not allow the expanding to continue.

On the galactic level, though, space is pretty damned empty. Galaxies attract each other gravitationally, but there is no significant repulsive force for matter on these length scales. So if you want to imagine the universe as a sort of gas, the partial pressure for matter is basically zero, or even slightly negative. Weather dynamics (which very much operate under positive pressure) aren't going to look anything like cosmology.

 

[Ceritus]

On the galactic level, though, space is pretty damned empty. Galaxies attract each other gravitationally, but there is no significant repulsive force for matter on these length scales. So if you want to imagine the universe as a sort of gas, the partial pressure for matter is basically zero, or even slightly negative. Weather dynamics (which very much operate under positive pressure) aren't going to look anything like cosmology.

Well was just curious figure I would ask those who are more educated in the subject

 

[Alkatran]

Faster and faster? Why's that, then?

Well, that's what we're observing. Doesn't mean that's necessarily the way it is, just really looks that way right now.

 

[Eos of the Eons]

To me, I look at "space" as "nothing". You can fill that space with anything. On our planet it is rare to find an empty space not filled with gas or some other solid or liquid matter because we have an atmosphere. In space you can find things...planets, stars, dust, etc. But space is itself nothing. Light doesn't even bounce off of it.

So how can "nothing" end? Nothing won't have a beginning either. The "big bang" tries to show how a universe can "begin"...but "space/nothing" is there and it simply has all this happening in it. So I believe it to be finite based on my point of view already. Nothing I have ever seen can change this view, since nothing else makes sense to even start to explain space as anything but nothing.

So from what I've seen, galaxies and everything else in space just goes on forever and ever, there is no beginning or end, and everything can move away from each other constantly forever into the neverending nothing.

 

[Iamme]

What *I'd* like to know is how astronomers determined that the universe's outer edge is out at 13.5 billion light years away (or is that diameter? I can't remember), or so. How do they know that? How can they 'see' through all the clusters of stars and gases and clouds, out to that distance? I have seen the National Geographic map of the universe. I have a large fold out one at home somewheres. I could never figure out how they could determine where we are and how they know the universe ends where it does.

I believe that philosophically, it makes no sense for the universe to have a start and an end. It makes no sense that there'd be this original ball of energy (like the ludicrous claim of it being like the size of a pinhead) , somewheres, that expanded outward (the big bang). Why not infinite pinheads of energy, then? THAT would make more sense to me.

Let me say it in another way: Picture a giant dark room. Picture a HUGE dark room (represents the emptiness of space). Then, out of nowheres, for reasons yet we do not understand, appears some highly compact point of energy, that suddenly expands and envelops this big dark room (the Big Bang, and now what we see today). Does that really make any logical sense? It sounds MORE believable to me, *IF* that is the case, to then believe that some God determined "x marks the spot", and determined to just start out with a certain amount of energy at his point of choosing.

 

[Iamme]

To me, I look at "space" as "nothing". You can fill that space with anything. On our planet it is rare to find an empty space not filled with gas or some other solid or liquid matter because we have an atmosphere. In space you can find things...planets, stars, dust, etc. But space is itself nothing. Light doesn't even bounce off of it.

So how can "nothing" end? Nothing won't have a beginning either. The "big bang" tries to show how a universe can "begin"...but "space/nothing" is there and it simply has all this happening in it. So I believe it to be finite based on my point of view already. Nothing I have ever seen can change this view, since nothing else makes sense to even start to explain space as anything but nothing.

So from what I've seen, galaxies and everything else in space just goes on forever and ever, there is no beginning or end, and everything can move away from each other constantly forever into the neverending nothing.

Exactly!

I guess that means you are too smart to be an astronomer then. I guess the astronomers are too busy checking out the trees to notice that they are in a forest.

 

[Eos of the Eons]

What *I'd* like to know is how astronomers determined that the universe's outer edge is out at 13.5 billion light years away (or is that diameter? I can't remember), or so. How do they know that? How can they 'see' through all the clusters of stars and gases and clouds, out to that distance? I have seen the National Geographic map of the universe. I have a large fold out one at home somewheres. I could never figure out how they could determine where we are and how they know the universe ends where it does.

Hey, I'm pretty ignorant on this subject myself. I don't mean to disrespect astronomers here though, and they could have a good answer that would appease both of us.

Where's Phil?


Even so though...what is beyond our universe if it does only go for x distance and is only y years old? It would be just nothing, which is what space is, so even if galaxies do "end" at some point, then space can still go on and on as a bunch of black nothingness...eh?

Anybody is welcome to enlighten me!

 

[Ziggurat]

To me, I look at "space" as "nothing". You can fill that space with anything. On our planet it is rare to find an empty space not filled with gas or some other solid or liquid matter because we have an atmosphere. In space you can find things...planets, stars, dust, etc. But space is itself nothing. Light doesn't even bounce off of it.

So how can "nothing" end? Nothing won't have a beginning either. The "big bang" tries to show how a universe can "begin"...but "space/nothing" is there and it simply has all this happening in it. So I believe it to be finite based on my point of view already. Nothing I have ever seen can change this view, since nothing else makes sense to even start to explain space as anything but nothing.

Except that in general relativity, space ISN'T nothing. It still has shape, even when there's nothing occupying that space. You can even make waves in it, waves which consist of nothing EXCEPT the distortion of that space. And since general relativity is such a excellent description of physical reality (with numerous experimental confirmations, the latest being Gravity Probe B which will demonstrate how space gets twisted around a rotating body), taking the position that space is simply nothing really overlooks a lot of what we observe in the universe.

 

[Orangutan]

We suffer from our biology and everyday experience when we try to imagine the BigBang. Just thinking about it people imagine themselves as an external observer, placing themselves in a space and time outside the universe, and get to watch it as it explodes without regard for the speed of light. The problem is There is no space or time outside the universe and c is finite. We are in an bubble of space time expanding in all directions at the speed of light. Remembering this try to imagine what you observe when you watch the big bang from the inside. It will always appear that you are at the center of the bang, and the universe is wizzing away from you in all directions.

(EOS) Space time is not empty either. There is a constant sea of quantum particles and antiparticles appearing and dissapearing, as opposed to the void outside the spacetime bubble, google hawking radiation.

So basically when you think of space outside the universe you model is wrong. I know it's hard to do but you have to remember to observe the bigbang from the inside.

(I'm no expert btw I just read the more popular cosmology and physics books).


O.

Edits for clarity.

 

[toddjh]

As to the original question, the universe is a finite volume, but that volume is unbounded.

Just as a side note, the universe is not necessarily finite. If the universe is flat or open, as it appears to be, then it's possible (perhaps even likely) that it's infinite in volume.

Jeremy

 

[Iamme]

We suffer from our biology and everyday experience when we try to imagine the BigBang. Just thinking about it people imagine themselves as an external observer, placing themselves in a space and time outside the universe, and get to watch it as it explodes without regard for the speed of light. The problem is There is no space or time outside the universe and c is finite. We are in an bubble of space time expanding in all directions at the speed of light. Remembering this try to imagine what you observe when you watch the big bang from the inside. It will always appear that you are at the center of the bang, and the universe is wizzing away from you in all directions.

(EOS) Space time is not empty either. There is a constant sea of quantum particles and antiparticles appearing and dissapearing, as opposed to the void outside the spacetime bubble, google hawking radiation.

So basically when you think of space outside the universe you model is wrong. I know it's hard to do but you have to remember to observe the bigbang from the inside.

(I'm no expert btw I just read the more popular cosmology and physics books).


O.

Edits for clarity.

I understand fully what you are saying.I just started to make a post that sounded just like yours, before I even read yours. But I abandoned the post because it got to be too lengthy, because I was not explaining well, what YOU have explained well.

I think the reason why people (and I am guilty of this) believe there HAS to be infinite universes is because you can't grasp the empty universe (nothingness) as being non-dimensional. I have believed that the nothingness of space is like a 'thing' that even though we SAY it's nothing...I have let my mind envision this space of being trillions of trillions of miles, which then should want to hold other galaxies and universes.

Another possible flaw in my thinking is saying that it makes no sense for energy/matter to have started "somewhere". Because when you are of the mindset that the emptiness of space is like some measurable place (a somewhere), you then create this paradox where it makes no sense for you to envision energy appearing at some particular spot without it also appearing in some OTHER spot out in the nothingness.

So the key to one's thinking should be to get rid of the mindset that there even IS a "nothing" (an empty space dimension). You first must grasp the concept that "something" (energy or whatever) just appeared. "Where" is irrelevant because if there is no such thing as a non-dimensional space, you don't have to concern yourself with a "where".

If you think along these lines, it becomes much easier to see how there could have been only one source of energy expanding outward, without the need for many such energies expanding outward.

I hope I explained that good enough.

 

[Eos of the Eons]

It still has shape, even when there's nothing occupying that space. You can even make waves in it, waves which consist of nothing EXCEPT the distortion of that space.

How do we know this?

We are in an bubble of space time expanding in all directions at the speed of light.

How do we know this?

hawking radiation

I'm finding it really hard to believe.


Somebody tried to explain the balloon analogy to me. Thing is, there's space inside and outside of balloons.

I don't know if I'll ever "get" this stuff. I don't think I'll ever have the time to learn it all in a way that I could "get" it.

 

[Orangutan]

It still has shape, even when there's nothing occupying that space. You can even make waves in it, waves which consist of nothing EXCEPT the distortion of that space.

How do we know this?

If I may be so bold as to answer for Ziggurat, I belive he's pointing to frame dragging as an example of being able to distort space. Here's a link to a story about it in laymans tems. Frame Dragging.

: We are in an bubble of space time expanding in all directions at the speed of light.

How do we know this?

It's what we observe. Expanding universe

:hawking radiation

I'm finding it really hard to believe.

That's the perfect place to start! Quantum mechanics is very difficult to understand. It's counter-intuitive because we live in macro universe. Hawking radiation was a prediction based on quantum mechanics before it was observerd. (A good way to test a theory). There are endless resources on the web about either of these but I have never found a better explination of quantum mechanics and general relativity than in "The Elegant Universe" ($10.85 at amazon.com). and "A brief history of time" (chapter 3 talks about an expanding universe, chapter 7 about hawking radiation $12.24, you can even take a peek inside that one at [/quote]LINK ).

Somebody tried to explain the balloon analogy to me. Thing is, there's space inside and outside of balloons.

Unfortunatly you missed the point of the ballon analogy, It's only the surface your supposed to look at as a 2D representation of 3D space. and shows how any observer may see all other points expanding away from him. It's an example I try and not use just because it looks like you're showing a 3d universe. Here's something different to try.

Take a pice of elastic. Cut a rubber band if you like. Now tie 3 knots in it. one in the middle and then 2 a little distence either side. Now practice stretching the band so that you can keep a knot of your chosing in the same spot over the table. You'll see that even though the stretch is the same every time, if you change your frame of reference it appears that you are in the center and everyone is expanding away from you. (It gets more complicated when you say "but I can see that I'm closer to one edge of the band." These problems go away when you consider the speed of light evens things out so you always appear in the center. Try stretching the band at the speed of light in either direction, you'll see what I mean ). The elastic band is just a random 1-dimensional line, but you can imagine that each not is a galaxy that just happens to line up in our universe.

I don't know if I'll ever "get" this stuff. I don't think I'll ever have the time to learn it all in a way that I could "get" it.

The 2 books I gave you are great examples. Even if you just get the elegant universe for it's chapters on general relativity and quantum mechanics it's a great start. There are no maths in them as they are an explination of the thories, not the thories themselves. If you start on the Superstring stuff in the rest of the book it really starts to blow your mind!

As you can probably tell I think this is a facinating subject.


O.

 

[wollery]

What *I'd* like to know is how astronomers determined that the universe's outer edge is out at 13.5 billion light years away (or is that diameter? I can't remember), or so. How do they know that? How can they 'see' through all the clusters of stars and gases and clouds, out to that distance? I have seen the National Geographic map of the universe. I have a large fold out one at home somewheres. I could never figure out how they could determine where we are and how they know the universe ends where it does.

Misconception. the Universe doesn't have an outer edge. the furthest we could possibly observe is 13.5 billion light years, but this isn't because the Universe has a 13.5 billion light year radius! It's due to the fact that when you look at something very far away the light takes time to reach you (travelling at the speed of light), and since the Universe is ~13.5 billion years old it's impossible to observe anything earlier than that, i.e. further away. 13.5 billion light years is the edge of the observable Universe. The age of the Universe is based on a number of measurements including galaxy recession speeds corelated with their distances, and the spectrum of the Cosmic Microwave Background Radiation.

I believe that philosophically, it makes no sense for the universe to have a start and an end. It makes no sense that there'd be this original ball of energy (like the ludicrous claim of it being like the size of a pinhead) , somewheres, that expanded outward (the big bang). Why not infinite pinheads of energy, then? THAT would make more sense to me.

Cosmologists freely accept that there may be infinitely many universes like this one, or indeed unlike this one!

Let me say it in another way: Picture a giant dark room. Picture a HUGE dark room (represents the emptiness of space). Then, out of nowheres, for reasons yet we do not understand, appears some highly compact point of energy, that suddenly expands and envelops this big dark room (the Big Bang, and now what we see today). Does that really make any logical sense? It sounds MORE believable to me, *IF* that is the case, to then believe that some God determined "x marks the spot", and determined to just start out with a certain amount of energy at his point of choosing.

Again, a misconception. The Universe isn't expanding into anything. There is no outside to the Universe, it defines its own space. This is the problem that many people have with the balloon analogy. In this case it is patently obvious that the balloon is expanding into the 3-dimensional space of the air around it, forced to do so by the air being blown into it. But to understand the analogy you must forget about the air and the cause of the expansion. You must concentrate only on the 2-dimensional outer surface of the balloon. This demonstrates the idea that the space itself is expanding, that there is no centre of expansion, no prefered position, and that although the galaxies are moving apart they aren't expanding into something else.