Does a finite universe make sense to you?

MiltMeyers

Glad to hear we are all about equal in knowledge. Now let me restate. that as we look out to a time and distance of the cosmic background that it fills the sky in every direction that we look. The universe is much smaller then and all directions we travel will take us back to that time. Now go beyound that event back to the singularity and it also would be in every direction we can go. So now I ask you what direction would you go to get to the edge of space time? To escape we need a new dimension a 5D but our universe is only 4D. I've always thought that space time was exspanding at C but of course the matter was at a slower rate. The real noodle problem is that we are in the oldest state of the universe and so is every man women or child. Any direction we go from us is back in time to a smaller universe. IE the Sun is in a universe 8 minutes smaller from were we are. This can only be if we are in a 4D sphere or bottle as I like to call it. Nothing is ever lost from it and since nothing can travel faster than light nothing is lost. Some have said that the greater the distance that the faster an object can go till it is going faster thanC, like maybe 2C. I say that that C is the limit and all you do when you add space time is lower the frequency. The faster an object goes fromus the lower the frequency and that is why the back ground is in the microwave range. That is why the red shift. That is the way I see things so feel free to jump in and straighten me out.

DaveC426913

You are confusing travelling with looking. When we look outward we see back in time, but we can't travel there.

mysearch

I have only quickly read through all the contributions, so apologises if my point has been raised before and I missed it. However, I was wondering whether a finite universe would have a gravitational centre of mass?

When Newton first came up with his theory of gravitation, he was unsure whether gravity acted with respect to the surface or centre of mass. Subsequently, he formulated what has become known as the Newton’s Shells:
http://en.wikipedia.org/wiki/Shell_theorem

However, the flip side of this theorem shows that a particle within the cavity, surrounded by a uniform shell, would feel no net force of gravity, or possible spacetime curvature is more exact according to GR. However, the question being raised is whether an infinite universe would act as an infinite thick shell to any point in the visible universe and thus have no centre of gravity? While, in contrast, a finite universe must have some form of centre of gravity? Just a thought.

MiltMeyers

Dave Yes I agree and what I should have said if we could travel instantaneously which we can't but it is a way to describe what we see as that is the shape of the universe. It was late and I'm really not a bright bulb.

Mysearch, the only thing like a center is the spot were the singularity was and it is now spread all over the universe so my answer, if you care is there is no center. You have to visualize a 4d sphere and that is very hard, to see what I mean. So the universe has no center and no outside and nothing before the initial singularity.

mysearch

I am not pretending that I know the actual answer, but would be genuinely interested in how a 4D-sphere changes the basic physics of gravitation. Newton’s shell theorem provides some tangible mechanism by which gravity might cancel out in an infinite universe, but not a finite universe. While Newton's laws of gravity are superseded by GR, I believe Newton’s basic laws still applied in this case. The terms centre of gravitational mass may be misleading as it is really only referring to a point corresponding to the net resultant of all gravitational forces/curvature in a finite universe. So my response is really just another question:

How does a finite 4D sphere explain there being no centre of gravitation?

DaveC426913

You need to specify one more qualifier: boundary.

A finite bounded universe will have a bias in gravity, a finit but unbounded universe will not.

mysearch

Hi, accept the implication of the correction, but do not understand why. Can you qualify your statement about a "finite but unbounded universe" with any reference that explains the physics? Again, this is intended as a genuine inquiry and not as a smart-arse response. Thanks

DaveC426913

Well, that's where your 4D space comes in.

In the 2D "balloon" analogy the universe is finite (its width is the circumference of the balloon) yet unbounded (there is no edge, and no point on the surface is "privileged"). It also means no point on the surface is privileged with having a different mass distribution, and that means no point on the surface has a gravitational gradient differnt from anywhere else.

In the equivalent 4D universe, it has a finite size, yet, because it wraps around there is no boundary. This means no point is privielged with an different mass distribution because no point is "nearer an edge" than any other.

MeJennifer

Perhaps this is all confusing due to terminology but under GR a closed spacetime is always finite while an open spacetime is always infinite. In addition such spacetimes are also resp. spatially finite and spatially infinite.

MiltMeyers

Dave thats great as you have a way with words. Well said. Now as I see it space time is curved and exspanding even though the light we see looks like it is traveling a straight line. Light travels at C due to space exspanding at C so space time started first so it is the cause and light speed is the effect. I maintain this is not like either but space time is something and has a quantum foam were particles appear from space time and then disappear. It has a zero point energy. It seems to be that everything inside our universe is something and there is nothing outside not even nothing. Maybe there is an outside but it would have to be in the 5th demension. Okay who are you voting for and how much money do you make and is there a God? Please don't answer that as I was just kidding.

MeJennifer

Spacetime does definitely not expand.

No, you got that wrong.

MiltMeyers

Jennifer, hmmm if space time doesn't expand, why is the universe getting bigger? Also it is accelerating as time goes on. Does not the space between the galaxys make the universe bigger now than in the past? Maybe I'm using the wrong words? Please let me know were I'm going wrong.

I know that the speed of light C is not due to space time exspanding. So please explain how that works. Why is the c just about 186,000 mps and not 200000 mps? I'm truly happy as I think I'm going to learn something.

Thankyou;
milt

DaveC426913

The only sane choice: I live in Canada.

MeJennifer

Don't mistake spacetime for space.

Actually it could be any value it just depends on the units of measurement you use.

MiltMeyers

What keeps it from being faster or slower thru open space? Space is not an either or is it? I was taught many years ago that light propegated by each point on the wave front acts as a primary source and each point on that wave front acted as a primary wave source and so on. That was physics in 1959. Do you agree that the universe is exspanding at C?

Thankyou for your help.
milt

MiltMeyers

I'm so new here I didn't figure out how to post with a quote.

epkid08

Why wouldn't spacetime be expanding? Well for one, we assume space is expanding, so what does it mean for time to expand? Well, I'd say that if time wasn't 'expanding' we'd be frozen in time, but because spacetime is expanding, time and space continue to accelerate, as we continue traveling into the future.