I have heard the phrase "Space has no edge and no center" before and yet people refer to the universe as a finite area. If space is truly infinite could there be separate galaxies, in galaxy clusters, in universes far beyond our detection? If so would they all be subject to the same general laws of nature that we have become familiar with, or could they have had completely different means of interaction? Is this what people refer to when they talk about alternate universes? I am sort of a science novice and this question has always bugged me.

Alternate universes are merely speculation at this time. There is no reason to believe that the laws of physics are different elsewhere, even in althernate universes if any exist.

Note that the surface of a sphere is finite, but has neither an edge nor a center.

How can the universe be on a 2 dimensional sphere when there are many galaxies in all different directions, unless the thickness of the sphere were infinite, but that wouldn't be a sphere would it.

Dinosaur used an analogy so that you could visualize what is meant. The universe is obviously not a 2sphere. Now extend the spherical analogy to higher dimensions ...

I guess I do not follow. If the universe was a sphere, and I travelled on a single path would I end up back at earth? How could that happen if space has no edge and no center? Is our universe just expanding in an infinite vacuum like a bubble with all the galaxies inside of it?

How can the universe be on a 2 dimensional sphere when there are many galaxies in all different directions, unless the thickness of the sphere were infinite, but that wouldn't be a sphere would it.

Spheres are three dimensional.

What they are saying is, just like a 2D object can be wrapped into a sphear (3D) So could our 3D universe be wrapped into a 4D object. Thus like on a sphear, there would be no center or edges, but it would be finite volume (like the finite surface area of a sphear).

I travelled on a single path would I end up back at earth? How could that happen if space has no edge and no center? Is our universe just expanding in an infinite vacuum like a bubble with all the galaxies inside of it?
So yes if you had a rocket travel in 1 direction, eventualy it would end up back where it started. :)
It would happen the same way an airplane would end up back where it started if it moved in 1 direction allong the earth: eg. if an airplane takes off at the euquator from Brazill and travells allong the euquator, eventualy it will arriv back at Brazill.
Just, save yourself the aganoy and dont even try to visualize this example applied to a 3D object wraped into 4D.
-Andrew

Just, save yourself the aganoy and dont even try to visualize this example applied to a 3D object wraped into 4D.

Too late

:eek:

OctopusInk,

Check out these websites. Even if you just read the FAQs(Frequently Asked Questions) they should help you understand the current knowledge that we have about the universe. Be wary of what you read on the web. There is a lot of misinformation that can be very confusing. I am not saying the others that have responded here are wrong. Quite the contrary, I agree with them all, but to answer your questions on whether the universe is finite or not, and what shape it is, would require more typing than I care to do, and my answers would not be as good as what you will find on these websites.

http://www.astro.ucla.edu/~wright/cosmolog.htm

http://math.ucr.edu/home/baez/RelWWW/

http://www.nasa.gov/home/index.html

The nasa site is quite large, so you should use the search feature to ask your questions. Best of luck!

Wilgory

Spheres are three dimensional.
Off-topic, but geometers call ordinary spheres "2-spheres" because the boundary is 2 dimensional.

On-topic: This wikipedia article (http://en.wikipedia.org/wiki/Shape_of_the_universe) is a good summary.

Yup, but I was actually replying to How can the universe be on a 2 dimensional sphere when there are many galaxies in all different directions, unless the thickness of the sphere were infinite, but that wouldn't be a sphere would it. but the thread hadn't updated to show your post and usage of 2-sphere.
Mea culpa.

Ok, so from what I gather our galaxies are inside of a sphere rather than on the skin of the sphere which was my 2d comment. If that is the case and you traveled in one direction long enough how could you come around to the other side, wouldn't you just keep going into empty nothingness forever? If the universe was like the skin of a basketball what is inside the basketball? Thanks for your answers.

The way I think of the universe is answered in the example of what would you see if you were staring off in the opposite direction of the universe; Imagine being transported to the last planet on the edge of the last solar system of the last galaxy and as it rotates away from the centered star what would be there? It is sort of an asymptote effect I imagine where only a piece of matter smaller than the one prior to it could extend out further from the imaginary center of the galaxy. This pattern persists until the last atom, the last proton/photon/electron and then to the structure and fundamental forces holding it together.
Then the question emerges of what is the center of the universe...consider the opposite. The very center mass would have to be denser than everything around it, aka, a super-massive blackhole. The center of a super massive blackhole (and that SHOULD be the technical name if you ask me) would be a void of mass but an excess of the fundamental forces in the universe. The mass turns to pure energy. It is a donut effect. The only thing that exists on the outside limits of the universe is the only parts that exist in the center of the universe. If you stare too far into the abyss the abyss stares at you. (Nietszche)
Thus, there is no center or edge because they wrap into one another. And not like a circle around a sphere, but a sphere around structure A to the fourth power.

Ok, so from what I gather our galaxies are inside of a sphere rather than on the skin of the sphere which was my 2d comment. If that is the case and you traveled in one direction long enough how could you come around to the other side, wouldn't you just keep going into empty nothingness forever? If the universe was like the skin of a basketball what is inside the basketball? Thanks for your answers.
in answer to your first question:
The universe would be contained in the volume of the basketball,
but (and this is where it hurts) the skin of the basketball is in contact with the skin part opposite it (but it hasnt deflated, it's instead become a 4D object)
That is, if made an axis through our baketball universe, each point where the axis intersected the ball (2wice, like north and south poles on earth) would actualy be the same point in space! And this applies anywhere and everywhere. O.O

In answer to the second question... I havnt one :p
-Andrew