posted on May, 16 2006 @ 08:55 AM
First, to bring anyone not familiar with this subject up to speed...
Imagine you are 2-dimension, a square perhaps, and that you live in a - correspondinly - 2-dimensional universe. You would have width, and length, but
absolutely no height. You would go about your flat life with your flat friends and your flat business, all the while trapped on your 2-dimensional
plane of existance.
You have no concept of "up" or "down". These notions don't even exist to you. There's absolutely nothing in your field of experience that can
even help you grasp the notion. It's a direction that intersects your existance at a right angle, but which you can have no hope of "pointing" in
the direction of. Above and below are meaningless concepts.
However, this up and down do yet exist - invisible and altogether alien as they would be to you.
But let's say that your universe is not actually 2-dimensional. It may be, seemingly, 2-dimensional physically, but on the absolute grandest of
scales your universe wraps around itself to form a giant sphere. You would have no clue it's a sphere because you're so tiny, and because you can't
see or touch or point or sense this "3rd dimension" - so to you it appears that the universe goes on to infinite in every direction. But if you
could somehow mark your exact position in the cosmos, and you began travelling in a PERFECTLY straight line, then eventually you would somehow return
back to where you began.
Furthermore, let's pretend this isn't just a sphere, but a balloon - expanding. From your flat surface, everything in the universe appears to be
flying away from you. Light from far away objects is red-shifted, because the galaxy it's from actually is receding (2-dimensionally) away from you
at an incredible pace.
This is what astrophysicists think is happening. However, to make it apply for us, you just need to take that example, and shift every
dimension up by 1. We are 3-dimensional creatures living in an, otherwise unknown to us, 4-dimensional universe.
How does the universe fold upon itself? Through gravity. Or, as it should more properly be said, gravity is the cause of the universe folding upon
itself. Let's go back to our 2-dimensional concepts. You have a sheet of paper, which is space in your apparently 2-d universe. Put this paper on a
bowl, and put something in the middle of the paper. See how this causes the paper to bend? If you were to roll something along this paper, it would
fall inwards towards the middle of the bend. This is what gravity is - it's the curvature of space and time in a way that makes it look like things
are attracted to each other - when in reality it's just space-time being bent.
So, you often hear about the universe expanding forever, or contracting and destroying itself. The question astrophysicists are looking to answer is
whether the universe is
If the universe is closed, it means that at the moment of inception, the universe had enough mass to close in on itself. It's a balloon that's
expanding. Eventually it will slow down, stop, and begin contracting. The simple way of putting it is that, in this universe, if you draw a big enough
equilateral triangle, it's angles must add up to MORE than 180 degrees - because the space must curve back in upon itself.
However, if the universe is open, that means it could look like any unconfined 4-d object. One that is often pictured is a "saddle" universe, with
space time warping and curving forever, but space will become infinite. The simple way of putting it for this is that, if you draw the same triangle
as before, it's angles must add up to LESS than 180 degrees - because the space must be free of interacting with other space.
However, I recently had an idea
What if the universe is both OPEN and CLOSED at the same time?
We tend to picture the closed universe as being the OUTSIDE surface of an expanding balloon. What if, perhaps, it's the inside surface? In this
universe, the triangle would APPEAR to have a triangle with sides less than 180 degrees, but space would be connected.
I wonder what kind of differences this would have to a closed universe, if any?