/sci/ - Science & Math

Okay, OP. I have a real serious question. Please consider it carefully, because it's kind of complicated.

I was reading Carl Sagan's Cosmos, and he talked about the big bang not being all of the universe's matter exploding out of one corner of it, as I had previously imagined it, but rather as the universe itself expanding, the space itself expanding. I envisioned a 6-dimensional hypersphere, where the 3 dimensions of space are squeezed into the surface.

Then, just today, I suddenly realized that, if the volume of this hypersphere were increasing at an even or low-exponential rate, the rate of expansion of the hypersphere's radius would actually be *de*celerating. And it hit me: objects in the three dimensional "shell" of the universe would be "pressed" into the fabric by momentum, resulting in curvature... and GRAVITY!

(Picture related.)

I'm not sure why Carl Sagan didn't explain it like this. Is this not a preferred model? I looked around on Wikipedia, and this seems to be what I'm referring to – the FLRW metric (http://en.wikipedia.org/wiki/Friedmann%E2%80%93Lema%C3%AEtre%E2%80%93Robertson%E2%80%93Walker_metri
c).

Is this how the FLRW metric visualizes the universe? As an expanding 6-dimensional hypersphere? Or am I totally misunderstanding everything about spacetime and gravitation? Feel free to call me stupid if I am.

(For reference, I'm interested because I'm going to be going to college to major in physics and math, and I want to get a graduate degree in astrophysics at some point, so I'll be working with all this stuff one day.)

Also for reference, the circle in my diagram represents a six-dimensional hypersphere. The radius of the circle is the fourth dimension, its width as a circle is the fifth, and its thickness as a sphere is the sixth. The three euclidean dimensions are represented as a flat plane, stretched like a tarp over the surface of the sphere, and expanding uniformly in all directions.