|
||||||
|
|
|||||
 |
Are there any other geometries for the universe beside the ones we are discussing? |
 |
Yes, certainly. The geometries we are discussing are the complete range of isotropic and homogeneous geometries. If you throw out those requirements many other geometries are possible. |
|
How can local spacetime have a changing curvature and still fit into the description of the overall geometry of the universe (flat, spherical, hyperbolic)? |
|
The overall geometry of the universe is the overall gravitational field of the universe. Obviously the individual things in the universe have their own gravity too. Think of the gravity of a galaxy like a dimple in the overall flat, spherical or hyperbolic geometry. |
|
Star Trek proposes "warping" space to "shorten" distance between two points. My impression is that this would require a ridiculous amount of energy, if it were even possible. Is it possible? |
|
Your impression is correct. Space is bendable; massive bodies do it all the time. But space is very hard to bend (it is very stiff if you will). All the mass of the sun produces only a very modest curvature in space. I doubt any human contrivance could accomplish much in the way of space warping. |
|
In what way does matter affect spacetime? |
|
It changes its geometry. That is, matter determines what constitutes freefalling (inertial) worldlines in spacetime. |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Copyright © 2005 John F. Hawley |