Shape of the Universe: Flat or Curved?

[moonman]

I'm not overly familiar with GR, but I have heard that gravity is basically a result of the curvature of space. Its not an attractive force so much as its a consequence of traveling on a curved surface. But I've also read that observing cosmic microwave background hot spots leads to a flat universe. So can the universe be flat, if GR claims gravity needs curves?

 

[SpaceTiger]

Its not an attractive force so much as its a consequence of traveling on a curved surface.

Tomato, tomawto.

But I've also read that observing cosmic microwave background hot spots leads to a flat universe. So can the universe be flat, if GR claims gravity needs curves?

I think this was covered by someone else in another thread recently, but the basic idea is that massive objects are like little "dimples" in spacetime, despite its overall flatness. Imagine a large, flat rubber sheet with a few marbles resting on the surface. The marbles make an impression locally, but the overall sheet is flat. In the real world, the small-scale curvature due to gravitationally bound objects can be demonstrated with phenomena like gravitational lensing.