Understand Shape of Universe: Spatially Flat?

[kent davidge]

What actually means to say that the universe is spatially flat? Would it be that, if one could extend two straight rods of infinite length (assuming a universe with no boundaries and infinite amount of material for making the rods, LOL), they would remain parallel?

 

[mfb]

Yes. It also means angles in triangles add up to 180 degrees.

 

[kent davidge]

Yes. It also means angles in triangles add up to 180 degrees.

Ok. Now, in a closed universe, what would be an interpretation for its closed form, besides angles not adding to 180°?

 

[Jorrie]

Ok. Now, in a closed universe, what would be an interpretation for its closed form, besides angles not adding to 180°?

Your straight rods will converge and cross over at some large distance in any direction.

Take note that in our presently accelerating expansion universe, even it it has a small positive spatial curvature, your rods will break long before they reach that crossover point, because they cannot extend past our Hubble radius.

 

[kent davidge]

Your straight rods will converge and cross over at some large distance in any direction.

Take note that in our presently accelerating expansion universe, even it it has a small positive spatial curvature, your rods will break long before they reach that crossover point, because they cannot extend past our Hubble radius.

Thanks.