Re:'Dark fluid' with negative mass could dominate the universe
by dragonwriter on Wednesday December 05, 2018 @05:04PM
(#18613114)
> If you stand on the balloon it doesn't make sense to ask "where is the balloon expanding from?".
Sure it does, and there is a well-defined answer, it's just the answer does not lie on the surface of the balloon. (And for a perfectly spherical balloon, is equidistant from every point on the surface.)
Re:'Dark fluid' with negative mass could dominate the universe
by danbruc on Wednesday December 05, 2018 @06:28PM
(#18613826)
That of course only works because the surfaces of balloons we are used to are always embedded in spacetime. There is however no [good][known] reason to assume that spacetime itself is embedded in any space.
Re:'Dark fluid' with negative mass could dominate the universe
by OscarCunningham on Wednesday December 05, 2018 @10:58PM
(#18615273)
I've always thought this would be an interesting experiment. Assume that spacetime does live in a higher dimensional space, and try to arrange masses so that spacetime is forced to intersect itself. See if anything interesting happens.
Of course this probably requires some stellar engineering.
If you stand on the balloon it doesn't make sense to ask "where is the balloon expanding from?". Its expanding in every direction. Every observer on the balloon sees all points around them getting farther away.
Now try to picture that but in 3d. It might help to think of it as like a cake with raisins in it expanding in the oven.