"No, we know the room is curved by mass, and that causes gravity."
Where's the context? (btw the room is curved by mass, energy and pressure, AFAIK)

As we only see the stars as a projection without curve, the sum of angles has to be 180° which does not prove anything.

Btw the accelerating expansion of the universe is something that could (!) be a result of a finite, bend universe.

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