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Do cosmologists know for sure that the Big Bang is propelling all matter away? (lemm.ee)

submitted 11 months ago* (last edited 11 months ago) by aCosmicWave@lemm.ee to c/asklemmy@lemmy.ml

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Is it at all possible that instead of being pushed away, we are instead getting pulled toward something huuuuuge via gravity? As if we are falling into something way greater than ourselves? I thought this was a wild idea but after I Googled it I found out that there is such a thing as a “Great Attractor”. Something 150 million light-years away is literally pulling all nearby galaxies towards it but no one knows exactly what it is.

So how do we know there aren’t any other Great Attractors, Greater Attractors, ad infinitum?

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[–] Shurimal@kbin.social 4 points 11 months ago

Geometrically speaking, if you draw a really, really big triangle between, say three galaxies, the angles of the triangle add to 180° in a flat universe. In a non-flat space, this would not be the case. For example, if you draw a triangle between, say, New York, Berlin and Rio de Janeiro on the surface of the Earth, the three angles between the lines would add to more than 180° since Earth is topologically a sphere and not flat. And if you draw three lines beween three points on a saddle shape like a Pringles chip, you'll find that the angles add up to less than 180°.

Fun fact: topologically speaking, no matter how you fold or bend a sheet of paper, it remains flat. A cilinder is a flat surface with zero curvature!