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/sci/ - Science & Math

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10809422 No.10809422 [Reply] [Original]

If space is flat how come we can move up and down in it?

Checkmate, scifags.

>> No.10809444

>>10809422
>1 in Euclidean space
It isn't sectional and it isn't Ricci.
Do any physics autists know what omega 0 is?

>> No.10809520

>>10809444
what the fuck is omega 0 ?

>> No.10809568

>>10809444
>>10809520
it's basically the curvature. you can think of omega_0=1 meaning that a triangle has 180 degrees if you sum its internal angles, but omega_0>1 means a triangle has more than 180 degrees and omega_0<1 means a triangle has less than 180 degrees.

sort of like if you walk on a sphere from the equator to the north pole, turn 90 degrees and walk to the equator, then turn 90 degrees and walk back to where you started, you made a triangle with 270 degrees because you're on a curved surface

>> No.10809570

>>10809422
WELL ITS 3D

>> No.10809572

>>10809568
Is it literally the sum of the angles of an equilateral triangle with side one over 180 degrees?

>> No.10809575

>>10809568
I know what curvature is. What's the definition?

>> No.10809579

>>10809572
>local man who thought he knew a wee lil bit of Riemannian finds out he knew less than nothing
>>10809575
Here you go https://en.wikipedia.org/wiki/CAT(k)_space

>> No.10809590

>>10809579
not a single mention of omega zero

>> No.10809599

>>10809422
Flat doesn't mean two dimensional.

>> No.10809737

>If space is flat how come we can move up and down in it?
no, you can't, don't even try

>> No.10810065

>>10809444
Omega 0 is the density parameter.
The 0 denotes that is is the one we measure today (not that important though, since the difference 1-Omega doesnt change sign, so the different regimes in the picture stay distinct ).
Different density parameter are usually calculated for different types of energy/matter, this one is all of these together minus the curvature term. So it does indeed determine the curvature of the universe.
See here: https://en.wikipedia.org/wiki/Friedmann_equations#Density_parameter

or Mukahonvs "Physical Foundations of cosmology" page 10/11 (he refers to it as cosmological parameter).

>> No.10810165

>>10810065
Thanks, lad.