Universe flatness On: https://en.wikipedia.org/wiki/Shape_of_the_universe
It is written:

"The exact shape is still a matter of debate in physical cosmology, but experimental data from various independent sources (WMAP, BOOMERanG, and Planck for example) confirm that the universe is flat with only a 0.4% margin of error. On the other hand, any non-zero curvature is possible for a sufficiently large curved universe (analogously to how a small portion of a sphere can look flat)."


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*I'm not really sure what it means: doesn't light bend near the sun (masses in general)?

*It's just the point of view that makes we see the light bending?

*Flatness means that general relativity doesn't work in an absolute way?

*General relativity is just a way of watching the universe: in order to see a curved line straight we see the sraight lines curved?

 A: There are a bunch of caveats to the statement about flatness, but to answer your questions:

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*This is talking about the overall, large-scale curvature of the cosmology, zoomed out so far that whole galaxies are points.  Any curvature due to objects like the sun is too small to matter on this scale.


*In general relativity, the fact that light rays bend is not a point of view thing.  The presence of curvature is locally measurable


*The flatness being discussed here is, again, an averaged out comsological flatness.  It's also worth saying that it is not the flatness of spacetime, but rather just of the three-dimensional spatial sections.  The spacetime is still curved.


*I don't understand what this means, but the point is that geodesics are not straight lines, they are the closest thing possible to a straight line in a curved geometry.  Just like how you could tell that you're not travelling in a straight line while moving on the globe, you can tell that your geodesic is not straight (at least when you compare it to nearby geodesics)
