Just what the question asks. Assuming the Friedmann-Rovertson-Walker (FRW) metric, what measurements can be performed to determine the spatial curvature of the universe.
I know that by using Boltzmann equation and all that one can calculate that photons become decoupled around T~3000K and because temperature scales as T~1/a we can determine that the redshift of the ...
Why there is a straight line (or perhaps a flat surface) in the middle of the Planck full sky map? and zoom (it makes it seem that the big bang was a collision between two unknown surfaces)