starship-design: [Fwd: Spider-web sensor reveals a flat universe]

[Steve VanDevender <stevev@efn.org>]

Curtis Manges writes:
 > Well, folks, Earth may not be flat, but the universe apparently is. I'm
 > not sure what this means, but it's pretty cool.

This is a major item of debate in cosmology.  If the global curvature of
the universe (in the general relativistic sense of the overall curvature
of spacetime) is positive, then the universe is "closed", and the
current expansion of the universe will slow down, stop, and then reverse
towards collapse.  If the curvature of the universe is "flat", then the
universe will expand forever; if the curvature is negative, then the
expansion will accelerate.  Unfortunately it is not definitively clear
which of these cases is true.

Different attempts at estimating the expansion rate of the universe have
given different results.  Last year, another group said that the
measurements of the redshifts of very distant supernovae indicated that
the expansion of the universe was accelerating, meaning that the global
curvature would be negative.  So far estimates of the total mass in the
universe give a mass that is too small for positive curvature.