According to Our Modern Theories, the Geometry of the Entire

Multiple Choice

According to our modern theories, the geometry of the entire universe (all of space-time) may be curved or warped. This is a pretty bizarre notion; what other discovery in astronomy has helped us believe that space may be able to curve or warp?

A) supernova explosions and the elements they produce
B) how the light output of cepheid variables changes with time
C) the existence of dwarf elliptical galaxies
D) the properties of black holes
E) the error in the shape of the mirror on the Hubble Space Telescope