The observable universe consists of the galaxies and other matter that can, in principle, be observed from Earth at the present time because light and other signals from these objects have had time to reach Earth since the beginning of the cosmological expansion. Assuming the universe is isotropic, the distance to the edge of the observable universe is roughly the same in every direction. That is, the observable universe is a spherical volume (a ball) centered on the observer. Every location in the Universe has its own observable universe, which may or may not overlap with the one centered on Earth.