Problem horizonta

When we look at the CMB it comes from 46 billion comoving light-years away. However, when the light was emitted the universe was much younger (300,000 years old). In that time light would have only reached as far as the smaller circles. The two points indicated on the diagram would not have been able to contact each other because their spheres of causality do not overlap.

Problem horizonta (also known as the homogeneity problem) is a cosmological fine-tuning problem within the Big Bang model of the universe. It arises due to the difficulty in explaining the observed homogeneity of causally disconnected regions of space in the absence of a mechanism that sets the same initial conditions everywhere. It was first pointed out by Wolfgang Rindler in 1956.

The most commonly accepted solution is cosmic inflation. Different solutions propose a cyclic universe or a variable speed of light.

Spoljašnje veze

• Different Horizons in Cosmology