Opposite sides of the universe have the same temperature,yet according to the standard Big Bang theory,these points are too far apart for light to have traveled from one side to the other in the age of the universe;that is,they cannot have exchanged heat to even out their temperature.Why,then,do they have the same temperature?
A) Light (and heat)could travel much faster in the early universe,allowing them to exchange heat while the universe was young.
B) The expansion of the universe has always been the same everywhere;therefore,all parts of the universe have the same temperature,regardless of whether they have ever exchanged heat or not.
C) Pure coincidence
D) They were originally close together and evened out their temperature,then a rapid inflation of the universe carried them far apart.

Question

Quizplus · Accepted Answer

The most widely accepted explanation for this phenomenon is that the opposite sides of the universe were once close enough to exchange heat and even out their temperature. However, during a period of rapid inflation early in the universe's history, they were quickly carried apart and became too distant for light or heat to travel between them. This phenomenon is known as the "horizon problem." Therefore, choice D is the best answer.

Opposite Sides of the Universe Have the Same Temperature,yet According