Big Bang is a past horizon, though in practice our view is also limited by the opacity of the universe at early times. So our view cannot extend further backward in time, though the horizon recedes in space. If the expansion of the universe continues to accelerate, there is a future horizon as well. English astronomer Fred Hoyle is credited with coining the term "Big Bang" during a 1949 BBC radio broadcast, saying: "These theories were based on the hypothesis that all the matter in the universe was created in one big bang at a particular time in the remote past." It
Chronology of the universe Bang cosmology immediately after the event which began our known universe. During this epoch, the temperature and average energies within the universe were so inconceivably high compared to any temperature we can observe today, that everyday subatomic particles could not form, and even the four fundamental forces that shape our universe—electromagnetism, gravitation, weak nuclear interaction, and strong nuclear interaction—were combined and formed one fundamental force. Little is understood about physics at this temperature; different hypotheses propose different scenarios. Traditional big bang cosmology predicts a gravitational singularity before this time, but this theory relies on the theory of general relativity, which