At the time of the Big Bang, some 13.7 billion years ago, the entire universe was concentrated in a single point. This point had an extremely small size — much smaller than the size of any known particle — and an incredibly high density and temperature. The term “Big Bang” actually refers to the moment when the universe started expanding, as opposed to some kind of explosion as the event’s name implies.
Where in space did the Big Bang happen?
Brian McDonald, Walton Beach, Florida