Eleanor Catton, of Ilam School, asks :-
Why did the big bang happen?
Frank Andrews, an Astronomer at the Carter Observatory, Wellington, responded.
Your question cannot yet be answered satisfactorily. The trouble is that we cannot go back before the Big Bang to see what happened. Currently scientists think that they can study the universe back to just the smallest fraction of a second AFTER the Big Bang.
The principle areas of science which deal with studies of this kind are called PARTICLE PHYSICS, which studies the most basic building blocks of matter and energy, and QUANTUM MECHANICS which help us understand how these building blocks behave and interact with each other. The Big Bang not only created everything that is in the universe, but it also created space and time. Because time starts at the instant of the Big Bang, it is not possible to talk about what happened before the Big Bang because time did not exist, nor did space. In a way, it's like asking what is outside the universe. If the universe is absolutely everything that exists or can exist, then we can't talk about anything as being outside or before the universe.
At present scientists sometimes wonder if the universe just came into existence by pure chance. Maybe it didn't have a cause. Some scientists think that chaos theory, a fairly new way of thinking about some of these things may one day help us understand what initiated the Big Bang.