The simplest answer is that there was no ‘before’ the Big Bang, for it marked the birth of both space and time. An idea put forward by Stephen Hawking and James Hartle, called the ‘no boundary’ proposal, states that, as we wind back the clock closer and closer to the Big Bang, time begins to lose its meaning and becomes more like a dimension of space. We therefore end up with smooth four-dimensional space at a point of the universe’s origin. So it is meaningless to ask what happened before the Big Bang, in the same way that it is meaningless to ask what point on the surface of the Earth lies
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