Tommy asked:

What exploded in the ‘Big Bang’ and what caused ‘it’ to explode?

Answer by Tony Fahey

The big bang theory is an attempt to explain what happened at the very beginning of our universe. Although many astronomers and physicists agree that our universe did in fact have a beginning, and that beyond that there was nothing, for me, Stephen Hawking, in his A Brief History of Time, takes a more reasonable approach to this debate when he says, ‘…even if there were events before the big bang, one could not use them to determine what would happen afterward, because predictability would break down at the big bang’. (1998, p.49). In other words, we cannot say with certainty that there was nothing before the big bang, only that if there was, we cannot know anything about it.

Anyway, the standard big bang theory argues that our universe sprang into existence as a ‘singularity’ around 13.7 billion years ago. A ‘singularity’ is a term used by mathematicians to describe how the general theory of relativity predicts that there is a point in the universe where the theory itself breaks down. Bill Bryson, in his A Short History of Nearly Everything, gives us some idea of a singularity when by comparing it to the size of a proton. The proton, he says, is so small that a dib of ink on the dot of an ‘I’ can hold something like 500,000,000,000 of them. Now if we want to compare this to the size of a singularity we must reduce the proton down to a billionth of its normal size into a space that would make the proton look enormous. (see 2003, p.27)

Thus, with regard to the first part of the above question: ‘What exploded in the ‘Big Bang’?’, we can say that what exploded to cause the big bang was a ‘singularity’. However, it should be pointed out that many experts, rather than holding that there was a single blinding explosion, say that it was (and continues to be) more an expansion than a sudden ‘big bang’. It should also be said that big bang theorists argue that the singularity did not appear in space; rather that space, as did time, began with the big bang.

With regard to the second part of the question, whilst experts insist that we can know, with some certainty, that the big bang, and the events that occurred thereafter, arose as a consequence of the explosion of the singularity, since prior to the big bang, nothing existed: neither space, time, energy, nor matter, they are forced to concede that we simply cannot say what caused ‘it’ to explode.