The bowler beats the bat and the ball hits the batsman’s pad.  There is a loud appeal and the umpire calls for ‘hawkeye’ to predict where the ball was going. Hawkeye is a system that tracks the flight of the ball and predicts, using the laws of physics, where the ball would have gone if the batsman’s pad had not got in the way.  The batsman’s innings depends on the prediction.Those same laws of physics and tracked trajectory of the ball can be run in reverse, to predict where the ball came from.  The prediction will be completely accurate back until the point when the ball left the bowler’s hand.  The prediction will extrapolate back a series of parabolas, to infinity.

It’s common sense.  Hawkeye makes valid predictions where the assumptions included in the model are correct.  But where the assumptions break down, the prediction will be wrong.  So it is with all science.  Where assumptions break down then science will be wrong.  We test our assumptions where we have data – back as far almost as the beginning of the universe, but we cannot test beyond there.  And so although science can make predictions of what was before the beginning of the universe, it would be wrong to believe them.  We have to accept that we don’t know, and can never know whether there was a ‘bowler’ or whether the ball came bouncing from infinity…

The headline of the following and similar articles are therefore completely misleading

Stephen Hawking Claims To Know What Happened Before The Big Bang

although the text is more accurate: “Hawking had previously said in one of his lectures that the events that occurred before the Big Bang have no consequences that can be observed, therefore they are not defined because there is no way to measure what happened…….  Even the amount of matter in the universe can be different to what it was before the Big Bang, as the Law of Conservation of Matter, will break down at the Big Bang.”  Hawking recognised that the laws of physics ‘change’ …. allowing the existence of the ‘bowler’.