I had to smile. I am standing in a circle with Prof Jim Al-Khalili and others, discussing the new findings about the big bang. To be honest, my head doesn't really get itself around gravitational waves at the best of times, but before breakfast it's all too much. But then comes a moment of insight. Someone asks Al-Khalili – a professor of theoretical physics – what came before the big bang. What caused the cause of all things?

His answer is clever but unsatisfying. It's like asking what is south of the South Pole, he says. In other words, it's a mistaken question. Why the smile? Because, say, a hundred years ago, these questions would have been asked of theologians – if God created everything who created God? And, of course, we had no answer either. Or gave some similarly evasive version of the South Pole answer. But now that people don't care what religion has to say, it is physicists who are facing a very similar interrogation. My smile was … good luck, mate. Over to you. And what made the situation even more delicious was that Al-Khalili is also now president of the British Humanist Association. We are turning our physicists into theologians – even the atheist ones. What are gravitational waves, I ask my scientist friend Adam Rutherford. "Think of them as divine burping," he says.

It seems odd to argue that science is long behind the curve, and way behind theology, but when it comes to cosmology it feels very much like that to me. It's not that I think what they say is untrue. Science is better at dealing with truth questions than theology. Rather, I think that it doesn't much matter existentially. At least, I can't see how something that happened 13bn years ago helps me understand anything about what I am up to this morning. The theologian Dietrich Bonhoeffer had this one right back in the 1940s: "How wrong it is to use God as a stop-gap for the incompleteness of our knowledge. If in fact the frontiers of knowledge are being pushed further and further back (and that is bound to be the case), then God is being pushed back with them, and is therefore continually in retreat. We are to find God in what we know, not in what we don't know."

Likewise, there is no answer to the meaning of life hidden behind an exploding gas of atoms. So why do the Sheldons of this world persist in aping the theologians and looking for deep meaning in so distant a place? It's not just that there is no God of the gaps – there is no ultimate meaning in the gaps either. Neither science nor theology can provide any sort of answer by looking in this non-place. But the popular imagination still assumes that there is something about cosmology that is a big deal for the human condition.

Those scientists who stick to the more prosaic certainties of the scientific method resist the temptation to speak loosely about knowing the mind of God. Of course, some will say that these are just lively metaphors. Well, hello. That's precisely what theologians have been saying about their language for years. What is so amusing about the current interest in popular science is that we too often assume it has come to replace theology as a way of answering ultimate questions. And the problem with this assumption is that turns scientists into the very thing they were supposed to be replacing. The best of them stick to the cool reason of experimentation. But at the point where science bleeds into metaphysics, some have started sounding surprisingly like Thomas Aquinas banging on about the "uncaused cause".