Rereading the lecture, I am struck by the restricted nature of the two cultures that interested him. It was as if literary intellectuals were a major force in society, and there should be concern that they did not understand the second law of thermodynamics.
Nowhere in his discussion do other "cultures" appear; there are no lawyers, bankers, politicians, sportspeople, artists, or members of the public at large. I also detect a sort of snobbery in his arguments, which closely reflects Oxbridge life.
The lecture is also deeply disappointing in the analysis as to why the apparent mutual incomprehension should exist, and all his evidence is no more than Oxbridge anecdote.
Nevertheless the idea of the two cultures has become synonymous with the problems associated with the public understanding of science. Taking a broader view than Snow, we can ask whether there is now, 40 years later, a better understanding of science by the public, always remembering that there is no one public. There are, in this sense, many publics, which range from children to members of parliament.
There is no good evidence on which we can base such a judgement, not least because it is hard to know what we mean by public understanding of science. It certainly does not mean the extent to which people understand the second law of thermodynamics. I have even been told by several distinguished physicists that they themselves find it very difficult to understand - a relief, as I myself do not understand it except at a superficial level.
There have been major changes, not least the whole idea of the public understanding of science, which came from a Royal Society report in 1985 chaired by Walter Bodmer. The report strongly encouraged scientists to interact with the public and to feel no shame in collaborating with the media.
Some measure of the possible progress stemming from that report is that the government-funded research councils now have as part of their mission statement that they should make their research accessible to as wide a public as possible.
There is also the recognition that scientists need to understand the public, particularly their concern about the applications of science.
Another sign of progress is the intense interest in popular science, though I do wonder if the interest is not possibly due to seeing science as a kind of magic, rather than a result of genuine understanding.
Have those million or so readers of Stephen Hawking's book, A Brief History of Time, learnt some physics? Snow missed, I think, an essential feature of science that can make it rather alienating, namely that the world is not built on a basis that fits with common sense, natural expectations. Much of public understanding of science is respect without comprehension.
Even the evidence that we rotate about the sun is hard to believe and to understand. The mechanism of the tides is no trivial matter; Galileo himself failed to solve the problem.
Even basic scientific ideas are not always common knowledge; some 30 per cent of the population believe that tomatoes do not contain genes or DNA unless they have been genetically modified. And I repeatedly find that those who are concerned about human cloning fail to recognise that the cloned child has a mother and a normal birth, and will have to go to school.
But what would I like non-scientists to know about science? That science is the best way to understand how the world works, and the nature of the evidence upon which it is based. For example, in medicine and health we must rely on clinical trials, not anecdote. But certainly not understanding the second law, or any other, as Snow would have liked.
The writer is professor of biology as applied to medicine at University College LondonReuse content