On Radio 4's Today programme this morning there was a debate between a pair of scientists about the amount of sunlight we should be exposed to (audio clip here). Everyone knows that UV light can cause skin cancer, but apparently people are now avoiding sunlight so much that we are in danger of becoming Vitamin D deficient. Vitamin D is apparently good not only for fixing calcium in our bones, but also for helping our bodies' own defences against cancer.
The trouble was that neither of the scientists on the programme really got to grips with the other's argument. So instead of a constructive and instructive discussion, we had a situation where two people simply repeated, over and over, a single point. Both of them were exaggerating the other person's position in order to make theirs look like the only reasonable choice. This is not good argument, and it is certainly not good science.
The worst of it is that the two weren't actually all that far apart. One was saying that we need three to five minutes a day of direct exposure to sunlight to make enough Vitamin D. (He didn't make clear whether this was supposed to be whole body exposure or whether face and hands alone would do.) The other was saying that we need to be careful to avoid overexposure for fear of getting skin cancer. I don't really see how these two are at all contradictory. Assuming all you need to show is your face and hands, you'll get more than enough exposure just walking to the shops. I am so fair-skinned that I have been known to get sunburn on a cloudy day. So I tend to avoid the sun. Nevertheless I'm sure that on average I get more than three to five minutes a day. At least in the summer, anyway. I really don't think there's many people so scared of cancer that they run out to the car on a sunny day with a newspaper over their heads, nor so desperate for Vitamin D that they lie out in the sun all day long, risking sunburn and skin cancer, to make sure they get it.
But one scientist accused the other of wanting people to throw away their suncream, and the other accused him of expecting them to lock themselves away in the cellar. The problem is really the irresponsibility of this unwillingness to acknowledge the other. The enire basis of scientific enquiry surely falls down if we cannot bear to take account of the criticism of others. (Can anyone spell "peer review"?) Science is supposed to be a discipline of reason. Scientists must therefore behave in a reasonable manner, or how can we believe what they say?