Le coeur a ses raisons, que la raison ne connait point, said Blaise Pascal, that Gallic polymath famous among meteorologists for having verified that atmospheric pressure falls and falls the higher up you go into the mountains: "The heart has its reasons, of which reason knows nothing." He was referring, of course to "the cruel madness of love", but as in so many facets of our lives, science may well have found the answer.
You may recall from Weather Eye a day or two ago that the earth's magnetic field changes in intensity as time goes by, as can be clearly seen in the records kept at geophysical observatories. This is partly because it is sensitive to variations in the "solar wind", the stream of electrically charged particles emanating continually from the sun. For example, sudden increases in this solar wind - solar "gusts", as it were - that occur unpredictably from time to time, are known to cause "magnetic storms" that drive magnetic compasses awry, and make radio communications subject to sudden interruption.
But the orientation of the earth in relation to the sun changes gradually with the seasons, and so too, therefore, does the angle at which the solar wind approaches us from space. This gives an annual rhythm to these variations in magnetic intensity, a rhythm which is most noticeable in very high latitudes within the Arctic and Antarctic circles. The magnetic index, as it is called, is high around the vernal and autumnal equinoxes, and at its lowest in June and December around the times of the summer and the winter solstices.
But now we come to the interesting bit. Studies of the Inuit peoples, who live in the extreme north of Canada, have apparently revealed that their conception rates vary rhythmically in a way that is similar to, but the inverse of, the change in the magnetic index. By examining the available records of births, and subtracting the required nine months, it has been found that over the past 75 years, conceptions have been relatively few in the weeks adjacent to the equinoxes, but rise gradually in number to reach noticeable peaks around June and late December.
Why this should be so, no one, as yet, has ventured to suggest. It is still a mystery as to how magnetics, terrestrial or otherwise, might affect our human inclinations or our success in reproductive matters.
But it must surely be an attractive area of investigation - in several different senses of the phrase - for a young geophysicist at a loss for material with which to fill his folder labelled "Research Undertaken in Pursuance of my Ph.D.".