The origins of the belief that cows lie down when it is going to rain"

You will probably be aware of the superstitious belief that if cows lie down, it is a sure sign that rain is on the way. You will probably be unaware of the solid scientific basis behind this belief.

If you inspect a cow's legs, to the naked eye they seem much like yours, or mine in that they appear to be a flesh covered bone encased in skin. Under the microscope though, the subtle but all important differences are made clear.

The cow's leg is actually a micro-porous structure. It has the ability to absorb large quantities of moisture very rapidly. When rain is imminent, the relative humidity levels increase, thus the air is holding much more moisture. Consequently, the cows legs absorb this moisture and, as with most substances when soaked in water, begin to soften. Eventually, enough moisture will be absorbed to soften the cow's legs beyond the point where they can still support the weight of the cow, and it will have no option but to lie down just before this point, or fall down. Shortly after this time, relative humidity levels will reach the point where rain will begin to fall.

'Hang on' I hear you say, 'I've seen cows crossing streams, or standing in boggy ground. Explain that away Mr Clever-clogs!' Well, my friend, the explanation lies in the nature of micro-porous substances. While the cow's legs are highly absorbent of moisture at a microscopic level, macroscopic quantities of water will be washed straight over the legs in much the same way that dry baked ground, whilst being absorbent, will allow a heavy downpour to run off the surface rather than soaking in.