My father used to hang a chain which dragged along the road from the back of our car. He said it would prevent my sister from getting car sick. I thought it was some kind of placebo effect but later I discovered that my husband鈥檚 family did this for their car-sick dog. Does it work and, if so, how?
鈥� The use of chains to cure car sickness is an example of pseudo-science based on a fundamental misapprehension of the real cause of the complaint.
鈥淐hains on cars are an example of pseudo-science based on a misapprehension of the cause鈥�
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Car sickness, like other forms of motion sickness, is caused by a conflict between the perception of movement by the eyes and that sensed by the vestibular system of the inner ear. In the case of car sickness, the nausea can be exacerbated by feelings of claustrophobia, unpleasant smells, overeating or lack of ventilation 鈥� all classic causes of nausea in their own right, of course.
However, it was once widely believed that the cause of car sickness was undischarged static electricity, generated by the friction between the car鈥檚 tyres and the road. A car is essentially a metal box insulated from the ground by its rubber tyres, which is why you are generally safe from a lightning strike if you鈥檙e sitting in one with the doors closed; to put it technically, the car body acts as a . This led people to believe that car sickness might be relieved by discharging the static via a conductive chain linking the chassis to the ground.
Static discharge chains have long been used by tankers delivering petrol. Any residual charge in the vehicle could create a spark when its delivery hose was brought close to the filling station鈥檚 storage tank, so it became a safety requirement that the chain be lowered to eliminate the charge before any fuel was pumped into the tanks. The theoretical risk of an electrical discharge causing an explosion at petrol pumps is also the reason that mobile phone use is banned at filling stations.
The chains on tankers, however, were far more substantial affairs than the flimsy aluminium-and-rubber versions sported by many cars between the 1960s and the 1980s. Even if there had been any validity to the theory (except in terms of profit for the suppliers who sold them to gullible motorists), any beneficial effect would have been mitigated as soon as the car built up speed, and the chains were inevitably lifted off the ground by the slipstream to leave them waggling forlornly in mid-air.
Hadrian Jeffs, Norwich, UK