"Right" answers are the origin of the specious

Newton Cartoon

Despite learning no useful physics at all as a student in the early 1980s,I did pick up some top tips about the scientific process which I remember to this day.And chief among these is to be wary of getting the right answer by the wrong means. I still cringe at how I succeeded in convincing my room-mate and fellow physicist to go along with some quite specious explanation of an experimental result by my constant refrain of "Well,it gives the right answer,doesn't it?"

As it turned out,not only was my explanation the purest twaddle,but so was the "answer" it was supposed to account for. The experience did at least teach me that while bogus explanations often reveal themselves by failing to match reality, they don't always: sometimes they can do a worryingly convincing imitation of the genuine article.And such specious success can go unchallenged for years.

Take the attempts of astronomers to understand the Moon's orbit around the Earth.Reputedly the only problem that ever made Isaac Newton's head ache,Lunar Theory is notoriously complex,with a host of subtle effects demanding explanation.One such emerged in 1749,when Richard Dunthorne of Cambridge University reported that ancient accounts of eclipses pointed to a gradual speeding up of the Moon in its orbit.The acceleration was extremely small - a speed increase of about 0.00001 mph over a century - yet is explanation posed a major challenge.

In 1786,the brilliant French astronomer Pierre de Laplace announced that he had found the cause : the pull of the other planets on the Earth.This changed the orbit of the Earth around the Sun,thus altering the Sun's influence on the Moon - which duly accelerated. Laplace estimated the acceleration,obtaining a figure very close to that found by Dunthorne.Everyone cheered,and went home.

And so matters stood for the next 60 years,until the Cambridge mathematician John Couch Adams looked again at the problem,and found Laplace's theory could explain barely half the troublesome acceleration.Academic uproar followed,with some astronomers insisting that the old explanation must be right,because it "gave the right answer". We no know that both the figure and the acceleration and Laplace's explanation of it are wrong (the actual cause lies in the effect of the tides),but for years no one seriously questioned either.

For the past few months,a similar controversy has been running in the pages of Physics World over a more down-to-Earth matter; whether wearing a magnetic bracelet offers any health benefits.Many scientists would simply scoff at the idea,but it takes a physicist to come up with a natty demonstration that such bracelets are,at best,placebos. In the January issue of the magazine,Robert Park,of the University of Maryland,highlighted the feeble nature of the magnets involved by pointing out that just a few sheets of paper slid under them was enough to stop them sticking to a fridge door.How,then,might they be expected to penetrate the much thicker layers of the skin?

The following month,however,a reader wrote to Physics World pointing out that this was the right demonstration of the wrong phenomenon.All Park's experiment proved was that a few sheets of paper were enough to cut the magnetic field to levels where the magnet could not support its own weight.But,the reader asked,so what? perhaps much weaker fields could still bring health benefits. A likely story,one might think.Yet a letter in this month's Physics World moves the debate on still further.Two researchers from the University of Zaragoza, Spain,cite experimental evidence that modest magnetic fields do indeed affect living creatures.Indeed,they suggest red blood cells can be affected by relatively feeble magnetic fields,producing changes in blood flow and skin temperature.

So it now seems tat not only was Park's debunking" experiment ill-conceived,but that the "right answer" it was designed to demonstrate - that weak magnetic fields cannot bring health benefits - may also be wrong. Until a natty debunking experiment does emerge,I suppose I should take the many personal testimonies I've heard on the efficacy of these bracelets at face value.But I can't help but recall another scientific top tip I learned some years ago: that the plural of "anecdote" is not "data".
Robert Matthews





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Sunday Telegraph 12 Mar2000 File Info: Created Updated 24/4/2001 Page Address: http://www.fortunecity.com/emachines/e11/86/rightans.html