[FRIAM] models and magnetism

[Nicholas Thompson]

Hi Hywel, hi Frank.  

I took a little time to search for "data" on my raving that Newton must have used  magnets as a model for his theory of gravitation.  My hypothesis was that Newton  played with magnets as a kid.  To me, the term "mathematical model" is a bit of a misnomer because,  while models can be mathematized, a model is at is core a metaphor to some concrete, tangible, denotable experience that the modeler has had.  Thus, a model train in the hands of a child provides the best metamodel  for a scientific model.  By the way, although the best models are explicit, models can -- and very often are -- implicit, revealed by the words one uses to descibe a phenomenon, as, when one says that a particle has "wants".  

Was I correct?  Well, more or less.  Steel magnets, bar magnets, etc., seem to come after newton, not precede him.  However, lodestones, as objects of curiosity, date from 600 BC.    By the 12 century AD, people were using them to magnize needles which could then be floated on water so that they always pointed north.  Compasses were made in that way, early on.  Also, people were from classical times rubbing amber , glass and other substances with furs and cloths to produce objects that attracted and repelled other objects.  I am guessing that given Newton's time, he was strongly influenced by William Gilbert.  Below is a description of Gilbert's role which I gleaned from the website,  http://www.rare-earth-magnets.com/magnet_university/history_of_magnetism.htm

thanks, all, for a stimulating discussion.  

Nick 

1600 - Static Electricity (De Magnete)
 In the 16th century, William Gilbert(1544-1603), the Court Physician to Queen Elizabeth I, proved that many other substances are electric (from the Greek word for amber, elektron) and that they have two electrical effects. When rubbed with fur, amber acquires resinous electricity; glass, however, when rubbed with silk, acquires vitreous electricity. Electricity repels the same kind and attracts the opposite kind of electricity. Scientists thought that the friction actually created the electricity (their word for charge). They did not realize that an equal amount of opposite electricity remained on the fur or silk. Dr. William Gilbert, realized that a force was created, when a piece of amber (resin) was rubbed with wool and attracted light objects. In describing this property today, we say that the amber is "electrified" or possesses and "electric charge". These terms are derived from the Greek word "electron" meaning amber and from this, the term "electricity" was developed. It was not until the end of the 19th century that this "something" was found to consist of negative electricity, known today as electrons.
Gilbert also studied magnetism and in 1600 wrote "De magnete" which gave the first rational explanation to the mysterious ability of the compass needle to point north-south: the Earth itself was magnetic. "De Magnete" opened the era of modern physics and astronomy and started a century marked by the great achievements of Galileo, Kepler, Newton and others.
Gilbert recorded three ways to magnetize a steel needle: by touch with a loadstone; by cold drawing in a North-South direction; and by exposure for a long time to the Earth's magnetic field while in a North-South orientation. 






Nicholas S. Thompson
Emeritus Professor of Psychology and Ethology, 
Clark University (nthompson at clarku.edu)
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