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 ([EMAIL PROTECTED])
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