OIL CRACKS |
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There are many words
of long standing which the scientist has been accustomed to use with
a meaning that might or might not be the same as its customary one.
Sometimes he restricts the meaning of the word. The physicist adopted
the word "current" when he described the changed properties
of a wire connected to a voltaic battery as an electric current.
In 1827, G. S. Ohm discovered the constancy of the relation between
electromotive force and current and gave the ratio the name of "resistance".
Sometimes, a scientist will take an ordinary word and expand or widen its
meaning, so that a single thing gives its name to a group or category.
"Salt", for example, is a material that is essential for human
beings and animals, and has a long association with social history.
Its name appears in the English language in such a word as "salary",
meaning that the money one earns is meant, in the first turn, for buying
what Is most necessary for human existence.
The chemist, however, uses the word to denote a class of compounds, which
he defines as the products of replacing the hydrogen of an acid, wholly
or in part, by a metal. Common salt is a compound which comes only
to a limited extent within the terms of this, definition and only to this
limited extent do these two salts mean the same thing.
Sometimes, a scientist will seize a word and force it to do work for
which it has no qualifications. Such is the case of a family of related
words - "force", "work", "power" and "weight".
In mechanics, force does not mean strength. It seems to say no
more than that a force is a push or a pull, and since in physics all things
must be measured it acquires, from Newton's Law of Motion, a quantitative
sense, which makes it the product of mass and acceleration. This,
of course, is quite different from anything that the word "force"
implies in everyday use.
A weight, one is surprised to learn, is not only the familiar block
of metal with a ring on top, but a force. This is logical, because
things fall under their own weight with an acceleration (due to gravity),
so that the weight of a thing has to be the force with which the Earth
attracts it.
As to "work", the physicist has decided that a force
works, or does work, only when it moves something. I may push and pull
in vain at some immovable obstacle, and find that, nevertheless, mathematically
I have done no work.
After this, it is quite easy to accept the idea that power has
come to mean the rate at which work is done; or that metals suffer from
"fatigue", or that oils can be made "to crack".
