Science and music / [by Sir James Jeans].

  • Jeans, James, 1877-1946.
Date:
1947
Catalogue details

Licence: In copyright

Credit: Science and music / [by Sir James Jeans]. Source: Wellcome Collection.

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    I0^ THE VIBRATIONS OF AIR number of molecules which dart about to-and-fro at very high speeds, each moving in a straight path until it either collides with another molecule or runs into some solid object. When either of these events occurs, the molecule just bounces off and starts on a new path. The larger the molecules are, the more they will interfere with one another’s motion, so that we can measure their size by examining to what extent they inter¬ fere with one another. We find that they are of very different sizes, the simplest substances having the smallest molecules, as we might perhaps expect. The simplest and smallest of all molecules, the mole¬ cule of helium, which consists of a single atom, has a diameter of rather less than Fig. 39. The spring a hundred-millionth part of an inch. The of air can be tested in molecule of hydrogen, with two atoms, is or cafpump (dTed rather more than a hundred-millionth of atthe™ti«end). if an inch in diameter, while that of air down it bounces up is larger still. The molecules of water again, as though the /tt . piston were resting vapour (H20) and carbon dioxide (C02), on a spring. each of which contains three atoms, hive diameters of nearly two-hundred-millionths of an inch. Even the smallest particle of matter we can see must obviously contain an immense number of these excessively minute molecules; in actual fact, a tiny drop of water is found to contain millions of millions of millions. If the molecules of air in an ordinary room were put end to end they would form a chain which would go round the earth