Space‐charge wave

There is a good deal to physics besides nuclei, uncertainty, and relativity, as every hopeful student learns. Much of it, however, has disappeared from the forefront of science, some of it moving to the engineers, and the rest remaining mostly a storehouse of tools, useful in the free‐for‐all attack on the current frontier. I can remember that spectroscopy was once a romantic subject, with its explanation of the “nebulium” lines. So was the conduction of electricity through gases.