Fourier's theorem is not only one of the most beautiful results of modern analysis, but it may be said to furnish an indispensable instrument in the treatment of nearly every recondite question in modern physics.

Large increases in cost with questionable increases in performance can be tolerated only in race horses and fancy women.

There cannot be a greater mistake than that of looking superciliously upon practical applications of science. The life and soul of science is its practical application.

I can never satisfy myself until I can make a mechanical model of a thing. If I can make a mechanical model, I can understand it. As long as I cannot make a mechanical model all the way through I cannot understand.

[Of the ether] it is no greater mystery at all events than the shoemakers' wax.

To measure is to know.

There is nothing new to be discovered in physics now. All that remains is more and more precise measurement.