The Manga Guide to Relativity

40 Chapter 1

What Is Light?

Maxwell’s equations tell us that light is an electromagnetic wave. The color of light is

determined by the wavelength of the electromagnetic wave. Red light has a wavelength

of 630 nm, and blue light has a shorter wavelength of approximately 400 nm, where

one nanometer (1 nm) = one billionth of a meter (10

–9

m). Electromagnetic radiation at

different wavelengths takes many forms, such as radio waves, X-rays, and gamma (γ) rays

(see Figure 1-1).

Although light may seem common enough—it is all around us, after all—it is fun-

damental to both relativity and quantum theory, the cornerstones of modern physics.

But befor