Douglas Hofstadter, a physicist and Pulitzer Prize-winning author, first predicted the existence of the butterfly in 1976, when he imagined what would happen to electrons subjected to two forces simultaneously: a magnetic field and the periodic electric field.
The energy spectrum, or pattern of energy levels, that these dueling forces create is said to be "fractal," that is, infinitely smaller versions of the pattern appear within the main one. This effect is common in classical physics, but rare in the quantum world.
"When you plot the spectrum, it takes on the form of a butterfly. Zoom in on the spectrum and you see the butterfly again, zoom in and see butterfly again," said Professor Dean. The light and dark sections of the pattern, respectively, correspond to light "gaps" in energy level that electrons cannot cross and dark areas where they can move freely.