Levy distributions have the elegant property that we now call "selfsimilarity." Price changes in longer time periods are simply the sum of changes in shorter time periods, and Levy distributions are invariant under addition. If changes in short time periods were independent and all followed the same Levy distribution, then so would changes over longer periods. The "scale" used in the analysis time periods of a minute, an hour, a day, a week, a month, a year would therefore not matter: the form of the distribution would be unchanged.

Donald MacKenzie, An Engine, Not a Camera, loc. 492