and Rudolph Franz (1826–1902). Wien's displacement law states that the black body radiation curve for different temperatures peaks at a wavelength inversely proportional to the temperature. Named for Wilhelm Wien. (See also Wien approximation.) Wiio's laws: The fundamental Wiio's law states that "Communication usually fails, except by accident". Wike's law of low odd primes: "If the number of experimental treatments is a low odd prime number, then the experimental design is unbalanced and partially confounded." Winter's law: A sound law operating on Balto-Slavic short vowels. Named after Werner Winter Wirth's law: Software gets slower more quickly than hardware gets faster. Wiswesser's rule gives a simple method to determine the energetic sequence of electron shells. See also Aufbau principle. Wolff's law: Bone adapts to pressure, or a lack of it. Woodward–Hoffmann rules, in organic chemistry, predict the stereochemistry of pericyclic reactions based on orbital symmetry. Wright's law also known as Experience curve effects was probably first quantified in the industrial setting sometime in 1936 and postulates that as production doubles the cost of production will decline by a constant percentage. Named after aerospace engineer Theodore Paul Wright (no relation to the Wright brothers) who was working for Curtiss-Wright aircraft during explosive growth in the "Golden Age of Aviation". Yao's principle, in computational complexity theory: the expected cost of any randomized algorithm for solving a given problem, on the worst case input for that algorithm, can be no better than the expected cost, for a worst-case random probability distribution on the inputs, of the deterministic algorithm that performs best against that distribution. Named for Andrew Yao. Yerkes–Dodson law, an empirical relationship between arousal and performance, originally developed by psychologists Robert M. Yerkes and John Dillingham Dodson. Zawinski's law: Every program attempts to expand until it can read mail. Those programs which cannot expand are replaced by ones which can. Zeeman effect: Splitting of a spectral line into several components in the presence of a static magnetic field. Zipf's law, in linguistics, is the observation that the frequency of use of the nth-most-frequently-used word in any natural language is approximately inversely proportional to n, or, more simply, that a few words are used very often, but many or most are used rarely. Named after George Kingsley Zipf (1902–1950), whose statistical body of research led to the observation. More generally, the term Zipf's law refers to the probability distributions involved, which is applied by