  A message of any sort can be regarded as a source of information. Claude. E.
Shannon showed in the last century that information ("what we don't already
know") is equivalent to the entropy as defined in statistical mechanics. A
string of experimental observations is like a succession of words; they both
convey information and can be characterized by their entropy. For the fluid
flow measurements and simulations to be discussed here (pipe and soap film
flow, GOY model), the entropy depends on controllable parameters such as the
Reynolds number. The information theory approach is applicable to measurements
of any type including those governed by intractable equations or systems where
the governing equations are not known. This contribution is dedicated to the
memory of Leo Kadanoff, an inspiring teacher and one of the most important
scientific leaders of the last half century.
