"The area of turbulence is one of the most challenging research fields in modern science that, despite remaining unsolved, has led to many new innovative concepts and new research fields in a number of disciplines."
"I became interested in turbulent liquid and gas flows at the end of the thirties. From the very beginning it was clear that the theory of random functions of many variables (random fields), whose development only started at that time, must be the underlying mathematical technique. Moreover, I soon understood that there was little hope of developing a pure, closed theory, and because of the absence of such a theory the investigation must be based on hypotheses obtained by processing experimental data."
 By Konrad Jacobs (http://owpdb.mfo.de/detail?photoID=7493) [CC BY-SA 2.0 de (http://creativecommons.org/licenses/by-sa/2.0/de/deed.en)], via Wikimedia Commons