The existence of mysterious relations between all these different domains is the most striking and delightful feature of mathematics (having no rational explanation).
Vladimir ArnoldHydrodynamics procreated complex analysis, partial differential equations, Lie groups and algebra theory, cohomology theory and scientific computing.
Vladimir ArnoldMathematics is a part of physics. Physics is an experimental science, a part of natural science. Mathematics is the part of physics where experiments are cheap.
Vladimir ArnoldAll mathematics is divided into three parts: cryptography (paid for by CIA, KGB and the like), hydrodynamics (supported by manufacturers of atomic submarines) and celestial mechanics (financed by military and other institutions dealing with missiles, such as NASA).
Vladimir Arnold