Hannes Alfvén was a Swedish electrical engineer and plasma physicist. This paper helds the record for being the shortest paper to directly lead to a Nobel Prize. In 1942, Hannes Alfvén combined the equations for fluid mechanincs and electromagnetism to predict that plasmas could support wave-like variation in the magnetic field, a wave phenomenon that now bears his name - Alfvén waves. This would become the foundational paper for the study of magneto-hydrodynamics, or MHD, for which Alfvén would receive the Nobel prize in 1970. This is also the only Nobel Prize ever awarded in the field of plasma physics.  This paper was published right in the middle of World War II - the day Stalin's and Hitler's armies were fighting brutally at Stalingrad and Allied forces in North Africa were preparing to attack their adversaries near El Alamein.  Hello. This is a comment. I can write math like $\sqrt{5}$. It's amazing that Alfvén's original derivation that led to his Nobel Prize (a uniform magnetic field in the z-direction, a static equilibrium, and an incompressible perturbation of velocity in an invariant x-direction) is still taught today in most MHD courses around the world. Alfvén's attempt to explain sunspots as manifestations of MHD waves propagating up from the deep interior failed. It was only in 1948, 6 years later, that during a lecture in Chicago things changed for Alfvén waves. Enrico Fermi was in the audience and asked Alfvén to explain his ideas about MHD waves: 'Fermi listened to what I said about them for five or ten minutes, and then he said: "Of course such waves could exist." Fermi had such authority that if he said "of course" today, every physicist said "of course" tomorrow. Actually, he published a paper in which he explained them in such a clear way that no one could doubt their possible existence.' Fermi's paper was titled 'On the Origin of the Cosmic Radiation', in which he explained that the origin and acceleration of cosmic rays was linked to Alfvén waves.