We all just enjoyed the detection of gravitational waves due to two colliding black holes.聽 David Ritz Finkelstein, who passed away in January, was the first, in 1958, who identified Schwarzschild's solution of the GR equations as corresponding to a region in space from which nothing escapes.聽 This compelled Penrose and Wheeler to believe that those things actually do exist.聽 He is of course also known for the related Eddington-Finkelstein coordinates.
Personally I first met David Finkelstein, not in a Black hole, but in Prague, in 1994 at a quantum structures conference.聽 David's main concern had always been the fundamental structures of nature, for quantum theory, for GR, and even more so, for the two together.聽 He indeed very early on accepted von Neumann's concern that something is fundamentally wrong with Hilbert space.聽 This was the start of a quest in a world of exotic structures, and his travels have inspired many scientists, and continue to do so. Among many others, this includes quaternionic quantum theory and quantum sets.聽 David was a proper maverick scientist, and this statement is intended in entirely positive terms. Not only his outstanding intellect, but also his integrity and generosity where exceptional.
But he was a lot more than that.聽 The second time I met him was in 1997 in Atlanta Georgia, where he lived and was hosting a meeting again on quantum structures.聽 In the weekend he took some friends and me out to the movies, to watch Seven Years in Tibet.聽 A bit cheeky that was, since he was to meet the Dalai Lama two days after.聽 Indeed, David was for a while the Dalai Lama's physics teacher.聽
The last time I met David Finkelstein, in 2014 in Cambridge, was at a meeting dedicated to Eddington.聽 During the conference dinner I had geared up for producing a wall of electronic noise and guitar distortion, with Ian Durham featuring on harmonica.聽 Not surprisingly, we successfully emptied the senior common room where the conference dinner had taken place, with one notable exception.聽 David Finkelstein, then 84 years young, was still there and clearly enjoying it.聽 He later explained that he always has had an interest, not surprisingly, in experimental music and other weird stuff.聽 More generally, David had a great interest in art, history, and many other things, and their interwovenness with science.聽 Why not have a look at David Finkelstein's analysis of Albrecht Durer's engraving MELENCOLIA I, that can be found on the arXiv.
A truly original thinker, and equally so, a truly original human has passed away.聽