> What many don’t realize is that the double slit experiment (with particles), proposed by Feynman in 1963, was for decades only a thought experiment. Finally, in 2013, it was successfully performed with electrons.
Total crackpot, electron diffraction was observed in 1927 by several different groups of people[1][2] some of them who later in 1937 shared the Nobel Prize in Physics[3].
[1] http://www.nature.com/nature/journal/v119/n3007/pdf/119890a0...