I am not the first to doubt that Enrico Fermi would make the much discussed ‘mistake’ on the blackboard shown in the 1991 US stamp (Figure 1). In a letter to Nature in 1992, Richard Garwin wrote “...it is difficult to believe that Fermi could have written it...”, and then goes on to write “The most probably explanation is that Enrico Fermi, a great physicist, both in theory and experiment, and a man full of fun and humour, was having a little fun with the photographer.”[2]. In a Symposium on Fermi in 2001, Jim Cronin suggested that ‘”He might have been pulling our leg”[1].
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However, I have not been able to think of a physical process or object that the diagram describes. While striking and appealing, I think it too is a subtle but, with some thought obvious, ‘mistake’. My hypothesis is that this too is a witty protest– Fermi was told to draw a diagram as well as write some equations on the board, and he drew a picture that has no basis in physics. I personally think it is a brilliant response to a spur-of-the-moment need in its clarity and appeal [5]
