Hmm, it looks like (TFA author) Purcell's "Back of the Envelope" AmJPhys column, paywalled for decades by AAPT, is currently available online.[1] "a monthly fe

Hmm, it looks like (TFA author) Purcell's "Back of the Envelope" AmJPhys column, paywalled for decades by AAPT, is currently available online.[1] "a monthly feature [...] from January 1983 through July 1984. Three new "order-of-magnitude" problems were presented each month [...] there were 57 problems, the discussion of which fills something like 150 column-inches". Eg, the ratio of tide influence from Moon and Sun is 7/3, so what is the ratio of their mean density? [1] https://www.aapt.org/Publications/AJP/Readers/back_of_the_envelope.cfm https://www.aapt.org/Publications/AJP/Readers/back_of_the_en...