During the recent total solar eclipse in the US, I overlapped my hands, using the gaps between my fingers to form 鈥減inholes鈥�. Just before the start of totality, someone noticed that the shadows formed through this 鈥減inhole camera鈥� onto a white board were so sharp that the individual hairs on my arms were visible. How thin must the solar crescent be for the shadows to be this sharp, and how soon before totality would this occur?
Herb Petitjean, Versailles, Kentucky, US
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