|MadSci Network: Science History|
Galileo discovered sunspots by looking at the sun through his telescope. Unable to leave well enough alone, he continued to look at the sun through his telescope, until he finally went blind.
This, at least, is the most plausible explanation; I suppose there might have been some of it in his family. He was around 55 or 60 when he went blind.
We received the following additional answer:
Galileo's blindness was certainly NOT due to his solar observations, which he made in 1613. A quarter of a century later, he became blind from cataracts and glaucoma, at the age of 72 (NOT "55 or 60").
This matter was well discussed by a professor of ophthalmology
-- see http://mintaka.sdsu.edu/GF/reading.html#Mulder
for the reference. Galileo's solar observations were made near sunset, when it is quite safe to look at the Sun, even through optical instruments.
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