Every physical measurement is a temperature measurement if your lab instrument is precise enough.
@niconiconi Do you know if we actually have temperature sensors that measure resonant frequency (and make use of thermal expansion's effect on sizes, which affects the frequencies)?
@robryk@qoto.org Yes. You can measure temperature by observing a crystal oscillator's frequency drift (with a known reference clock). Hewlett-Packard made this lab instrument in the 1960s, with a resolution of .0001”C. AFAIK it's still a really precise method by today's standard, but it went out of favor as the crystal needs to have a special cut with linear temperature coefficient. See HP Journal Vol. 16, No.7, 1965. http://hparchive.com/Journals/HPJ-1965-03.pdf Linear Technology App Note 61 shows how to build your own, see page 13: https://www.analog.com/media/en/technical-documentation/application-notes/an61fa.pdf
Fun fact: This phenomenon has been used as a deanonymization attack against Tor. By observing the 24-hour drift of the system clock, one can determine the longitude of the target server, latitude can further be determined by the change in day length. https://www.freehaven.net/anonbib/cache/HotOrNot.pdf
@niconiconi I wonder if someone used purposefully-badly-compensated (for lengthening of the pendulum) grandfather clocks to compute average temperatures over longer periods of time.
