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Dolbear’s Law

Posted Jan 23rd 2017 by

How hot is it? Ask a Cricket!

Did you know that snowy tree crickets can help you accurately determine the temperature outside?

Back in the 1890s Amos Dolbear, a noted American Physicist and Inventor, discovered the relationship between the number of degrees outside and the number of times snowy tree crickets would “chirp” in 60 seconds. Dolbear, a major contributor to science who authored several books and pamphlets in his lifetime, published his findings in an 1897 article appropriately titled, “The Cricket as a Thermometer.”

Commonly referred to as the tree cricket, Dolbear discovered that the

Oecanthus fultoni would chirp 80 times per minute when the outside

temperature was 60˚ F and 120 times per minute when the outside

temperature was 70˚ F. So, a Tree Cricket chirps 4 times more per minute for each rising degree in temperature.

Dolbear stated, “The rate of the chirp seems to be entirely determined by the temperature and this to such a degree that one may easily compute the temperature when the number of chirps per minute is known. “

Why Don’t Crickets Chirp When It’s Cold?

If it is below 50˚ F, you may not hear much chirping from either the tree cricket or from well-known field crickets. Why? Dolbear noted that, “Below a temperature of 50˚ the cricket has no energy to waste in music and there would be but 40 chirps per minute.”