Monday, December 03, 2007

Cricket Thermometer

Outdoor temperature can be determined by counting the chirps of a cricket.

Crickets chirp by rubbing their wings or legs over each other. Yet it is only the males of the species that make this noise — they do so to attract mates. Therefore, when you're happily listening to the soothing sound of crickets chirping, you're actually eavesdropping on a courting ritual meant to warn off other lust-filled male crickets and to draw interested females to the ones doing the

The notion that counting the chirps of crickets can serve as an informal way of working out the temperature is not new — in 1897, physicist Amos Dolbear proposed the reverse of that idea, stating outdoor temperature determined the number of cricket calls one would hear. Over the years, his way of looking at this relationship was turned on its head — people now count the chirps to get the temp rather than consult the thermometer to figure out how many cricket calls they will hear.

We've encountered a variety of "cricket chirp thermometer formulas" over the years. One specifies counting the chirps over a 40-second interval, then adding 38 to that number to achieve the current temperature. Another say it's chirps over 14 seconds then add 38. Yet a third says it's number of chirps heard in 15 seconds then add 48.

The formula endorsed by The Old Farmer's Almanac seems the most reliable:

To convert cricket chirps to degrees Fahrenheit, count number of chirps in 14 seconds then add 40 to get temperature.
Example: 30 chirps + 40 = 70° F

To convert cricket chirps to degrees Celsius, count number of chirps in 25 seconds, divide by 3, then add 4 to get temperature.
Example: 48 chirps ÷ 3 + 4 = 20° C

Dr. Peggy LeMone of The GLOBE Program (a science education program funded by NASA, NOAA, NSF, and others) studied the theory during the summer of 2007 at her home in Boulder, Colorado, and posted her findings post to her blog on 5 October 2007. Greatly simplifying her research, she found that when she counted the chirps during a 15 second span and then added 37 to that number, the resultant figure did closely approximate the actual air temperature (Graph 1). However, when she slightly adjusted the formula by recording chirp counts at 13 second intervals, then adding 40, the results even more closely adhered to the actual air temperature (Graph 2). Her findings (chirps in 13 seconds plus 40) confirms The Old Farmer's Almanac's wisdom (chirps in 14 seconds plus 40).

Graph 1

Graph 2

Now, granted, this mode of determining the temperature will work only when there are crickets about. Also, it's accurate only down to 55 degrees Fahrenheit or so, because crickets either aren't about or aren't in the mood for love at lower temperatures.

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