# Crickets and other temperature scales

Even after the thermometer was invented, it wasn't obvious how to set its readings. Scientists bickered over which points on the scale should be tied to something in the natural world. Some favoured 'blood heat” or body temperature. In northern Europe, where thermometers were refined in the eighteenth century, people didn't expect air temperature to soar beyond blood heat. That made it a natural point on which Daniel Gabriel Fahrenheit fixed the high end of his scale, which he calculated as 100°F. Zero Fahrenheit was measured using a set mixture of ice, water and salt In between was the freezing point of fresh water, set at 32°F. Although the Fahrenheit scale, published in 1724, nicely enclosed the range of typical European weather, Anders Celsius adopted a different approach. He used the freezing and boiling points of water – 0°C and 100°C respectively. This made each Celsius degree 1 -8 times larger than a Fahrenheit degree.

Although the Celsius scale was coarser, its logic fitted nicely with the metric system that emerged later. Celsius is now the international standard, although Fahrenheit is still what most people in the United States use. Physicists prefer degrees Kelvin – identical to a reading in Celsius plus 273.15°. The baseline of this scale, zero Kelvin, is thus equal to-273.15°C (roughly -459°F) and is also known as absolute zero. Scientists have cooled atoms towithin a few billionths of a degree of this ultimate chill, while outer space averages a nippy 3°K. For a biologically based temperature scale,you can't beat crickets. The metabolism of these cold-blooded creatures speeds up with temperature, so you can estimate how warm it is (in degrees F) by counting the number of times a cricket chirps within a 14-second period and then adding 40 to the count For degrees C, count the chirps within 7 seconds and add 5.