Part 16 — The Paris Thermometer

When we were in Paris this spring our friend M showed us a new kind of thermometer that tells the temperature of things by the frequency-mix of light they give off. Actually this is an old invention but the new one is user-friendly and nicely designed. It looks like an eyeball on a long stem growing out of a talking flowerpot.

You open your mouth and put the eyeball up to your mouth and it sees what invisible colors of infrared glow are coming out of your mouth. Then a voice coming from the flowerpot might say "219 degrees." That is mouth temperature on the new scale. Or it might say "2.19 grade." One grade of temperature, on the new scale, is a giant step of a hundred degrees.

Thermal glow at any temperature has a keynote frequency proportional to the temperature. (In the language of Freshman Physics, the word for this frequency is, "kayTee-over-haitch-bar", but this needn't concern us.) The important thing is that the flowerpot can detect the keynote frequency of the radiant heat—indeed it tells the temperature from its keynote frequency!

What this device does is look at the blend of frequencies in a thermal glow and then it will either tell you the actual frequency of the keynote or it will tell you the temperature that goes with it.

Depending on how you want the answer it will either say "2.19 grade", or, if you want to know the frequency, it will say "2.19 mmmm...quinze per minute."

The brief hum drowns out something it may be saying and then you hear "quinze" indicating a frequency 10¹⁵ per minute.

I pointed the eyeball at the sun and it said "40.8 grade." Another time, when I wanted the answer a different way, it said "40.8...quinze...."

If you point it at light which is a pure frequency (not the blend of thermal glow at some temperature) it doesn't tell a temperature but simply tells the frequency of the light. One time I pointed it at some green light and it said "200 quinze." All the visible colors have frequencies around 150 to 250 quinze on the flowerpot's per minute scale.

Something wonderful was baking something in the oven. Very briefly I opened the oven door and pointed the eyeball into the oven. The voice in the flowerpot said 3.2 quinze. So that frequency is the "keynote" in the blend of infrared in a baking oven. Madame always gets the icecream at Berthillon's. For desert she had many different kinds with interesting colors. I pointed eyeball into one of the cartons of ice cream and the voice said "1.93 ...quinze...."

The livingroom was at a comfortable temperature for after-dinner conversation, and we pointed the device at a wall to find out what "room temperature" is on the new scale. It turned out to be 2.07 grade, and of course the keynote frequency in the thermal glow was 2.07 quinze.

They live close to the Eiffel Tower, with a good view of it from their balcony. At eleven o-clock we watched the tower's hourly scintillation. The physicist daughter is one of those people who, like the young Dane Ole Römer, has measured a Planck quantity, and she was there as well. What a splendid evening!