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Column: When it comes to using instruments: 'Measure, but verify'
Rudi Kiefer

Albert Einstein once wrote: “Look deep into nature, and then you will understand everything better.” I don’t have Einstein’s mega-mind but I too enjoy observing processes that go on around us. For that reason, instruments are abundant at my place. 

Rain was falling in North Georgia as the last remnants of tropical storm Nicholas passed through. The digital thermometer on the wall, fed by a wireless sensor on the north side of the house, read 71.6 degrees. Gone are the July days when the swimming pool reached a delightful high of 86 degrees. Now it’s dropped to 75.1, still cooling slowly. I like to monitor it with a small battery-operated digital unit that’s mounted in a dry place, with only the sensor wire reaching a couple of feet down into the water.

One can learn a lot from such observations. Even when the mercury hit 83 degrees a few days earlier, the pool wouldn’t warm significantly. But during hours of bright sunshine, I could see the temperature creeping up, 1/10 of a degree at a time. Conversely, nighttime lows in the 60’s didn’t cool it much. In miniature, my pool acts like the world’s oceans. Water heats and cools slowly. Direct heat radiation from the sun appears to be much more effective than the mere contact with warm air. The larger the water body, the slower its rate of adjustment. Beach water temperature in Savannah last week was an enviable 82 degrees. That’s from the internet, my sensor wire doesn’t extend that far. 

The day with the most hours of sunlight was June 21. Now, during fall, the ocean is still warm enough to continue producing tropical storms for weeks to come. But my swimming pool, containing much less water than the Atlantic Ocean, will soon dip down to the 70-degree mark where swimming loses some of its magic. It’s best to know before jumping in.

Instruments can produce a “senior moment” sometimes. Once, on a February trip in western Virginia, I was checking creek temperatures with a probe that you hurl out as far into the water as possible. The readout climbed to 85 degrees. Shivering in the 26-degree air, I recalibrated. Retried. Recalibrated. Frustrated with the apparently faulty instrument, I finally dipped my hand into the water. It felt as warm as a tub bath. This unexpected encounter with a thermal stream suggested another principle: “Measure, but verify.”

Rudi Kiefer, Ph.D., is a professor emeritus of physical science at Brenau University. His column appears Sundays and at

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