Witnessing a total solar eclipse could change your life. Unpredicted eclipses have changed the progression of historical events. The unexpected environmental effects of a sudden darkness at midday can be very unsettling to people and animals alike.

On July 29, 1878, Thomas Edison observed the total eclipse of the Sun as part of Henry Draper’s Expedition to Rawlins, Wyoming Territory. (Although this year’s total eclipse will pass through Wyoming, the City of Rawlins will be some distance south of the total path this time.) Edison was there to test a new invention that could detect infrared light and estimate the temperature of objects remotely, and he planned to try and estimate the heat of the Sun’s corona while the solar photosphere was blocked by the Moon.

Edison’s preparations for the eclipse were not as cautious as they should have been. Because total eclipses happen close to home so very rarely (2017 is the first year that the totality has appeared in US skies since 1979), and due to the practicalities of 19th century life, most astronomers arrived at the observing site early to uncrate their heavy observing equipment and build observing shacks, and mix concrete to make steady piers. Edison arrived with a few days left before the eclipse, without time to build a protective structure, so he used the existing shelter provided by a chicken coop. On eclipse day, as the sky darkened, the bewildered chickens literally came home to roost, disrupting his observations.

Illustration of Edison’s Tasimeter

Edison named the infrared-detecting device his “tasimeter”, and he was trying to break ground in a new scientific field in competition with the director of Pittsburgh’s Allegheny Observatory, Samuel P. Langley. Instead of letting Langley test the tasimeter’s eclipse performance alongside more proven devices such as the thermopile, Edison tried to “scoop” the competition with his solo work, and failed.

Although Langley also failed to estimate the heat coming from the solar corona with his thermopile, less than a year later he had invented the first bolometer, which is commonly used today in its most refined designs. Langley’s bolometer was so sensitive that it could detect the heat produced by a cow from a quarter of a mile away.

Although the temperature of the Sun’s corona has since been measured with bolometers, the reason why it is so hot – about 1.5 million Kelvin, considerably hotter than the Sun’s surface (5800K) – remains a theoretical problem in physics to this day.

Therefore, if you want to simulate an eclipse, or to prepare for the real thing, don’t neglect the auditory experience. Consider all possible distractions that could disrupt observations in advance, and avoid them. If you are standing near a farm in Wyoming, as the darkness approaches the sound of confused barnyard animals will reach a crescendo.

The new book American Eclipse offers a more in-depth view of the Solar Eclipse of 1878, following the trevails of Edison, planet hunter James Craig Watson, and astronomer Maria Mitchell.

“On the Total Solar Eclipse of July 29th, 1878”, George F. Barker, Proceedings of the American Philosophical Society, Vol. 18, pp. 103-113, 1878. ( https://archive.org/details/jstor-982766 )

“Eclipse Vicissitudes: Thomas Edison and the Chickens”, J. Donald Fernie, American Scientist, Vol. 88, No. 3, May-June 2000. ( http://www.americanscientist.org/issues/pub/2000/3/eclipse-vicissitudesthomas-edison-and-the-chickens/1 )

Eric Briggs

Eric Briggs

SciDome Support at Spitz, Inc.
Eric has been an expert user of the Starry Night astronomy simulation software since its original release in 1997. He joined Spitz in 2008, providing support and training for Starry Night Dome and other software on SciDome planetarium systems.

Eric is the co-discoverer of 10 supernovae (and counting).
Eric Briggs

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