I traveled to Salem, Oregon, to observe the eclipse of August 21, 2017 at a point along its path of totality. My observation point was from the top of a hill 4 miles east of Highway 5 in Salem over recently plowed farmland. My equipment was simple: an opaque plastic sheet big enough to cover my face with a rectangular 1.25 × 5 inch eye-viewing port covered with dark plastic filter.
At about t-30 min, I started to see a slight dark irregularity at 2 o’clock on the side of the solar circle. By t-15, the image had developed into a what looked like a Venn diagram of a bright circle half overlaid by a dark circle. The gentle breeze started to pick up speed. At t-10, the swallows started flying, chasing airborne insects low and fast a few feet above the field as they usually do at dusk. But, the temperature of the breeze was noticeably cooler.
At t-5, there was a bright crescent with more than half the area obscured by the dark moon. Light was dimming, but in contrast to normal dusk, there were no shadows, since the sun was directly overhead. It reminded me of a landscape painting of dusk before the artist added in the long shadows common at sunset. The breeze was now noticeably cold, possibly due to radiative cooling of the land and reduced solar flux.
Figure 1 – Total eclipse image from Salem, OR. The white filaments were visible to the eye, extending about three diameters from the dark image. (Photo courtesy of J.G. Stevenson.)At t-0, the sky was dark (Figure 1) but not totally, more like a half-moon night. I’d expected darker. Only a few stars were visible. The camera image did not pick up the faint filamentous lines extending outward for about three image diameters connecting the 6:00 with the 8:00 lobes. I noticed an even fainter connection between the 2:00 and 11:00 lobes. Are these filaments, flares from the sun, or could they be scattering from high-altitude cirrus clouds illuminated by sunlight outside the ring of totality?
This was my first eclipse. I could have been more prepared by running a video recorder to give me split-second, detailed observations.
A review in Science (August 18, 2017, pg. 629) showed that the eclipse attracted the attention of a large audience in America. This includes the volunteer Citizen Continental-America Telescopic Eclipse, who used 68 identical telescopes to study the sun’s corona during the eclipse from Oregon to South Carolina. The teams deployed high-altitude balloons carrying cameras. This is an interesting exercise in crowd-sourcing scientific observations. I’m eager to see if anything comes from this—even if it does not, the experience was worth the effort.
Want to catch a future eclipse? Please see the table in Sun Moon Earth: The History of Solar Eclipses from Omens to Doom to Einstein and Exoplanets by Tyler Nordgren (ISBN 978-0-465-06092-4) for the next event near you. But you better hurry, Nordgren also predicts that the number of eclipses will decrease, so that in 563 million years, the last one will appear. During the intervening time, the moon will slowly move away from the earth, which will decrease the sharpness of the moon’s shadow.
His last chapter presents an interesting hypothesis to explain how the moon’s orbital tilt operates through gravity to produce ocean tides to create a repetitious bathing of the rocks and tide pools, which over eons gave rise to life. Nordgren extends his hypothesis to predict that the sun, moon, and earth may be much more unique than simply cataloging Goldilocks solar systems. Perhaps.
With a smile,
Bob
Robert L. Stevenson, Ph.D., is Editor Emeritus, American Laboratory/Labcompare; e-mail: [email protected]