Einstein Theory Triumphs with a Solar Eclipse
Around 1916, Einstein had proposed that we stop thinking of gravity only as a force, and start thinking of it as a warping of the fabric of space and time. But since the Earth’s gravity is so pathetic by cosmic comparison, he had no way to measure distortions of space and time. Resourceful as he was, Einstein used an eclipse of the sun as an opportunity to test his theory. A 1919 solar eclipse proved the correctness of Einstein’s idea.
The 1919 eclipse provided an opportunity to photograph the stars and compare their locations to a star chart. Einstein predicted that photographs of the stars would appear to be in the “wrong place.” Sure enough. A headline from the NYTimes in November 1919 read “Einstein Theory Triumphs” and “Stars Were not Where They Seemed or Were Calculated to Be But Nobody Need Worry.”
Starlight grazing the Sun’s surface is more visible to observers on Earth during a total eclipse. And the moon blocking the sun allows people to measure the bending angle of the light rays. Einstein had rightly figured that light rays passing close to the Sun would be deflected by gravity to a greater extent than predicted by classical Newtonian physics. Sure enough, an object like the Sun puts a distortion in the space-time fabric.
This experiment has been replicated during many other eclipses over the years, and always with the same Einsteinian result. In two weeks, during the All American Eclipse, Bobby E. Powell, a physicist at the University of West Georgia, will be redoing the experiment with his students at a site near Lexington, S.C.
The “All American” event is viewable only in the United States across a 68-mile wide diagonal swath of land between Oregon and South Carolina. On August 21st for a little more than two and half minutes, the Moon will darken the Sun along this diagonal path.
The Earth, Moon and Sun line up exactly once every 18 years. In order to glimpse this cycle of planetary movement, you have to be standing directly in the shadow of the moon, as the shadow moves along a narrow path on the Earth for a short time.
Though San Francisco is not in the totality’s path, Bay Area folks will still be able to see 76% of the Sun’s diameter covered by the Moon between 9:01 am and 11:37 am (unless Karl The Fog eclipses the partial eclipse). This makes a case for kids to bring safety glasses to their first day of public school. It also quite possibly makes for the best back-to-school day ever.
The few minutes of total eclipse (when the Sun is completely covered) are safe for your naked eye, but any time that even a small piece of the bright Sun shows, you should protect your eyes from its damaging rays.
The safety glasses are cheap ($2/pair) and enough of an important safety measure that Astronomy professor Andrew Fraknoi is single-handedly distributing hundreds. Thanks to the generosity of the Gordon and Betty Moore Foundation near San Francisco and Google, two million safe eclipse glasses will be made available through public libraries.
If you can’t get a hold of a pair of these glasses, go maker-chic and fashion a homemade device a few days ahead of time. Here are a few suggested do-it-yourself methods, some include kitchen utensils: https://www.calacademy.org/explore-science/how-to-view-a-solar-eclipse-2017.
“And, please don’t look at the eclipse with binoculars” begs Fraknoi. Who wants to be the sad clown who put his own eyes out by staring at the sun?
Just before the Moon completely covers the Sun, the sky will get significantly darker, and you may see “the diamond ring effect,” reports Fraknoi.
For a second, you see the faint ring of the Sun’s last crescent of light and then the bright flash of the last glimpse of the Sun. The flash is the light of the Sun glimpsed through a valley on the edge of the Moon.
Author of a kid’s book “When The Sun Goes Dark,” Fraknoi has an asteroid named after him. “It’s a boring one,” he claims.
Though few of us will ever have an asteroid named after us, we can still take a gamble and play the role of citizen scientist.
During eclipse events, animals do strange things. Birds reportedly stop singing, spiders may tear down their webs, and gray squirrels retreat to their dens. The Cal Academy of Sciences in San Francisco is inviting citizen scientists to take advantage of this once-in-a-lifetime opportunity to record animal behavior during the eclipse using the iNaturalist app. Who knows? Spotting something truly bizarre could make you a naturalist star.
Another data-gathering project, the Eclipse Megamovie needs help stitching together thousands of images taken along the path of the 2017 total solar eclipse. The Eclipse Megamovie will gather images of this eclipse from over 1,000 volunteer photographers, amateur astronomers, and members of the general public.
The project is expected to enrich knowledge of the Sun’s dynamic atmosphere. The data gathered will be made available publicly and are expected to allow scientists to analyze the Sun’s corona. This is how the light gas helium was discovered, incidentally. During an 1868 eclipse, Norman Lockyer and his buddy examined the light of the corona during an eclipse and found the gas floating in the air. Fraknoi’s book augments this detail with nifty illustrations.
Whether you sign on to a project to further science, teach a kid to use a colander to watch the eclipse, or take an outdoor work “meeting,” the day is surely one you won’t soon forget. Also, mark the year 2024 in your calendar. It’s our next stateside chance to follow a moon shadow.