Borrego Sun - Since 1949

The Eclipse That Made Einstein Famous


Last updated 6/26/2019 at 3:24pm

On a day when you have nothing better to do, drive a friend east of Christmas Circle down Palm Canyon Drive to DiGiorgio Road. Have her hold up a dime, on edge, and then drive a mile further east to Borrego Valley Road, then a quarter mile past the intersection.

You will be able to see your friend 1¼ miles away, if she’s wearing a brightly colored outfit, but it would take more than an eagle eye to resolve the edge of that dime in her hand, 1.75 arc-seconds in width. That is the same degree of separation that Albert Einstein predicted 100 years ago after conducting a thought experiment: “What would I see,” Einstein asked himself, “if I was riding on a beam of light?” It’s about light bending under the force of gravity, the warping of space itself.

Borrego’s resident astronomy expert and syndicated columnist Dennis Mammana (, told the fascinating tale of “Einstein’s Eclipse” in his last lecture of the season at The Springs at Borrego May 26, replete with slides and expert commentary on how one extraordinary man made so much difference in the world of science. It made Einstein a household name, Mammana said, and also changed our understanding of the way the universe works forever.

Predicting such a precise measurement difference by direct experiment is one thing, but as Mammana explained, for Einstein to conceive it all in his head, and then find the right equations to support the concept, is quite another wonderous notion altogether.

The Sun is a very massive thing, but trying to detect a very slight 1.75 arc-seconds of deflection in a light beam’s path requires it being at once outside the lunar disk yet within the Sun’s corona.

During normal daytime hours, there is too much glare from the Sun, and of course the Sun is not visible at night. The only event that could detect such a difference was a total Solar eclipse, where the lunar disk would cover up the entire Solar disk. The photography of such an event, using equipment available at the time, was going to be a challenge.

Full story in the June 13 issue of the Borrego Sun.