Dr. Marc Siegel: Solar eclipse - science, safety, and wonder

Sun worship is not new, in fact, the 14th century B.C. Egyptians worshiped the sun god in a religion known as Atonism. In modern times we acknowledge the crucial importance of the sun as our provider of life sustaining energy, but we generally do not worship it. This Monday, however, with the first total solar eclipse to cross the entire country coast-to-coast since 1918, the obsessive fascination with viewing it is bordering on religious fervor.

Is it safe to directly view the eclipse? Certainly not without special protective eyewear that comply with international safety standards for direct observation of the sun (ISO 12312-2). NASA has emphasized that the filter must be from an approved manufacturer. The American Astronomical Society has also provided tips for safe viewing as well a list of reputable manufacturers of eyewear.  If you can see any objects including your hand in front of your face then the eyewear is definitely faulty. Across our land, eclipse glasses are selling out of pharmacies and photo stores much faster than they can be restocked, and libraries are holding onto them for special eclipse viewing sessions. Scalpers are asking prices usually reserved for sports playoff games.

Unfortunately, there is no proven treatment and though there is often improvement over time, some of the eye damage may be permanent, so the best idea is to avoid the exposure in the first place.

According to NASA, if you happen to be in the direct path of the total eclipse across the south/central U.S. you could theoretically choose the exact moment when the moon is directly positioned across the Sun and only the corona is visible to view the eclipse without eye protection. But to try to gauge that exact moment correctly could be risky too.

Dr. Joel Schuman, Chairman of Opthalmology at NYU Langone Health, told me that “eyewear that meets the ISO 12312-2 standard should be safe,” provided of course that it is in good condition and you wear it the entire time you are viewing the eclipse and not add on a magnifying telescope, binoculars, or camera. Dr. Martin Leib, professor of pphthalmology at Columbia University, said that he thinks that the safest way to view the eclipse is with your back to the sun, cutting a tiny hole in a paper plate and allowing the image of the eclipse to pass through and project onto another paper plate for your safe viewing.

If you try to look directly at the sun on a normal day, your eyes will water and begin to burn if you stare for more than a minute or two. This discomfort will get you to turn away. With the eclipse, you can end up staring for longer and not even realizing you are damaging and scarring your retina (solar retinopathy) until later, when you begin to experience symptoms. A central part of the retina can be damaged (macula) and your vision may become less sharp, you may develop blind spots, see wavy instead of straight lines, and a central yellow spot may appear which develops into a red spot over several days or weeks. Unfortunately, there is no proven treatment and though there is often improvement over time, some of the damage may be permanent, so the best idea is to avoid the exposure in the first place.

Fascination with solar eclipses has damaged retinas (the essential camera of the eye) through history. There is a story that Isaac Newton himself viewed an eclipse through a mirror and ended up with temporary blindness.

Perhaps Newton was prescient in his fascination with eclipses, since the total solar eclipse of 1919 was used by British scientist Arthur Eddington to show that Newton’s absolutes of space and time were incorrect and that Einstein’s newer theory of relativity (that gravity affected light, space, and time) was more accurate.

Monday’s total solar eclipse is not likely to have the same long term impact on scientific theory, though it is definitely exciting for all and a moment for our country to safely unite behind a celebration of nature’s wonder.