I'm writing a report about the solar eclipse happening over north America and was wondering why looking at a solar eclipse is worse than looking at the sun regularly. In addition what alternate materials can be used to make eclipse glasses that are safe to look through.
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3$\begingroup$ I don't think it is worse except that the lack of solar glare may fool you into thinking you can look safely - you can't. $\endgroup$– adrianmcmenaminCommented Aug 21, 2017 at 17:37
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1$\begingroup$ Maybe do a little more research on your own first? $\endgroup$– user21Commented Aug 21, 2017 at 19:40
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2 Answers
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Normally people don't focus their eyes on the sun; its always in the sky but noone usually has a reason to look at it so you never focus on it, and most know not to. During an eclipse thats exactly where you want to look and focus on, and focussing on it makes it even more dangerous (guessing due to time spent with same area of your retina receiving the focussed energy from it rather than moving around your view and unfocussed spot).
During totality (darkest part of 100% eclipse) your eyes start to adjust for the dark sky and open up, allowing even more light in; as sun comes out of totality it gets very very bright again quite quickly, and your eyes might not be ready for it - use protection as you see the diamond ring start to get bigger/brighter (or only look at the diamond ring on the way into totality for safest view, when its getting darker).
The same effect as totality is almost had by using eclipse glasses or other dark viewers that cover your head/eyes, and switching from that view back to unprotected view of the sun could be equally as dangerous for the same reason.
(I'm not an expert).
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$\begingroup$ Don't use your own materials to make eclipse glasses. I've heard some people/places say you can use a certain high spec. of welders glasses, but even those don't usually properly filter out the other light (UV etc.) safely - and you can damage your eyes permanently without even knowing it at the time, until later (no pain receptors on the retina to send hurt back to the brain and tell you its damaging it). $\endgroup$– BreezerCommented Sep 11, 2017 at 23:00
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2$\begingroup$ I'm not sure it's good to explain a situation involving safety without citing some authoritative source. $\endgroup$– uhohCommented Sep 11, 2017 at 23:37
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It's not inherently less safe.
It's just that it's safe to look at the Sun during the total phase, but people keep staring at it after totality is over, when it's not safe anymore. That's where the problem is.
When the photosphere starts showing again, the safe period is over. You can look at the "diamond ring" for, like, a second or two - but that's it. Unfortunately, some people are lulled into a sense of security and keep looking at the Sun a long, long time after totality is over. They keep staring at it fixedly until it hurts and they feel compelled to avert their gaze - but it's quite possible that the damage is done already at that point.
It's the gradual nature of what happens after totality that traps people into a dangerous situation. Totality is over, you've seen the diamond ring for a second or two - that's it, show's over, avert your gaze, put the goggles on.
The safety of eclipse goggles cannot be confidently evaluated by amateurs. Are there ways to make eclipse goggles that are safe? Yes. Can anyone guarantee that those are safe with 100% confidence? No. So don't do it.
The only goggles that are guaranteed to be safe are those that comply with the ISO 12312-2 international safety standard.
https://eclipse.aas.org/eye-safety/iso-certification
Personally, I prefer goggles made from the Baader AstroSolar Silver/Gold Film, which complies with the ISO standard, and show the Sun in its original color - as opposed to many other goggles that color the Sun green, red, orange or other unrealistic hues.
answered Sep 11, 2017 at 23:27
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$\begingroup$ It may indeed be more unsafe. Your eyes are somewhat dark-adapted during totality, so your pupils have dilated. When the Sun begins to re-appear, it is very small areas that appear first, and this light is therefore imaged to a very tiny spot on the retina. You should not just make up your own explanation when it comes to issues of safety. $\endgroup$– uhohCommented Sep 11, 2017 at 23:37
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$\begingroup$ I don't think the danger is just people continuing to look at the Sun after totality. People have been known to stare at the Sun during partial eclipses. I've read accounts of people with crescent-shaped scars on their retinas. $\endgroup$ Commented Oct 8, 2017 at 4:44