Solar eclipse, I don't understand why we can't look 😬

[Abouteffingtime]

I'm not stupid....really.

So mormally, if you look at the sun, its bright, but doesn't appear do any harm. (Based on my random viewing of the sun on occasion...) Can anyone explain to me why the solar eclipse is different?

Or, is it actually different?

OP - the problem is not that people look once when the eclipse is at 90 or 100%. The concern is that people will repeatedly look at the sun when it is at 10%, 20%, 30% etc, which will cause accumulated damage. The entire eclipse lasts over an hour from start to finish and some people might be tempted to look multiple times, even if only briefly. People will also force themselves to look longer than they would when accidentally glancing at the sun, especially in the early stages of the eclipse.

It is also a problem if people are looking when it is at 90%, or even 98% eclipse. It won't hurt in the way it would to look at a 20% eclipse. It can still do serious long term damage

She was responding to the nonsensical response to the government advice by itsbinnadness.
**

Yep, because people will look much longer. So staring at a 90% eclipse for 10 seconds will be the same radiation dose as starting at the full sun for 1 second - but far more tolerable so people are likely to do it for even longer.

Oh ok, I thought it was one of those 'nanny state gone mad' type posts.

No. Staring at the sun at 90% eclipse for 10 seconds will have the same effect on the retina as staring at the full sun for 10 seconds. You just won't feel it as much at the time.

https://www.iac.es/en/outreach/news/protect-your-eyes-during-eclipse

Even 1% of sunlight getting through is enough to damage your eyes.

There was! It just wasn't from PrettyLittleRose 😁

To put it another way imagine the full sun. If you look at it you will be getting a full circles worth of radiation. If you imagine looking at a partly covered sun then you are getting 100% radiation from the part that isn't covered. So the damage done will be done at the exact same intensity. It's just that it might be a crescent shape permanently burnt into your retina not a circle. So the damage is a different shape but the level of damage is the same.

Don't stare at the sun

🌕is the shape burnt on your retina from looking at an uneclipsed sun
🌓is the shape burnt onto your retina from looking at a half eclipsed sun
🌒is the shape burnt onto your retina from looking at a 90% eclipsed sun

I would probably rather have the last shape than the first. But in all cases you have intense damage done. A partly eclipsed sun doesn't burn with less intensity

Of course it's safe to glance at the sun. We don't go about our lives deliberately facing away from the sun at all times so that we never catch a glimpse of it.

One of these days I'm going to have to read that book again. I liked John Wyndham books; another fave was The Midwich cuckoos.

I wouldn't. Only time I've ever directly looked at the sun during an eclipse event was through a piece of welding safety glass.

I'm sorry, this is simply incorrect. The amount of damage done to the retina is proportional to the dose, which is radiation intensity x exposure time. The radiation intensity is (roughly) proportional to the percentage of the disk visible.

Starting at a 90% occluded sun for 10 seconds is the same dose as staring at the full sun for 1 second. But staring at a 90% occluded sun for 1 second is 10% of the dose of staring at the full sun for 1 second.

Ah yes, I see what you mean - I forgot of course that the radiation is focused in the eye and was considering the dose over the entire retina (was thinking of it in terms of standard radiation physics from a radiating, not a converged source). You are of course completely correct and I retract my previous reply.

I’m a little irritated to learn that you shouldn’t use your phone to look, either. I have left it too late for glasses. I may head up the hill with my phone and take occasional sneak peaks. Or I may decide it’s too hot to climb the hill (31 degrees, but it’s hotter every time I check!) and sit in my garden experiencing the shade instead.

Which direction do I need to look to see the meteors later, does anyone know?

Maybe we need to define glance.
If sweeping my eyes across the sky my gaze passes over the actual sun very briefly it will not do any damage but that would be very brief (less than a second) since instinctively your eyes jump away immediately. I wouldnt even call that as a glance, maybe a micro glance. I guess deliberately "glancing" at the sun or a partial solar eclipse implies you would look for longer than that even if not for very long. It's just not worth doing deliberately. The idea you can "safely" look at the the sun if you do it in one second glances is false basically and even though I'm sure there's a measurable amount of "safe time to do it" (microseconds) I don't think it's worth working out exactly how many 100ths of a second it would take to do permanent damage. It's probably better to just not look at it.

You were lucky... https://www.bbc.com/news/articles/cy5d19q9kngo
Peter Smith, from Taunton, viewed the solar eclipse 27 years ago wearing a borrowed welder's mask having thought it would provide protection from the sun's rays.
^^
But the next morning he noticed flashing in his eyes alongside headaches and later discovered both of his retinas had been damaged.

Don't do that. Goodness me what are you suggesting 🤔 🤔

Can anyone explain the colander option? How does that work?

I agree with all that, however, before this thread I was worried that looking at an eclipse was more dangerous than looking at the sun, because that's what the advice implies. Like the eclipse magnifies it or something. In the 1999 eclipse my parents made us stay inside with the curtains closed just in case we saw it. That has always been infamous in my family as a massive paranoid parenting moment but I was honestly wondering whether I need to do the same thing lest anyone catch an accidental glimpse and be instantly blinded.

Also, surely the time of day of this eclipse has some impact on safety? The peak is after 7pm when UV is low, you could probably look at the sun safely at that time anyway, like watching a sunset.

It works the same way a pinhole camera does or even looking at the dappled pattern of shadows caused by leaves. Normally if you look down at the ground through a colonder or stand underneath a tree looking at the ground you see the shadows of the leaves/the light through the holes on the colander. What you also "see" without realising is the light of the sun. When the sun is partly covered by the moon this also causes a shadow on the ground in the spaces between the leaves or the holes in the colander or the pinhole camera in the shape of the eclipse. The reason why you need a colander etc to see the shadow of the moon passing over the sun is because the sun's light is diffused out over the globe so without a particular point for the light to pass through and cast the shadows it would just seem to get a bit darker and then lighter again.

https://electronics.howstuffworks.com/question131.htm

I'm not suggesting people do tha, rather the opposite. Just if people do want to damage their retinas in a pretty way a partial eclipse is a very good way to do it. If you don't want to do this then don't look directly at the eclipse.

You don't usually look directly at a bright sun for more than a moment. It's physically too uncomfortable to do so, unless you are looking at something like a hazy sunset. The eclipse will make the sun go pin-point like, therefore it will be easy to look at for an extended period, but the light will still damage your eyes.

The light shines through the holes and onto a surface. You look at the pattern on the surface.