We only know how dangerous eclipses are because of modern science and the danger isn’t apparent since it doesn’t cause immediate pain. I was wondering how people 500yrs ago on the equator in South America or Africa would have protected themselves (or not) when an eclipse came. Some tribes did believe that they were ‘‘gods’’ so would they have stared at the eclipse with their naked eyes?
A supplementary question - does it actually hurt during or after staring at the eclipse, and any more than ‘normal’ [?] staring at the sun would hurt, or is it a gradual accretion of damage to sight?
A total eclipse is safe to look at. A partial eclipse is just as dangerous and painful to look at as the Sun at any other time. The only increased danger from a partial eclipse is that a lot of people will be will be attempting to look at the Sun at that time. But they’re only doing that because they’ve heard that there will be an eclipse: If you don’t look directly at the Sun, you probably won’t even notice a partial eclipse, until you get to 80% or 90% or so.
In a society without the astronomical knowledge to be able to predict eclipses, you might have a few people who just happen to glance at it and notice, and anyone they point it out to, and in the aftermath of totality you’d probably have some who look up to see if the Sun is still doing that weird thing, but the total number of people watching is going to be much lower than nowadays.
Remember as well that before and (especially) after the eclipse the Sun will be visible, and observers might easily damage their eyes at these times.
There may be one or two accounts of named individuals that were affected in this way in ancient times, as some ancient natural philosophers were keen observers but somewhat foolhardy (like Pliny at Vesuvius), but I haven’t found any who were blinded.
I’d be surprised if there weren’t at least a few people who had their retina damaged at every eclipse in a populated place. I know in last year’s eclipse, I was tempted to keep looking at it after totality ended, since it wasn’t bright enough yet to cause me to look away. That’s the danger time, but in the past, there were no eclipse glasses to put on and no media to spread the word that you need to put them on immediately.
Having witnessed several partial eclipses… you probably don’t have to wait quite that long. There’s a noticeable dimming of sunlight from about 40% onward. Granted, that might not be noticed if you are unaware of the eclipse or otherwise busy, but you do have a phenomena where the light decreases even if there isn’t a cloud in the sky.
Then is becomes a matter of whether or not the people on the group know it’s an eclipse and have any reason to look at the sun.
Its a funny question, that comes up a lot. Given that the news has to tells us repeatedly to NOT look at the sun.
Galileo was blind by the end of his life. And it was noted, at the time, that it was due to excessive sun viewing, magnified, as he tracked sunspots. Although telescopes had just been invented, not by him, it seems no one could have warned him not to view a magnified sun for long periods of time frequently.
I’m given to understand that the Ancient Chinese also monitored sunspots. I don’t know if there’s any sort of record like, “Shen did labor in the study of the solar disk, predicting the health of the Emperor, until his 34th year. Then, as with all others, he was too blind to work in that capacity, and moved on to money counting.”
During a partial eclipse, I was viewing the sun through safe filters provided by a physicist. It was a cloud-free, hot Summer day. The light was dimmed, like a cloudy day, because of the eclipse. My sister was sun-tanning, and I had to point it out to her, she hadn’t noticed until I mentioned it.
That’s the answer to all of these threads. Unless it was your job to look at the sun all day, everyone was too busy working with their head down, to notice partial or semi-eclipses. And it wasn’t anyone’s job, to look at the sun, until Galileo. I recall some Greek philosopher noticed sunspots, and his contemporaries said, “Aristotle never mentions that, so the spots must be in your eyes.” If there was, there should have been a record, and Galileo shouldn’t have been taken by surprise. And he was.
I rather suspect that because solar eclipses are so rare and the human population so small, the number, if any, was negligible.
As has been pointed out before on the Dope, this is almost certainly a myth.
No, the relevant Chinese records aren’t like this. There were those employed to record and interpret prophetic signs, but sunspots visible to the unaided eye are sufficiently rare that it wouldn’t have been worth trying to specially monitor for them. When they are seen, they’re recorded as something rare that happens to have been noticed.
Largely depends on the degree of the eclipse. Most partial eclipses would pass unnoticed by virtually everyone, but as Chronos has noted, that changes above 80-90%. Daylight becomes eerie and seemingly unnatural and most anyone will wonder what’s going on.
Of course, cloud cover easily confuses even that, but historically some partial eclipses would have been noticed even without prior awareness.
One factor that hasn’t been mentioned is that there will be a spectrum of possible damage, short of total blindness. And few people, even without warnings, are likely to stare long enough for the latter to be a serious possibility. Which isn’t to say that the warnings are irresponsible, for you’re much more likely to inflict permanent damage well short of blindness. The question is then whether such cases might be recorded prior to the advent of modern eyecare. I suspect not. They couldn’t do anything about it after the fact and probably could still function okay enough in everyday life, just as most others with most eye defects would have had to. They might not even have mentioned that they had a problem to others.
Regardless of the history of what actually happened, Galileo certainly did have someone to tell him not to stare at the Sun (directly or through a telescope): Himself. Staring directly at the Sun hurts, which is why people don’t usually do it.
There is an instinct to close one eye when viewing bright light directly. I would imagine that few people would have gone completely blind, but many may have lost or damaged the retina of one eye looking at it.
Having seen three total eclipses, I can vouch for that, though I reckon it was 90%+. But the sun is so powerful that even if the eclipse is not total by less than 1% you should not look at it without a filter. Only if the eclipse is completely total is it safe to look with the naked eye.
The problem is that the blink reflex and pain response seems to be regulated by the total amount of light entering the eye. A 99% eclipse would be totally safe if the light were spread out more, but the 1% visible has the same surface brightness of the sun. It easily damages the eye in that area but there is no instinct to look away. A smaller problem is that your pupil has probably dilated and so lets in even more light.
Damage from arc welding has a similar problem; the total amount of light isn’t that high and so it’s easy to look at. But all the light is concentrated in one point and so is very damaging.
As an aside, it’s easy to see minor partial eclipses with no equipment, assuming you know one is happening. You just glance at the sun and look away. You’ll see the cutout in the afterimage. This isn’t really a recommended way of viewing an eclipse, but it’s not damaging if you keep the exposure low (a fraction of a second).
I saw the eclipse last year and this was one part that really surprised me. Half of the sun could be blotted out and you would barely notice. It is still brighter than a regular cloud over it.
Apparently we perceive light in a very logarithmic fashion. Half the light does not appear half as bright.
Yep. A full moon is around a half million times more dim than bright sunlight. Sure a moonlight night is a lot darker than a sunny day, but it sure doesn’t seem like a half million times dimmer. From the same chart, an overcast day can be 100 times dimmer than full sunlight (but doesn’t seem like it.) Half the sun blocked out is nothing.
(I started a thread about this last year.)
From what I’ve heard, you don’t feel pain when your eyes get damaged from looking at the sun. The damage may not show up right away, either.
I wonder if eye damage from looking at the partially eclipsed sun might be behind that belief that a lot of people seem to have that the light from the partially eclipsed sun is somehow dangerous.
On the other hand, while a mostly-eclipsed Sun will damage your eye just as surely as an uneclipsed Sun would, the area of the damage would be smaller.
I will confess that, when the eclipse was getting to the diamond-ring stage, I did look at it naked-eye (it was starting to cloud over right at that moment, and the thin clouds and the eclipse glasses combined were too much). And yes, I probably did do some damage to my retinas in the process. I don’t regret it.
I think some of you are underestimating how many people would notice an eclipse. The most noticeable change during an eclipse is how shadows cast by sunlight change. For people who spend most of their daylight hours outside, this is very noticeable if there is anything nearby creating a shadow.
And I think you’re overestimating how attentive people in general are. The clues are there, if you pay attention to clues. Most people don’t.
But Chronos . . . that’s where the fun is.