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Comment by pi-err | Hacker News Reader

A bit OT but how did ancient civilizations know that they should NOT watch an eclipse with a naked eye? The knowledge would have been lost or unavailable at each occurence. Remote areas would probably never get the word. So how didn't they get massive eye damages back then?

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The same way any civilisation 'knows' anything - speculatively, one guy stares for too long, gets permanent blotches in his vision, tells his friends not to do the same... word gets around, and as far as basic reasoning capacity goes, we're no different from Neolithic hunter-gatherers, even if they might have been more inclined to rationalise it as "the sun-god cursed my eyes for gazing too long at his radiance" than "the intense light scarred my retinas".

Like most dangers communicated to people in the modern world, the danger of looking at the sun is way overblown. You can look at the sun for over a minute straight without any damage. How much damage, how fast, what kind of damage, and how this varies with peoples genetics is not well known, of course. Doing such experiments would harm peoples eyes. How long can you look at a little bit of the sun right around the total eclipse? Very not known. But "safety first" and you get things like and emergency warning sent out to all cell phones before the eclipse saying not to look at the sun. Looking at the bright sun is not a pleasant sensation. I imagine people in ancient times were more in-tune with their physical senses and were less likely to do things that hurt them just for curiosity sake.

"What kind of damage" is pretty well-known.

See e.g. "Light-Induced Damage to the Retina" http://photobiology.info/Rozanowska.html

You are right. Many experiments on animal eyes are highly likely to translate well to human eyes.

With a little more thought maybe all these warnings exaggerating the dangers of the sun to your eyes are a good idea. It seems that humans know or learn "Don't stare into the sun" is a good idea but during an eclipse some people forget that.

Well, we can assume that they knew not to look directly at the Sun on a normal day, right? So there was perhaps already an understanding that caution was warranted.

But how do you know they didn't get eye damage? Seems reasonable to think that people did sustain damage to varying degrees. It still happens today... not even that rare, actually.

Also, assuming they weren't running for cover due to mistaking a total solar eclipse as a bad omen, they may have been interested in other things that prevented them from staring for extended periods. The 360 degree sunset, for example.

Ever seen an eclipse? It generally not obvious that it's happening until just before totality and it's fine to look at during totality. Generally when people go blind watching an eclipse, it's because they knew it was coming and wanted to watch it happen. So a lot of folks probably didn't even think to look up until it was safe to do so.

I wonder if there's any documentation of great panics around these.

I'd imagine the people of the time would think this was some sort of negative sign from their sun god (Horus) and madly prostrate or panic. I think it'd be abnormal for people to stare it as they'd be too afraid but that's just conjecture.

Did you never stare straight at the sun as a kid?

Note that sea captains in the age of the sextant were typically blind in one eye by using the sextant on the one star visible during the day (our sun). But this wasn't from a single viewing, it was from many many viewings, presumably the majority of which were while they were midshipman. They were smart enough to sacrifice one eye, covering the other while looking at the sun.

Nevertheless it's a bad idea, especially with both eyes, and eclipses are more dangerous.

Seems like it would have been trivial to put a filter in front of the upper mirror of a sextant during daylight hours to avoid this. I know that the sextant was an optical device that became commonly used after Newton's Opticks was published, and that Newton temporarily blinded himself while researching it, so there might have been an inkling among the educated that staring directly at the sun was dangerous. But I don't know whether optical filters were known then, or came into use later, as adjuncts to photography. It's definitely too soon for arc welding.

> A bit OT but how did ancient civilizations know that they should NOT watch an eclipse with a naked eye?

Doesn't it hurt when you look at the sun? Any time I've ever accidentally glanced at the sun it's literally a blinding pain and my eyes just close reflexively.

It has never made sense to me when people say, "Don't stare at the sun". It's roughly the same as saying, "Don't stick your hand in the fire." Well duh, it hurts.

Back when I was a kid I used to stare at the sun fairly often, you look at it long enough and you get this sort of shimmering blueness over the bright area and it's no real issue to keep looking at it.

Used to do that during long car trips to pass the time, I don't have any issues with my sight as an adult but it's definitely a necessary warning.

Almost all the stories I have heard of people getting eye damage from staring at the sun have been people on drugs. Usually, the intense pain causes you to look away.

> A bit OT but how did ancient civilizations know that they should NOT watch an eclipse with a naked eye?

How does your civilization know NOT to watch an eclipse with a naked eye?

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