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Old 08-18-2017, 05:52 PM
Darren Garrison Darren Garrison is offline
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How did ancient people see eclipses?

Not what explanations and opinions they had on eclipses, but how did they actually view them? Yes, the total eclipses would have been dead obvious, but what about partial eclipses. Did people stare directly at the sun, or just not notice that it happened?
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Old 08-18-2017, 06:23 PM
What Exit? What Exit? is online now
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How ancient?

There are some recorded records of eclipses from early Greeks and Chinese sources.
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Old 08-18-2017, 06:29 PM
gogogophers gogogophers is offline
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They probably noticed. And they probably grimaced as they observed.
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Old 08-18-2017, 06:44 PM
Xema Xema is offline
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Originally Posted by Darren Garrison View Post
... what about partial eclipses. Did people stare directly at the sun, or just not notice that it happened?
No need to stare - you can glance at the sun and see it's partially eclipsed. If it's more than about 15%, it would be very hard not to notice.
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Old 08-18-2017, 08:24 PM
Grey Grey is online now
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Heck you can see the eclipse in leaf shadows thanks to the pin hole effect.
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Old 08-18-2017, 08:30 PM
Arkcon Arkcon is offline
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They looked up, and sketched or recorded in some other way what they saw.

They may have blinded themselves temporarily as a result. They may have shortened the amount of their life time of being sighted.

Its been recorded that Galileo's viewing of the magnified sun for sunspots was the cause of his late-life blindness. This was known even in his time. People who look at the sun end up blind.

We're cautioned by the news and school books NOT to do this.
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Old 08-18-2017, 09:15 PM
PastTense PastTense is online now
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Now is the time to mention the Greeks used a computer to calculate them:

Quote:
The Antikythera mechanism (/ˌśntɪkɪˈθiːrə/ ANT-i-ki-THEER-ə or /ˌśntɪˈkɪθərə/ ANT-i-KITH-ə-rə) is an ancient Greek analogue computer and orrery used to predict astronomical positions and eclipses for calendar and astrological purposes. It could also track the four-year cycle of athletic games which was similar (though not identical) to an Olympiad, the cycle of the ancient Olympic Games.
https://en.wikipedia.org/wiki/Antikythera_mechanism

Youtube video:
https://www.youtube.com/watch?v=DiQSHiAYt98
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Old 08-18-2017, 09:28 PM
HeyHomie HeyHomie is offline
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What could an ancient viewer have had on hand that could have helped him safely view the eclipse?

Two bonus questions: When did we start weaving (several layers of woven cloth could function as a crude form of shade through which to observe the sun/an eclipse)? And when did we start making shaded glass?
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Old 08-18-2017, 10:06 PM
Darren Garrison Darren Garrison is offline
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Originally Posted by Xema View Post
No need to stare - you can glance at the sun and see it's partially eclipsed. If it's more than about 15%, it would be very hard not to notice.
Yes, but how often do you as much as glance directly at the sun (when it isn't low on the horizon?) Unless you notice a dimming of the light, why would you be looking at the sun at all? (I'm asking in the context of the warnings of eye damage from even brief glances at the sun.)

I used "ancient" as a shorthand for "any time or place without tinted eclipse glasses."
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Old 08-18-2017, 11:13 PM
Lord Feldon Lord Feldon is offline
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Sometimes the sun rises or sets while eclipsed. In that case, it would be hard not to notice it. And all it takes is one person in a community to look at the sun and then start shrieking that something is wrong with it.

Last edited by Lord Feldon; 08-18-2017 at 11:15 PM.
  #11  
Old 08-18-2017, 11:23 PM
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Quote:
Originally Posted by HeyHomie View Post
What could an ancient viewer have had on hand that could have helped him safely view the eclipse?
How about a piece of something thin with a pinhole? When were pinholes invented?
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Old 08-18-2017, 11:53 PM
AK84 AK84 is online now
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Originally Posted by HeyHomie View Post
What could an ancient viewer have had on hand that could have helped him safely view the eclipse?
Reflection in a pool (or a bucket) of water. Which is not particularly safe either, however.
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Old 08-19-2017, 12:16 AM
puzzlegal puzzlegal is offline
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It's quite noticeable. The light gets dimmer, shadows look weird, and if you glance at the sun you see a bit taken out of it.
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Old 08-19-2017, 12:23 AM
Nava Nava is offline
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Quote:
Originally Posted by HeyHomie View Post
What could an ancient viewer have had on hand that could have helped him safely view the eclipse?
Amber or other transparent colored gems could be used; amber can be sliced into sheets.

Last edited by Nava; 08-19-2017 at 12:24 AM.
  #15  
Old 08-19-2017, 01:04 AM
Tom Tildrum Tom Tildrum is online now
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Relatively few pre-modern people would have had foreknowledge of an impending eclipse and the resources to obtain gems or sheets of amber in preparation.

There aren't any accounts of mass blindness associated with an eclipse among pre-modern people, as far as I know. Presumably if there were such instances, the stories would have circulated in the run-up to this eclipse. This suggests to me that with a certain amount of common sense and care, the mass of people can get through an eclipse just fine without special tools.
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Old 08-19-2017, 01:51 AM
standingwave standingwave is offline
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Quote:
Originally Posted by Musicat View Post
How about a piece of something thin with a pinhole? When were pinholes invented?
Quite some time ago in the form of the camera obscura. No doubt, inspired by seeing projections from a canopy of leaves or perhaps wickerwork. Earliest know writings come from 400 BCE China followed closely by Aristotle. Seems reasonble that predates written history as the article suggest. Fascinating.
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Old 08-19-2017, 07:14 AM
Darren Garrison Darren Garrison is offline
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Originally Posted by puzzlegal View Post
It's quite noticeable. The light gets dimmer, shadows look weird, and if you glance at the sun you see a bit taken out of it.
I was near dead center for the annular eclipse of 1984 (the "x" where it crosses 2017 marks my spot) and I don't recall anything noticeable about it in the surrounding environment (but I was 12 at the time.)

Oh, and besides the reflecting dish method, I looked directly at it.

Last edited by Darren Garrison; 08-19-2017 at 07:14 AM.
  #18  
Old 08-19-2017, 07:26 AM
Xema Xema is offline
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Quote:
Originally Posted by Darren Garrison View Post
Yes, but how often do you as much as glance directly at the sun (when it isn't low on the horizon?)
Occasionally - for a very short time. No eye damage thus far.

Quote:
Unless you notice a dimming of the light, why would you be looking at the sun at all?
Curiosity. Watching it emerge from or disappear behind a cloud. Watching a bird that happens to fly near it. Catching a baseball. Etc.

The change in light due to even a slight eclipse would of course attract much attention.

Quote:
I'm asking in the context of the warnings of eye damage from even brief glances at the sun.
Those warnings are probably overdone - or at least over-interpreted. They speak of the possibility of eye damage, and some people hear it as a near certainty.
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Old 08-19-2017, 07:33 AM
Darren Garrison Darren Garrison is offline
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Quote:
Originally Posted by Xema View Post
The change in light due to even a slight eclipse would of course attract much attention.
But the moon creeps across the sun much more slowly than a cloud passing in front of it, and the eye has a huge dynamic range for adjusting to different lighting conditions. I'm not so sure that they would notice a very slow decrease in light level at all unless it approached twilight conditions.

Last edited by Darren Garrison; 08-19-2017 at 07:34 AM.
  #20  
Old 08-19-2017, 12:08 PM
gogogophers gogogophers is offline
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Quote:
Originally Posted by Darren Garrison View Post
But the moon creeps across the sun much more slowly than a cloud passing in front of it, and the eye has a huge dynamic range for adjusting to different lighting conditions. I'm not so sure that they would notice a very slow decrease in light level at all unless it approached twilight conditions.
IMHO you are wrong, But then again, maybe the ancients were exceptionally unobservant.
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Old 08-19-2017, 12:56 PM
Darren Garrison Darren Garrison is offline
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Originally Posted by gogogophers View Post
IMHO you are wrong, But then again, maybe the ancients were exceptionally unobservant.
I'm not saying that the ancients were unobservant, but that if there was an unannounced partial eclipse, I'd never know about it even if I was standing directly under it.
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Old 08-19-2017, 01:25 PM
Hari Seldon Hari Seldon is offline
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I have looked at the sun many times with no harm. Of course it was on the horizon and therefore heavily filtered by the atmosphere. But if extra air is all the filter you need, I think the danger is oversold. During an annular eclipse a centered a couple hundred miles south of here (and thus not annular here) I watched it through a couple CDs.
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Old 08-19-2017, 02:10 PM
John Mace John Mace is offline
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How about a piece of something thin with a pinhole? When were pinholes invented?
Shortly after the invention of the pin.
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Old 08-19-2017, 02:27 PM
gogogophers gogogophers is offline
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Originally Posted by Darren Garrison View Post
I'm not saying that the ancients were unobservant, but that if there was an unannounced partial eclipse, I'd never know about it even if I was standing directly under it.
Perhaps not, but someone amongst you, WOULD notice.
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Old 08-19-2017, 06:59 PM
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Its been recorded that Galileo's viewing of the magnified sun for sunspots was the cause of his late-life blindness. This was known even in his time.
Almost certainly a myth. Initially Galileo seems to have been rather careful about only looking at the Sun with telescopes through clouds or close to sunset. (Neither procedure is remotely recommended, but they can work.) He then fairly quickly latched on to the recommendable standard projection methods that are absolutely safe.

In terms of his ultimate blindness, that was indeed late-life, so it's difficult to see why his early sunspot observations should produce damage that manifested itself as a progressively debilitating degeneration several decades later. (And in both eyes at that; my experience is that telescopic observers almost exclusively use one particular eye.) Nor can I think of any references to anyone suggesting this at the time.

That said, I've pointed out on the Dope before that there are historical examples of early modern astronomers damaging their eyesight by looking at the Sun. Including Isaac Newton. It's just that Galileo probably wasn't one of them.
  #26  
Old 08-19-2017, 07:04 PM
Mangetout Mangetout is offline
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Quote:
Originally Posted by Darren Garrison View Post
Yes, but how often do you as much as glance directly at the sun (when it isn't low on the horizon?) Unless you notice a dimming of the light, why would you be looking at the sun at all? (I'm asking in the context of the warnings of eye damage from even brief glances at the sun.)
Before modern clocks and wristwatches, glancing at the sun was one way to tell the time.
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Old 08-21-2017, 09:57 AM
apLundell apLundell is offline
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Quote:
Originally Posted by Darren Garrison View Post
But the moon creeps across the sun much more slowly than a cloud passing in front of it, and the eye has a huge dynamic range for adjusting to different lighting conditions. I'm not so sure that they would notice a very slow decrease in light level at all unless it approached twilight conditions.
I think you would. Shadows look odd during an eclipse.

Partially because it's getting dimmer, but the shadows are still distinct. (Unlike when a cloud obscures the sun.) But mostly because shadows change shape.

https://petapixel.com/2012/05/21/cre...solar-eclipse/

Someone who spends a lot of time outside would notice this pretty quickly. It'd be perfectly natural to glance back at the sun to see what was up.
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Old 08-21-2017, 05:55 PM
Darren Garrison Darren Garrison is offline
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So I noticed a significant drop in temperature after only around 50 percent coverage, but didn't notice a change in the light until around 80 to 90 percent coverage.
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Old 08-21-2017, 06:04 PM
aceplace57 aceplace57 is offline
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There's a story in the Bible about a battle that was almost won. God gave a few more hours of light so the Israelites could secure victory.

Isn't that now thought to be an eclipse reference?

It went dark. Light comes back. Seems to fit.
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Old 08-21-2017, 06:20 PM
RedSwinglineOne RedSwinglineOne is offline
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We saw about 79% coverage here today and although the light looked a bit strange, it wasn't strange enough to made me look at the sun if I hadn't know what was going on.
It would be easy for me to imagine it going unnoticed by a large number of people.

We did get some hazy clouds pass by though, and when that happened you could look at the sun directly with no problem and then the eclipse was clear. The sun was low enough in the sky at that time that it could have been noticed without "looking" for it.
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Old 08-21-2017, 06:52 PM
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Ancient people spent much more time outside than you do. And even when inside, depended much more on sunlight than you do.

Also, depending on where you are, sunlight may be much more direct and clear. I notice this, of course, as an Australian: your sunlight is so murky, of course you don't notice changes in the sun.... but I think Greece and parts of the Mediterranean also have a reputation for strong clear light???
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Old 08-21-2017, 07:53 PM
UncleRojelio UncleRojelio is offline
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I probably shouldn't have done this but there was some cloud cover during the eclipse here. I glanced up as a cloud passed over and the naked eye view of the eclipse through the edge of the cloud was startling.
  #33  
Old 08-21-2017, 11:29 PM
rowrrbazzle rowrrbazzle is offline
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Originally Posted by Darren Garrison View Post
I was near dead center for the annular eclipse of 1984 (the "x" where it crosses 2017 marks my spot) and I don't recall anything noticeable about it in the surrounding environment (but I was 12 at the time.)
I observed the annular eclipse of 1994, which covered a bit more of the Sun than yours. https://en.wikipedia.org/wiki/Solar_...f_May_10,_1994

The dimmer light was noticeable, though not as dramatic as a total eclipse. I did manage to spot Venus with the naked eye, but after I looked away I couldn't find it again.
  #34  
Old 08-22-2017, 09:17 AM
ZipperJJ ZipperJJ is offline
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Quote:
Originally Posted by Xema View Post
No need to stare - you can glance at the sun and see it's partially eclipsed. If it's more than about 15%, it would be very hard not to notice.
Hmm...here in Ohio where we had about 80% coverage, I glanced up at about 1:30 when it was 20-30% covered and could not tell one bit that there was an eclipse. It was cloudless and the sun was bright as heck. And circular.

It wasn't until I put my glasses on and looked up that I saw the distinct coverage by the moon.

Later in the event when it was at 80% it was hard to tell what was eclipse and what was clouds, as the clouds had rolled in by then. The sun still looked like a big circle here. And all of the unfiltered photos I saw online afterwards, it just looked like a regular sun tooo.
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Old 08-22-2017, 06:45 PM
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Quote:
Originally Posted by HeyHomie View Post
What could an ancient viewer have had on hand that could have helped him safely view the eclipse?
Clouds, pinhole cameras via the trees.

Quote:
Two bonus questions: When did we start weaving (several layers of woven cloth could function as a crude form of shade through which to observe the sun/an eclipse)?
How thin a layer can you weave? You would need a fairly transparent cloth to not have the cloth blur the image.


Quote:
Originally Posted by Xema View Post
The change in light due to even a slight eclipse would of course attract much attention.
Quote:
Originally Posted by Darren Garrison View Post
But the moon creeps across the sun much more slowly than a cloud passing in front of it, and the eye has a huge dynamic range for adjusting to different lighting conditions. I'm not so sure that they would notice a very slow decrease in light level at all unless it approached twilight conditions.
Here we had about 75% occlusion. At peak coverage, the sky was slightly darker blue toward the horizon, kinda like evening or a storm moving in but without clouds. The human eye has a huge dynamic range, so much so that bright full sunlight and full moon nights are both within the range. The progression of the eclipse takes place over about 45 minutes, so that's a very gradual lessening of the light. It takes a very large occlusion before there is a perceptible change in the sky, because the eye is adapting to the light level.

Shadows do show changes, if you have tall trees. The trees have to be tall enough for the openings between the leaves to function like a pinhole camera. We looked around here, but the trees aren't quite tall enough to give really good images. We could see a few crescents, but nothing like the images show in apLundell's link.

Quote:
Originally Posted by Xema View Post
Those warnings are probably overdone - or at least over-interpreted. They speak of the possibility of eye damage, and some people hear it as a near certainty.
The thing is, if you stare at an eclipse, even a 90% occluded one, there is still enough light to burn your retinas. And since they don't have pain receptors, you may not notice until the next day. The real problem is a full sun is bright enough to make you shut your eyes - it is difficult to stare. A small to mid eclipse probably will work the same. The problem is getting into a high occlusion eclipse, where the light is reduced enough it may not force you to close your eyes, but will still be bright enough to cause damage. That's why the need for the warning. Our local news channel had a story on a 70ish year old man who burned his eyes as a kid looking at an eclipse. It's not worth the risk.

Quote:
Originally Posted by ZipperJJ View Post
Later in the event when it was at 80% it was hard to tell what was eclipse and what was clouds, as the clouds had rolled in by then. The sun still looked like a big circle here. And all of the unfiltered photos I saw online afterwards, it just looked like a regular sun tooo.
Cameras have much less dynamic range than eyeballs. You need solar filters for cameras just like you need solar filters for your eyes. The Sun overwhelms the film/sensors into just a bright spot.

Quote:
Originally Posted by aceplace57 View Post
There's a story in the Bible about a battle that was almost won. God gave a few more hours of light so the Israelites could secure victory.

Isn't that now thought to be an eclipse reference?

It went dark. Light comes back. Seems to fit.
There are certainly some people who interpret it that way, just like there are some people who interpret it to mean that God turned on a celestial light bulb to give them more light or God turned the Earth backwards a bit to lengthen the day. A story about God interceding to aid the Israelites in battle does not need an objective explanation - it could simply be mythology.
  #36  
Old 08-22-2017, 07:07 PM
Bones Daley Bones Daley is online now
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Quote:
Originally Posted by aceplace57 View Post
There's a story in the Bible about a battle that was almost won. God gave a few more hours of light so the Israelites could secure victory.

Isn't that now thought to be an eclipse reference?

It went dark. Light comes back. Seems to fit.
More likely that God didn't trust the Israelis in the dark ... just like the Brits, and their empire on which the sun never set ...

Last edited by Bones Daley; 08-22-2017 at 07:08 PM.
  #37  
Old 08-22-2017, 09:14 PM
Xema Xema is offline
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The problem is getting into a high occlusion eclipse, where the light is reduced enough it may not force you to close your eyes, but will still be bright enough to cause damage.
I did some experiments Monday, as the eclipse progressed.

I concluded that until at least 40% of the sun is covered, the change seems really small and would be easy to miss. You can definitely do a quick glance and see that an eclipse is underway - but you have absolutely no tendency to make it anything but very short.

At 80%, the change in light was significant - probably few ancient people would have been unaware. But it still isn't dramatic - if you just stepped outside, you might not notice. At 90%, it would be hard not to.

Even at 95%, the light is plenty bright enough that any glance will be very short. I couldn't imagine any normal person wanting to do anything that could be called staring.

Past 95%, I did no glancing without eclipse glasses until the diamond ring appeared. Even a few seconds before totality, it still seemed very bright.
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