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.
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.
Shortly after the invention of the pin. 
Perhaps not, but someone amongst you, WOULD notice.
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.
Before modern clocks and wristwatches, glancing at the sun was one way to tell the time.
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.
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.
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.
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.
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.
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???
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.
I observed the annular eclipse of 1994, which covered a bit more of the Sun than yours. Solar eclipse of May 10, 1994 - Wikipedia
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.
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.
Clouds, pinhole cameras via the trees.
How thin a layer can you weave? You would need a fairly transparent cloth to not have the cloth blur the image.
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.
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.
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.
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.
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 …
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.