why can't we watch an eclipse?
- Thread starter fire400
- Start date
Your eyes won't melt. What happens is that when it's dark outside, your pupils dialate to let more light in. Hence during totality, your eyes have opened wide to basically night-time levels. When the Sun first peeks out from behind the Moon at the end of totality, your eyes can't react quickly enough to the sudden increase in brigfhtness, and hence MAY get damaged slightly (loose sensitivity). In any case, it helps discourage fools from looking through a telescope at an eclipse with no filter on.
you really shouldn't ever look at the sun, and as said before, its even worse when your pupils dilate and then you look at the sun because you could damage your retinas. I know just looking at the sun for a second gives me purple dots in front of my eyes for awhile after that, if some fool stares at it during an ecliplse they could have permentant damage and not jsut retinal after images like when you glance at the sun.
PowerEngineer
Diamond Member
- Oct 22, 2001
- 3,570
- 738
- 136
You can directly view a solar eclipse dujring the period of time that it is "total". During the partial phases on a solar eclispe, the sun is still pouring UV radiation from the exposed part of its disk into your eyes which is not good. I think the risk of damage from the visible light part of the spectrum is less serious. Here's one of many links on the subject; google for more...
I'll speculate that it has something to do with the extremely high contrast, though I'll tell you up front that I'm not a retina person. Contrast is defined as (max I - min I)/(max I + min I), where I is light intensity. When a very high contrast (~1) occurs, it would cause some sort of high energy gradient in the retina. Some rods/cones would be at maximum output, while others adjacent would have no output. This might result in cell damage. Again, just speculation, but it sounds cool, right? 
I've always heard that the outside of the sun is the brightest, so when the moon eclipses it, the brightest part of the sun is being exposed
You certainly may watch an eclipse to your heart's content.
Go down to your local welding supply store and pick up some goggles or a mask that have #14 welders shade in them. #12 is the most popular but isn't enough.
Grab a beer and a lawn chair and you're all set!
Go down to your local welding supply store and pick up some goggles or a mask that have #14 welders shade in them. #12 is the most popular but isn't enough.
Grab a beer and a lawn chair and you're all set!
forrestroche
Senior member
- Apr 25, 2005
- 529
- 7
- 81
The thing about damage to your eyes is just an urban myth. There's actually no danger. It's like the whole thing about asbestos.
I heard a different story about it, but I might be WAY off: A much higher fraction of some of the invisible eye-damaging radiation is preserved than that of visible light, so even if it looks less bright (which it mostly won't, due to the contrast), you're unknowingly damaging your eyes even more. But like I said, I may be WAY off about this, cause I heard it in my childhood.
sao123
Lifer
- May 27, 2002
- 12,653
- 205
- 106
which part? when he said he stared at a partial eclipse? or when he said that his vision didn't change?
When he said he has 100/100 vision. 100/100 vision is not the same as 20/20 vision, at least in the Snellen visual acuity system (the one that everyone uses). 100/100 doesn't really exist in this system.
Oops. Thought those numbers referred to the left and right eye. Anyway, what I meant was that it messed up my eye and now I'm shortsighted to .125.
That doesn't make sense either. There is no reason radiation should induce a dioptric change, myopic or otherwise. 0.125 diopters is totally negligible. My prescription is -4.25 diopters. If a myopic shift of 0.125 diopters was the downside of looking at an eclipse, I doubt anyone would not look. So, just admit that you're BSing and step away from the keyboard.
LOL he isnt lying! 100/100 = 20/20 lol what a geek answer.
20/100 is what would be bad. "what you see at 100 yards i can only see at 20 yards" etc etc
Read up on Snellen visual acuity. 100/100 is not equal to 20/20. This stems from the way in which schematic eye models are constructed. This goes all the way back to the work of Gullstrand, which I won't go into right now. However, basically visual acuity is based on such models. 20/20 vision means that one can clearly see in detail at 20 feet what a 'normal', emmetropic patient can see at 20 feet. 20/15 means you can see at 20 feet what the average Joe can see at 15 feet (meaning you have better vision). Thus, if 100/100 were really a used measure of visual acuity, you would be able to see at 100 feet what an average emmetrope could see at 100 feet. This does not mean that your vision would match the average emmetrope at 20 feet, however, as you may be hyperopic (implying worse vision at near distances), your vision may be very different at 20 feet. Ergo, 20/20 != 100/100 in a Snellen visual acuity sense.
so is it bad that mine is 20/400? i remember standing outside vividly and watching the eclipse in elementary school. And i can't count how many times in Shop class someone would walk up behind me and lift my welding helmet while i was welding
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