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Because you didn't look at it during an eclipse, when its more dangerous than looking at it on a regular day.

QAPereo 9y ago
It's only more dangerous because of the potential lack of discomfort/pain and subsequent reflex to look away; in terms of time you can safely spend looking there is no difference.
dec0dedab0de 9y ago
I think it's more dangerous to look at the sun on a regular day, It's just more tempting to look during an eclipse.
kobeya 9y ago
Looking at the Sun for exactly the same period of time is less dangerous during an eclipse because a sizable percentage of the radiation, but not all, is blocked by the Moon. Where the danger comes in is that normally the Sun is so bright that if you mistakenly look into it your natural reflexes cause you to flinch away, prevent anything more than a momentary glimpse lasting fractions of a second. During an eclipse the Sun is dim enough that you could stare at it without "visual pain" (for lack of a better term -- whatever you call something that is too bright) to such a degree as to cause instinctual look-away reflexes. As a result if you were dumb enough, ignorant enough, or presidential enough, you could stare straight at the eclipse for seconds or 10's of seconds during totality. During that time it will not seem "too bright", but nevertheless your eyes will be focusing intensely damaging UV radiation onto your cornea, causing those cells to malfunction and die, which is what causes blindness. That said, this is highly educated, rational crowd. I would not feel comfortable giving this explanation to a gathering of the general public because it can easily be misconstrued to mean "this guy says looking at the Sun during the eclipse is not as dangerous as everyone says it is" which has the exact opposite implication with respect to safety. I expect this is why the "looking at the Sun during an eclipse is more dangerous" meme got started -- it results in better safety.
- jl6 9y ago
  Why is the light reduced by a huge amount during an eclipse but the UV is still at dangerous levels?
  - deadmetheny 9y ago
    Because the moon is in front of the sun. The brightness is reduced during partial coverage to the point that you won't reflexively look away anymore, but the UV is still there and still causes eye damage.
    - deadmetheny 9y ago
      So why am I being downvoted for answering a question, exactly?
      - jstanley 9y ago
        I didn't downvote you, but the reason some did is probably because we want to know why the UV is still there. Merely restating that the UV is still there contributes nothing.
  - amluto 9y ago
    As I understand it, the relevant factors are the brightness per unit solid angle (aka surface brightness), the aperture (area of your pupil). The degree of danger for a given time spent starting at the sun is proportional to the product. The surface brightness of the sun is the same during a partial eclipse: each bit of sun is just as bright as if there was no eclipse -- there's just less of the sun visible. This is true in visible and UV, so the ratio of UV to visible light is unchanged. The problem is that everything gets darker, so your eyes dilate, which increases the danger. Also, partial eclipses are neat, so you're more likely to stare. During totality, it's a whole different ballgame. You can't see the bright part of the sun, and all that's left has much less surface brightness. I think it's roughly comparable to the moon.
  - saltcured 9y ago

It's only more dangerous because of the potential lack of discomfort/pain and subsequent reflex to look away; in terms of time you can safely spend looking there is no difference.

dec0dedab0de 9y ago

I think it's more dangerous to look at the sun on a regular day, It's just more tempting to look during an eclipse.

kobeya 9y ago

Looking at the Sun for exactly the same period of time is less dangerous during an eclipse because a sizable percentage of the radiation, but not all, is blocked by the Moon. Where the danger comes in is that normally the Sun is so bright that if you mistakenly look into it your natural reflexes cause you to flinch away, prevent anything more than a momentary glimpse lasting fractions of a second. During an eclipse the Sun is dim enough that you could stare at it without "visual pain" (for lack of a better term -- whatever you call something that is too bright) to such a degree as to cause instinctual look-away reflexes. As a result if you were dumb enough, ignorant enough, or presidential enough, you could stare straight at the eclipse for seconds or 10's of seconds during totality. During that time it will not seem "too bright", but nevertheless your eyes will be focusing intensely damaging UV radiation onto your cornea, causing those cells to malfunction and die, which is what causes blindness. That said, this is highly educated, rational crowd. I would not feel comfortable giving this explanation to a gathering of the general public because it can easily be misconstrued to mean "this guy says looking at the Sun during the eclipse is not as dangerous as everyone says it is" which has the exact opposite implication with respect to safety. I expect this is why the "looking at the Sun during an eclipse is more dangerous" meme got started -- it results in better safety.

jl6 9y ago
Why is the light reduced by a huge amount during an eclipse but the UV is still at dangerous levels?
- deadmetheny 9y ago
  Because the moon is in front of the sun. The brightness is reduced during partial coverage to the point that you won't reflexively look away anymore, but the UV is still there and still causes eye damage.
  - deadmetheny 9y ago
    So why am I being downvoted for answering a question, exactly?
    - jstanley 9y ago
      I didn't downvote you, but the reason some did is probably because we want to know why the UV is still there. Merely restating that the UV is still there contributes nothing.
- amluto 9y ago
  As I understand it, the relevant factors are the brightness per unit solid angle (aka surface brightness), the aperture (area of your pupil). The degree of danger for a given time spent starting at the sun is proportional to the product. The surface brightness of the sun is the same during a partial eclipse: each bit of sun is just as bright as if there was no eclipse -- there's just less of the sun visible. This is true in visible and UV, so the ratio of UV to visible light is unchanged. The problem is that everything gets darker, so your eyes dilate, which increases the danger. Also, partial eclipses are neat, so you're more likely to stare. During totality, it's a whole different ballgame. You can't see the bright part of the sun, and all that's left has much less surface brightness. I think it's roughly comparable to the moon.
- saltcured 9y ago