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Title: Can you really go blind by staring at the Sun?
Source: [None]
URL Source: http://www.sciencefocus.com/qa/can-you-really-go-blind-staring-sun
Published: Aug 21, 2017
Author: Steven A Collins
Post Date: 2017-08-21 10:54:04 by no gnu taxes
Keywords: None
Views: 7110
Comments: 21

It’s possible, but the hazard is often exaggerated. Even at midday, a normal eye will only let in enough light to heat the retina by about 4°C. You need at least 10°C to cause thermal damage. Looking at the Sun during an eclipse for more than a minute can cause damage, because your pupils are more dilated during this, but it doesn’t result in total blindness and isn’t usually permanent. If the Sun is within 10 minutes of setting below a sea-level horizon, the more dangerous short-wavelength light is absorbed by the atmosphere and it should be quite safe to look at the Sun.

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Begin Trace Mode for Comment # 6.

#1. To: no gnu taxes (#0)

18 seconds. If you look directly at the sun for more than 15 seconds, you will burn a permanent spot on your retina that will never heal. A GLANCE probably won't destroy your vision, but what is going on up there is fascinating, and draws you in, and you really LOOK - and then you're blind for life.

It isn't just during an eclipse. Stare at the sun on any day, and you'll burn your retinas blind. But who stares into the Sun? It's when there's an eclipse that the problem comes, because everybody wants to LOOK, and when looking, people are drawn to stare. And that will leave you blind.

Vicomte13  posted on  2017-08-21   11:02:08 ET  Reply   Untrace   Trace   Private Reply  


#4. To: Vicomte13 (#1)

You overlook that significant damage can be caused by sunburn to the inner eye. And no pain receptors to warn you of the danger.

18 seconds. If you look directly at the sun for more than 15 seconds, you will burn a permanent spot on your retina that will never heal.

I do think this is a little overhyped.

Tooconservative  posted on  2017-08-21   11:51:24 ET  Reply   Untrace   Trace   Private Reply  


#6. To: Tooconservative (#4)

I do think this is a little overhyped.

Yes. A one second, two second glance isn't going to do anything. But 15-18 seconds will leave you with a blind spot for life. That's not a huge margin. I'll go out at the eclipse and glance at it when it happens, but that's just it - a glance - no staring at it.

Stare at the midday sun for more than a few seconds on any day and you will be blind for life.

Vicomte13  posted on  2017-08-21   12:50:25 ET  Reply   Untrace   Trace   Private Reply  


Replies to Comment # 6.

#7. To: Vicomte13 (#6)

You are cautious. I can't say overcautious because we shouldn't encourage anyone to ever stare directly at the sun. Nothing good can come from it.

Tooconservative  posted on  2017-08-21 14:27:33 ET  Reply   Untrace   Trace   Private Reply  


#8. To: Vicomte13 (#6)

No, I won't be staring at the sun. I see no useful purpose in it and it does nothing good for you. However....

................................

http://boards.straightdope.com/sdmb/showthread.php?t=102708

I have done some research on this topic. From what I have found, no one has ever gone totally and permanently blind from looking at the Sun. Solar retinopathy (retinal damage from looking at the Sun) is, however, a complicated issue.

The damage comes mostly from ultraviolet light which can damage chemicals in your eye. Many people claim erroneously that infra-red can cook your eye, but this is almost certainly not true; IR light is not absorbed well by your eye. In general, your pupil constricts so rapidly that there isn't time to hurt your eye easily. Staring at the Sun can indeed damage your retina, but there are many cases of full recovery from people who have looked at the Sun for long periods of time. Interestingly, the pupil blocks just barely enough light (on average) to prevent damage; so in some of the population the pupil does not constrict enough. The lens also yellows with age, protecting older people more from the UV light. Therefore, children are more susceptible to damage than adults.

All in all, better safe than sorry; avoid staring at the Sun.

The reason solar eclipses are dangerous is because during totality the pupil dilates, letting in more light since the Sun is blocked. When the Moon slips off the Sun, even the thin sliver of solar surface can be enough to flood your retina with damaging photons, since the pupil is wide open.

A very interesting website with a lot of information has been put together by astronomer Andrew Young. He also puts to rest the legend that Galileo went blind by looking at the Sun; he has excellent counter-evidence for that.

no gnu taxes  posted on  2017-08-21 14:46:17 ET  Reply   Untrace   Trace   Private Reply  


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