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  • - [Narrator] Whether it's to map the stars,

  • spy on other planets, or study the sun,

  • humans have been looking to the skies for millennia,

  • but some objects are safer to observe than others.

  • For example, astronomer Mark Thompson put a pig's eye

  • behind a regular telescope and aimed it at the sun,

  • and it burned a hole straight through the lenses

  • in about 20 seconds.

  • Now looking at the sun through a telescope

  • is an especially terrible idea,

  • but just how bad is it to glance up with the naked eye?

  • On a clear day the sun shines up to 5000 times brighter

  • than an average light bulb.

  • When something that bright strikes your eye,

  • a few things can happen.

  • If it's only for a moment the worst you'll experience

  • is a blurry splotch on your vision called an after image.

  • Normally light reaches the retina at the back of your eye

  • where it triggers photo receptors

  • that relay the information to your brain.

  • This is how you're able to see anything,

  • but bombard them with too much light at once,

  • and you can actually damage the cells and proteins

  • that help them process light.

  • Since your retina has no pain receptors

  • the damage won't hurt,

  • but it will leave the blurry splotch on your vision.

  • Usually it clears up in a few minutes

  • that is unless you keep staring.

  • Now you're doing more damage

  • than just overloading your retina.

  • For starters you're giving your eyes

  • an abnormally high dose of UV radiation,

  • the same stuff that causes sunburns.

  • Like your skin the cornea at the front of your eye

  • can also burn and that will hurt.

  • The cornea protects the rest of your eye,

  • and is therefore covered in pain receptors

  • that alert you whenever a pesky eyelash is on the loose,

  • but UV radiation isn't the only issue.

  • Too much visible light can penetrate your eye

  • and damage the retinal tissue

  • which causes a condition called solar retinitis.

  • This means parts of retina

  • can no longer process light normally,

  • so you can end up with entire chunks

  • of your vision blurred out.

  • Depending on the extent of the damage

  • recovery can take weeks, months,

  • and in severe cases over a year,

  • but in rare cases the damage is so extreme it never heals

  • leading to a rare condition called solar retinopathy.

  • This usually only shows up in reckless eclipse gazers.

  • Turns out during a solar eclipse most of the sun's light

  • is blocked which can actually trick your brain

  • into thinking it's safe to stare.

  • Normally our bodies have a built-in defense mechanism

  • against staring at the sun.

  • Specifically when we squint we look up

  • which minimizes the amount of light coming in

  • and protects our cornea and retina,

  • but during a solar eclipse the sun doesn't appear

  • bright enough to trigger our defense mechanisms,

  • so we can end up staring for longer than is safe.

  • Suffice to say there's nothing good

  • about staring at the sun,

  • so do your eyes a favor and avoid looking at it.

  • After all, there are around 6000 stars

  • in the night sky which you can safely observe

  • for as long you wish.

- [Narrator] Whether it's to map the stars,

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B2 中上級

あなたがあまりにも長い間太陽を見つめるときに何が起こるか (What Happens When You Stare At The Sun For Too Long)

  • 30 1
    Seraya に公開 2021 年 01 月 14 日
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