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Vision is arguably the most compelling human sense.
视觉可以说是最令人信服的人类感官。
Words and stories and sounds allow us to imagine strange beasts and faroff worlds, but seeing makes us truly believe they exist.
文字、故事和声音能让我们想象出奇怪的野兽和遥远的世界，但视觉能让我们真正相信它们的存在。
And that's why we place so much effort into correcting the optics of our eyes when they don't work, whether with glasses or contact lenses or surgery.
这就是为什么当我们的眼睛不能正常工作时，我们会花那么多精力去矫正我们的视力，不管是戴眼镜、隐形眼镜还是做手术。
But if you're in a pinch, bleary-eyed or missing your glasses, there's a simple trick that will allow you to see clearly,
但必要时，如果你近视或没戴眼镜，有一个简单的技巧可以让你看得更清楚，
just make a tiny, tiny hole using your fingers, look through it, and the world will become clear again.
把你的手掌握出一个非常非常小的洞，从这个洞向外看，世界就会再次变得清晰起来。
This works no matter how blurry your vision is -- take off your glasses and give it a try! Amazing, right?!
不管你的视力有多差，这招都管用——摘掉眼镜，试一试吧！很惊奇，对吧？！
But to explain this wizardry, we just need to remember how seeing works.
但要解释这一神奇现象，我们只需要记住视觉是如何起作用的。
Light travels outwards from a source, bounces off of objects in its path, travels into your eye and onto your retina, where it forms an image.
光从光源向外传播，经过物体的反射，进入你的眼睛，并进入你的视网膜，在那里形成一个图像。
If your eye had no lens, light from a single source would hit your retina in lots of places and result in a smeared-out mess,
如果你的眼睛没有晶状体，来自单一光源的光线会打到你的视网膜的很多地方，导致一片模糊的混乱，
which is exactly what happens when I take the lens off of my camera.
这正是我从相机上拿掉镜头时所发生的情况。
A lens focuses that spread-out light back into a single point, corralling it into a crisp image on your retina.
晶状体将分散的光线聚焦到一个点上，将其聚集在视网膜上形成清晰的图像。
And after a little excitation of light-sensitive nerves and interpretation from your brain, you see. But wait!
经过一点光敏神经的刺激和大脑的解释，你就明白了。但是等等！
When we look at an object, the background and foreground are usually blurry, because a lens can only focus light coming from one distance away.
当我们看向一个物体时，其背景和近景通常都是模糊的，因为晶状体只能聚焦远处的光。
If an object is too near or too far, its light will again be spread out on your retina leaving you with a blur.
如果一个物体太近或太远，它发出的光会再次扩散到你的视网膜上，留下一片模糊。
Fortunately, muscles in our eyes allow us to accommodate by squeezing the lens, which changes its focal length so we can see at different distances,
还好，我们眼部的肌肉可以通过挤压晶状体来调节焦距，这样我们就可以看到东西不同距离处的物体，
except when we can't, or when our lenses become damaged - in which case we need glasses.
除非我们看不见，或者我们的晶状体损坏了——在这种情况下我们需要戴眼镜。
Unlike a lens, a pinhole or other small opening can focus light coming from any distance:
与晶状体不同，针孔或其他小孔可以将来自任何距离的光线聚焦：
because it's such a small opening, it only allows light to come through in one place, and thus in only one direction from any particular source.
因为这是一个非常小的开口，它只允许光从一个地方通过，因此从任何特定的来源只有一个方向。
So there's no blur, and everything is in focus! If you're familiar with photography,
所以从这个小孔看到的物体不会模糊，一切都是焦点！如果你熟悉摄影，
this is why using smaller and smaller apertures makes everything in your photo come into focus.
这就是为什么使用越来越小的光圈可以让你的照片中的一切都聚焦。
Of course, small openings like pinholes and camera apertures create crisp images by blocking rather than focusing light,
当然，像针孔和相机光圈这样的小开口通过阻挡而不是聚焦光线来产生清晰的图像，
so the images are much darker, which is a major reason why we use lenses rather than pinholes for glasses, telescopes, and eyes.
所以图像要暗得多，这就是我们用透镜而不是针孔来装眼镜、望远镜和眼睛的主要原因。
And yet, in a pinch, looking through a tiny hole made with your fingers can help you see. Now do you see why?
但在紧要关头，通过你的手指挖出的一个小洞可以帮助你看清东西。现在你明白为什么了吧?
