Learn all about the human eye…
了解人眼
You carry around a pair of cameras in your head so incredible they can work in bright sunshine or at night. Only 2.5cm in diameter, they can bring you the image of a tiny ant or a twinkling star trillions of kilometres away. They can change focus almost instantly and stay focused even when you're shaking your head around. These cameras are your eyes…
你头上带着一对照相机，这样它们就可以在明亮的阳光下或夜晚工作了。直径只有2.5厘米，它们能给你带来数万亿公里外的一只小蚂蚁或一颗闪烁的恒星的影像。它们几乎可以立即改变焦点，即使你摇头也能保持注意力集中。这些相机是你的眼睛。
Eye-Popping Fact ONE: A crucial part of your eyes is as flimsy as a wet tissue!
令人瞠目结舌的事实一：你眼睛的关键部位就像湿纸巾一样脆弱！
A fly darts towards your head! Light bounces off the insect and enters your eye's cornea, a clear covering over your eye. The light passes through your pupil, the black circle in the centre of the iris, to the lens. The lens focuses the light onto your retina – a thin but vital lining on the back of your eye that is as flimsy as a wet tissue. Your retina acts like camera film, capturing the picture of the fly. This image is sent to the brain, which instantly tells you to – duck!
一只苍蝇飞向你的头！光线从昆虫身上反射，进入你的眼角膜，一个覆盖在你眼睛上的透明物。光线通过你的瞳孔，虹膜中心的黑色圆圈，到达镜头。晶状体将光线聚焦到视网膜上，视网膜是你眼睛后部一层薄而重要的内层，薄如湿组织。你的视网膜就像照相机的胶片，捕捉苍蝇的照片。这张图片被发送到大脑，大脑会立即告诉你-鸭子！
Eye-Popping Fact TWO: You blink more than 10,000 times a day!
令人瞠目结舌的事实二：你每天眨眼超过一万次！
Your sight is incredibly important , so your body has ways to protect your eyes. Each eye sits on a cushion of fat, surrounded by protective bone. Your eyebrows prevent sweat dripping into your eyes, while eyelashes keep dust and other particles out. The eyelids act as windscreen wipers, spreading tear fluid with every blink to keep your eyes moist and wash away bacteria. You blink more than 10,000 times a day! And if anything gets too close, your eyelids slam shut with amazing speed. How fast does this happen? In the blink of an eye – about 2/5 of a second!
你的视力非常重要，所以你的身体有办法保护你的眼睛。每只眼睛都坐在脂肪垫上，周围有保护性的骨头。你的眉毛可以防止汗水滴入眼睛，而睫毛可以防止灰尘和其他微粒进入眼睛。眼睑起着挡风玻璃雨刷的作用，每眨眼一眨眼，都会散开泪液，保持眼睛湿润，洗去细菌。你每天眨眼超过10000次！如果有什么东西靠得太近，你的眼皮会以惊人的速度猛地闭上。这种情况发生得有多快？一眨眼之间——大约2/5秒！
Eye-popping Fact THREE: Your eyes adjust in milliseconds to ANY movement of your head!
令人瞠目结舌的事实三：你的眼睛可以在几毫秒内适应你头部的任何运动！
You bounce your eyes around all the time. Even when you're not running or jumping, your head doesn't stay still. Why isn"t everything a blur when you"re moving? The eyes automatically adjust to the movement of your head with great speed and precision. They're good at following a moving object, and even better at adjusting to the motion of your head. Test it: Keeping your head still, hold up your hand about 30cm away, and quickly move it back and forth. As fast as your eyes are, your fingers become blurry. Now keep your hand still and move your head back and forth. Amazingly, your fingers stay in focus!
你的眼睛一直在跳动。即使你没有跑步或跳跃，你的头也不会保持静止。为什么你搬家的时候一切都不模糊？眼睛会自动适应你头部的运动，速度和精度都很高。他们善于跟踪移动的物体，甚至能更好地适应你的头部运动。测试：保持头部静止，将手举离30厘米左右，快速前后移动。你的眼睛越快，手指就越模糊。现在手不要动，头要前后移动。令人惊讶的是，你的手指保持专注！
Eye-Popping Fact FOUR: Your eyes see everything upside down and backward!
令人瞠目结舌的事实四：你的眼睛看到所有东西上下颠倒！
Your eyes are amazing, but the images they send to your brain are a little quirky – they're upside down, backward and two-dimensional! Lucky for you, the cameras in your head come with an impressive software package – your brain – that can fix these problems. The brain automatically flips the images from your retinas right side up and combines the images from each eye into a three-dimensional picture.
There is a small area of each retina, called a blind spot, that can't record what you're seeing. Your brain makes adjustments for this, too. But sometimes it can be fooled! Check it out – hold the tips of your two index fingers together, about 15cm in front of your eyes. Now separate them slightly and look past them at something in the distance. A floating finger that looks like a sausage appears between your fingers. You just fooled your brain into seeing something that isn't there!
你的眼睛是惊人的，但他们发送到你的大脑的图像是有点古怪-他们颠倒，向后和二维！幸运的是，你脑袋里的摄像头有一个令人印象深刻的软件包——你的大脑——可以解决这些问题。大脑会自动将视网膜上的图像向上翻转，并将每只眼睛的图像组合成三维图像。
每个视网膜上都有一小块区域，叫做盲点，不能记录你看到的东西。你的大脑也会对此做出调整。但有时它会被愚弄！检查一下-把两个食指的指尖放在一起，大约在眼睛前面15厘米。现在把它们稍微分开，然后从它们旁边看远处的东西。一个看起来像香肠的漂浮手指出现在你的手指之间。你只是愚弄了你的大脑去看不存在的东西！
Eye-Popping Fact FIVE! Your pupils change size whenever the light changes!
令人瞠目结舌的事实五！只要光线改变，你的瞳孔就会变大！
Your black pupils may be small but they have an important job – they grow or shrink to allow just the right amount of light to enter your eyes to let you see. Try this: Go into a windowless room, turn off the light and close the door so there is just enough light to see the pupils in your eyes in the mirror. Your pupils will be far larger than usual, having grown to their maximum size to capture as much light as possible. Now, turn on the light while still watching your pupils. You'll see them shrink to a small dot almost immediately – right before your very, um…eyes!
你的黑瞳孔可能很小，但他们有一个重要的工作-他们成长或缩小，以允许恰到好处的光线进入你的眼睛，让你看到。试试这个：走进一个没有窗户的房间，关上灯，关上门，这样就有足够的光线在镜子里看到你眼中的瞳孔。你的瞳孔将比平时大得多，已经长到最大尺寸以尽可能多地捕捉光线。现在，在看学生的时候把灯打开。你会看到它们几乎立刻缩小成一个小点-就在你的眼睛前面，嗯…眼睛！
