我与液态氮的亲密接触瞬间

Protected By Science My hand is like a red-hot poker to the liquid nitrogen, but an insulating layer of nitrogen gas forms- a phenomenon known as the Leiden-frost effect- keeping my hand safe and warm for a fraction of a second. Mike Walker

被科学所庇护——根据莱顿弗罗斯特效应，液态氮在我的皮肤表面形成了一层隔绝的气态层，从而在瞬间使我的手保持安全与温暖。Mike Walker 拍摄。

When I first saw this photograph of a man’s hand submerged in liquid nitrogen at somewhere below -320° F, my immediate thought was, “That guy must be crazy! One second in that stuff, and you’re shopping for new skin!” My shock was tempered only slightly by the fact that it was my hand, and we’d taken the picture just a minute earlier.

当我第一眼看到一个男人把手浸在液态氮（低至华氏零下320°）里的照片时，第一反应就是：这家伙一定是疯了！把手放在那玩意儿里一秒钟，你就得购买新皮肤了！”但当意识到照片里的手正是我自己的手，而这张照片恰是我们一分钟前刚刚拍下的事实时，我的震惊缓和下来。click here.

I hadn’t realized that my hand was quite so deep into the liquid. Amazingly, I barely felt the cold at all. My skin didn’t get hurt for the same reason that water droplets dance on a hot skillet. An insulating layer of steam forms almost instantly between the water and the metal, keeping the droplets relatively cool as they float for several seconds without actually touching the hot surface. To liquid nitrogen, flesh is like that skillet—a surface hundreds of degrees above its boiling point. So the moment my hand touched the liquid, it created a protective layer of evaporated nitrogen gas, just as the skillet created a layer of steam. That gave me just enough time to put my hand in and pull it out again. Any longer than that, and frostbite would have set in.

我不曾意识到我的手在液态氮瓶中如此深入。令人惊奇的时，我甚至没感觉到冷气的存在。我的皮肤一点也没有受到伤害，这与小水滴在平底煎锅上跳舞的原理是一致的——水与金属接触的瞬间会产生一层蒸气层，使得小水滴可在上面漂浮几秒且不接触金属的热表面。在我的试验中，对于液态氮来说，比其沸点高几百度的皮肤就是那个平底锅。所以在我亲密接触液态氮的瞬间，它产生了一层氮蒸汽保护层，就像平底锅所产生的水蒸汽层。这给了我足够的时间把手伸进伸出。而如果时间再长一点，冻伤就不可避免。

Hot water:droplets on a very hot skillet take longer to evaporate than they would on a less-hot surface where no insulating gas layer forms.  Mike Walker

水滴在十分炙热的平底锅表面的蒸发时间要比那些不太热的，没有形成隔绝蒸汽层的表面上花的时间更长。摄影： Mike Walker

The phenomenon is called the Leidenfrost effect (after Johann Gottlob Leidenfrost, the doctor who first studied it in 1756). I’d known about it for years, but when it came time to test it in real life, I have to admit that I used my left hand, the one I’d miss less.

这一现象被称为莱顿弗罗斯特效应，是由Johann Gottlob Leidenfrost博士1756年首次发现并由此而命名的。我知道这个科学定理已有些年头了，但在我亲自验证它的时候，我得承认，我用了我可能会怀念得少一些的左手。

I drew the line at another classic example of the effect. According to the books, it’s possible to stick a damp finger directly into molten lead without getting burned, if you do it fast enough. After some consideration, and remembering the times I’ve been burned by molten lead, I decided that it probably wouldn’t make a very good picture anyway.

我没有用另一个经典实验来验证这一效应。书上说，如果你的动作足够迅速，你可以在融化的铅里伸进一根湿手指而可能不被烫伤。经过深思熟虑，加上记起我被融铅烫伤的次数，我决定放弃，毕竟，那不一定会进行地很完美。

ACHTUNG!

警告！严禁模仿！如果液态氮浸湿了你的衣服，你就不会被莱顿弗罗斯特效应庇佑了。你会立即被冻伤。