LIGHTNING
闪电
They say lightning strikes the tallest thing around. That 8217;s the kind of maddeningly inexact statement that immediately sparks all kinds of questions. How far is “around”? I mean, not all lightning hits Mount Everest. But does it find the tallest person in a crowd? The tallest person I know is probably Ryan North.2 Should I try to hang around him for lightning safety reasons? What about other reasons? Maybe I should stick to answering questions rather than asking them.So how does lightning pick its targets?
人们总说闪电会击中附近最高的东西。这种极其含糊的说法简直就是个招人质疑的活靶子，“附近”是多远？我说，好像不是所有的闪电都会击中珠穆朗玛峰吧。但闪电会击中人群中长得最高的人吗？我所知道的最高的人应该是瑞恩•诺斯3了。那出于安全考虑，我是不是只要站在他旁边就不会被闪电击中了呢？如果是其他原因呢？也许我应该回答问题，而不是提出问题。那么闪电是如何选择目标的呢？
The strike starts with a branching bundle of charge-the “leader”-descending from the cloud. It spreads downward at speeds of tens to hundreds of kilometers per second, covering the few kilometers to the ground in a few dozen milliseconds.
闪电最先会形成一个叉状电荷，又被称为先导。先导会从云端伸出向下延伸，以每秒几十到几百千米的速度向地面传播，在几十毫秒的时间内穿过几千米长的空气到达地面。
The leader carries comparatively little current-on the order of 200 amps. That 8217;s still enough to kill you, but it 8217;s nothing compared to what happens next. Once the leader makes contact with the ground, the cloud and the ground equalize with a massive discharge of more like 20,000 amps. This is the blinding flash you see. It races back up the channel at a significant fraction of the speed of light, covering the distance in under a millisecond .
先导中的电流相对较小，大约在200安培这个数量级，这点电流也足够电死你了，但与之后发生的相比就有点相形见绌了。一旦先导接触到地面，云层和地面之间就会发生剧烈的电荷中和过程，放电电流将会超过2万安培。在这个过程中你就会看到一道亮眼的闪光，接着先导会以光速的几分之一速度原路返回，在不到1毫秒的时间内就能回到云端。
The place on the ground where we see a bolt “strike” is the spot where the leader first made contact with the surface. The leader moves down through the air in little jumps. It 8217;s ultimately making its way toward the (usually) positive charge in the ground. However, it “feels” charges within only a few tens of meters of its tip when it 8217;s deciding where to jump next. If there 8217;s something connected to the ground within that distance, the bolt will jump to it. Otherwise, it jumps out in a semi-random direction and repeats the process.
我们看到的闪电“击中”地面的地方，就是之前先导最先接触到地面的地方。先导在空气中呈跳跃状向下传播，它最终会向着（通常是）地面上的正电荷前进。不过，它在决定下一步跳向哪里时只能“感知”尖端附近几十米范围之内的电荷。如果在这个范围内地面上连着什么东西，那么闪电就会跳到这个东西上，否则就会半随机地挑选一个方向，然后重复这一过程。
To figure out where lightning is likely to hit, you roll the imaginary 60-meter sphere across the landscape.4 This sphere climbs up over trees and buildings without passing through anything (or rolling it up). Places the surface makes contact-treetops, fence posts, and golfers in fields-are potential lightning targets.
为了找出闪电会击中哪里，你在地面上滚动着这个假想的半径60米的球。5这个大球会爬到树上或建筑上面而不会穿过它们（也不会把它们卷进去）。与大球表面接触的地方——树顶、栅栏以及正在打高尔夫的人——都是潜在的被雷击的目标。