时差N小时:航天飞机为什么发光?

During the space shuttle's third flight, back innineteen eighty two, astronauts Jack Lousma and C.Gordon Fullerton saw something remarkable. Abovethe tail of the shuttle, where there should have beenempty space, they saw a faint orange glow instead,flickering with ghostly light. Was the space shuttlehaunted? What was going on?

时光倒转回1982年，在宇航员杰克·洛思马和查尔斯·戈尔登·福勒顿进行第三次航天飞行时，他们看到了惊奇的一幕。在飞机尾部原应是空白的地方，出现了微弱的橙色辉光，诡异地扑闪着。难道航天飞机上也闹鬼?这到底是怎么回事?

To understand this phenomenon, known as "shuttle glow," you should know something aboutthe region of space where the shuttle orbits. NASA shuttles stay in low Earth orbit, which isgenerally about a hundred and seventy miles above the Earth's surface. At that height, theatmosphere has tapered away to almost nothing--less than a billionth of the pressure it is atground level--but there are still gasses there. Indeed, low Earth orbit is well within theionosphere, a major part of our atmosphere.

为了弄清楚“航天飞机辉光”这一现象，有一点你应该注意到，那就是航天飞机飞行轨道所在的区域。美航局的飞机飞行时，一般保持在近地轨道上，即距离地表一百七十英里的地方。在这样的高度，大气程锥形逐渐减少——大气压力比地表的十亿分之一还小——但这里仍然有空气存在。实际上，近地轨道基本被电离层覆盖。而电离层是大气的重要组成部分。

The thin gasses of the ionosphere rush past the space shuttle at about five miles per second,forming a very fast, very thin wind. This wind is so thin you'd never be able to feel it, even ifyou stuck your head out the space shuttle window the way a dog sticks it's head out a movingcar. The wind causes two things to happen.

飞机以每秒5英里的速度驶过之后，电离层稀薄的空气就会形成一股快速流动的细风。人类无法感觉到这种细风，即使你将头伸到飞机窗外(像狗一样将头伸出飞速行驶的汽车)也感觉不到。这种细风会引起两件事情。

First, it erodes the surfaces of some materials.The erosion is slight, but it can be significantfor camera lenses or other sensitive equipment. Second, the shuttle's surface can scoop upatoms from this wind, and these atoms can undergo chemical reactions. One reaction,involving nitrogen and oxygen, can produce a luminous orange glow. And that's what theastronauts saw. It wasn't a ghost--it was shuttle glow.

第一，它会侵蚀一些材料的表面。这种轻微的侵蚀用照相机或者其它敏感的设备看很明显。第二，航天飞机的表面会从细风中捕获原子，并且这些原子能发生化学反应。有一种氮和氧的反应就能产生明亮的橙色辉光。这就是宇航员所看到的光。它不是鬼火，而是辉光。