LONGEST SUNSET
最长的落日
Q. What is the longest possible sunset you can experience while driving, assuming we are obeying the speed limit and driving on paved roads?
Q．假设你遵守交通法规不超速驾驶，并且在铺有路面的道路上行驶，那么你能观赏到的最长日落会持续多久？
——Michael Berg
——迈克尔•伯格
A. TO ANSWER THIS, WE have to be sure what we mean by “sunset.”
A．要回答这个问题，首先我们要确定什么叫“日落”。
This is a sunset:
这算是一个日落：
Sunset starts the instant the Sun touches the horizon, and ends when it disappears completely. If the Sun touches the horizon and then lifts back up, the sunset is disqualified.
日落在太阳开始没入地平线的那一瞬间就算开始了，当太阳完全没入地平线以下之后日落也就结束了。如果太阳碰了一下地平线又重新升了起来，那这就不能称为日落。
For a sunset to count, the Sun has to set behind the idealized horizon, not just behind a nearby hill. This is not a sunset, even though it seems like one:
要算得上日落，太阳必须没入理想地平线之下，而非只是躲在附近一座小山后面。以下这种情况虽然看起来像日落，但其实不是：
The reason it can 8217;t count as a sunset is that if you could use arbitrary obstacles, you could cause a sunset at any time by hiding behind a rock.
至于原因很简单：你不能随便躲在某个看不见太阳的障碍物后面就说太阳落下去了，否则你只要藏在石头背后就随时能够制造出一场日落。
We also have to consider refraction. The Earth 8217;s atmosphere bends light, so when the Sun is at the horizon it appears about one Sun-width higher than it would otherwise. The standard practice seems to be to include the average effect of this in all calculations, which I 8217;ve done here.
注意我们要考虑折射情况。地球的大气层会使光线弯折，因而当太阳实际碰到地平线的时候，你会发现太阳实际比地平线高出一个身位。在所有常规的计算中这种情况的平均效应都已经被考虑在内，我这里也是。
At the equator in March and September, sunset is a hair over two minutes long. Closer to the poles, in places like London, it can take between 200 and 300 seconds. It 8217;s shortest in spring and fall (when the Sun is over the equator) and longest in the summer and winter.
如果你身处赤道，那么3月和9月的日落略微比2分钟多一点。在像伦敦这样靠近极点的地方，日落可能长达200～300秒。日落的持续时间在春季和夏季最短（在这些时候太阳直射点在赤道上方），在至日和春分（秋分）的时候最长。
If you stand still at the South Pole in early March, the Sun stays in the sky all day, making a full circle just above the horizon. Sometime around March 21, it touches the horizon for the only sunset of the year. This sunset takes 38–40 hours, which means it makes more than a full circuit around the horizon while setting.
如果你在早春3月在南极站定，太阳整天都高高挂在天上，在地平线上方绕一整个圈子。有时在3月21日前后太阳会落到地平线之下，这也是一年中唯一一次。这样的日落会长达38～40小时，这也意味着在日落的过程中太阳转了一整圈还不止。
But Michael 8217;s question was very clever. He asked about the longest sunset you can experience on a paved road. There 8217;s a road to the research station at the South Pole, but it 8217;s not paved-it 8217;s made of packed snow. There are no paved roads anywhere near either pole.
但是迈克尔的问题问得很好。他问的是你在铺有路面的道路上能看到的最长的日落有多久。有一条路通向南极的科研站，但它没有铺路面——它是由雪堆出来的。两极附近都没有任何一条铺有路面的道路。
The closest road to either pole that really qualifies as paved is probably the main road in Longyearbyen, on the island of Svalbard, Norway. (The end of the airport runway in Longyearbyen gets you slightly closer to the pole, although driving a car there might get you in trouble.)
能够符合上述标准的离极点最近的道路估计是挪威斯瓦尔巴特群岛上朗伊尔城的主干道。（如果你能开到朗伊尔城中的机场跑道末端，你可以离极点更近一点，不过这么做你可能会惹上大麻烦。）
Longyearbyen is actually closer to the North Pole than McMurdo Station in Antarctica is to the South Pole. There are a handful of military, research, and fishing stations farther north, but none of them have much in the way of roads; just airstrips, which are usually gravel and snow.
朗伊尔城离北极的距离比南极洲的麦克莫多站离南极的距离还近。还有一大把军事基地、研究站和钓鱼站离北极更近，不过它们都没有铺有路面的道路，有的只是用碎石或雪铺成的飞机跑道。
If you putter around downtown Longyearbyen,1 the longest sunset you could experience would be a few minutes short of an hour. It doesn 8217;t actually matter if you drive or not; the town is too small for your movement to make a difference.
如果你在朗伊尔城中心城区1闲逛，你能看到的最长的日落差几分钟满一小时。至于你有没有开车基本不会有什么影响，因为这个城市实在是太小了。