《那些古怪又让人忧心的问题》第105期:最长的落日(2)
But if you head over to the mainland, where the roads are longer, you can do even better.
If you start driving from the tropics and stay on paved roads, the farthest north you can get is the tip of European Route 69 in Norway. There are a number of roads crisscrossing northern Scandinavia, so that seems like a good place to start. But which road should we use?
如果你从热带地区开始驾车，一直在铺有路面的道路上行驶，那么能跑到的最北的地方是挪威的欧洲69号公路末端。斯堪的纳维亚北边有许多互相交叉的道路，因而那里是启程的好地方。但我们该选择哪条路呢？Intuitively, it seems like we want to be as far north as possible. The closer we are to the pole, the easier it is to keep up with the Sun.
从直觉上来看，我们要尽可能地往北跑。我们离极点越近，就越容易追上太阳。
Unfortunately, it turns out keeping up with the Sun isn't a good strategy. Even in those high Norwegian latitudes, the Sun is just too fast. At the tip of European Route 69-the farthest you can get from the equator while driving on paved roads-you'd still have to drive at about half the speed of sound to keep up with the Sun. (And E69 runs north-south, not east-west, so you'd drive into the Barents Sea anyway.)
但事实上试图追上太阳不是一个好的策略。即使你在像挪威这样的高纬度地区，太阳移动的速度还是太快了。在欧洲69号公路的尖端——从赤道开始通过铺有路面的道路你能达到的最北边的地方——你仍然需要以约音速的一半的速度才能赶上太阳。（而且欧洲69号公路是南北向，而不是东西向，所以一直开下去就会跌入巴伦支海。）Luckily, there's a better approach.
幸运的是，我们还有更好的办法。If you're in northern Norway on a day when the Sun just barely sets and then rises again, the Terminator (day-night line) moves across the land in this pattern:
当太阳在挪威北部靠近地平线时，晨昏线（terminator）以如下方式滑过大陆：(Not to be confused with the Terminator, which moves across the land in this pattern:)
不要跟《终结者》系列中的终结者搞混了，它是这么移动的：I can't decide which terminator I'd rather have to run from.
我都不知道逃离哪一个要更容易。2To get a long sunset, the strategy is simple: Wait for the date when the terminator will just barely reach your position. Sit in your car until the terminator reaches you, drive north to stay a little ahead of it for as long as you can (depending on the local road layout), then U-turn and drive back south fast enough that you can get past it to the safety of darkness.2
要想看到更长的日落，你的策略很简单：静静等待晨昏线正要达到你所在的位置。在晨昏线抵达你所在的位置之前乖乖地待在车里，晨昏线抵达之后你就往北开，尽可能长时间保持你在晨昏线前面一点点（取决于当地的道路布局），在撑不下去之后掉头往南开，速度越快越好，直到你进入黑暗处的庇护。3Surprisingly, this strategy works about equally well anywhere inside the Arctic Circle; so you can get this lengthy sunset on many roads across Finland and Norway. I ran a search for long-sunset driving paths using PyEphem and some GPS traces of Norwegian highways. I found that over a wide range of routes and driving speeds, the longest sunset was consistently about 95 minutes-an improvement of about 40 minutes over the Svalbard sit-in-one-place strategy.
令人惊喜的是，这一招在北极圈内的任何地方都有差不多好的效果，因而你能在芬兰和挪威的许多道路上看到这么长的日落。我用PyEphem4和挪威高速GPS记录搜索了一下能看到最久日落的驾驶路线，我发现在不同的路径和时速条件下，最长的日落差不多都是95分钟左右——比使用一动不动待在斯瓦尔巴特群岛这种策略提升了近40分钟的时间。But if you are stuck in Svalbard and want to make the sunset-or sunrise-last a little longer, you can always try spinning counterclockwise.3 It's true that it will add only an immeasurably small fraction of a nanosecond to the Earth's clock. But depending on who you're with . . .
不过如果你被困在斯瓦尔巴特群岛而又想看到更长一点的日落——和日出——的话，你可以试试逆时针转动身体。5是的，你可以多看到几分之一纳秒的风景，但如果考虑一下你是和谁在一起……. . . it might be worth it.
……这么做有可能是值得的。1 Get a picture with the “polar bear crossing” sign.
1． 和“北极熊过马路”的标志拍张照。2 These instructions also work for the other kind of Terminator.
2． 这招也适用于你遇上终结者的时候。3 xkcd, “Angular Momentum,” .
3. 参考xkcd网站上“角动量”一章，
