《那些古怪又讓人憂心的問題》第105期:最長的落日(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?
如果你從熱帶地區開始駕車，一直在鋪有路面的道路上行駛，那麼能跑到的最北的地方是挪威的歐洲69號公路末端。斯堪的納維亞北邊有許多互相交叉的道路，因而那裏是啓程的好地方。但我們該選擇哪條路呢？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.
從直覺上來看，我們要儘可能地往北跑。我們離極點越近，就越容易追上太陽。
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.)
但事實上試圖追上太陽不是一個好的策略。即使你在像挪威這樣的高緯度地區，太陽移動的速度還是太快了。在歐洲69號公路的尖端——從赤道開始通過鋪有路面的道路你能達到的最北邊的地方——你仍然需要以約音速的一半的速度才能趕上太陽。（而且歐洲69號公路是南北向，而不是東西向，所以一直開下去就會跌入巴倫支海。）Luckily, there's a better approach.
幸運的是，我們還有更好的辦法。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:
當太陽在挪威北部靠近地平線時，晨昏線（terminator）以如下方式滑過大陸：(Not to be confused with the Terminator, which moves across the land in this pattern:)
不要跟《終結者》系列中的終結者搞混了，它是這麼移動的：I can't decide which terminator I'd rather have to run from.
我都不知道逃離哪一個要更容易。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
要想看到更長的日落，你的策略很簡單：靜靜等待晨昏線正要達到你所在的位置。在晨昏線抵達你所在的位置之前乖乖地待在車裏，晨昏線抵達之後你就往北開，儘可能長時間保持你在晨昏線前面一點點（取決於當地的道路佈局），在撐不下去之後掉頭往南開，速度越快越好，直到你進入黑暗處的庇護。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.
令人驚喜的是，這一招在北極圈內的任何地方都有差不多好的效果，因而你能在芬蘭和挪威的許多道路上看到這麼長的日落。我用PyEphem4和挪威高速GPS記錄搜索了一下能看到最久日落的駕駛路線，我發現在不同的路徑和時速條件下，最長的日落差不多都是95分鐘左右——比使用一動不動待在斯瓦爾巴特羣島這種策略提升了近40分鐘的時間。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 . . .
不過如果你被困在斯瓦爾巴特羣島而又想看到更長一點的日落——和日出——的話，你可以試試逆時針轉動身體。5是的，你可以多看到幾分之一納秒的風景，但如果考慮一下你是和誰在一起……. . . it might be worth it.
……這麼做有可能是值得的。1 Get a picture with the “polar bear crossing” sign.
1． 和“北極熊過馬路”的標誌拍張照。2 These instructions also work for the other kind of Terminator.
2． 這招也適用於你遇上終結者的時候。3 xkcd, “Angular Momentum,” .
3. 參考xkcd網站上“角動量”一章，
