《那些古怪又讓人憂心的問題》第14期:最後的人類之光
THE LAST HUMAN LIGHT
Q. If every human somehow simply disappeared from the face of the Earth, how long would it be before the last artificial light source would go out? THE LAST HUMAN LIGHT
Q．如果所有人類都消失了，那麼最後一個人造光源會何時熄滅？A. THERE WOULD BE A lot of contenders for the “last light” title.
A．“最後的人造光源”這一頭銜有好多競爭者呢。——阿蘭
The superb 2007 book The World Without Us, by Alan Weisman, explored in great detail what would happen to Earth's houses, roads, skyscrapers, farms, and animals if humans suddenly vanished. A 2008 TV series called Life After People investigated the same premise. However, neither of them answered this particular question.
艾倫.韋斯曼在2007年出了一本很棒的書，名字叫《沒有我們的世界》。這本書詳盡地探討了在人類突然消失後地球上的建築、道路、摩天大樓以及動物們都會經歷什麼。2008年推出的一部電視劇《人類消失後的世界》也討論了相同的情景。不過這兩者都沒有回答你提的這個問題。We'll start with the obvious: Most lights wouldn't last long, because the major power grids would go down relatively fast. Fossil fuel plants, which supply the vast majority of the world's electricity, require a steady supply of fuel, and their supply chains do involve humans making decisions.
那我們就先從簡單的入手：絕大多數燈都撐不了多久，因爲主要的電網會很快崩潰。供應世界大部分電力的化石燃料發電廠需要持續的燃料補給才能源源不斷地發電，而供應鏈需要人類來作決策。Without people, there would be less demand for power, but our thermostats would still be running. As coal and oil plants started shutting down in the first few hours, other plants would need to take up the slack. This kind of situation is difficult to handle even with human guidance. The result would be a rapid series of cascade failures, leading to a blackout of all the major power grids.
沒有了人類，電力需求也會下降，但恆溫器仍會繼續工作。隨着火電廠在最初的幾個小時內停轉，剩下的發電廠開始共同承擔電力缺口。這種調控過程即使在有人監管的時候也是十分困難的，因而結果就是剩下的發電廠也接連迅速地陷入停頓，造成主要電網完全停電。However, plenty of electricity comes from sources not tied to the major power grids. Let's take a look at a few of those, and when each one might turn off.
然而，很多地方不需要外部電網供電也能正常工作。讓我們選取其中幾個例子，看看它們會在什麼時候熄滅。Many remote communities, like those on far-flung islands, get their power from diesel generators. These can continue to operate until they run out of fuel, which in most cases could be anywhere from days to months.
許多偏遠的社區（比如那些在偏僻小島上的社區）的電力來源於柴油發電機。只要柴油不用完發電機就能一直輸出電力，它所能堅持的時間一般在幾天到幾個月之間。Diesel generators
柴油發電機Generating stations that don't need a human-provided fuel supply would be in better shape. Geothermal plants, which are powered by the Earth's internal heat, can run for some time without human intervention.
無須人類供給燃料的發電站，相對來說處境要好一些。地熱發電廠由地球內部的地熱驅動，可以在無人監控的情況下運行一段時間。Geothermal plants
地熱發電廠According to the maintenance manual for the Svartsengi Island geothermal plant in Iceland, every six months the operators must change the gearbox oil and regrease all electric motors and couplings. Without humans to perform these sorts of maintenance procedures, some plants might run for a few years, but they'd all succumb to corrosion eventually.
根據冰島史瓦森吉島上地熱發電廠的維護日誌，操作人員需要每6個月就更換一次齒輪箱中的機油，並給所有發電機和鏈接機構塗上潤滑油。沒了人類來進行這些維護性操作，這些發電廠可能還會繼續運行數年，但最終會因部件生鏽損壞而停止工作。Wind turbines
風力發電機People relying on wind power would be in better shape than most. Turbines are designed so that they don't need constant maintenance, for the simple reason that there are a lot of them and they're a pain to climb.
依靠風力發電機的人們處境會比大多數人強。風力發電機設計之初就是按照不需持續維護的標準來設計的，原因很簡單：風力發電機數量太多，而且爬到頂上去維護很累人。Some windmills can run for a long time without human intervention. The Gedser Wind Turbine in Denmark was installed in the late 1950s, and generated power for 11 years without maintenance. Modern turbines are typically rated to run for 30,000 hours (three years) without servicing, and there are no doubt some that would run for decades. One of them would no doubt have at least a status LED in it somewhere.
一些風車可以在無人干預的情況下運行很長一段時間。丹麥的蓋澤爾風力發電機建造於20世紀50年代末期，在無人維護的條件下連續工作了11年。現代的風力發電機的標準是不需維護正常工作3萬小時（3年），其中肯定會有一些發電機能夠連續運轉幾十年。而在這些發電機中，肯定在某個地方至少有一個顯示狀態的LED燈。most of the wind turbines would be stopped by the same thing that would destroy the geothermal plants: Their gearboxes would seize up.
但到頭來，大多數風力發電機還是會慢慢停止工作。原因和地熱發電廠類似：發電機的齒輪箱壞了。Hydroelectric dams
水力發電站Generators that convert falling water into electricity will keep working for quite a while. The History Channel show Life After People spoke with an operator at the Hoover Dam, who said that if everyone walked out, the facility would continue to run on autopilot for several years. The dam would probably succumb to either clogged intakes or the same kind of mechanical failure that would hit the wind turbines and geothermal plants.
通過將水的勢能轉化成電能的水力發電站能夠繼續運行很長一段時間。歷史頻道播放的《人類消失後的世界》中節目組詢問了胡佛大壩的一位操作員，他表示即使所有人員立即撤離，整個發電站還是能在自動運行模式下繼續工作數年。水力發電站最終也會停止工作，原因不外乎進水口堵住了，或是和風力發電機或地熱發電廠一樣遇到了機械故障。Batteries
電池Battery-powered lights will all be off in a decade or two. Even without anything using their power, batteries gradually self-discharge. Some types last longer than others, but even batteries advertised as having long shelf lives typically hold their charge only for a decade or two.
靠電池發光的燈會在一二十年內全部熄滅。即使沒有連接任何用電器，電池自身也會慢慢放電。某些品種的電池電力會比其他電池的電力更加持久一些，但即使號稱“電力持久”的電池也會在一二十年的時間內流失完所有電能。There are a few exceptions. In the Clarendon Library at Oxford University sits a battery-powered bell that has been ringing since the year 1840. The bell “rings” so quietly it's almost inaudible, using only a tiny amount of charge with every motion of the clapper. Nobody knows exactly what kind of batteries it uses because nobody wants to take it apart to figure it out.
當然也有一些例外。在牛津大學克拉倫登實驗室中有一個靠電池驅動的電子鐘，自1840年來一直在發出聲響。不過這個聲響太過輕微，每次振動響板只消耗極少電量，因而人耳幾乎聽不到。沒有人確切知道它用的到底是什麼電池，因爲沒人打算把它拆開來一探究竟。Sadly, there's no light hooked up to it.
可惜，這個電子鐘上沒有燈泡。Nuclear reactors
核電站Nuclear reactors are a little tricky. If they settle into low-power mode, they can continue running almost indefinitely; the energy density of their fuel is just that high. As a certain webcomic put it:
核電站有些難說。如果核電站進入低功率模式，那麼它們幾乎能夠無限期地運行下去，因爲核燃料的能量密度實在是太高了，正如某網絡漫畫所展現的：Unfortunately, although there's enough fuel, the reactors wouldn't keep running for long. As soon as something went wrong, the core would go into automatic shutdown. This would happen quickly; many things can trigger it, but the most likely culprit would be a loss of external power.
不幸的是，雖然燃料足夠，核電站仍然撐不了多長時間。只要有什麼零部件損壞，反應核心就會自動關閉。自動停堆會很快發生，因爲很多事件都能觸發這一行爲，不過最有可能的誘因是外部供電中斷。It may seem strange that a power plant would require external power to run, but every part of a nuclear reactor's control system is designed so that a failure causes it to rapidly shut down, or “SCRAM.”1 When outside power is lost, either because the outside power plant shuts down or the on-site backup generators run out of fuel, the reactor would SCRAM.
你可能覺得發電廠要外部供電才能運轉這一點很不可思議，但核電站的控制系統的設計宗旨即爲任何一處系統失靈都會導致這個發電站迅速關閉，這一過程叫作“緊急停堆”（SCRAM）1。當外部能源消失時，不管是因爲別的電站都關閉了還是自帶備用發電機的燃料耗盡，都會導致反應堆停工。Space probes
太空探測器Out of all human artifacts, our spacecraft might be the longest-lasting. Some of their orbits will last for millions of years, although their electrical power typically won't.
在所有人造物體中，太空飛船應該會是最能抵抗時間侵襲的東西。一些探測器能夠在太空中保存幾百萬年，不過探測器上的電力系統可支撐不了這麼長的時間。Within centuries, our Mars rovers will be buried by dust. By then, many of our satellites will have fallen back to Earth as their orbits decayed. GPS satellites, in distant orbits, will last longer, but in time, even the most stable orbits will be disrupted by the Moon and Sun.
幾個世紀後，火星探測器就將被火星塵土所掩埋。到那時，大多數衛星都已經隨着軌道高度的衰減而落回地球。GPS衛星在更高的地球軌道上，能夠堅持的時間也更長，但隨着時間的推移，再穩定的軌道也會受到月球和太陽的干擾。Many spacecraft are powered by solar panels, and others by radioactive decay. The Mars rover Curiosity, for example, is powered by the heat from a chunk of plutonium it carries in a container on the end of a stick.
許多太空飛船的電力都來自太陽能面板，還有一些則靠放射性物質衰變獲取電力。比如說火星探測器“好奇號”就是靠一根小棒末端連着的容器中的一塊鈈衰變釋放的熱量驅動的。Curiosity could continue receiving electrical power from the RTG for over a century. Eventually the voltage will drop too low to keep the rover operating, but other parts will probably wear out before that happens.
“好奇號”上配備的放射性同位素熱電式發電機（RTG）可以持續供電一個世紀以上，最終它輸出的電壓將低到不足以維持探測器繼續運行，但在此之前，其他部件可能早就已經損壞了。So Curiosity looks promising. There's one problem: no lights.
看上去“好奇號”很有潛力，但有一個問題：沒有燈光。Curiosity has lights; it uses them to illuminate samples and perform spectroscopy. However, these lights are turned on only when it's taking measurements. With no human instructions, it will have no reason to turn them on.
“好奇號”確實有光源，用來照亮樣本或進行光譜分析。但這些燈只會在進行測量工作時打開，沒了人類控制中心的指令，這些燈不會自己亮起來。Unless they have humans on board, spacecraft don't need a lot of lights. The Galileo probe, which explored Jupiter in the 1990s, had several LEDs in the mechanism of its flight data recorder. Since they emitted infrared rather than visible light, calling them “lights” is a stretch-and in any case, Galileo was deliberately crashed into Jupiter in 2003.2
除非有人在飛船中，否則一般太空飛船不需要很多的燈。20世紀90年代探索木星的“伽利略號”探測器在它的飛行數據記錄儀中安裝了一些LED燈，但這些LED燈發出的是紅外線而不是可見光，因而把它們叫作“燈”有些不太合適。而且不管怎麼說，2003年人們操縱“伽利略號”探測器故意讓其墜毀於木星表面。Other satellites carry LEDs. Some GPS satellites use, for example, UV LEDs to control charge buildup in some of their equipment, and they're powered by solar panels; in theory they can keep running as long as the Sun is shining. Unfortunately, most won't even last as long as Curiosity; eventually, they'll succumb to space debris impacts.
其他一些衛星也裝有LED燈。比如一些GPS衛星會用紫外LED燈來控制設備的電荷聚積，這些燈的電力來自太陽能電池板。理論上來講，只要太陽一天不熄滅，這些燈就能一直亮下去。不幸的是，大多數的燈可以堅持的時間甚至還不如“好奇號”，最終它們都會被太空垃圾撞毀。But solar panels aren't used just in space.
但別忘了太陽能電池板不只是用在太空中。Solar power
太陽能Emergency call boxes, often found along the side of the road in remote locations, are frequently solar-powered. They usually have lights on them, which provide illumination every night.
在偏遠地區的路邊，經常可以看到的緊急通話盒通常都是由太陽能驅動的。盒子上面一般都裝有燈具，用於在晚上產生照明。Like wind turbines, they're hard to service, so they're built to last for a long time. As long as they're kept free of dust and debris, solar panels will generally last as long as the electronics connected to them.
和風力發電機一樣，這些電話盒維護起來很困難，因而在最初就被設計成能使用很長時間。只要不受灰塵和碎屑的干擾，只要連接其中的電子元件不損壞，太陽能電池板就一直能夠發電下去。A solar panel's wires and circuits will eventually succumb to corrosion, but solar panels in a dry place, with well-built electronics, could easily continue providing power for a century if they're kept free of dust by occasional breezes or rain on the exposed panels.
太陽能電池板的導線和電路最終都會因腐蝕而損壞。但在一些乾燥的地方，只要電器元件質量過硬，並且能依靠偶爾的微風和雨水清除積灰，這些太陽能電池板就能夠毫無壓力地持續供電長達一個世紀。If we follow a strict definition of lighting, solar-powered lights in remote locations could conceivably be the last surviving human light source.
如果我們嚴格定義“人造光源”，那麼毫無疑問，偏遠地區靠太陽能驅動的燈會是堅持時間最久的人造光源。But there's another contender, and it's a weird one.
但別忘了還有另一個不太常見的競爭者。Cherenkov radiation
切倫科夫輻射Radioactivity isn't usually visible.
一般而言，輻射是不可見的。Watch dials used to be coated in radium, which made them glow. However, this glow didn't come from the radioactivity itself. It came from the phosphorescent paint on top of the radium, which glowed when it was irradiated. Over the years, the paint has broken down. Although the watch dials are still radioactive, they no longer glow.
"切倫科夫輻射一些手錶的錶盤上鍍有化學元素鐳，它能發出淡淡的亮光。然而這種亮光並不來源於放射性本身，而是來自鐳上的一層磷光塗料，當這種塗料受到放射性物質的照射時就會發出光亮。隨着時間的推移，這層塗料會慢慢失效。雖然錶盤本身還是在不停地釋放射線，但它再也不會發光了。Watch dials, however, are not our only radioactive light source.
然而錶盤並不是唯一的輻射發光源。
When radioactive particles travel through materials like water or glass, they can emit light through a sort of optical sonic boom. This light is called Cherenkov radiation, and it's seen in the distinctive blue glow of nuclear reactor cores.
當放射性顆粒穿過水、玻璃等材料時，它們會發光，原理類似於超音速產生的音爆——只不過聲波換成了電磁波。這種光芒被稱爲“切倫科夫輻射”，在覈電站堆芯你可以看到它那標誌性的藍色輝光。Some of our radioactive waste products, such as cesium-137, are melted and mixed with glass, then cooled into a solid block that can be wrapped in more shielding so they can be safely transported and stored.
一些放射性廢料，比如銫-137，會被融化然後混入玻璃中，冷卻後形成的固體塊會被包裹在更多層的保護層中，這樣這些放射性廢料就能被安全妥善地運輸和儲存。In the dark, these glass blocks glow blue.
在黑暗中，這些玻璃塊會發出藍色的微光。Cesium-137 has a half-life of thirty years, which means that two centurieslater, they'll still be glowing with 1 percent of their original radioactivity. Since the color of the light depends only on the decay energy, and not the amount of radiation, it will fade in brightness over time but keep the same blue thus, we arrive at our answer: Centuries from now, deep in concrete vaults, the light from our most toxic waste will still be shining.
銫-137的半衰期爲30年，因而兩個世紀後它仍然在發出藍光，但放射性水平將只有起初的1％。由於光的顏色取決於衰變的能量，而與輻射量無關，因此它的亮度會隨着時間的推移而慢慢黯淡下來，但仍然會保持藍色。1 When Enrico Fermi built the first nuclear reactor, he suspended the control rods from a rope tied to a balcony railing. In case something went wrong, next to the railing was stationed a distinguished physicist with an axe. This led to the probably apocryphal story that SCRAM stands for “Safety Control Rod Axe Man.”
1當恩里科?費米參與建造第一座核反應堆時，他把控制棒用繩索懸掛在頂部的橫杆上。一旦出現什麼閃失，站在橫杆旁邊的另一位傑出的物理學家就會揮動斧頭砍斷繩索釋放控制棒。因此有了一種（大概是假的）說法，說SCRAM的意思是“安全控制棒旁拿斧子的人”（Safety Control Rod Axe Man）。2 The purpose of the crash was to safely incinerate the probe so it wouldn't accidentally contaminate the nearby moons, such as the watery Europa, with Earth bacteria.
2 這次故意墜毀的目的是安全地焚燬這顆探測器，這樣它就不會在無意之中讓地球細菌污染附近的幾顆衛星（比如滿是水的歐羅巴）了。3 The USSR built some lighthouses powered by radioactiv
3 蘇聯建造了一些靠放射性衰變驅動的燈塔，但目前它們都已經不運作了。
