有必要擔心外星人入侵嗎

MOUNTAIN VIEW, Calif. — For more than a half-century, a small group of astronomers has sought intelligent company among the stars. They’ve done so by turning large radio antennas skyward, hoping to eavesdrop on signals from an advanced society. It’s a program known as SETI, the Search for Extraterrestrial Intelligence.

加利福尼亞山景城——半個多世紀以來，一些天文學家一直在探尋星際中的智慧生命，探尋我們的同伴。他們爲此架設朝向天空的大型無線電天線，以期捕獲來自科技先進的世界的信號。人們稱這一探索計劃爲“地外文明搜尋計劃”（Search for Extraterrestrial Intelligence，簡稱SETI）。

But now some researchers propose that we should do more than simply don headphones and await E.T.’s call: We should make serious efforts to encourage a response from putative aliens by deliberately transmitting our own messages. It’s a simple idea, akin to tossing a bottle into the cosmic ocean. But recent arguments for what’s termed active SETI have loosed a storm of controversy, one that has even washed into the halls of academe.

不過，現在有一些研究者建議，我們不能只是側耳傾聽，等待外星人的召喚，而要做更多、更積極的努力，主動傳遞出自己的信息，鼓勵可能存在的外星人做出迴應。這是個簡單的想法，如同向浩瀚的宇宙扔一隻瓶子。不過最近，被稱作“主動探尋地外文明”的想法引發了諸多討論，颳起了一場爭議的風暴，甚至蔓延到了學術界。

Why is this? Why has the sending of dispatches to worlds many trillions of miles distant suddenly become a hot-button issue? The simple answer is that there’s now a perception that advertising our existence could be a mortal threat to the planet.

這是爲什麼呢？爲什麼向遠在萬億英里之外的世界發送信息會驟然成爲熱點話題？答案很簡單，因爲現在有一種看法認爲，廣泛宣示人類的存在可能會對我們的星球造成致命威脅。

The reasoning is this: While no one has yet offered decisive proof for life beyond Earth, in the past two years astronomers have learned that tens of billions of habitable planets suffuse our galaxy. Consequently, to believe that only Earth has spawned intelligence is to insist that our world is the site of a miracle. That point of view rarely appeals to scientists.

原因在於：儘管尚未有人能給出存在地外生命的確鑿證據，但過去兩年間，天文學家們瞭解到，我們的銀河系遍佈着數以百億的宜居星球。因此，讓人相信只有地球產生了智慧生命就等於堅持認爲我們生活的世界全然是一塊奇蹟之地。科學家不喜歡這種假設。

The aliens could very well be out there. And that realization has spurred a call by some for broadcasts intended to elicit a communication from at least the nearest other star systems. But we know nothing of the aliens’ possible motives or behavior. Therefore, it’s conceivable that betraying our existence might prompt aggressive action from space.

地球以外很可能存在外星人。這種認識引起一些人呼籲發出廣播信號，意在引發至少與最近星系的交流。不過，我們對外星人的動機和行爲一無所知。因此可以想像，泄露人類的存在可能會激起來自太空的侵略行動。

Broadcasting is likened to “shouting in the jungle” — not a good idea when you don’t know what’s out there. The British physicist Stephen Hawking alluded to this danger by noting that on Earth, when less advanced societies drew the attention of those more advanced, the consequences for the former were seldom agreeable.

向地外發送廣播信號就像“在叢林中大聲叫喊”，如果你不知道周圍存在着什麼，那麼這樣做可能很不明智。英國物理學家史蒂芬·霍金(Stephen Hawking)便暗示過這種危險——他指出，在地球上，如果較落後社會引起了較先進社會的注意，那對前者來說很少是件好事。

It’s a worry we never used to have. Victorian-era scientists toyed with plans to use lanterns and burning pools of oil to contact postulated Martians. In the 1970s, NASA bolted greeting cards onto spacecraft that will leave our solar system and wander the vast reaches between the stars. The Pioneer and Voyager probes carry plaques and records with information about what humans look like and where Earth is, as well as a small sampling of our culture.

過去，我們從來沒有這種擔心。維多利亞時代的科學家設想過用點亮燈盞和大量燃油的方式與設若存在的火星人取得聯繫。到了20世紀70年代，美國國家航空航天局將問候賀卡栓牢在航天器上，並隨航天器離開太陽系、在恆星之間的廣闊空間漫遊。“先驅者”號和“旅行者”號探測器則攜帶鍍金鋁板和鍍金銅質唱片，承載着人類長什麼模樣和地球位於何方的信息，還包括一個人類文化的小樣本。

Those messages move at the speed of rockets. But in 1974, a three-minute encoded pictogram was transmitted using the large radio antenna at Arecibo, Puerto Rico. It moves at the speed of light, 20,000 times faster. More recent radio transmissions include a Beatles song beamed by NASA to the North Star, a Doritos advertisement launched to a planetary system in the Big Dipper, and a series of broadcasts sent to nearby stars using an antenna in Crimea.

上述這些信息的傳遞速度與火箭相同。不過1974年，波多黎各的阿雷西博天文臺(Arecibo)用大型無線電天線發送了一個3分鐘的編碼圖片符號，運行速度已達光速，比之前的信息快2萬倍。更近期發送的無線電信息有：美國宇航局向北極星傳送的一支甲殼蟲樂隊的歌，向北鬥星座一個行星系發送的一段“立體脆”食品廣告，以及通過在克里米亞的一部天線向近地恆星發送的一系列無線電信號。

When most people believed that aliens were no more than easy black hats for Hollywood, the idiosyncratic nature of these messages could be easily dismissed. But if cosmic company is a legitimate possibility, shouldn’t we offer up something more edifying than pop music and snack food? A deliberate transmission should represent all of humanity — not short-circuit the important question of who will speak for Earth.

在大多數人認爲外星人不過是好萊塢的噱頭的時代，人們很容易對這些怪怪的選擇不以爲然。但如果真的有可能存在外星生命，我們難道不應當發送比流行音樂和小吃零食更有助益的信息嗎？深思熟慮後發送的信息應當能代表全體人類——而不能迴避誰可以代表地球這一重要問題。

Consequently, recent conferences on the merits of active SETI have sought the advice of social scientists. Among their worries is whether to be up front about humanity’s seamy side: Should we tell the extraterrestrials about war and injustice?

所以，最近就“主動探尋地外文明”的好處方面，有討論會開始向社會科學家尋求意見。諸多擔憂中有一條，是否要誠實展現人類醜陋的一面。我們需要告訴地外文明我們有戰爭和不公正現象嗎？

Personally, I think this concern is overwrought. Any society that can pick up our radio messages will be at a level of development at least centuries beyond our own. They would be no more incensed by our bad behavior than historians who learned that Babylonians attacked one another with spears. It seems naïve to imagine that, by shielding aliens from the less flattering aspects of humanity, we would somehow lessen any incentive to do us harm. If there’s a danger, mincing words is unlikely to eliminate it.

就個人而言，我認爲這種擔憂過慮了。能接收到地球無線電信息的社會必定處在比我們先進至少幾世紀的發展水平。他們對人類的不良行爲產生的憤怒不會比歷史學家發現巴比倫人自相殘殺更嚴重。認爲只要對他們掩蓋我們不光彩的一面，就可以降低他們加害我們的動機，這種想法似乎太天真。如果確有危險存在，我們不太可能通過文過飾非把這種危險消除。

A better approach is to note that the nearest intelligent extraterrestrials are likely to be at least dozens of light-years away. Even assuming that active SETI provokes a reply, it won’t be breezy conversation. Simple back-and-forth exchanges would take decades. This suggests that we should abandon the “greeting card” format of previous signaling schemes, and offer the aliens Big Data.

一種更好的做法，是先認識到離我們最近的地外智慧生命可能至少也隔着幾十光年的距離。即使主動SETI的行爲引起了一個迴應，那也不會是順暢的聊天。簡單的一問一答也要幾十年。這意味着，我們要放棄以前那種“問候卡”式的信號發送模式，向外星人發送大數據。

For example, we could transmit the contents of the Internet. Such a large corpus — with its text, pictures, videos and sounds — would allow clever extraterrestrials to decipher much about our society, and even formulate questions that could be answered with the material in hand. Sending the web on its way would take months if a radio transmitter were used. A powerful laser, conveying bits much like an optical fiber, could launch these data in a few days.

比如，我們可以發送互聯網內容。文本、圖片、視頻和音頻彙編的大型數據庫可以讓聰明的外星人破解更多有關人類社會的信息，甚至思考出一些用手頭資料能夠解答的問題。採用無線電廣播發射機傳送網絡信息需要幾個月時間；而用強激光傳送這些數據只需幾天，很像用光導纖維傳輸。

Sending messages — even big ones — is technically feasible. However, there’s still the highly controversial matter of whether to broadcast at all. Who decides? One could simply let the public weigh in, but doing so wouldn’t address the security issue. Even if a majority is comfortable with a transmission, how does that mitigate the possible danger?

向地外傳送信息乃至大量信息，從技術角度來講是可行的。不過，要不要向地外發送信息還是一個爭議極大的問題。誰來做這個決定？我們完全可以讓公衆參與決策，但這並不能解決安全問題。即便多數人願意發送信息，那就能消除潛在危險了嗎？

The inability to gauge this peril prompts some critics to argue that, given the possibly existential threat posed by active SETI, we should choose the side of caution. We should simply forbid powerful transmissions to the skies. Indeed, a small consortium of academics in California has drafted a petition urging this.

由於無法測量這種危險，一些批評者提出，考慮到主動尋找地外文明可能造成的威脅，我們寧可慎重，應當禁止向外太空進行大功率傳輸。事實上，加州一小部分學者已經就此起草了請願書，呼籲這麼做。

It’s a wary approach. It’s also poor insurance. Any extraterrestrials with technology advanced enough to threaten us will surely have antennas larger than our own, instruments that can pick up the television and radio signals broadcast willy-nilly since World War II. We are already shouting into the jungle, albeit with less volume than a deliberate signal. But the dangerous creatures may have good hearing.

這種做法雖謹慎，卻也不是萬無一失。技術發達程度足以威脅我們的地外文明必定擁有比我們更大的天線等強大設備，能夠接收二戰以來人類發送的雜亂的電視信號和無線電信號。我們已經在對着叢林大喊了，只不過音量沒有主動發送的信號那麼大。但危險生物的耳朵也可能很尖。

Additionally, if we forbid high-powered transmitters aimed at the sky, we shut out such obvious future technologies as better radars for aviation and tracking dangerous asteroids. Do we really want to hamstring our descendants this way?

此外，如果禁止高功率設備向天空發射信號，我們顯然就阻斷了未來技術的發展，研製不出在航空飛行及追蹤危險小行星領域性能更加優越的雷達。我們真的要就此束縛後世兒孫的發展嗎？

A decision to engage in active SETI has not been made. The benefit — learning our place in the cosmos — is only hypothetical, and so is the danger. But I, for one, would hesitate to let a paranoia based on nothing more than conjecture shackle the activities of our children and our children’s children. The universe beckons, and we can do better than to declare that future generations should endlessly tremble at the sight of the stars.

是否應當開展主動SETI還沒有定論。這麼做的好處——瞭解我們在宇宙中的位置——只是一種假設，但其風險也是假設。但就個人而言，我會猶豫是否讓一種只有猜想做基礎的疑神疑鬼心理束縛住我們的孩子、孩子的孩子的行動。宇宙在召喚，我們應該能做得更好，而不是讓未來一代人看到星星就陷入無盡的恐懼戰慄中。