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Stephen Hawking 提出關於宇宙的大問題

Stephen Hawking asks big questions about the universe

 

Photo of three lions hunting on the Serengeti.

講者:Stephen Hawking

2008年2月演講,2008年4月在TED上線

 

翻譯:TED

編輯:朱學恆、洪曉慧

簡繁轉換:洪曉慧

後製:洪曉慧

字幕影片後制:謝旻均

 

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閱讀中文字幕純文字版本

 

關於這場演講

為了配合TED2008主題,史蒂芬霍金教授提出一些關於宇宙的大問題-宇宙如何誕生?生命如何起源?我們是宇宙中唯一的生命嗎?並探討如何著手回答這些問題。

 

關於Stephen Hawking

史蒂芬霍金的科學研究已揭示了宇宙起源、時間本質及宇宙最終命運。他寫給一般大眾閱讀的暢銷書使數百萬人對物理有了正確的認識。

 

為什麼要聽他演講

史蒂芬霍金也許是在世的物理學家中最著名的一位。他是宇宙學與量子重力學專家,並熱衷於黑洞理論,他探索宇宙起源、時間本質和宇宙最終命運的傑出成就,為他贏得包括大英帝國勳章在內的多項榮譽。對大眾來說,他最廣為人知的就是身為暢銷書《胡桃裡的宇宙》及《時間簡史》作者,使數百萬人對理論物理有了正確的認識。

 

雖然運動神經元疾病ALS將霍金限制在輪椅上,但無法阻止他四處演講,在電視節目亮相,如《星艦迷航記:銀河飛龍》及《辛普森家庭》-並計畫進行Richard Branson的維珍銀河太空軌道旅遊。(他最近乘坐零重力公司的「嘔吐彗星」體驗無重力飛行。)他是一位真正的學術名人,他以公開露面引起對全球潛在危機的關注-如全球暖化-並為人類的未來發聲:「讓一部分人類永遠離開地球,對人類未來而言是勢在必行之事,」他這麼說。

 

霍金擔任劍橋大學Lucasian數學教授,並持續在高等物理及宇宙一般理論兩方面做出貢獻。

 

「我們只是生存於一個非常普通恆星的一個小行星上,品種較為先進的猴子。但我們可以瞭解宇宙。這讓我們與眾不同。」

-史蒂芬霍金

 

Stephen Hawking的英語網上資料

Website: Stephen Hawking's homepage

Books: Books by Stephen Hawking

PBS: Stephen Hawking's Universe

Wikipedia: Stephen Hawking

 

[TED科技‧娛樂‧設計]

已有中譯字幕的TED影片目錄(繁體)(簡體)。請注意繁簡目錄是不一樣的。

 

Stephen Hawking 提出關於宇宙的大問題

 

沒有一個東西比宇宙更大或更久遠,我想討論的問題是,第一、我們從哪裡來?這個宇宙如何誕生?我們在宇宙中是孤單的嗎?宇宙有沒有任何外星生物?人類的未來是什麼?

 

一直到一九二零年代之前,人們認為宇宙本質上是固定的,不會隨著時間改變。之後,人們發現宇宙是一直在膨脹的,遠方的星系正漸漸地遠離我們,這表示它們過去彼此曾經更靠近。如果我們反推回去,會發現大約在一百五十億年前,我們必定全都彼此緊靠在一起,這就是大爆炸,即宇宙的開始。

 

但在大爆炸之前,是否有宇宙呢?如果沒有,那是什麼創造了宇宙?為什麼宇宙是經由大爆炸而形成呢?我們一般認為的宇宙理論有兩部分,第一是類似Maxwell方程式及廣義相對論的定律,決定宇宙的演化是在同一時段中決定了所有宇宙的狀態。第二是宇宙的初始狀態是毫無疑問的。

 

我們在第一部份有不錯的進展,除了在最極端的條件下,我們對宇宙演化的法則已有所知。但一直到最近,我們對宇宙的初始狀態仍不甚瞭解。然而,宇宙演化理論和初始狀態的分界,在於時間與空間是分開並獨立的假設。在極端條件下,廣義相對論及量子理論允許把時間當作另一個維度的空間,這移除了時間與空間的分界,這使得宇宙演化理論亦可決定宇宙的初始狀態,宇宙可自發性的從一片空無的狀態中產生。

 

我們甚至可以計算宇宙從不同狀態中誕生的機率,這些預測與由WMAP衛星觀測到的(威爾金森微波背景輻射各向異性探測衛星)宇宙微波背景輻射相當一致,這是最早期宇宙留下的印跡,我們認為我們已經解決宇宙創造的奧秘,或許我們應該為宇宙申請專利,並向每個生存於此的人收費。

 

現在轉到第二個大問題,宇宙中只有我們,還是也有其他生命?我們相信生命是在地球上自我衍生的,因此,在其他適合生存的星球上也可能出現生命,這樣的星球在銀河系裡應該有很多。

 

但我們不知道生命最初是如何形成的,對於生命起源的可能性,我們有兩個可觀察的證據,第一是來自三十五億年前的海藻化石。地球在四十六億年前形成,前五億年或許太熱而不適合生物生存,所以生命可能在五億年後才在地球上出現,這相較於地球這類壽命有百億年的星球,只是一段很短的時間,這意味著生命出現的機率相當高。如果機率非常低的話,那可以預期要發展出生命得花上近百億年時間。

 

另一方面,似乎從未有外星人來拜訪過我們,我不信那些飛碟的報導,他們為什麼只出現在那些怪人面前?如果政府為了保密而壓下這些報告,將外星人帶來的科學知識據為己有,就目前來說,這似乎是個既奇怪又無效的政策。此外,雖然SETI計畫已進行廣泛探索(SETI:尋找外星智慧計畫),我們也還沒收到任何外星電視問答節目,這似乎顯示在我們現階段文明發展的方圓數百光年範圍內,並沒有任何外星文明,賣保險給那些怕被外星人綁架的人,似乎是個相當安全的選擇。

 

這帶我們進入最後一個大問題,人類的未來。如果我們是銀河裡唯一的智慧生物,我們應該確保能永續生存,但我們正進入一個越來越危險的人類歷史時期,伴隨著我們使環境變好或變壞的科技能力,我們的人口及我們對地球有限資源的消耗以指數成長。但我們的基因密碼仍帶有自私和好鬥本能,這或許在過去有利於我們生存,這將使我們在未來一百年難逃人為的災難,更別提未來的千年或百萬年了。我們長時間生存的唯一機會,不是一直侷限在地球,而是擴展到太空,這些大問題的答案,是顯現我們過去幾百年取得的可觀進展,但若要繼續超越未來數百年,我們的未來在太空。這就是為什麼我贊成人為控制,或者我應該說人為駕駛的太空旅行。

 

我一生都在探索對宇宙的瞭解,並尋找這些問題的答案。我很幸運,我的殘疾並沒有造成嚴重障礙,事實上,這或許使我比大多數人擁有更多時間從事知識上的追求,終極目標是一套完整的宇宙理論,我們已有良好的進展,感謝聆聽。

 

Chris Anderson:教授,如果你必須二選一做猜測的話,您目前是比較相信還是不相信,我們是銀河裡唯一擁有我們現在水準或更高水準的智慧文明?回答這個答案就花了七分鐘,讓我深刻體會到,這整個演講真是難以置信慷慨的為TED付出。

 

Stephen Hawking:我認為我們可能是幾百光年內唯一的文明,否則我們應該已收聽到無線電波;另一種可能是,其他文明並沒有維持很久就已自我毀滅。

 

CA:霍金教授,謝謝您的解答,我想,我們將會把它當成這一周其他演講的善意提醒。教授,衷心感謝您今天所做的卓越貢獻,並將您的大哉問與我們分享,衷心感謝您。

 

(掌聲)

 

以下為系統擷取之英文原文

About this talk

In keeping with the theme of TED2008, professor Stephen Hawking asks some Big Questions about our universe -- How did the universe begin? How did life begin? Are we alone? -- and discusses how we might go about answering them.

About Stephen Hawking

Stephen Hawking's scientific investigations have shed light on the origins of the cosmos, the nature of time and the ultimate fate of universe. His bestselling books for a general audience have given… Full bio and more links

Transcript

There is nothing bigger or older than the universe. Your questions I would like to talk about are: One, where did we come from? How did the universe come into being? Are we alone in the universe? Is there alien life out there? What is the future of the human race?

Up until the 1920s, everyone thought the universe was essentially static and unchanging in time. Then it was discovered that the universe was expanding. Distant galaxies were moving away from us. This meant they must have been closer together in the past. If we extrapolate back, we find we must have all been on top of each other about 15 billion years ago. This was the Big Bang, the beginning of the universe.

But was there anything before the Big Bang? If not, what created the universe? Why did the universe emerge from the Big Bang the way it did? We used to think that the theory of the universe could be divided into two parts. First, there were the laws like Maxwell's equations and general relativity that determined the evolution of the universe, given its state over all of space at one time. And second, there was no question of the initial state of the universe.

We have made good progress on the first part, and now have the knowledge of the laws of evolution in all but the most extreme conditions. But until recently, we have had little idea about the initial conditions for the universe. However, this division into laws of evolution and initial conditions depends on time and space being separate and distinct. Under extreme conditions, general relativity and quantum theory allow time to behave like another dimension of space. This removes the distinction between time and space and means the laws of evolution can also determine the initial state. The universe can spontaneously create itself out of nothing.

Moreover, we can calculate a probability that the universe was created in different states. These predictions are in excellent agreement with observations by the WMAP satellite of the cosmic microwave background, which is an imprint of the very early universe. We think we have solved the mystery of creation. Maybe we should patent the universe and charge everyone royalties for their existence.

I now turn to the second big question: Are we alone, or is there other life in the universe? We believe that life arose spontaneously on the Earth, so it must be possible for life to appear on other suitable planets, of which there seem to be a large number in the galaxy.

But we don't know how life first appeared. We have two pieces of observational evidence on the probability of life appearing. The first is that we have fossils of algae from 3.5 billion years ago. The earth was formed 4.6 billion years ago and was probably too hot for about the first half billion years. So life appeared on earth within half a billion years of it being possible, which is short compared to the ten billion-year lifetime of a planet of Earth-type. This suggests that a probability of life appearing is reasonably high. If it was very low, one would have expected it to take most of the ten billion years available.

On the other hand, we don't seem to have been visited by aliens. I am discounting the reports of UFOs. Why would they appear only to cranks and weirdos? If there is a government conspiracy to suppress the reports and keep for itself the scientific knowledge the aliens bring, it seems to have been a singularly ineffective policy so far. Furthermore, despite an extensive search by the SETI project, we haven't heard any alien television quiz shows. This probably indicates that there are no alien civilizations at our stage of development within a radius of a few hundred light years. Issuing an insurance policy against abduction by aliens seems a pretty safe bet.

This brings me to the last of the big questions: The future of the human race. If we are the only intelligent beings in the galaxy, we should make sure we survive and continue. But we are entering an increasingly dangerous period of our history. Our population and our use of the finite resources of planet Earth are growing exponentially, along with our technical ability to change the environment for good or ill. But our genetic code still carries the selfish and aggressive instincts that were of survival advantage in the past. It will be difficult enough to avoid disaster in the next hundred years, let alone the next thousand or million.

Our only chance of long-term survival is not to remain lurking on planet Earth, but to spread out into space. The answers to these big questions show that we have made remarkable progress in the last hundred years. But if we want to continue beyond the next hundred years, our future is in space. That is why I am in favor of manned -- or should I say, personed space flight.

All of my life I have sought to understand the universe and find answers to these questions. I have been very lucky that my disability has not been a serious handicap; indeed, it has probably given me more time than most people to pursue the quest for knowledge. The ultimate goal is a complete theory of the universe, and we are making good progress. Thank you for listening.

Chris Anderson: Professor, if you had to guess either way, do you now believe that it is more likely than not that we are alone in the Milky Way, as a civilization of our level of intelligence or higher? This answer took seven minutes, and really gave me an insight into the incredible act of generosity this whole talk was for TED.

Stephen Hawking: I think it quite likely that we are the only civilization within several hundred light years; otherwise we would have heard radio waves. The alternative is that civilizations don't last very long, but destroy themselves. CA: Professor Hawking, thank you for that answer. We will take it as a salutary warning, I think, for the rest of our conference this week. Professor, we really thank you for the extraordinary effort you made to share your questions with us today. Thank you very much indeed. (Applause)
 


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