(Music) Sometimes when I'm on a long plane flight, I gaze out at all those mountains and deserts and try to get my head around how vast our Earth is. And then I remember that there's an object we see every day that would literally fit one million Earths inside it. The sun seems impossibly big, but in the great scheme of things, it's a pinprick, one of about 400 billion stars in the Milky Way galaxy, which you can see on a clear night as a pale, white mist stretched across the sky. And it gets worse. There are maybe 100 billion galaxies detectable by our telescopes, so if each star was the size of a single grain of sand, just the Milky Way has enough stars to fill a 30 foot by 30 foot stretch of beach three feet deep with sand. And the entire Earth doesn't have enough beaches to represent the stars in the overall universe. Such a beach would continue for literally hundreds of millions of miles. Holy Stephen Hawking, that is a lot of stars. But he and other physicists now believe in a reality that is unimaginably bigger still. I mean, first of all, the 100 billion galaxies within range of our telescopes are probably a minuscule fraction of the total. Space itself is expanding at an accelerating pace. The vast majority of the galaxies are separating from us so fast that light from them may never reach us. Still, our physical reality here on Earth is intimately connected to those distant, invisible galaxies. We can think of them as part of our universe. They make up a single, giant edifice, obeying the same physical laws and all made from the same types of atoms, electrons, protons, quarks, neutrinos that make up you and me. However, recent theories in physics, including one called string theory, are now telling us there could be countless other universes, built on different types of particles, with different properties, obeying different laws. Most of these universes could never support life, and might flash in and out of existence in a nanosecond, but nonetheless, combined they make up a vast multiverse of possible universes. in up to 11 dimensions, featuring wonders beyond our wildest imagination. And the leading version of string theory predicts a multiverse made of up to 10 to the 500 universes. That's a one followed by 500 zeroes, a number so vast that if every atom in our observable universe had its own universe and all of the atoms in all of those universes each had their own universe, and you repeated that for two more cycles, you'd still be at a tiny fraction of the total -- namely, one trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillionth. But even that number is minuscule compared to another number: infinity. Some physicists think the space-time continuum is literally infinite, and that it contains an infinite number of so-called pocket universes with varying properties. How's your brain doing? But quantum theory adds a whole new wrinkle. I mean, the theory's been proven true beyond all doubt, but interpreting it is baffling. And some physicists think you can only un-baffle it if you imagine that huge numbers of parallel universes are being spawned every moment, and many of these universes would actually be very like the world we're in, would include multiple copies of you. In one such universe, you'd graduate with honors and marry the person of your dreams. In another, not so much. There are still some scientists who would say, hogwash. The only meaningful answer to the question of how many universes there are is one, only one universe. And a few philosophers and mystics might argue that even our own universe is an illusion. So, as you can see, right now there is no agreement on this question, not even close. All we know is, the answer is somewhere between zero and infinity. Well, I guess we know one other thing: This is a pretty cool time to be studying physics. We just might be undergoing the biggest paradigm shift in knowledge that humanity has ever seen.
(音樂) 有時候,在搭長程航班的時候 我會一邊看著外面的山和沙漠 一邊讚嘆地球是如此浩瀚無邊 接著就想到 其實我們每天都會看到 能裝下一百萬顆地球的龐然大物 太陽夠大了吧! 但若宏觀而論, 太陽就如針頭般渺小 在銀河系約四千億顆恆星中, 它也只是其中一員 銀河就是在無雲的夜晚裡可以看到的 橫跨天空的一條淡淡的白色霧般的光帶 更誇張的是 用當今望遠鏡所觀測到的銀河系 已高達一千億個 如果把恆星視為一粒細沙 那麼我們所在的銀河系裡 所有恆星放在一起 就是一個長寬各三十呎 深三呎的沙坑 (一呎=30公分) 而地球上 所有沙灘的沙粒集合起來 還夠不上整個宇宙裡的恆星的數量呢! 大概要有個綿延幾億哩的沙灘才比得上 (一哩=1.6公里,地球週長約四萬公里) 哇咧 史蒂芬 霍金 哩! 恆星有這麼多啊! (史蒂芬 霍金 是著名的物理學家) 霍金跟其他的物理學家開始相信 真相, 可能更大, 超乎想像的大 首先, 我們的望遠鏡能觀察到的一千億個銀河系 可能只是整體的一小塊而已 空間是一直在膨脹擴張的 而且膨脹的速度一直在增加, 絕大部分的銀河系 都是快速的遠離我們 快到它們的光線根本到不了我們這裡 但是,在地球上的物理現象 仍與這些看不到的遙遠的銀河系們緊密關連 我們可以把這些銀河系當作我們的宇宙的一部份 整體屬於一個巨大的架構 遵循相同的物理定律,由相同型態的原子,電子 正子,夸克,中微子 (這些是基本粒子) 組成你跟我,還有整個宇宙 但是最近發展的一些物理學理論 其中一種叫做 "弦理論" 推論說可能有無窮多的宇宙存在著 而且每個宇宙是由不同的基本粒子組成的 具有不同的特性,遵循不同的運作規律 這些宇宙大部分無法演化出生命型態 也許可能只存在一微秒 (十億分之一秒) 然後就消失 但是不管怎麼短暫,這些宇宙 都是多元宇宙的各種可能性之一 有高達 11 個空間維度, 有著超出我們所能想像之外的奇妙性質 而目前弦理論的最先進的版本 預測說一個多元宇宙是由 10 的 500 次方個單一宇宙組成的 這個數字是 1 後面跟著 500 個 0 這個數字有多大? 如果我們把所觀察到的 單一宇宙裡面的每一個原子 都算自成一個單一宇宙 然後再把這些 原子的宇宙裡的每個原子 再算各自成一個單一宇宙 再這樣重複兩層來算 所得的單一宇宙的數量 仍然只是這個大數字的一小部份 只有 一 兆 兆 兆 兆 兆 兆 兆 兆 兆 兆 兆 兆 兆 兆 兆 分之一而已!(1兆=1萬億) 而這麼大的數字,跟 無窮大 比起來, 仍舊是微不足道的 有些物理學家認為,所謂的 時空連續體 基本上就是無窮的, 裡面包含了無數個 所謂的 "口袋宇宙" 各自有不同的特性與物理定律 你的腦袋還跟的上 (能理解) 嗎? 再來個新的, 量子理論 這個理論已經毫無疑問的被證明其正確性 但是如何解讀卻仍摸不著頭緒 有些物理學家認為,唯一的解讀方式, 是從 很大數量的平行單一宇宙 在每個時間點被衍生出來 而這些單一宇宙中 多數與我們現存的世界非常類似 可能每個單一宇宙都有一個你 也許在其中的一個平行單一宇宙中 你以很好的成績畢業,並且與夢中情人結婚 在另外一個平行單一宇宙中,可能沒這麼好命 也有一些科學家認為,這真是鬼話連篇! 這些科學家認為,關於有多少個宇宙這個問題, 唯一合理的答案數字是 一個 只有一個宇宙 還有一些哲學家和神秘主義者 甚至會說連我們所在的宇宙也只是個幻影 所以囉,如你所見的 這個問題目前並沒有大家有共識的答案 還早得很哩! 我們目前只知道,宇宙的數量的正確答案, 應該在 零 與 無窮大 之間 另外我們可能還知道一件事情 就是,現在是研究物理學的一個最佳時機 因為,物理學正經歷著 人類有史以來最重大的知識典範轉移