Stephen Wolfram：宇宙的本質是計算這和量子力學衝突嗎？

01-11

【果殼網專訪】斯蒂芬·沃爾夫勒姆：宇宙的本質是計算
可是沃爾夫勒姆卻覺得自己發現了某種本質的東西。
1983年，他做出了自己最得意的發現：「Rule
30」。這是一套規則組，處理的是更加簡單的一維細胞自動機，每一次迭代的產物變成新的一行列印在下面。可是，從一個活細胞出發，它卻生成了一套極其複雜
的無盡花紋
Rule 30的全部規則，以及從一個黑點開始的迭代結果。每一次新的迭代就是新的一行，而每一個細胞的死活由且僅由它自己和它左右兩側的細胞在上一行的狀態決定。之所以是30，因為按順序排列的二進位數00011110對應的十進位就是30。

250次迭代後的Rule 30。左邊緣看起來還有一定規律，但大部分區域看起來近乎是隨機的。
如此簡單的程序能生成如此複雜的行為，這意味著什麼？沃爾夫勒姆認為，這正是我們宇宙的本質；我們的世界就是計算，就是一套簡單的規則生成的複雜現象。

鑒於有段時間還挺把他的new kind of science當回事的，所以來湊湊熱鬧。

總的來說，Wolfram這本書里的很多東西都很有意思，只不過之前都已經被其他的計算機科學家發現過了=- =

我相信這些東西是他自己發現的，只是他作為一個民間計算機科學家，不知道而已= -=

這些東西對於物理學家（根據Wolfram的說法，費曼也覺得他這套東西很牛）可能覺得很新鮮，對於學計算機的其實早已經被做出來了。Stephen同學很可能literally重新創造了輪子。。

這裡引用一篇亞馬遜上對A New Kind of Science的review，我覺得對這門書評價的已經十分全面了。

Amazon.com:

Joe Weiss" review of A New Kind of Science

The Emperor"s New Kind of Clothes
This review took almost one year. Unlike many previous referees (rank them by Amazon.com"s "most helpful" feature) I read all 1197 pages including notes. Just to make sure I won"t miss the odd novel insight hidden among a million trivial platitudes.
On page 27 Wolfram explains "probably the single most surprising discovery I have ever made:" a simple program can produce output that seems irregular and complex.
This has been known for six decades. Every computer science (CS) student knows the dovetailer, a very simple 2 line program that systematically lists and executes all possible programs for a universal computersuch as a Turing machine (TM). It computes all computable patterns, including all those in Wolfram"s book, embodies the well-known limits of computability, and is basis of uncountable CS exercises.
Wolfram does know (page 1119) Minsky"s very simple universal TMs from the 1960s. Using extensive simulations, he finds a slightly simpler one. New science? Small addition to old science. On page 675 we find a particularly simple cellular automaton (CA) and Matthew Cook"s universality proof(?). This might be the most interesting chapter. It reflects that today"s PCs are more powerful systematic searchers for simple rules than those of 40 years ago. No new paradigm though.
Was Wolfram at least first to view programs as potential explanations of everything? Nope. That was Zuse. Wolfram mentions him in exactly one line (page 1026): "Konrad Zuse suggested that [the universe] could be a continuous CA." This is totally misleading. Zuse"s 1967 paper suggested the universe is DISCRETELY computable, possibly on a DISCRETE CA just like Wolfram"s. Wolfram"s causal networks (CA"s with variable toplogy, chapter 9) will run on any universal CA a la Ulam von Neumann Conway Zuse. Page 715 explains Wolfram"s "key unifying idea" of the "principle of computational equivalence:" all processes can be viewed as computations. Well, that"s exactly what Zuse wrote 3 decades ago.
Chapter 9 (2nd law of thermodynamics) elaborates (without reference)on Zuse"s old insight that entropy cannot really increase in deterministically computed systems, although it often SEEMS to increase. Wolfram extends Zuse"s work by a tiny margin, using today"s more powerful computers to perform experiments as suggested in Zuse"s 1969 book. I find it embarassing how Wolfram tries to suggest it was him who shifted a paradigm, not the legendary Zuse.
Some reviews cite Wolfram"s previous reputation as a physicist and software entrepreneur, giving him the benefit of the doubt instead of immediately dismissing him as just another plagiator. Zuse"s reputation is in a different league though: He built world"s very first general purpose computers (1935-1941), while Wolfram is just one of many creators of useful software (Mathematica). Remarkably, in his history of computing (page 1107) Wolfram appears to try to diminuish Zuse"s contributions by only mentioning Aiken"s later 1944 machine.
On page 465 ff (and 505 ff on multiway systems) Wolfram asks whether there is a simple program that computes the universe. Here he sounds like Schmidhuber in his 1997 paper "A Computer Scientist"s View of Life, the Universe, and Everything." Schmidhuber applied the above-mentioned simple dovetailer to all computable universes. His widely known writings come out on top when you google for "computable universes" etc, so Wolfram must have known them too, for he read an "immense number of articles books and web sites" (page xii) and executed "more than a hundred thousand mouse miles" (page xiv). He endorses Schmidhuber"s "no-CA-but-TM approach" (page 486, no reference) but not his suggestion of using Levin"s asymptotically optimal program searcher (1973) to find our universe"s code.
On page 469 we are told that the simplest program for the data is the most probable one. No mention of the very science based on this ancient principle: Solomonoff"s inductive inference theory (1960-1978); recent optimality results by Merhav Feder Hutter. Following Schmidhuber"s "algorithmic theories of everything" (2000), short world-explaining programs are necessarily more likely, provided the world is sampled from a limit-computable prior distribution. Compare Li Vitanyi"s excellent 1997 textbook on Kolmogorov complexity.

On page 628 ff we find a lot of words on human thinking and short programs. As if this was novel! Wolfram seems totally unaware of Hutter"s optimal universal rational agents (2001) based on simple programs a la Solomonoff Kolmogorov Levin Chaitin. Wolfram suggests his simple programs will contribute to fine arts (page 11), neither mentioning existing, widely used, very short, fractal-based programs for computing realistic images of mountains and plants, nor the only existing art form explicitly based on simple programs: Schmidhuber"s low-complexity art.
Wolfram talks a lot about reversible CAs but little about Edward Fredkin Tom Toffoli who pioneered this field. He ignores Wheeler"s "it from bit," Tegmark Greenspan Petrov Marchal"s papers, Moravec Kurzweil"s somewhat related books, and Greg Egan"s fun SF on CA-based universes (Permutation City, 1995).
When the book came out some non-expert journalists hyped it without knowing its contents. Then cognoscenti had a look at it and recognized it as a rehash of old ideas, plus pretty pictures. And the reviews got worse and worse. As far as I can judge, positive reviews were written only by people without basic CS education and little knowledge of CS history. Some biologists and even a few physicists initially were impressed because to them it really seemed new. Maybe Wolfram"s switch from physics to CS explains why he believes his thoughts are radical, not just reinventions of the wheel.
But he does know Goedel and Zuse and Turing. He must see that his own work is minor in comparison. Why does he desparately try to convince us otherwise? When I read Wolfram"s first praise of the originality of his own ideas I just had to laugh. The tenth time was annoying. The hundredth time was boring. And that was my final feeling when I laid down this extremely repetitive book:exhaustion and boredom. In hindsight I know I could have saved my time. But at least I can warn others.

量子力學什麼的實在是民科泛濫。

只說一點我知道的：衝突不是必然的。Wolfram想要表達的觀點就是我們能從certainty里生出uncertainty來。能不能？誰知道。有沒有可能？有，而且挺有的。

Wolfram表達的一種可能的世界觀是，這個世界其實是確定的，但是表現出不確定性來。由於計算不可約，只有真正發生了，你才知道什麼會發生。這顯然是一種可能的，而且還比較靠譜的世界觀。

順帶說個別的：我覺得很多在知乎討論物理的人缺乏科學精神（當然他們可能本來也是業餘的）。我們現在普遍認為所有已有的物理模型都是唯象的，什麼意思，就是在一定範圍內管用，但未必（也往往不）是廣泛適用的。而有人問，這個世界是什麼樣的啊？然後你講一個模型，然後說這個世界就是這樣的。

扯淡，同等解釋力的模型多著呢。

再比如量子力學是不是真隨機。我們只能說，絕大多數物理學家，出於信仰，認為量子力學是真隨機。Conway證明了一個自由意志定理，表示在他的那三條假設下，我們可以證明量子力學是真隨機。絕大多數人都覺得這個是靠譜的。但是也有個別人反對=- =

Free will theorem

-----------最近好像被人翻出來了這篇答案，附送一篇Scott Aaronson噴這本書的review----------------

Scott Aaronson表示，這本書當本科生的大一閱讀材料挺不錯的：0

https://arxiv.org/abs/quant-ph/0206089

去年wolfram過來我們學校做講座，剛好談到了這個問題，首先，這段採訪中，wolfram的意思的表達方式有點奇怪，容易產生很不得了的感覺

我大概理解的意思，是物理學所有現有的規則和以後的規則，都是一個終極規則的衍生，是終極規則的不同的表現形式，就像自由落體的計算公式和天體運動的計算公式，都可以歸結到牛頓定律上一樣，只不過是在不同的情形下有著不同的數學表達，本質是一樣的

他舉這張圖的意思是，即使是一個非常簡單的規則，也可能創造出很複雜的系統，因而一個規則創造像宇宙這樣複雜的系統是存在可能的

所以「宇宙是一個程序」這樣的表達感覺有點過火，wolfram的想法我覺得是完全合理的，而且就是物理學家在做的事情，尋找相似處，總結和歸納

而題主所說的量子物理，他即使不確定也是有一套自己的規則體系的，海森堡的不確定性原理也是有數學表達的，所以量子物理可以說是「現有的規則」中的一部分，即使宇宙是一個程序，程序也是允許不確定的

最後說一點題外話，wolfram在提問環節的時候明確的表示了他不相信人腦是程序，因為他認為程序只能執行編寫者的意願，無法產生慾望

再說一點題外話，wolfram絕對不僅僅是個工程師，他一開始是個粒子物理學家來著==他15歲的第一篇paper講的就是粒子物理==

混沌系統和量子力學是兩碼事，3體問題無解可不是海森堡的鍋。

不知道是哪位大牛，但是還是很想吐槽一下。

一、王小波

我對數學也有過興趣，這種興趣是從對方程的興趣發展來的。人們老早就知道二次方程有公式解，但二次以上的方程呢？在十九世紀以前，人們是不知道的。在十七世紀，有個義大利數學家，又是一位教授，他對三次方程的解法有點心得。有天下午，外面下著雨，在教室里，他準備對學生講講這些心得。忽聽「喀嚓」一聲巨響，天上打下來個落地雷，擦著教室落在花園裡——青色的電光從狹窄的石窗照進來，映得石牆上一片慘白。教授手捂著心口，對學生們轉過身來，說道：先生們，我們觸及了上帝的秘密……我讀到這個故事時，差點把腸子笑斷了。三次方程算個啥，還值得打雷——教授把上帝看成個小心眼了。

二、混沌學

簡單的規則生出「極其複雜」結果。這是個典型的混沌模型。

混沌學是1972年提出的，比題主提到的成果要早。

混沌還有許多數學模型，比如更加著名的「蟲口模型」

x(n+1)=u*x(n)*(1-x(n)),u屬於[0,4],x屬於(0,1)

這個簡單的規則，取初值後迭代，也會產生極其複雜的無盡的輸出結果。

混沌學已經發展得極其完備，用混沌觀點解讀宇宙學中某些觀測結果工作也已經基本做完。

現在翻炒這個概念，並且把它來解釋「宇宙的本質」

我只能參考一，或者回答：42了。

量子力學的本質也是計算啊！物質就是信息，運動學就是計算。

看果殼載的採訪，似乎Wolfram的本質世界觀仍舊是決定論。他認為只要我們能夠構建一個完備的規則，搞清楚所有變數，世界就是完全可計算的。這和牛頓的想法如出一轍。

很多時候人們說的「隨機性」，其實是建模時用的黑箱：我不了解一個系統的全部規則，所以我假定這個系統有某些額外的因素在提供「隨機」的輸入。這個意義上的「隨機」，只是證明你還沒為這個系統建立完整的模型而已。

但是量子力學，卻是真隨機，不存在什麼人類暫時沒有能力探測到的「局部隱變數」

其實雖然量子力學，甚至是弦論看起來很複雜，但是就背後的原理和規則的模式來看是簡單的。

個人觀點，「宇宙的本質是計算」這句論斷，其實同「宇宙的本質是數學」一樣，沒有什麼實質性的含義。因為計算同數學一樣，只不過是一種抽象的工具。廣義的計算應該包含所有已知的數學。

人類連宇宙的起源都無法搞清楚，怎麼能夠談論宇宙的本質。而宇宙的起源問題，是一個著名的終極問題。

Wolfram用這個標題，有點嘩眾取寵。

我覺得他對時空本質的看法可能更靠譜。

What Is Spacetime, Really?

不衝突。

事實上問題里的兩樣東西沒法衝突。

理解他的一個破題的思路是想清楚計算到底是什麼樣的過程/東西。

抽象意義的計算和在物理世界的計算的過程與實現。

似乎"t hooft也有一種量子力學的元胞自動機詮釋，不知道有什麼關係。。

Wolfram其實只是個優秀的工程師，拿個圖出來只是故弄玄虛罷了，沒啥實際內容。談到宇宙，還讓人隱約聞到一股民科的味道。

Stephen Wolfram：宇宙的本質是計算 這和量子力學衝突嗎？

Stephen Wolfram：宇宙的本質是計算這和量子力學衝突嗎？