“計算科學之父”圖靈如何用數學破譯自然界

Many have heard of Alan Turing, the mathematician and logician who invented modern computing in 1935. They know Turing, the cryptologist who cracked the Nazi Enigma code, helped win World War II. And they remember Turing as a martyr for gay rights who, after being prosecuted and sentenced to chemical castration, committed suicide by eating an apple laced with cyanide in 1954.

很多人都聽說過艾倫·圖靈(Alan Turing)，知道他是一位數學家和邏輯學家，在1935年發明了現代計算。他們知道圖靈是一位密碼學家，破譯了納粹的Enigma密碼，幫助同盟國贏得了第二次世界大戰。他們還知道，圖靈是同性戀權利的殉難者，在被起訴並被判處化學閹割後，他於1954年吃了一個塗有氰化物的蘋果，自殺身亡。

But few have heard of Turing, the naturalist who explained patterns in nature with math. Nearly half a century after publishing his final paper in 1952, chemists and biological mathematicians came to appreciate the power of his late work to explain problems they were solving, like how zebrafish get their stripes or cheetahs get spots. And even now, scientists are finding new insights from Turing’s legacy.

但很少有人知道圖靈是一位博物學家，他用數學來解釋自然界的圖案。在他1952年發表最後一篇論文後的近半個世紀裏，化學家和生物數學家們開始意識到，他後期的工作可以用來解釋他們正在解決的問題，例如，斑馬魚的條紋或獵豹的斑點是如何形成的。甚至到現在，科學家們還在從圖靈的遺產中找到新的洞見。

Most recently, in a paper published Thursday in Science, chemical engineers in China used pattern generation described by Turing to explain a more efficient process for water desalination, which is increasingly being used to provide freshwater for drinking and irrigation in arid places.

最近一次，在週四發表在《科學》雜誌(Science)上的一篇論文中，中國的化學工程師利用圖靈描述的斑圖生成理論闡釋了一種更有效的海水淡化處理方法。海水淡化正越來越多地被用於乾旱地區的飲用水和灌溉用水供給。

Turing’s 1952 paper did not explicitly address the filtering of saltwater through membranes to produce freshwater. Instead, he used chemistry to explain how undifferentiated balls of cells generated form in organisms.

圖靈那篇1952年的論文沒有明確提到，可以通過薄膜過濾鹽水來產生淡水。他是用化學解釋了沒有明顯差別的細胞球是如何在生物體中產生形狀的。

It’s unclear why this interested the early computer scientist, but Turing had told a friend that he wanted to defeat Argument From Design, the idea that for complex patterns to exist in nature, something supernatural, like God, had to create them.

尚不清楚這爲什麼引起了這位早期計算機科學家的興趣，但圖靈曾對一位朋友說他想推翻目的論證，即自然界中存在的複雜圖案一定是某種超自然的東西創造出來的，比如上帝。

A keen natural observer since childhood, Turing noticed that many plants contained clues that math might be involved. Some plant traits emerged as Fibonacci numbers. These were part of a series: Each number equals the sum of the two preceding numbers. Daisies, for example, had 34, 55 or 89 petals.

圖靈從小就是敏銳的自然觀察者，他注意到許多植物包含着可能與數學相關的線索。有些植物的性狀中存在斐波那契數列。這個數列的一個特徵是：每個數字等於前面兩個數字的和。例如，雛菊有34、55或89個花瓣。

“He certainly was no militant atheist,” said Jonathan Swinton, a computational biologist and visiting professor at the University of Oxford who has researched Turing’s later work and life. “He just thought mathematics was very powerful, and you could use it to explain lots and lots of things — and you should try.”

“他當然不是一位激進的無神論者，”牛津大學(University of Oxford)的客座教授、計算生物學家喬納森·斯溫頓(Jonathan Swinton)說。他研究了圖靈的後期工作和生活。“他只是認爲數學非常強大，你可以用它來解釋很多東西——你應該試一試。”

And try, Turing did.

圖靈的確嘗試了。

“He came up with a mathematical representation that allows form to emerge from blankness,” said Dr. Swinton.

“他提出了一種數學表達式，可以從無到有地生成形狀，”斯溫頓說。

In Turing’s model, two chemicals he called morphogens interacted on a blank arena. “Suppose you’ve got two of these, and one will make the skin of an animal go black and the skin of the animal go white,” explained Dr. Swinton. “If you just mix these things in an arena, what you get is a gray animal.”

在圖靈的模型中，兩種被他稱作成形素(morphogen)的化學物質在一個空白區域相互作用。“假設你有兩種成形素，一種會讓動物的皮膚變黑，另一種會讓動物的皮膚變白，”斯溫頓博士。“如果把它們混合在一起，動物的皮膚就會變成灰色。”

But if something caused one chemical to diffuse, or spread, faster than the other, then each chemical could concentrate in evenly spaced localized spots, together forming black and white spots or stripes.

但如果某種原因導致一種化學物質擴散得比另一種快，它們就會集中在間隔均勻的局部區域，形成黑色和白色的斑點或條紋。

This is known as a “Turing instability,” and, the Chinese researchers who published the new paper determined that it could explain the way shapes emerged in salt-filtering membranes.

這被稱作“圖靈不穩定性”。發表這篇新論文的中國研究人員斷定，它可以解釋鹽過濾膜中出現的結構。

By creating three-dimensional Turing patterns like bubbles and tubes in membranes, the researchers increased their permeability, creating filters that could better separate salt from water than traditional ones.

通過在膜上製造氣泡和管道等三維圖靈結構，研究人員增加了它們的滲透性。這種過濾器能夠比傳統過濾器更好地分離鹽和水。

“We can use one membrane to finish the work of two or three,” said Zhe Tan, a graduate student at Zheijang University in China and first author of the paper, which means less energy and lower cost if used for large-scale desalination operations in the future.

“我們可以用一張膜完成兩到三張膜的工作，”浙江大學的研究生譚喆說。他是該論文的第一作者。這意味着如果將來用於大規模的脫鹽作業，消耗的能源和成本都會降低。