研究人員解決牛頓的三體問(wèn)題了嗎?

研究人員解決牛頓的三體問(wèn)題了嗎?

If you thought that Issac Newton made physics simple, think again. The laws of motion might themselves be simple equations, but the actual motions of objects according to these laws can get complicated fast.

如果你認(rèn)為是艾薩克·牛頓使物理學(xué)變得簡(jiǎn)單，那你就錯(cuò)了。運(yùn)動(dòng)定律本身可能是簡(jiǎn)單的方程，但根據(jù)這些定律，物體的實(shí)際運(yùn)動(dòng)很快就會(huì)變得復(fù)雜起來(lái)。

Our solar system contains far more than just three bodies, which makes the three-body problem particularly embarrassing. (Photo: NASA)

For instance, imagine a universe with just two objects in it: say, two stars. Newton's laws are reasonably sufficient for helping us to understand how these gravitationally bound objects will interact with each other. But add a third object — a third star, perhaps — and our calculations become dicey.

例如，想象一個(gè)只有兩個(gè)物體的宇宙:比如說(shuō)，兩顆星星。牛頓定律足以幫助我們理解這些受引力束縛的物體之間是如何相互作用的。但是再加上第三個(gè)物體——也許是第三顆星——我們的計(jì)算就變得不可靠了。

This problem is known as the three-body problem. When you have three or more bodies interacting according to any inverse square force (like gravity), their interactions conflict in a chaotic way that makes their behavior impossible to predict precisely. This is a problem because, well ... there are a lot more than three bodies in the universe. Even if you just narrow the universe down to our own solar system, it's a mess. If you can't even account for three bodies, how are you supposed to predict the motions of a sun, eight planets, dozens of moons, and the countless other objects that make up our solar system?

這個(gè)問(wèn)題被稱(chēng)為三體問(wèn)題。當(dāng)你有三個(gè)或更多的物體根據(jù)任何反方力(如重力)相互作用時(shí)，它們的相互作用以一種混亂的方式發(fā)生沖突，使得他們的行為無(wú)法準(zhǔn)確預(yù)測(cè)。這是個(gè)問(wèn)題，因?yàn)橛钪嬷杏腥齻€(gè)以上的物體。即使你把宇宙縮小到我們自己的太陽(yáng)系，也是一團(tuán)糟。如果你連三個(gè)物體都沒(méi)有考慮，你應(yīng)該如何預(yù)測(cè)太陽(yáng)以及組成太陽(yáng)系的八個(gè)行星、幾十顆衛(wèi)星和無(wú)數(shù)其他物體的運(yùn)動(dòng)?

Because you only need three bodies to make it a problem, even if you just try to analyze the motions of the Earth, sun and moon, you can't do it.

因?yàn)槟阒恍枰齻€(gè)物體就能把它變成一個(gè)問(wèn)題，即使你只是試圖分析地球、太陽(yáng)和月球的運(yùn)動(dòng)，你也做不到。

The two-body answer

雙體答案

Physicists get around this problem by instead treating all systems like two-body systems. For instance, we analyze the interactions of the Earth and the moon alone; we don't factor in the rest of the solar system. This works well enough because the Earth's gravitational influence on the moon is way stronger than anything else, but this cheat can never truly get us 100 percent there. There's still a mystery at the heart of how our complicated solar system all factors in.

物理學(xué)家們通過(guò)把所有的系統(tǒng)都看成是兩體系統(tǒng)來(lái)回避這個(gè)問(wèn)題。例如，我們單獨(dú)分析地球和月球的相互作用;我們不考慮太陽(yáng)系的其他部分。這已經(jīng)足夠好了，因?yàn)榈厍驅(qū)υ虑虻囊τ绊懕绕渌魏螙|西都要大得多，但這種欺騙不可能真正讓我們百分之百地到達(dá)那里。在我們復(fù)雜的太陽(yáng)系中，所有因素是如何形成的，其核心仍然是個(gè)謎。

Needless to say, it's an embarrassing conundrum for physicists to have, especially if our goal is to make perfect predictions.

不用說(shuō)，這對(duì)物理學(xué)家來(lái)說(shuō)是一個(gè)尷尬的難題，尤其是如果我們的目標(biāo)是做出完美的預(yù)測(cè)。

But now, an international team of researchers, led by astrophysicist Dr. Nicholas Stone of Hebrew University of Jerusalem's Racah Institute of Physics, think they might finally have made progress on a solution, reports Phys.org.

但是現(xiàn)在，一個(gè)由耶路撒冷希伯來(lái)大學(xué)拉卡物理研究所的天體物理學(xué)家尼古拉斯·斯通博士領(lǐng)導(dǎo)的國(guó)際研究小組認(rèn)為，他們可能終于在解決方案上取得了進(jìn)展，Phys.org報(bào)道。

In formulating their solution, the team looked at one guiding principle that seems to apply across certain types of three-body systems. Namely, centuries of research has revealed that unstable three-body systems all eventually expel one of the trio, and inevitably form a stable binary relationship between the two remaining bodies. This principle provided a crucial clue for how this problem might be solved in a more general way.

在制定他們的解決方案時(shí)，該團(tuán)隊(duì)著眼于一個(gè)指導(dǎo)原則，似乎適用于某些類(lèi)型的三體系統(tǒng)。也就是說(shuō)，幾個(gè)世紀(jì)以來(lái)的研究表明，不穩(wěn)定的三體系統(tǒng)最終都會(huì)排斥其中的一個(gè)，并不可避免地在剩下的兩體之間形成穩(wěn)定的二元關(guān)系。這一原則為如何以更普遍的方式解決這一問(wèn)題提供了重要的線索。

So, Stone and his colleagues crunched the math and came up with some predictive models that could be compared against computer modeling algorithms of these systems.

因此，斯通和他的同事們分析了這些數(shù)學(xué)問(wèn)題，并提出了一些可與這些系統(tǒng)的計(jì)算機(jī)建模算法相比較的預(yù)測(cè)模型。

"When we compared our predictions to computer-generated models of their actual movements, we found a high degree of accuracy," shared Stone.

斯通說(shuō):“當(dāng)我們將預(yù)測(cè)結(jié)果與電腦生成的它們實(shí)際運(yùn)動(dòng)的模型進(jìn)行比較時(shí)，我們發(fā)現(xiàn)它們的準(zhǔn)確率很高。”

He added: "Take three black holes that are orbiting one another. Their orbits will necessarily become unstable and even after one of them gets kicked out, we're still very interested in the relationship between the surviving black holes."

他補(bǔ)充道:“以三個(gè)相互環(huán)繞的黑洞為例。它們的軌道必然會(huì)變得不穩(wěn)定，即使其中一個(gè)被踢出，我們?nèi)匀粚?duì)幸存的黑洞之間的關(guān)系非常感興趣。”

While the team's success represents progress, it's still not a solution. They've only shown that their model lines up against computer simulations in special case scenarios. But it's something to build on, and when it comes something as chaotic as three-body systems, that scaffolding goes a long way in helping us to understand how our theories might be used to more accurately construct models of reality.

雖然團(tuán)隊(duì)的成功代表著進(jìn)步，但它仍然不是一個(gè)解決方案。他們只展示了他們的模型在特殊情況下與計(jì)算機(jī)模擬一致。但它是建立在一定基礎(chǔ)上的，當(dāng)它涉及到像三體系統(tǒng)這樣混亂的東西時(shí)，支架在幫助我們理解如何將我們的理論用于更準(zhǔn)確地構(gòu)建現(xiàn)實(shí)模型上大有幫助。

It's a critical step toward a fuller understanding of how our universe operates.

這是全面了解我們的宇宙如何運(yùn)作的關(guān)鍵一步。