物理学的未来

译者 dlq

ON SEPTEMBER 23rd researchers at CERN, Europe’s main particle-physics laboratory, caused a stir. They suggested that neutrinos—ethereal particles which pervade the universe but rarely interact with anything while they are doing so—can travel faster than light. According to Albert Einstein’s special theory of relativity, this is impossible.

9月23日，欧洲最大的粒子物理实验室CERN（欧洲核子研究中心）的研究员们给世界抛出了一颗重磅炸弹。他们指出，谜一样的中微子充盈着整个宇宙但是几乎不与任何物质发生相互作用，但是一旦它们相互作用中微子将超越光速。根据爱因斯坦的狭义相对论，这是不可能的。

Physicists from OPERA, one of the experiments at CERN, sent beams of neutrinos through the Earth’s crust from the organisation’s headquarters on the outskirts of Geneva to an underground laboratory 730km (450 miles) away beneath Gran Sasso, a mountain in the Apennines. The neutrinos appeared to be reaching the detector 60 nanoseconds faster than light would take to cover the same distance—a small deviation, and one that might be written off as experimental error if an experiment in America, called MINOS, had not detected a similar anomaly in 2007.

CERN下属实验室OPERA（译者注：即Oscillation Project with Emulsion Tracking Apparatus的首字母缩写，直译即“戏剧”，不少科学家开玩笑称这的确很戏剧化）的物理学家接受到了日内瓦市郊总部发出的中微子束，它穿过地壳到达距日内瓦730km的意大利亚平宁山格兰萨索峰的地下实验室。通过相同的距离，中微子到达探测器的时间比光早了60ns，略有差别。倘若不是2007美国MINOS实验探测到了类似结果，这一差别将被忽略。

The MINOS result, too, was thought an error. Now researchers are not so sure. Most are unwilling to believe Einstein was wrong. A few, though, are contemplating the idea that OPERA’s neutrinos are interacting with the matter of the Earth’s crust in a way, hitherto unknown, that allows them to take a shortcut through one of the extra seven dimensions that are hypothesised, by some versions of theoretical physics, to exist alongside the familiar four of length, breadth, height and time. If that is true, it would take physics beyond the theory of relativity, just as Einstein took the subject beyond Newton’s laws of motion and gravity, and might allow physicists to merge relativistic ideas with those of quantum theory—a goal of the subject for almost a century.

MINOS的结果同样被认为是实验错误造成的。目前研究者还不确定。大部分科学家都不愿相信爱因斯坦错了。即便如此，部分科学家认为OPERA发射的中微子以一种目前不知的方式和地壳中的物质发生了相互作用，使得它们可以从隐藏的七维中走捷径到达。根据某些理论物理，除了长、宽、高、时间四维之外还有隐藏的七维。如果这是真的，这将取代相对论，就像爱因斯坦取代牛顿运动定律一样，也可能使得物理学家将相对论与量子力学结合，这是近百年来物理学的目标。（译者注：弦论认为宇宙是有十一维的，除了我们所知的四维，还有七维隐藏着，这是一种将相对论和量子力学结合的方法之一。另一种是圈量子理论，不过两者的实验证据都不是十分充分。）

As science cuts ever deeper into the fabric of nature, discoveries like this have become the preserve of huge, costly machines. Ironically, the news arrived at the moment one such device faces execution. At 2pm on September 30th, the last day of the American fiscal year, Helen Edwards, a septuagenarian American physicist, will press a red switch, and then a green one. By doing so, she will kill the Tevatron—a particle accelerator (pictured above), with a circumference of 6.3km, that she helped, in her younger days, to build.

随着科学研究的深入，像这样的发现已经演变成了维持大型烧钱机器的运作。相反，在这一消息公布的同时，一台机器面临搁置。9月30日下午2时，美国财政年度预算的最后一天，年过七旬的物理学家海伦·德华兹（Helen Edwards）按下了红色按钮然后是个绿色的。她这么做，就意味着海伦早年曾帮助建造，周长为6.3km的万亿电子伏特加速器（Tevatron，上图所示）将被关闭。

Grand OPERA

完美“戏剧”

For a quarter of a century before CERN’s Large Hadron Collider (LHC) began working in earnest in 2009 the Tevatron, at the Fermi National Accelerator Laboratory (Fermilab) in Batavia, near Chicago, dominated high-energy physics. It was the first machine to smash particles together with energies in excess of 1 trillion electron-volts—or 1 TeV, whence its name. This led to the discovery of the top quark, the heaviest elementary particle seen to date and the penultimate piece of the jigsaw puzzle known as the Standard Model that is the best description physicists have of the basic components of the universe.

CERN大型强子对撞机(LHC）2009年初开始运作，在这之前的四分之一个世纪芝加哥附近巴达维亚的费米实验室已将 Tevatron用在高能物理领域。顾名思义，这是世界上首次用1Tev高能轰击粒子。它也因此发现了顶夸克，按照物理学家描述宇宙基本组成的标准模型，顶夸克是已知最重的粒子，也是物理界完美拼图中的倒数第二块。

For a few months in 2010 it looked as though the Tevatron might get a reprieve in order to find the last (and heaviest) missing bit of the model—the Higgs boson, which is thought to give other particles their mass. That would have been a delicious victory, as the LHC’s first goal is the discovery of the Higgs. In the event, though, Congress pulled the plug.

2010年的几个月里尽管 Tevatron为了寻找标准模型中最后（也是最重的）的希格斯玻色子（标准模型认为正是它使得其他粒子具有质量）而暂免关闭。那是不错的胜利，因为LHC的首要目标就是发现希格斯子。但这一次，国会取消了预算。

Before September 23rd, that was a matter of wailing and gnashing of teeth. It still is, of course. No one likes having his toys taken away. But if the OPERA result holds up, Fermilab may find itself in a far more interesting position than it expected.

9月23日之前 Tevatron的科学家仍在咬着牙在等待。这是当然的。没有人想失去它。但是如果OPERA的结果得到证实，费米实验室将发现它的处境将比之前想的更加微妙。

Discovering the Higgs is important, no question. It is, though, a bit old hat given that, as a theory, the Higgs mechanism goes back to the 1960s. Supraluminal neutrinos, if they really exist, are something completely new. And Fermilab is well placed to investigate them. It already whips up the world’s most intense beams of neutrinos, using kit that has nothing to do with the Tevatron. As luck would have it, a project called NOvA, which should start collecting data in the spring of 2013, will send neutrinos through the Earth’s crust from Batavia to an underground detector 810km away in Minnesota. If NOvA finds the same result as OPERA and MINOS, then the post-Einsteinian era of physics really will have begun, and Fermilab will be in the thick of it.

毫无疑问，寻找希格斯子很重要。而希格斯机理可以追溯到上世纪六十年代。超光速中微子如果真的存在，这将是物理界新的革命。费米实验室很适合去研究它们。通过轰击科学家已经能够产生世界上最强烈的中微子流，但这和Tevatron毫无关系。如果幸运的话，一个名为NOvA的项目将在2013年春启动，它将从巴达维亚发射中微子穿过地壳到达810km外明尼苏达州的地下探测器。如果NOvA得到了和OPER、MINOS一样的结果，那么物理学的后爱因斯坦时代已经到来，而费米实验室当然将成为其中的中流砥柱。

Indeed, NOvA is only the start. Pier Oddone, Fermilab’s boss, plans to follow it with the Long Baseline Neutrino Experiment (LBNE), which will send a yet-more intense beam of the particles to an underground laboratory in South Dakota. After that, the mysteriously named Project X will push the intensity of the neutrino beam still higher.

当然NOvA只是个开始。费米实验室的老板皮耶·奥登 （Pier Oddone）计划将跟进长基线中微子实验（LBNE），将向南达科塔地下试验室发射更强烈的粒子束。之后，未知项目“项目X”将把中微子能量推到更高。

A bold vision, then, and one that might just have become far more important than its prophets could possibly have imagined. The plan does, however, depend on American taxpayers stumping up huge amounts of money. The price tag for LBNE alone is $1 billion. And that is causing nervousness. Late in 2010 one government agency, the National Science Foundation, unexpectedly withdrew its support for the construction of the South Dakota laboratory. The Department of Energy adopted the orphaned project, but Congress then failed to appropriate the $17m needed to get it going, so the whole thing hangs in the balance. The fate of Project X, too, is uncertain, though its prospects are helped by the fact that India is keen to get in on the fundamental-physics game and has made what Dr Oddone calls “a very substantial commitment” to the endeavour.

我们大胆想象一下，也许结果将比预言的更重要。当然，这些计划也是需要美国纳税人掏一大笔钱的。省着点花的话，仅LBNE就需10亿美元。2010年末，美国国家科学基金会意外地不再支持南达科塔实验室的建设。能源部接管了这个孤立项目，但是之后国会没有批准其一千七百万美元的预算，所以又回到了原点。项目X的命运也一样前途未卜，尽管印度想在基础物理方面有所突破使得它还有那么点希望，这也使得奥登尽力地做出“一个十分有效的承诺”。

For all mankind?

Though it may gall those Americans who would like their country to continue to go it alone in matters physical, that multinational deal over Project X may represent the future. It already looks likely that the successor to the LHC, a device called the International Linear Collider (ILC), will be built in Japan (if it is built at all). Most physicists agree it would be America’s for the asking if Americans wanted it, but the current Congress seems not to, because it would entail doling out half of the $20 billion the ILC is expected to cost.

尽管上述事实使得那些想让本国继续在多项物理领域独领风骚的美国人纠结不已，但只有跨国合作才使得项目X略有未来。就像ILC已经获得的成功那样，国际直线对撞机（ILC）将在日本建成（如果它在建的话）。多数物理学家认为它应该是美国的如果美国人想要的话，但是当前国会并无兴趣，因为它需要承担ILC两百亿美元预算的一半费用。

Even if it ends up on the other side of the Pacific, though, America will be expected to make some sort of financial contribution to the ILC. And the odd American accent is not unknown even in the corridors of Geneva. In matters of particle physics, then, patriotism is passé. The “E” in CERN originally stood for “European”, but the organisation already boasts Israel as a member, and India, Japan and the United States as observers. Moreover, more than two dozen other non-European countries have co-operation agreements with CERN. The passing of the Tevatron may cause the shedding of a manly (and womanly) tear or two among America’s physicists. But physics belongs to no one country. That said, you can bet the lads and lasses at Fermilab will be happy to grab any credit they can for helping dethrone relativity. For in their heart of hearts, even the sceptics who say they think the result from OPERA must be a mistake hope that it is not.

尽管最后它将坐落于太平洋的另一岸，美国仍被期望给予ILC财政资助。即便是在日内瓦总部的走廊，奇怪的美国口音亦不少见。在粒子物理领域，爱国主义是不合时宜的。CERN中的E代表的是“欧洲人（European）”，但是该组织吸纳了以色列为其一员，印度、日本和美国为观察员。而且，另有不只两打的非欧洲国家和CERN有合作协议。 Tevatron的搁置也许会引起美国物理学家男人（或者女人）的眼泪。而我敢打赌说费米实验室的怪蜀黍和御姐们将很高兴他们可以抓住任何推翻相对论的机会。而在他们心中，尽管有个声音告诉他们说OPERA的结果是错误的，但是他们都希望不是。