Physicist does the math on Star Trek’s “Picard maneuver”
Physicist does the math on Star Trek’s “Picard maneuver”
物理学家推演《星际迷航》中的“皮卡德机动”
It turns out Jean-Luc Picard was an even better starship helmsman than the writers knew. A physicist has gone through the details of a warp-speed trick from the first season of Star Trek: The Next Generation and found a subtlety the show missed. But instead of a plot hole, the detail he found actually makes the maneuver more impressive… as well as a great opportunity to teach about a lesser-known feature of the theory of relativity.
事实证明，让-卢克·皮卡德（Jean-Luc Picard）作为星舰舵手的水平比编剧们想象的还要高。一位物理学家深入研究了《星际迷航：下一代》第一季中一个曲速飞行技巧的细节，并发现了一个剧中被忽略的微妙之处。但这并非剧情漏洞，他发现的这个细节实际上让这一机动动作显得更加令人印象深刻，同时也成为了科普相对论中一个鲜为人知特性的绝佳机会。
Níckolas de Aguiar Alves, a physicist at the Federal University of ABC in Brazil, first watched Next Generation as a master’s student. When he got to the episode “The Battle” in the show’s first season, the plot reminded him of his relativity coursework. In “The Battle,” a Ferengi leader reminds Picard of a battle he fought years ago as captain of a ship called the Stargazer. Under fire from a mysterious attacker, Picard’s ship’s shields were down. He had to get closer without taking a hit, so he made a gamble.
巴西联邦ABC大学的物理学家尼科拉斯·德·阿吉亚尔·阿尔维斯（Níckolas de Aguiar Alves）在攻读硕士学位时第一次观看了《下一代》。当他看到该剧第一季的“战斗”（The Battle）这一集时，剧情让他想起了自己的相对论课程。在这一集中，一位弗伦基人（Ferengi）首领提醒皮卡德，他多年前担任“星际迷航号”（Stargazer）舰长时曾经历过一场战斗。当时，皮卡德的飞船在神秘攻击者的炮火下护盾失效。为了在不被击中的情况下靠近敌舰，他孤注一掷。
Picard ordered the Stargazer to charge the enemy ship at warp speed (meaning faster than light), then stop abruptly and fire. By going faster than light, Picard anticipated that the other ship would see two images of the Stargazer: where it reached warp speed and where it stopped. If they fired on the wrong image, they would miss the Stargazer, and Picard could win the battle. Later in the episode, Riker mentions that the trick had been immortalized in Starfleet textbooks as the “Picard maneuver.”
皮卡德命令“星际迷航号”以曲速（即超光速）冲向敌舰，然后突然停止并开火。通过超光速飞行，皮卡德预判敌舰会看到“星际迷航号”的两个影像：一个是它达到曲速时的位置，另一个是它停止时的位置。如果敌舰向错误的影像开火，就会打偏，皮卡德便能赢得战斗。在这一集的后期，里克（Riker）提到这个技巧已被载入星际舰队教科书，并被命名为“皮卡德机动”。
As it turns out, it’s also not that far from what you can find in some physics textbooks. While warp speed is pure science fiction, physicists sometimes need to consider what happens when an object goes faster than light, and such an object really does leave two images. Something about the story bothered de Aguiar Alves at the time. But he forgot about it until years later, when he was working through a more practical problem involving particles in a medium with a slower speed of light.
事实证明，这与你在某些物理教科书中能找到的内容相差不远。虽然曲速飞行纯属科幻，但物理学家有时确实需要考虑物体超光速运动时会发生什么，而这样的物体确实会留下两个影像。当时，这个故事中的某些细节让阿尔维斯感到困扰。但他后来将其淡忘了，直到多年后，他在处理一个涉及光速较慢介质中粒子的实际问题时，才重新想起这件事。
Not trusting that he had done the math right, he started trying to work out the situation visually. “And after I drew one or two diagrams, I started noticing, ‘Hey, I think I’ve thought about something like this before,’” said de Aguiar Alves.
由于不确定自己的计算是否正确，他开始尝试通过视觉化方式推演这一情况。“在我画了一两张图表后，我开始意识到：‘嘿，我想我以前思考过类似的事情，’”阿尔维斯说道。
Three images, not two
三个影像，而非两个
The idea behind the Picard maneuver comes from the way a faster-than-light spaceship would outrun its own light. If the spaceship were going at a constant, faster-than-light speed, then another ship at rest would see two images, corresponding to two different times when light from the ship could reach them. But in the story, Picard’s ship isn’t going at a constant speed. He speeds up to warp speed, then stops close to the enemy ship. The Stargazer accelerates twice… and that changes the timing. After diagramming things out, de Aguiar Alves found that the enemy ship would see three images of the Stargazer, not two.
“皮卡德机动”背后的原理源于超光速飞船超越自身光线的方式。如果飞船以恒定的超光速飞行，那么另一艘静止的飞船会看到两个影像，分别对应飞船发出的光到达观察者的两个不同时间点。但在故事中，皮卡德的飞船并非以恒定速度飞行。他加速到曲速，然后在靠近敌舰时突然停止。“星际迷航号”经历了两次加速……这改变了时间点。经过绘图推演，阿尔维斯发现敌舰实际上会看到“星际迷航号”的三个影像，而不是两个。
While the details were wrong, de Aguiar Alves was impressed that the episode reproduced the core textbook idea mostly accurately. “The main thing they got perfectly, and I think it is a great illustration.”
虽然细节有误，但阿尔维斯对该剧能如此准确地还原教科书中的核心概念感到印象深刻。“他们完美地抓住了核心要点，我认为这是一个非常棒的演示。”
Physicists don’t expect faster-than-light space travel to ever be possible. But because light travels more slowly in substances like water, the math of faster-than-light travel is still useful. When a particle travels faster than light can in water, its shockwave emits a characteristic glow called Cherenkov radiation, the blue light seen in nuclear reactors.
物理学家并不认为超光速太空旅行在未来能够实现。但由于光在水等物质中的传播速度较慢，超光速旅行的数学模型依然具有实用价值。当粒子在水中的运动速度超过光速时，其产生的冲击波会发出一种特征性的光，即切连科夫辐射（Cherenkov radiation），也就是在核反应堆中看到的蓝光。
For de Aguiar Alves, the motivation was a more elusive physical phenomenon, called the memory effect. First theorized for gravitational waves, the memory effect happens when a wave passes by a particle and leaves a lasting effect on its motion. Theoretical physicists expect it to happen when ordinary electromagnetic waves pass a particle, too, but it requires very specific circumstances and is very hard to detect.
对阿尔维斯来说，他的研究动机是一种更难以捉摸的物理现象，即“记忆效应”（memory effect）。记忆效应最初是针对引力波提出的理论，指当波经过粒子时，会对粒子的运动留下持久的影响。理论物理学家预计，当普通的电磁波经过粒子时也会发生这种现象，但这需要非常特定的条件，且极难探测。
Recently, a physicist at the Niels Bohr Institute has argued that the effect should be more dramatic in a medium like water with a limited speed of light. Wanting to understand this better inspired de Aguiar Alves to try to picture how a memory-effect-influenced electron would be detected, and the diagrams he drew helped him picture the Star Trek scenario as well. “You get a lot of intuition very quickly, and pretty much for free, by just doodling,” said de Aguiar Alves.
最近，尼尔斯·玻尔研究所的一位物理学家提出，在光速受限的水等介质中，这种效应应该会更加显著。为了更好地理解这一点，阿尔维斯尝试构想如何探测受记忆效应影响的电子，而他所绘制的图表也帮助他理清了《星际迷航》中的场景。“通过简单的涂鸦，你可以非常迅速且几乎不费吹灰之力地获得很多直觉，”阿尔维斯说。