科学与数学en.wikipedia.org
单电子宇宙
One-electron universe
2011 — 2015，它一次次回到首页
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导读
维基百科条目介绍物理学家惠勒（John Wheeler）1940 年提出的“单电子宇宙”设想：宇宙中看似无数个电子其实只是同一个电子在时间中前后穿梭，逆时间运动的电子就表现为正电子。条目梳理了这一想法的由来、与费曼图/量子场论的联系，以及它为何不被当作严肃的可检验理论。
为什么经久不衰：它用一个极简到近乎荒诞的图景把反粒子、时间反演和全同粒子串在一起，是物理直觉的经典思想实验——即便不成立，也让人更懂粒子物理在说什么。
HN 评论精选
该设想优美但不可检验，且与正反物质数量不对称及量子场论中的闭合圈图像相矛盾。
我是物理教授。正如其他人所说，这是物理学中一个非常可爱的想法，涉及宇宙的一些巧妙性质（比如粒子的根本全同性、轻子数守恒、时间反演对粒子性质的影响），但是：1）它更像哲学而非科学：这个设想要么没有可检验的后果，要么其预测明显为假；2）观测上电子似乎远多于反电子，而该概念似乎要求数量完全相等，任何补救都很牵强；3）量子场论中电子-正电子形成时间上的“闭合圈”是自然出现的，这些圈并不连到那个假设中在全部时间里来回弹跳的“唯一电子”，所以它解释不了为何它们也一模一样。在我看来，这个想法的美全在于它居然能被提出来：它并不符合现实，却对粒子物理如何运作给出了惊人的直觉。
Steuard查看英文原文
Physics professor here. As others have said, this is a really cute idea in physics that touches on some neat properties of the universe (like fundamentally identical particles, conservation of lepton number, and the effects of time reversal on particle properties), but: 1. It's more akin to philosophy than to science: this suggestion either has no testable consequences (or if it does, its predictions look obviously false: see below). 2. In all of our observations of the universe there seem to be many more electrons than anti-electrons, but this concept would seem to imply that the number should be exactly equal. You can try to get around that, but anything you do is a stretch.[1] 3. The formalism of quantum field theory naturally includes plenty of situations where electrons and anti-electrons form "closed loops" in time. (The classic example is a something like a photon giving rise to a virtual e-/e+ pair that immediately annihilates back into a photon, but they can get a lot more complicated.) Those closed loops would not be connected to the hypothesized "one electron" bouncing back and forth through all of time, so this idea would fail to explain why they also look identical to the rest. So in my book, the beauty of this idea lies entirely in the fact that it could be suggested at all. It doesn't actually match reality, but it does give some striking intuition about how particle physics works. [1] You could suggest that there is some other (unobservably distant?) region of the universe where antimatter dominates, but there's absolutely no evidence to support that suggestion. As another idea, the quote in the link suggests that "maybe the extra anti-electrons are hiding in the protons or something". But anything of the sort would seem to eliminate the whole point of saying "it's all one electron" (which always has the same properties, etc.).
提出关键的可观测性问题：如何判定遥远星系的正反物质构成。
有人知道我们是否仍然相信宇宙中电子多于正电子（以及物质多于反物质）吗？我们有办法判断一个遥远星系是由物质还是反物质构成的吗？
scotty79查看英文原文
Does anyone know if we still believe that there are more electrons than positrons in the universe (also more matter than antimatter)? Do we have a way of checking if distant galaxy is made of matter or antimatter?
戏称单电子假设可以“消解”EPR 悖论中的超距关联。
这或许能解释 EPR 悖论：说测量第一个粒子的动量会影响它自身位置的不确定性是一回事，说它会影响另一个粒子位置的不确定性则完全是另一回事。爱因斯坦、波多尔斯基和罗森问：第二个粒子怎么“知道”自己动量精确而位置不确定？这意味着一个粒子在瞬时跨空间与另一个通信，即超光速，这就是悖论。答案：被测量的本来就是同一个电子！悖论不再存在。
unclebucknasty查看英文原文
Well, this could explain the EPR Paradox[1]: It is one thing to say that physical measurement of the first particle's momentum affects uncertainty in its own position, but to say that measuring the first particle's momentum affects the uncertainty in the position of the other is another thing altogether. Einstein, Podolsky and Rosen asked how can the second particle "know" to have precisely defined momentum but uncertain position? Since this implies that one particle is communicating with the other instantaneously across space, i.e. faster than light, this is the "paradox".[2] The answer: It's the same electron being measured! No more paradox. [1] http://en.wikipedia.org/wiki/EPR_paradox [2] http://en.wikipedia.org/wiki/EPR_paradox#Einstein.27s_oppositionition
类比《The Egg》——全宇宙只有一个个体在反复经历一切。
这让我想起 Andy Weir 的短篇《The Egg》：只不过不是电子，而是宇宙中的每个人其实都是同一个人。
amvp查看英文原文
Reminds me of this short story: The Egg by: Andy Weir http://galactanet.com/oneoff/theegg_mod.html Instead of electrons, everyone in the universe is the same person.
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