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光速悖论

(2022-03-28 13:42:27) 下一个

戴榕菁

前几天在写“光速不变其实并非一个简单的假设”的英文版“Constant Light Speed in Vacuum was not a Mere Postulation”时想到一个有关光速的悖论,一直没能得到很好的解释,拿来与大家分享一下。

假设在太空中有两束相距为L的具有一个宽度的平行光柱A和B(如图1),假设L=1c,其中c为真空中的光速,1表示1秒的时间长度以满足量纲要求。有一个长度为L的真空箱以速度V=3c/5在与光线垂直的方向向两束光柱运行(不要被L这个长度吓着,在太空中这不算什么,比物理学家戴森设想的戴森球的尺度小太多了)。真空箱的尾端有一小孔。假设当真空箱的前端碰到光柱B时向尾端的小孔发出一束激光。一秒钟后激光到达小孔。由于光速在真空中不随运动参照系而变,这束激光相对光柱A的速度也是c,因此一秒钟之后,它也应该到达光柱A,但是此时小孔与光柱A之间的距离为V=3c/5 。

也就是说,那束激光同时到达相距将近二十万公里的两个目标。这显然是不可能的。应该如何解释这个悖论?

图1关于光速悖论的思想实验示意图

自古希腊的芝诺以来,思想实验一直是人们用来制造悖论故事的有效的工具,而各种悖论故事又可以帮助人们发现人类逻辑的微妙之处或某些逻辑上的缺陷。本文提出这个悖论的目的不是为了否定狭义相对论的光速不变的条件。如我在“光速不变其实并非一个简单的假设”一文中指出的,要想否认真空中光速不变的条件需要否定其它一系列的相关前提。我这里只不过是与大家分享一个我自己在写文章时想到的至今还解释不了的一个悖论而已。相信读者中有很多相对论的专家可以一如既往地一眼就看出这个悖论的答案,欢迎来与大家分享。如果读者中没人解释得了这个悖论,相信它也自然会升级到更广的范围去吸引更多的人来解释。

文中的3/5是一个随意选的数,只是为了表明这个例子具有相对效应的尺度而已。如果有人需要运用洛伦兹变换的话,3/5这个数字运算起来比较方便,用洛伦兹变换开方出来正好是4/5。

顺便提一下,我在“光速不变其实并非一个简单的假设”一文及其英文版“Constant Light Speed in Vacuum was not a Mere Postulation”中都提到由于近些年发现真空中具有能量我们或许有必要验证一下光线是否会与真空能量发生作用。无巧不巧,理论与实验物理学家Hosenfelder在上个星期六的一则视频(https://youtu.be/Bo4al7sNPkE)中提到了这个问题,她说从遥远的星球射来的伽马射线没有出现如在介质中会发生的衍射现象这一点表明光线不会与真空能量发生作用(她的原话说光线在真空中不需要借助能量来运行)。

如果如她所说,来自遥远星球的伽马射线没有表现出任何与介质发生作用的特征的话,我们似乎如她所说可以认定光线不会与真空能量发生作用。

但另一方面,来自遥远的星球的伽马射线没有表现出任何诸如衍射这样的与介质发生作用的现象这一点在我听来似乎也有点奇怪,因为在这途中它几乎可以肯定会经过大量的布满宇宙尘埃的区域,难道都不会对它发生任何影响吗?如果果真如此,是否从另一方面说明gamma射线没有出现衍射现象只能表明它的抗干扰能力强?坦白说,在这方面我是外行,既然专家Hosenfelder说了来自远方的伽马射线没有衍射现象表明光线不会和真空能量发生作用,我们就先接受专家的意见吧。。。。。。

 

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评论
USOH007 回复 悄悄话 可否这样看:相对于以3/5c速度运动的真空箱和两个光柱组成的参照系,按狭义相对论的动尺变短效应,其本身的长度L及两个光柱之间的距离L均变为2/5c?如此一来,激光与末端的小孔不就同时抵达光柱B了吗?
慕容青草 回复 悄悄话 对了,我忽略了一点:这里所谓的悖论是针对相信光速不变的人来说的,对于那些本来就不相信的人来说,是否悖论取决于他与相对论的光速不变的区别是什么。。。。下面是我与一位声称不认同光速不变但又有他自己的理论的人之间的对话:

Javad Fardaei
2 hrs ago
Dear Dai
I am sure, you know, there is different between Sunlight and Laser beam light.
The property of sunlight is from high frequencies to low frequencies, and from short wavelength to high wavelength, that each ray has its own speed, but laser beam has just one frequency and wavelength.
Sunlight has visible to invisible character...
Unfortunately science mislead itself for century by saying "speed of light" is constant which it is not.
sadly, our icons did not detect this simple phenomenon, either. What I am saying is right and it conform by science as well. Science is wrong on light and sunlight speed
https://www.academia.edu/70960207/Science_is_wrong_on_Light_and_Photon
regards & thank you.
Like

Rongqing Dai
9 mins ago
well, for the sake of the paradox that I am presenting here, what kind of light is not important.....in the container, the reason I am using laser is to create a sense of concentrated beam over a300000km length....just for psychological reason.....it does not really matter.....even if it is just a single photon, the paradox still holds since it is in vacuum without any medium.......as for beam A and beam B, the type of light is even less important.....they are just used as position markers.....if you can imagine well, then you might just assume there are two virtual empty pillars....I use beams of light for, again, making it easy for people to imagine.....

The real deal here is that no one (not even Einstein) has ever tried to put two relatively moving frames of reference connected as the targets of the SAME photon (or beam) to examine the logic behind the constancy of the speed of light.....Although there have been many critics of the constancy of the speed of light like yourself, I would say that this essay is the first one that provides a realistic paradox that no one can deny!

As for you, a critics of the constancy of the speed of light, it might or might not be a paradox depending on how you differ from the constancy of the speed of light.....if your difference is only in whether sunlight and other lights are the same, then it would still be a paradox.....if you don't agree with that the speed of light in vacuum is independent of the selection of frame of reference, then it is no longer a paradox for you....

This paradox holds only to the mainstream physicists who believe that the speed of light in vacuum is constant to all frames of reference......
慕容青草 回复 悄悄话 下面是我在本文的英文版贴出的地方加的提示,同样适用于这里:

A courtesy reminder

I have been often surprised by how poorly professionals read very short essays....so as a courtesy reminder for anyone who would come to comment: Please answer the question whether the laser beam would hit the hole and the beam A or B at the same time as a proof that you do have the ability to understand this short essay.....
慕容青草 回复 悄悄话 居然没有一个人能读懂这个悖论?人类文明衰败如此???下面是我在一个专业讨论论坛上的留言:



It seems that academic physicists are collectively so intellectually crippled simply because they are so weak in philosophical thinking.....

A typical symptom is that when given a writing they would start a big talk and draw conclusions without even comprehending the content....Recently I am presenting a paradox challenging the constancy of the speed of light and I have posted it in multiple places in the internet, but NOT a single PROFESSIONAL PHYSICIST seems to be intellectually capable enough even to read and grasp the content of that very short essay....the only thing they could do is to come and make IRRELEVANT comments------this is so typical with nowadays disabled professional community of physicists, they are just intellectually SO WEAK.

It makes me feel so bad every time when I need to teach them how to read and think and comment maturely like teaching little kids!!! How corrupted is nowadays community of professional physicists???

Here is another chance for those intellectually weak physicists: ARE you even able to read this short essay correctly:

https://www.academia.edu/s/3b35ce08b7?source=link

The edifice of physics is trembling......
慕容青草 回复 悄悄话 在万维博客与没读懂文章(或根本读不懂文章?)就鸡冻地胡扯的网友的对话:


作者:甄晓仁 留言时间:2022-03-29 12:48:52
应该不是悖论。光速不变是光速不随观察者所在坐标系而变。假设那激光灯固定在船头,对准船尾,再假设在船尾有一面朝前的反光镜。如果你的朋友站在两个柱子中间,跟那两个柱子相对静止,他会看到那激光源在B点发出的激光以相对于他和柱子的光速c在2/5秒时到达船尾,再以相对于他的光速走3/5秒到达A柱子,对他来说光速c不变。如果你站在那快船最前端的激光器旁边往船尾看,那激光会以相对于你的光速c往后照射,一秒钟后到达船尾,再过一秒后你能看到镜子里反射回来的光,对你来说光速也不变。如果你从船上下来问你朋友:你刚才看到往后照的光是不是走的比c慢,镜子反射后往前照的光是不是比c快?他会告诉你说,不是,我测出的前后方向的光速是一样的,但是从光源到镜子用的时间不到一秒,而反射光用了一秒多才回到箱子那头你站的地方,一来一回一共用了两秒,但光速前后方向都是c,本身没变。

作者:慕容青草 回复 甄晓仁 留言时间:2022-03-29 14:30:01
你尽可以发挥想象力构想更多的故事,但为了回答本文的悖论只需回答一个问题:那束光是否同时到达那个小孔与光柱A。。。至于其它无关的想象可以另写一篇文章去阐述,混在这里会误导他人。。。。

回复 | 0
慕容青草 回复 悄悄话 在文化走廊与网友的对话:

Kirn:脑子反应不过来,没看懂
慕容青草:注意力不要放在那两个光柱,它们只是用来表示距离的。重点是真空中光速不随惯性系选择而变。在那个长箱子里,因为它的长度是光速大小,所以1秒钟后,光正好从一头到达尾部。。。而那束激光发射时,船头与光柱A的距离也正好是光速大小,所以如果光对于光柱A的速度也正好是c,那么1秒钟之后,那束激光也应该到达光柱A。。。但这是不可能的,因为这时光柱A与船尾之间相差了有近二十万公里。。。
但是,如果你说因为光柱A相对于船头有一个速度V,所以,激光不会在1秒钟后到达光柱的话,那么你等于说激光相对于光柱A的速度要从光速中扣去速度V,那就违背了真空中光速不变的前提---这就是本文提出的悖论。。。
考虑到真空中光速不变已经是当今世界物理学的最不可动摇的基础,我相信应该很快就有人能站出来指出本文的悖论的错误。。。。。。。如果没有的话,问题就严重了!!!!!!------虽然可能比不上能量守恒被打破那么严重,也很严重!甚至比能量守恒被打破更严重。。。。。
光速不变是相对论与量子场论的基础,如果没人能指出本文的悖论有什么问题,整个现代物理学的大厦开始摇晃了。。。。。。之所以说这可能比我之前指出的能量守恒被打破更严重是因为至今为止我只指出宏观能量可以不守恒以及红移蓝移能量不守恒,还没有触及到作为现代物理的最基础的相对论和量子场论。。。。。。如果没有人能指出本文的悖论有什么问题,那就不一样喽。。。。。物理学的大厦要摇晃喽。。。。。。不过我相信,很快就会有人指出这里的问题的。。。。。中国著名网红李永乐曾经表示过相对论是不可置疑的。。。。这里如果有人认识他,不妨将此文发给他,相信他很快就能找出这里的问题。。。。
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