为什么速度超过光速就可以回到过去了呢？

gudong · 发表于 2004-1-12 16:45:00

Well, all this argument is based on something not real, so I guess we can say anything we want.
I think it over, and you are probabbly right, because there is no absolute time. when the speed is approch to c, the time is slow down, when the speed = c, time stops, and IF speed c, then time slowly reverse...this is where we start:为什么速度超过光速就可以回到过去了呢？
In this sense, IF speed c, then we not only see the past, but the actual time should be reversed, which means today I am 20, tomorrow I would be 18...

gudong · 发表于 2004-1-12 19:39:00

[这个贴子最后由gudong在 2004/01/12 04:45pm 第 1 次编辑]

下面引用由wncspring在 2004/01/12 01:31pm 发表的内容：
godong：关于“I remember the case if you travel at speed v, you will always see light travel at c, not c+/-v. I think same thing should apply to here too. ”我认为欠妥。光速不变是指在低速情况下，　...

I am actually not expert on this, but I remember the history... it is not because v is too small compare to c. in the early age, people think light travel at speed c in ether, and they knew earth is rotating around the sun, and they try to measure properties of ether through the changes of c, but found c is constant. this brought out the discover of relitivity.
so I think no mater what speed you are traveling, you will always see c. just when v is close to c, time is slow

wncspring · 发表于 2004-1-12 21:38:00

下面引用由gudong在 2004/01/12 11:39am 发表的内容：
I am actually not expert on this, but I remember the history... it is not because v is too small compare to c. in the early age, people think light travel at speed c in ether, and they knew earth ...

朋友：这是一个非常简单的问题。如果低能以超光速运动（但你的质量必须小于等于光子的质量），你今年20明年一定是小于20。小多少这和你超的光速大小有关。如果你是以3倍光速运动明年你一定是18；一倍明年你就是19；如果你以光速运动你永远是20。因为时间对于你是静止的。
但要真正理解这些你必须明白时间究竟是什么？“没时间”的真正含意是什么？如果你对这个话题感兴趣，我们可以通过信箱联系。

wncspring · 发表于 2004-1-12 21:52:00

下面引用由gudong在 2004/01/12 11:39am 发表的内容：
I am actually not expert on this, but I remember the history... it is not because v is too small compare to c. in the early age, people think light travel at speed c in ether, and they knew earth ...

我也不是这方面的专家，只是感兴趣而已。我认为光速是常数是相对于宏观物体的低速运动而言的。此时光速不变是因为变化量太小无关大局。就如同地球质量不会因一颗卫星堕落月球，而发生变化一样。不知恰当否？

cosdrong · 发表于 2004-1-13 08:32:00

先弄清楚我们到底在讨论什么,如果是物理学,那么假设可以是各种各样的,例如你完全可以假设光速是常数是相对于宏观物体的低速运动而言的,但请注意物理学是一门实验科学,除了你以此为前提(或者说公理)的理论(例如狭义相对论是以和您相左的观点即光速不变为公理的)必须在逻辑上相容以外,该理论做出的预言(只是为了解释一个现象而提出的理论没有价值,它必须可以预言一些新的可观测东西)还必须和实验相符合,狭义相对论满足上述这些原则(至少就当时的实验水平而言),所以我们说它是好的理论.另外,理论的假设要尽可能的简洁,所以事实上,在得到了MM实验的结论以后很多物理学家(例如落轮词)企图靠修正以太的属性来使以太的理论符合实验,而爱的工作仅仅是指出这样做根本没有必要.所以你看狭义相对论中爱的贡献并不多,连那个最重要的变换都是落轮词发现的.这也是为什么1911年的所尔瓦会议他只能站在旁边的原因之一.

cosdrong · 发表于 2004-1-13 08:45:00

而如果我们是在讨论科学幻想,我认为这一点都没有意义.特别是所谓的哲学.可能我的看法过激了-----我也希望过几年我会改变态度------哲学家最大的长处就是用一段自相矛盾的废话把人蒙住,然后你遵循着他那无逻辑的原则就被他催眠以至与开始认同他了.如果在古代,这通常还会演化成宗教,例如佛教或道教.
另外关于超光速,现在在实验上有两类现象是被认同的,一个是群速度可以快与光速(例如影子的移动速度),还有就是存在一类快子.在量子场论中也有讨论到关于超前波和滞后波的存在的.
最后是另一个原则性问题:在物理学中,我们从来不会形而上的去讨论一种现象是为什么(WHY),我们更关心的是怎么样(HOW).设想有人问为什么S=VT,这该怎么回答?

cosdrong · 发表于 2004-1-13 08:48:00

1911年

gudong · 发表于 2004-1-13 22:34:00

wncspring: I think we are on the same page about time flow is function of speed
cosdrong: Thanks for confirming c is constant. I wasn’’t 100% sure before.
About your why and how theory, I heard some similar one 20 days ago when attending graduation ceremony at university of colorado, one speaker, he is one of the founders in qwest, ( a quite large telecom company here in US), said a good engineer knows how, but a great ones ask why I think we should not satisfy knowing how, but also asks why in physics, engineering, or real life

wncspring · 发表于 2004-1-14 00:56:00

gudong ：非常愿意和你交朋友，我的英文水平有限，因此只能用中文与你对话。但我不知道 time flow is function of speed应该怎样理解。我没说过时间是速度的函数。

zhaolei9981 · 发表于 2004-1-14 02:00:00

是在时间轴上漫游，而不是回到过去

wncspring · 发表于 2004-1-14 02:02:00

下面引用由zhaolei9981在 2004/01/13 06:00pm 发表的内容：
是在时间轴上漫游，而不是回到过去

时间轴是什么概念?

gudong · 发表于 2004-1-14 19:30:00

Sorry it is hard for me to type chinese.
basicaly, what I am saying is relitivity puts an end on absolute time. time can be accurately measured only by the clock carried by the object. object travels at different speed will have different time. for example, A and B are twins, A live on earth, B travel at speed close to c, then after a while, B will be much younger than A.
similar, time also slow when close to big mass object. say A live at sea level, B live at high mountain, B will be younger than A, of couse the difference is small in this case.

为什么速度超过光速就可以回到过去了呢？