........

[Wah!!]

skynam 可否先理解看看相對論的光鐘實驗?

[鄧登凳]

推介這個簡單說明: http://www.phy.ntnu.edu.tw/demolab/java/relativity/

[skynam]

......

[鄧登凳]

...以前都提及講過,我認為影響改變不到光的速度或方向,主要原因是光的速度太快,如果一定要影響光的速度或方向,那就必需要有的一個條件,就是要比光速還要快更加快,才能夠有(機會)改變光速或光的方向...

不對。這種說法不單不合相對論, 更連經典力學(classical mechanics)中的伽利略變換(Galilean transformation)都不合。

如果說法合理, 那音速也可以是「太快」, 要改變音速, 一定要比音速更快...

但事實上, 音速是約每小時1230公里, 你騎單車每小時十公里(<1%), 經過一個固定頻率的發聲裝置, 己可感受頻率的改變, 即相對音速改變了。

光速的實驗, 結果和上面單車實驗不同, 結果是光速不變, 所以要放棄時間和空間可獨立轉換的伽利略變換, 而確立時空的概念。

[skynam]

......

[Wah!!]

空氣分子的平均速度大約是500m/s, 並不是skynam所說的接近零.

[skynam]

......

[鄧登凳]

相對速度同樣適用以超音速飛行的子彈和時速一二十公里的飛鳥。 子彈可不是由飛鳥射出的啊。

[skynam]

.......

[Wah!!]

時間都可以有快慢有速度,唔通真係當左時間係個鐘黎....哈哈

這就是時間的相對性, 每個不同速度的物體經歷的時間快慢都互相不同.

[skynam]

.......

[Wah!!]

GPS 系統就是用了時間相對性原理修正的。還有其他很多實驗都有對於相對論的驗證。

[skynam]

........

[Wah!!]

你先查查資料吧!!!
不引入相對論的修正, GPS是不可能做到現有精度的!


算了, 我查埋俾你睇.....
http://physicscentral.com/explore/writers/will.cfm

But in a relativistic world, things are not simple. The satellite clocks are moving at 14,000 km/hr in orbits that circle the Earth twice per day, much faster than clocks on the surface of the Earth, and Einstein's theory of special relativity says that rapidly moving clocks tick more slowly, by about seven microseconds (millionths of a second) per day.

...

To determine its location, the GPS receiver uses the time at which each signal from a satellite was emitted, as determined by the on-board atomic clock and encoded into the signal, together the with speed of light, to calculate the distance between itself and the satellites it communicated with. The orbit of each satellite is known accurately. Given enough satellites, it is a simple problem in Euclidean geometry to compute the receiver's precise location, both in space and time. To achieve a navigation accuracy of 15 meters, time throughout the GPS system must be known to an accuracy of 50 nanoseconds, which simply corresponds to the time required for light to travel 15 meters.

But at 38 microseconds per day, the relativistic offset in the rates of the satellite clocks is so large that, if left uncompensated, it would cause navigational errors that accumulate faster than 10 km per day! GPS accounts for relativity by electronically adjusting the rates of the satellite clocks, and by building mathematical corrections into the computer chips which solve for the user's location. Without the proper application of relativity, GPS would fail in its navigational functions within about 2 minutes.

[鄧登凳]

GPS的時間膨漲, 是狹義相對論下速度對時間的影響, 再加上廣義相對論下引力場對時間的影響, 兩者的合併結果, 相信樓主會較難理解。

單是狹義相對論的時間膨漲, 一般會用高速飛行的粒子的內部時鐘, 和外在"靜止"的時鐘來比較, 如: http://www.dw.de/%E7%9B%B8%E5%AF%B9%E8% ... /a-1509470

其實公立圖書館有很多相對論入門的書, 樓主何不去借一兩本看看。