評論
打印
What would Jill, standing on the platform, see through the window as the train whistles through?
這個時候站在月臺上的吉爾會透過窗口所看到是什么？
Well, between Jack dropping the ball and catching it again,
在杰克扔下球和接著球之間，
Jill would have seen him move slightly further down the track, resulting in her seeing the ball follow a triangular path.
吉爾會看到杰克和火車一起向前移動，結果她看到的球是以三角形的路線移動的。
This means Jill sees the ball travel further than Jack does in the same time period.
意思是，在同一個時間段里吉爾看到的球比杰克所看到的移動得更遠。
And because speed is distance divided by time, Jill actually sees the ball move faster.
因為速度等于距離除以時間，事實上，吉爾所看到球比杰克所看到的移動得更快。
But what if Jack's bouncing ball is replaced with two mirrors which bounce a beam of light between them?
但是，如果我們把杰克的球用兩面鏡子作代替，而在鏡子之間有一束光來回反彈。
Jack still sees the beam dropping down and Jill still sees the light beam travel a longer distance,
杰克依然會看到光束反彈，吉爾還是會看到該光束移動得更遠，
except this time Jack and Jill cannot disagree on the speed because the speed of light remains the same no matter what.
例外的是，這次杰克和吉爾卻會對光的速度有分歧。這是因為光的速度。無論如何還是保留不變。
And if the speed is the same while the distance is different, this means the time taken will be different as well.
如果速度是一樣的話，而距離卻不一樣，那花的時間將也不一樣。
Thus, time must tick at different rates for people moving relative to each other.
所以當人們對他人相對地移動時，時間一定以不一樣的速率流逝。
Imagine that Jack and Jill have highly accurate watches that they synchronize before Jack boards the train.
試想如果杰克和吉爾都有非常精確的手表。他們在杰克上火車前校對好時間。
During the experiment, Jack and Jill would each see their own watch ticking normally.
當這個實驗中，杰克和吉爾會看到自己的手表正常的走。
But if they meet up again later to compare watches,
但是如果他們在實驗結束后相遇，比對彼此手表時，
less time would have elapsed on Jack's watch, balancing the fact that Jill saw the light move further.
他們會發現杰克的手表會走慢一些，因此解釋了這事實：吉爾看到的光移動得更遠。
This idea may sound crazy, but like any good scientific theory, it can be tested.
這聽上去很詭異，但是，像任何一個完好的科學理論，它是可以被測試的。
In the 1970s, scientists boarded a plane with some super-accurate atomic clocks
在1970年左右，科學家們校對了一些超級準確的原子鐘，一起帶到飛機上去，
that were synchronized with some others left on the ground.
而數個原子鐘則留在陸地上。
After the plane had flown around the world, the clocks on board showed a different time from those left behind.
當飛機環球飛行之后，他們發現飛機上的原子鐘和地球上的原子鐘上顯示的時間是不一樣的。
Of course, at the speed of trains and planes, the effect is minuscule.
當然，以火車與飛機的速度，對時間膨脹的影響是很微小的。
