The length contraction in special relativity says that a rod moving along its axis will appear shorter by γ to a stationary observer. I think, however, not only the rod will appear shorter, but also each small segment of the rod will show its snapshot of different time as in the moving frame, in other words, the observer see part of rod in its current snapshot, but part of the rod in its past snapshot.(adsbygoogle = window.adsbygoogle || []).push({});

Am I correct? In order to make myself clearer, I come up with this experiment. Could you please tell me if it is valid or if there is any flaw. Thanks!

In a standard configuration, which frame O' is moving along the x-axis of frame O with speed v, clock is synchronized to 0 when origin O' coincides origin O. Also, let us use normalized scale. The unit of time t is second; the unit of x-axis x is light-second; and thus the velocity v = x/t is the ratio of speed with the light speed, 0<=v<1, γ=1 / sqrt(1-v^{2})

In frame O', there is a rod with length L', resting between x'=0 to x'=L'. The entire rod can change color uniformly with time. For example, the rod's color is blue at time t'=-L'*v but changes to red at time t'=0.

So for a stationary observer in frame O, at time t=0, he will see the rod's length to be L=L'/γ. That is not all. He will also see the rod's left end is red color, but the right end is blue color, and the color changes from red to blue gradually on the rod body.

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# Gradient colored rod

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