Length contraction and time dilation are said to be the two sides of the same coin (the same phenomenon as viewed from different frames).
That is to say, the time dilation and length contraction are symmetrical.
Length contraction, like time dilation, exists when there is relative motion and goes away when there is no relative motion, but there isn't any "accumulation" with length contraction, so there is nothing to be "left over".
Why isn't length contraction permanent even though time dilation is?
Now in my thought experiment, if I have two meter rods (each of them has an attached photon clock, so that the mirrors are at the end of the two rods), and initially synchronize the clocks, and send one rod (with the clock attached) to a journey at relativistic speeds, and bring it back , the rods won't change length, but the clocks will read different ticks (lets say the clock is able to register how many it ticked).
Now when the traveling rod (with a clock attached) travels, from the stationary frame (relative to Earth) you can see that the traveling rod undergoes length contraction because of its relativistic speeds.
Now when the the traveling rod (photon clock) arrives back:
you can see that the two rods are still the same length, so length contraction was just an apparent phenomenon, it is not real
you can see that the two clocks are now showing different ticks, because of time dilation one of the clocks ticked less (the traveling one) then the other clock, so time dilation is a real effect
Now if length contraction and time dilation are just the same phenomenon viewed from different frames, then how is that time dilation was real (the clocks), but length contraction was just apparent?
Question:
- If length contraction is just apparent (not real), then why is time dilation real?