ghwellsjr
Science Advisor
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Length contraction is just as physically real as time dilation is or else a light clock would keep a different time as it was rotated. (Remember MMX?)matheinste said:Yes I would be shocked because it it is not analgous to time dilation. This is how i interpretyuiop said:Would you agree that a lot of older texts claim that the twins experiment cannot be explained by SR because it involves acceleration (this is not true) and that GR is required to explain it. Would you not be shocked if you learned that the ruler of a traveling twin was shorter than the ruler of inertial twin when they came back together? Of course this does not really happen in the case length contraction, but it is not immediately obvious to a newcomer, why time dilation appears to be physically real and length contraction does not.
that particular "diffrerence" between the behaviour of a ruler and a clock, however, I am open to correction.
A clock measures and records the accumulated measure along the timelike vectors of the spacetime path taken, and on reuniting with its equavalent stay at home clock ticks at the same rate as before, while also displaying the different accumulasted time. A ruler measures, but does not itself record this cumulative measure of the spacelike vectors along the path taken, but similarly, of course is of the same length of its stay at home couterpart on reuniting.
Matheinste
A clock can be used to accumulate distance as well as time. If you know your speed relative to some other object, and there are many ways to know this, you can use your clock to determine how far you have traveled from that object. This is how the traveling twin knows how far he has traveled. Note that in the Twin Paradox, each twin has a different measurement of the distance traveled.