# Experimental relativity

are there any experiments to prove length contraction and time dilation?

are time dilation and length dilation inter dependent?
how can we say thaT THE LENGTH ALONG THE Y-AXIS DOES NOT CONTRACT
and from which side of the length contraction actually happens?

russ_watters
Mentor
Time dilation is the easy one because you can actually perform the twins paradox experimentally and see that its true. In a way, GPS satellites are constantly performing the twins paradox and the results are consistent with SR (and GR) to a high degree of precision.

Length contraction is tougher because you measure the length in different frames at the same time. Its tough to convince people that what they are both seeing is "real." However, if it isn't real, the equations don't work.

As russ said, time dilation is an easy one. Experiments involving high speed rockets and airplanes, carrying one of two highly accurate and near perfectly aligned atomic clocks have been carried out, and the results agree to the predictions of SR to great accuracy. Length contraction is a lot trickier to measure experimentally, but it really isn't neccessary. You see, if lengths didn't contract, or if they contracted along the y-axis as you suggested, then time dilation itself would be impossible, which we know isn't true from the previously mentioned experiments. Length contraction along the direction of motion is a direct consequence of time dilation, so by proving time dilation experimentally, we're also proving length contraction. So, to answer your question, they are interdependent.

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I notice you didn't ask whether or not relativistic mass increase can be experimentally measured. In case you're wondering, since relativistic mass and the equation e=mc^2 are related in much the same way as time dilation and length contraction are related, then every atomic bomb or nuclear reactor is an experiment testing special relativity. So, the answer to that one is also yes.