# How to test length contraction by experiment?

Relativistic length contraction is theoretically predicted but not directly tested, which lead to incorrect interpretation of the theory illustrated by Bell’s spaceship paradox and Ehrenfest paradox. But these paradoxes can help us designing experiments to test length contraction.

Ideal direct experimental proof should contain the following steps:
1. Measure the tested object’s length at rest, the value l0.
2. Put this object in motion.
3. Measure the object’s speed, the value v.
4. Measure the object’s length in motion, the value l.
5. Check if these 3 values verify length contraction law.

For doing this experiment, the difference of length l0  l should be in measurable range. If the object is a chunk of matter, l0  l is not measurable. For example, matter objects with the highest speed we can make are satellites, whose speed is generally 7.8 km/s. If a satellite is made of a string of 100 km long, the value of l0  l would be 0.03 mm, which is absolutely not measurable from the ground. This is why contraction of length has never been measured.

Below I propose two experiments inspired from Bell’s spaceship paradox and Ehrenfest paradox.