In almost all of the derivations using the postulates of special relativity (SR), we use experiments involving light signals. For example, we make a clock using a light signal or measure lengths using light signals, etc. The reason for doing this is never stated. Why do we do this?
Aren't there any other thought experiments that could help us achieve the expressions for time dilation and length contractions without using light signals?
Is it even possible to derive expressions for the Lorentz transformation without using experiments involving light signals in some form?
Please don't start off with space-time metric. I want to know if such a thing can be done using the two postulates given by Einstein.