My father’s passion is physics, and as he has a lot of time, he devoted it to study theory of relativity. Result of this studies is the experiment described below. If it’s correct, it proves that speed of light isn’t constant. Of course that is a big if, so treat it more like a riddle related to theory of relativity. Both myself and my father, we are interested in finding proof that the below experiment is not true. We’ve asked several people with PhD’s in physics in both Poland and USA but unfortunately til this day nobody was able to prove that this experiment is wrong. Probably we’re missing some factor, but finding it is the fun part of it. So have fun analyzing this experiment, and if you have any ideas how to disprove theories contained therein, feel free to reach out to my father (his e-mail and phone number are in the pdf).