I am surprised that not one single person here knows much about modern physics. It was known during the time of Einstein that physics is not predetermined and the study of that is quantum mechanics. You can look it up but it basically means that the motion of atoms can not be predicted and any regularities are a statistical bulk phenomenon that we can get approximations to, but never certainties. That is our basic understanding of physics today and one of the problems we have is that there is no theory that combines Einstein's theory of gravity and quantum physics.
Einstein himself didn't belief in free will yet he admitted that quantum mechanics made this belief hard for him and stated that even though things seem random they are not and there must be some deeper theory that proves it, but since then no such theory has been accepted. I learned this from the book Einstein: His life and universe so if you are interested in the beginning of modern physics you can read that or use google.
So no that you know that you have no proof that free will is not possible confirmed by Einstein himself and many other scientists. The question is that if nothing is predetermined how does free will no exist? Of course you can still say you don't have a choice, but it is odd to say that it is likely you could choose either choice yet not have a choice because the chemicals and elections in your brain are atoms and they can not be predicted.







