Maybe you can start by asking him why he does not believe in God and try to reason with him if he can stand it. It would not be a good idea to preach to the point of alienating him, for some people do turn to hate you for it. He could be an atheist and wholly support science which can turn religious with skilled direction. Maybe time would be a good thing to allow for he may not be interested today but another day he can be willing to talk to you.
