Einstein proved there is no God when he pointed out that all things which exist are relative to each other. Accordingly, an eternal God must, relative to this point in time (and whether or not the space time continuum commences from any set big bang event) therefore have existed at a point in time, an infinite amount of time ago. Therefore, God must traverse an infinite amount of time to reach this point in time and since an infinity cannot be traversed, God cannot exist.
"If a system of coordinates K is chosen so that, in relation to it, physical laws hold good in their simplest form, the same laws hold good in relation to any other system of coordinates K' moving in uniform translation relatively to K."
– Albert Einstein: The foundation of the general theory of relativity, Section A, §1
Thus, an eternal God that ever have had any effect on the universe at any point in time does not exist. There is only one thing that can be eternal as well as traverse an infinite amount of time because it is not relative to any other thing. Have a guess at what it is.
"The word God is for me nothing more than the expression and product of human weaknesses, the Bible a collection of honorable, but still primitive legends which are nevertheless pretty childish." A Einstein, 1954, letter to Eric Gutkind.