Perhaps it’s not meaningless to talk about what happened before the Big Bang. Perhaps there were many (infinitely many?) Big Bangs before it, randomly appearing after quasi-eternities of nothingness. Sean Carrol claims the Arrow of Time should go backwards and forwards in a symmetric or indistinguishable manner here, though locally (after our recent Big Bang) it seems to go from low entropy to high entropy. Found via this post, in turn found via MR.