no physical explanation yet. when i talk to leonard he says -- you know, leonard says one day we'll have an explanation. i say that's a promissory note. in the current economic situation i don't cake promissory notes. >> larry: faith doesn't require proof? >> sometimes when people set up some dichotomy, science versus physics i don't quite get it because the grand design is about what the modern theories of science say about the universe and if you want to believe something on faith you can. we don't -- we don't claim to prove in the book there is no god or tell you not to believe in god. we just talk about the answers of modern science to those two questions, how did the universe get here and why are the laws what they are? >> larry: how about those who say, an astronaut would say, look, is nothing -- the only thing is that blue planet. and how can you say nothing created that? that that came out of nothing? those rivers?