Do we have a continual build up of knowledge? Is there always room for new discovery? Or do we need to rebuild era after era? Ah, itis a great question. Iam enormously shocked at how far we have gotten in understanding how the universe works. But again, it seems empirically from our experience, that you need a small number of laws of physics and asmall number of fundamental ingredients to account ultimately for everything that we see. And so i don't worryd about the immense time scale or anything like that. It's quite the opposite.