The Big Bang model describes a smoothly expanding universe from a point where the current laws of physics break down. However if the universe is infinite, it would be infinite down to this point and presumably before it. This would imply instantaneous inflation from 0 to infinity. The universe would not pass through any intermediate stage. Is this a proper understanding of Alan Guth's original proposal, or would it have be substantially revised for an infinite universe? EDIT: I'm including the inflation period in the description "smoothly expanding" since I assume there are no discontinuities in the Big Bang description from the point where it starts. In the infinite case, the universe would already be infinite at this point so instantaneous inflation would have had to come before.