Have enjoyed Astronomy cast for several months but not tempted til now to register and comment--for the purpose of asking: What caused inflation and what halted it? Dr. Gay's reference to "inflaton" particle as causing inflation floored me. I had thought inflation was the "intrinsic" rate of big bang expansion until slowed by emergence of "mass" and gravity, i.e. graviton. If "inflaton" caused inflation, what caused its decay? graviton? Are "inflaton" and graviton related? I'm afraid your Inflation explanation raises more questions than it answered. Why did inflation last 1-33 seconds? What happened to cause expansion to slow to "historic" rates.

Thanks for all the hard work.