late...

Forgot to write last night, so quick post here. Gave a SLAC tour yesterday to a group of senior citizens. The part they were most interested in was the evidence for the big bang. I need to read up on this. How do we know actually how old the universe is? I know it has something to do with the CMB, but it's not clear to me how the calculation is made. Also I need a better answer for "What came before the big bang?" I said it was just a singularity before which time and space did not exist, but that felt unsatisfactory. They all kept saying how much they enjoyed the presentation, but it felt rather dull to me. I think I need to spice it up with some more humor, anecdotes. Right now it's too flat. I'll keep looking for examples.