He does take it seriously, but he doesn't want to freak out a bunch of younglings by overreacting, so he plays it off as a joke while giving Obi-Wan the answer he needs.

My math memory might be a little off here but in Base 1 1+1 would in fact be 11 right? Haha

Wait a second…there's actually enough people that believe in a geocentric universe to have a movie made?! I mean, this isn't intelligent design here I can at least see how people could squint and still believe that (I don't but it's not too high on the crazy scale) but the Sun revolving around the Earth?! Even…