How he knew true love

My grandmother and grandfather hung out in the same crowd somehow way back when. My grandmother was an art student, my grandfather a scholar of all things scientific, mathematic, philosophical. My grandmother thought my grandfather too good looking, too many girls were interested in him. I don't know what he thought of her, she was beautiful too. But somehow, one day, they were paired up on a double date. The first thing my grandfather said to her (and this is so typical, if you had known him) was: "What is the center of the Universe?" I don't know what kind of answer he expected to get, but it wasn't the one she returned: "Why, THIS is the center of the Universe." Apparently he was struck speechless (a first) and they were engaged to be married a week later.