"Absent-Minded Professor" joke

This great math professor was very absent minded. When they moved from Cambridge to Newton, his wife,
knowing that he would be absolutely useless on the move, packed him off to MIT while she directed the
move.
Since she was certain that he would forget that they had moved and where they had moved to, she wrote
down the new address on a piece of paper, and gave it to him.
Naturally, in the course of the day, an insight occurred to him. He reached in his pocket, found a
piece of paper on which he furiously scribbled some notes, thought it over, decided there was a
fallacy in his idea, and threw the piece of paper away.
At the end of the day he went home (to the old address in Cambridge, of course). When he got there he
realized that they had moved, that he had no idea where they had moved to, and that the piece of
paper with the address was long gone.
Fortunately inspiration struck. There was a young girl on the street and he conceived the idea of
asking her where he had moved to, saying, "Excuse me, perhaps you know me. I lived in this house
until this morning, and we've just moved. Would you know where we've moved to?" To which the young
girl replied,
"Yes daddy, mommy thought you would forget."