Beyond Counting Sheep

Why math is the hot new bedtime reading

One recent evening in West Caldwell, N.J., a library hosted a pajama party. Twenty little kids in princess nightgowns and football flannels counted out glittery animal stickers and pasted them onto homemade dominoes. Then they raced a stuffed pink frog on a carabiner up and down a zip line, raising and lowering their arms to speed it up and slow it down--physics in motion.

Laura Bilodeau Overdeck, a Princeton-trained astrophysicist turned stay-at-home mom, watched the scene intently. This pajama party was her idea. She's the founder of the nonprofit Bedtime Math, and she wants kids to fall in love with numbers....