PETWHAC

PETWHAC stands for Population of Events That Would Have Appeared Coincidental. Population may seem an odd word, but it is the correct statistical term. I won't keep using capital letters because they stand so unattractively on the page. Somebody's watch stopping within ten seconds of the psychic's incantation obviously belongs within the petwhac, but so do many other events. Strictly speaking, the grandfather clock's stopping should not be included. The mystic did not claim that he could stop...

 Galileo and the Altar Lamp Pendulum

IN 1583 Galileo Galilei (1564–1642), a youth of nineteen attending prayers in the baptistery of the Cathedral of Pisa, was, according to tradition, distracted by the swinging of the altar lamp. No matter how wide the swing of the lamp, it seemed that the time it took the lamp to move from one end to the other was the same. Of course Galileo had no watch, but he checked the intervals of the swing by his own pulse. This curious everyday puzzle, he said, enticed him away from the study of medi...

 The A not B Task

Emilie sits on her father's lap and excitedly stares at the shiny brass bell that the research assistant across the table is holding. Making sure Emilie is watching, the assistant places the bell into one of two matching wells in the table and then quickly covers both wells with identical cloths. Emilie is eager to grab the bell, as any eight-month-old would, but her father gently holds back her arms while the researcher distracts her with a funny face. After five seconds, Dad is signaled to ...