The very definition: The baby has fallen asleep. Left arm has too? Doesn't matter. We'll be landing in a few hours, probably.
I was able to leverage my rigorous professional training in this matter. I leaned down and, in a low monotone, I recited into her ear the name of every modern World Series winner. "In 1903 it was the Boston Pilgrims. In 1904 there was no World Series. In 1905 it was the New York Giants." And so on. I felt her start to become dead weight around 1930 (Philadelphia A's), and I was pretty sure she was out by 1948 (Cleveland Indians), but I kept going anyway.
