Lesson 2
The Caffeine Shadow
Work out how much of an afternoon coffee is still in you at bedtime, and choose the change that moves the most.
Builds on
Coffee leaves by halves
Have a coffee at noon and go to bed at midnight, and some of that coffee goes to bed with you. Your body clears caffeine steadily, but not at a fixed number of milligrams an hour. In each stretch of time it removes the same fraction of whatever is left. The time it takes to remove half is called the half-life.