How does jet lag work?

Ah, a most interesting question, one that touches upon the mysteries of modern travel. Jet lag occurs when your body's internal clock, or circadian rhythm, becomes out of sync with the local time at your destination. This typically happens after long flights across multiple time zones. If you arrive at your destination in the evening but your body still thinks it's morning, because your internal clock is set to the time zone you left, you may feel sleepy when you should be alert, and wide awake when you should be resting. The effect can be quite disorienting, especially after crossing several time zones in a single day. However, with a little patience and perhaps a well-timed nap or two, your body will soon adjust to its new rhythm.