Why Jet Lag Feels Worse Depending on Your Travel Direction

Jet lag is the pits, but it is even worse when you travel east. Michelle Girvan (a physicist at the University of Maryland who also co-authored a model published this week) says it’s because, “The body’s internal clock has a natural period of slightly longer than 24 hours, which means that it has an easier time traveling west and lengthening the day than traveling east and shortening the day.” It’s all due to a region of the brain called the hypothalamus, where our internal clock exists. Around every 24 hours, thousands of “pacemaker” cells in the hypothalamus synchronize—but of course traveling through timezones confuses them. The best trick is to set your watch to the destination time as soon as possible, and subjecting yourself to “brief flashes of bright light delivered at specific intervals” during and after your flight.