biological clock

Strontium atoms floating in the center of this photo are the heart of the world's most precise clock. The clock is so exact that it can detect tiny shifts in the flow of time itself. Courtesy of the Ye group and Brad Baxley/JILA hide caption

It doesn't take a transcontinental flight to end up out of sync with your body clock. It might just be that you stay up too late. iStockphoto.com hide caption