Circadian clocks regulate the timing of biological functions in almost all higher organisms. Anyone who has flown through several time zones knows the jet lag that can result when this timing is disrupted.

Now, new research by Cornell and Dartmouth researchers explains the biological mechanism behind how circadian clocks sense light through a process that transfers energy from light to chemical reactions in cells. The research is published in the journal Science.

Circadian clocks in cells respond to differences in light between night and day and thereby allow organisms to anticipate changes in the environment by pacing their metabolism to this daily cycle. The clocks play a role in many processes: timing when blooming plants open their petals in the morning and close them at night; or setting when fungi release spores to maximize their reproductive success. In humans, the clocks are responsible for why we get sleepy at night and wake in the morning, and they control many major regulatory…