Throw out all your clocks and your body still has a rough idea of the time of day. That’s because it has it’s own clock – the body clock. So how does your circadian rhythm get its rhythm? From the tick tock of your body clock. Or rather body clocks, as we have lots – an all-powerful master clock in the brain and other little clocks in different tissues and organs. The little clocks get their timing from the master clock and the master clock gets its timing from sunlight. Sunlight stimulates cells in your eyes that send signals to the brain, which uses this information to figure out the time of day and set the master clock.
Being exposed to bright light at night when your body should be winding down – say staring into a laptop screen – confuses your body clock.