Your body’s biological clock, which tells you to sleep once every 24 hours, is not the only thing that reminds you to shut down for repair. A new study has found that it’s actually light that governs your sleep patterns. Researchers at Johns Hopkins University found that you use light to reset your biological clock. Another sleep study found that if you turn down your lights two hours prior to bed, similar to natural dusk light, you start to relax and fall asleep naturally.