Research suggests that light looms as large in our well-being as sleep. Rosie Blau consults experts in California and Japan for Intelligent Life magazine.

Partly thanks to Panda, though, we at least know quite a lot about how light affects our body clock. When it comes to the internal clock, some types of light are more equal than others. The eye perceives three main colours in light: red, green and blue, each vibrating at a different wavelength. In the morning, high concentrations of blue occur naturally; by dusk we are left mostly with green and red. The blue light has the greatest impact on our circadian system, telling the brain that it’s morning and time to be alert, and setting our clock for the day. That is important because we sleep soundly, and our brain and body function better, when the internal signals of the body clock are in sync with external cues of day and night.