To make matters worse, modern society's electric light and bright screens at night trick our body clock into thinking it is still seeing daylight.

Paris, France's capital, displays why it is known as the "City of Lights" in this photo taken from on board the International ...

This is likely because we evolved to see the natural bright blue sky during the day, rather than indoor electric lights at night which are much less bright – or blue. As we age, our eyes change ...