I have to tell you, the cloudiest day is going to be much more brighter than your room. You could ask any photographer ... The outside is, usually, even when it's cloudy, you're going to get enough intensity to help you adjust your cycle to the day-night cycle.

My gut feeling is that most people would need at least 10 times less light than they use at night to see ... People use it because, most of the time, they didn't see the morning sunlight. They are actually hungry for light without their knowledge. So they switch all these lights on but at the wrong time because they woke up late.

In the human retinas, there are two types of photoreceptors—they are called rods and cones because of their shapes. And these rods and cones simply take the photon energy, which light is made off, and they change it in a way to an electrical signal that allows us to build the image of the environment in our cortices.