Some people couldn't sleep well when there is any illumination. I don't mean ill persons there is quite healthy ones who suffer from it.
My idea is simple. Let scientists invent device that can stop light, I don't mean just curtains. It could be black case with button and when you push it everything dive into twilight immediately. People can use this device for making shady areas in hot summer days.
Some information for your mind. Light is everywhere in our world. We need it to see!!! It carries information from the world to our eyes and than to brain. Seeing colors and shapes is second nature to us, still light is a hard understanding phenomenon when we study it more closely. In additional light acts like particles little light bullets that stream from the source. This explains how shadows work. Light also acts like wave's ripples in space instead of bullets. This explains how rainbows work. In fact, light are both. This "wave-particle duality" is one of the most confusing and