Why is it that when a light is on in a room with a window made out of glass, and it being dark out side the window. That you cannot see through the window and instead see light being reflected form the room around you. And vice versa when it is darker inside the room and brighter out side you can not see into the window form outside. Why is this that the window becomes more like a mirror when there is no light coming form behind it. As well if there is equal brightness or amount of photons on both sides do you get equal visibility on each side?