Human heat
We are in an interior room where natural light doesn’t come in. Generalization of electricity has meant that we solve this problem just by pressing a switch usually placed near the entrance that ignites an artificial source of light (i.e. a strip light). This source illuminates walls and objects contained in the room, and the same in all directions make this reflection, a fraction of reflected light reaching our eyes just allowing us to create an image of what surrounds us. But if we press the switch other time instantly becomes dark. The second action is natural because we daily experience proves this, but someone has stopped to think where the light go. It may seem a trivial question because if we turned off the light that is over, but it is not. Energy isn’t created nor destroyed, the room that we were hasn’t opening up so all the energy that enters the electrical wires trapped inside the room, yet we see the light disappears. Really this is absorbed by the walls, and it joins ener