Though slightly uncomfortable, thermal goggles offer almost 180° of wide angle vision in the IR spectrum. Engineered to seal tightly over the upper face of most humanoids, the standard thermal goggle blocks out all outside sources of light. Thermal goggles work on the principle that everything above absolute freezing emits thermal energy. To most sentient beings, thermal energy is simply felt as heat. With the aid of an electronic display screen in the goggles, heat can be viewed as colour gradations, greatly aiding in detection of objects. Since the viewer is looking at heat, not visible light, items and beings can be viewed in a totally dark room or in dense smoke. Some sentient and non-sentient beings can view other parts of the electromagnetic spectrum, but for most species, electronics are necessary to view the infrared spectrum.