You can see this at work in a toaster oven. When you turn the toaster on, you can feel some heat, but you see no light. As more electric energy is supplied and the wires get hotter, they begin to glow red. The only problem is that they would probably burn up before they reached that temperature. British astronomer Sir William Herschel discovered infrared radiation around 1800.
Any warm object gives off infrared radiation.
But remember, warm is a relative term. An ice cube in a cooler is warmer than a flask of liquid nitrogen, so it gives off more infrared radiation. With this technology, engineers can find heat leaks in buildings, doctors can find hidden tumors in the body, and biologists can even find diseased vegetation in a forest. Infrared imaging can even have applications in space. Light you cannot see .