The band of infrared light is a thousand times wider than that of visible light. All of it is invisible to our eyes. This is also the type of light that the remote control for your TV uses. Longer wavelength infrared light is emitted by hot objects in our world. So, although we can't see the thermal infrared light from a hot piece of metal like a soldering iron, we can feel it on our skin when we bring our hand close.
Scientists use many types of devices to detect and measure infrared light.
Even if we can't see it with our eyes through a telescope our specialized astronomical cameras can. We know that infrared radiation is light just like visible light because it has the same properties as visible light. Infrared can be focused and reflected like visible light. This means we can make infrared telescopes that look and work the way normal visible light telescopes do. A micron is defined as a millionth of a meter.