WHY does hot metal glow? When quanta of light move chaotically in space, physicists speak of a photon gas with a certain temperature.
Every object tends to equalize its temperature with the surrounding photon gas: a cold object is heated by this gas, and a hot object gives energy to the gas in the form of radiation.
At room temperature, this radiation is invisible photons of the infrared range. But when heated to 400-500 °C, visible red light appears; at higher temperatures, yellow, white, and blue light emerges.
