The relative colour temperature (CCT) of a light source is based on the principle that any object will emit light if it is heated to a high enough temperature. The colour of this light will change in a predictable way depending on the temperature. The reference point here is the so-called black body, an object that only exists in theory. In the model, this is heated until it changes from the black cold state to the hot white state. As the temperature rises, the spectrum of the light emitted by the black body would gradually change from dark red, through red, orange, yellow, white and finally to blue-white. The relative colour temperature of a light source now describes the colour of the emitted light, measured by the temperature (in degrees Kelvin) of a black body radiator that would emit light of the same colour.