Consider an electrical heating element, as can be found in an electric oven. With no electric
current flow through the element, it appears almost black, its room temperature color. With a current
flow, the element temperature rises and it appears to change color to a dull red, and perhaps to a
reddish orange. If its temperature continued to increase, eventually it would appear white. This
change in color signifies a shift in the maximum intensity of the emitted radiation to shorter
wavelengths, out of the infrared and into the visible. There is also an increase in total emitted energy.
The Planck distribution provides a basis for the measurement of temperature through color
comparison.