Blackbody radiation

A blackbody is a theoretical, idealized physical object that perfectly absorbs all electromagnetic radiation that hits it, reflecting absolutely nothing. Because it absorbs all light, a real-world approximation would look perfectly black at low temperatures.

As a blackbody's temperature increases, it emits radiation at shorter wavelengths, shifting from invisible infrared to red, then orange, yellow, white, and finally blue. This is why stars, which act roughly as blackbodies, have different colors based on their surface temperature.

Classical physics predicted that a perfectly black body at thermal equilibrium would emit an infinite amount of energy, a phenomenon known as the 'ultraviolet catastrophe.' To solve this, Max Planck proposed in 1900 that energy is emitted in discrete packets, giving birth to quantum mechanics.

The Stefan-Boltzmann Law calculates the total power radiated per unit area of a blackbody. It states that this energy is proportional to the fourth power of the object's absolute temperature.