Blackbody radiation
Any object that absorbs all light falling on it also glows, and the colour of that glow depends only on its temperature, not on what it is made of. This is blackbody radiation, and it explains why a heated iron bar goes red then white. Classical physics predicted that such an object would emit infinite energy at short wavelengths, which is plainly false. Planck fixed the prediction in 1900 by assuming energy is emitted only in discrete packets, and that assumption started quantum theory.
Why it matters
It is the specific experimental failure that forced physics to abandon the assumption that energy varies continuously.
Also written: black-body radiation, black body radiation
Where it comes up
Read about Blackbody radiation on Wikipedia
Sources
- Black-body radiation English Wikipedia
- Planck's law English Wikipedia
- Blackbody radiation Britannica
