It's interesting to note that the branch of physics we now call "quantum mechanics" actually got started from a phenomenon no one could understand called "cavity radiation".
If you take any body and heat it, the amount of energy radiated from it's surface is dependant on both the material it's made of and the temperature. BUT, if that thing is hollow and you drill a hole through it, and then heat it, the amount of energy radiated from it's surface is still dependant on the material and it's temperature, but the amount of energy radiating from the hole is dependant ONLY on temperature, not on the material it's made of. That is, the energy radiating from the hole is the same for all materials, and depends only on temperature.
Why the energy radiating from the hole would be independant of the material the body was made from was known as the "cavity radiation problem", and during the 1800's it was one of the greatest curiosities of science.
In 1899 a guy by the name of Wilhelm Wiens took home the Nobel prize for deriving an equation based on the particle theory of matter and the wave theory of energy that partially explained cavity radiation, but the results predicted from his equation didn't jive well with experimental data.
An up and coming physicist named Max Planck read all about Wilhelm Wiens' work on the cavity radiation problem, and found that by arbitrarily making some changes to the equation Wiens had derived, he could produce an equation that agreed with experimental data exactly.
Having a suspicion that his modified equation may also be theoretically correct, Planck set out to work backward through Wiens' derivation using his equation as the starting, er... ending point.
And, he found he could do it. All he had to do was make two assumptions that seemed to contradict the well accepted notion that matter consisted of particles and energy consisted of waves. Those two assumptions were:
1. That the atoms in the material can't vibrate at any energy level, only at certain distinct energy levels, and
2. That energy is absorbed and released only when an atom jumps to a higher or lower energy level. NO energy is consumed by the atom continuing to vibrate at the same energy level.
And on December 2, 1901, Max Karl Ernst Ludwig Planck presented the derivation of his equation for cavity radiation to the Berlin Physical Society. That is the day when the very first crack appeared in our understanding of matter consisting of solid particles and energy consisting of waves.
17 years later, when subsequent work had proven him correct, Max Planck was awarded the 1918 Nobel Prize in Physics for his discovery of the "Elemental Quanta". Neils Bohr subsequently used Planck's "Quantum Theory" to calculate out what the spectrum of monotomic hydrogen should be, and got it right to within expenrimental accuracy. Neils took home a Nobel for his efforts, too. And, those are the humble beginnings of the branch of physics we now call "Quantum Mechanics".
http://panda.unm.edu/courses/finley/p262/ThermalRad/ThermalRad.html
