There must be a whole number of full cycles between the walls of an oven.

Quantum Mechanics began as a problem in the early 1900¹s. Using well-founded equations, it was calculated that the energy in an oven is infinite for any temperature. According to Maxwell¹s electromagnetic theory, there has to be a whole number of peaks and troughs between the opposite walls of an oven. Nineteenth century thermodynamics showed that all waves in an oven, no matter their wavelength, have the same amount of energy. The energy carried depended on the temperature of the oven. Since there are an infinite number of possible waves, each contributing a finite amount of energy, it was concluded that there is an infinite amount of energy in an oven. Physicists knew this was absurd. Ovens can possess a great deal of energy, but definitely not an infinite amount!

Max Planck solved this problem by guessing that the energy carried by electromagnetic waves comes in packets. The size of the packet depends on the frequency of the waves. If there is a higher frequency the packets are larger, while their size is smaller at lower frequencies. He realized that if a wave happens to have large packets, each with more energy than it is supposed to contribute, then it contributes nothing because it cannot contribute a fraction of a packet. Therefore, the number of waves contributing energy became finite, and so did the calculations for the total amount of energy in an oven. Because the answers matched experimental observations, people were convinced that Planck was correct. The factor of proportion between a wave¹s frequency and the minimum "lump" of energy it can have is known as Planck's Constant, written (h-bar). Because Planck's constant is very small, the packets of energy are so tiny, changes in frequencies seem continuous but are really discrete.