 If, for example, an energetic photon collides with an electron in a Compton scattering experiment, there is a certain probability that a photon with a given smaller energy will emerge, and there is a certain probability that the electron will be kicked out with a given kinetic energy. […] However, because of the law of conservation of energy, there is a strong correspondence between the two energies: their sum must be close to the energy of the incident photon. Thus, the probability of getting a photon with energy \(E_1\) and an electron with energy \(E_2\), where \(E_1 + E_2\) is approximately equal to \(E\) (the energy of the incident photon), is much greater than the product of the probabilities of each energy occurring separately. (Salmon 1978a [1998: 133])