Black-body radiation plays an important role in Hawking’s black hole thermodynamics, which in turn plays an important role in loop quantum gravity. This is the reason why I have written-up the first five articles. They assume the prior knowledge on entropy as explained in “Entropy” and basic calculus. Boltzmann factor as listed in “Thermodynamics” would be also helpful but not essential. “Density of states,” which is necessary to understand black body radiation, assumes the knowledge of “Infinite potential well” listed in “Historical introduction to quantum mechanics.” The result of the last article whose prerequisite is the section “Applications of Calculus, the second part” was crucial to my research on Hawking radiation which we will review in our later article “Quantum corrections to Hawking radiation spectrum.” Currently “Bose-Einstein condensate” finds no direct application in particle physics or quantum gravity, but as it is important its own, I included it here. “Photon gas pressure” deals with the photon version of Boyle’s law. We will see that it is important in cosmology.