The first article is essential in understanding our article “Expanding universe” in section “The Basic Cosmology, the first part” The second and the third articles assume knowledge of calculus and special relativity as covered in section “Special Relativity" The fourth article assumes knowledge of Lorentz transformations, as covered in “Rotation and the Lorentz transformation, orthogonal and unitary matrices.” I strongly recommend you to read this article, since it shows the mathematical beauty of special relativity. “Mass-energy equivalence” shows the derivation of Einstein’s famous equation E is equal to m c squared. “Compton scattering” assumes familiarity with momentum conservation and energy conservation during collision process as covered in “Elastic collision in 2-dimensions.”