The Concept of Dark Energy is not Based on the Principles of Physics: Cosmological Data Can be clearly Explained Without this Concept Felix M Lev Independent Researcher, San Diego, 92010 CA USA Email: felixlev314@gmail.com Abstract The physics community has adopted the principle that when new experimental data appears, physicists should first try to explain it based on existing science. Only if all such attempts fail can new exotic explanations be brought in. However, in the case of cosmological acceleration, the opposite approach was taken: without serious attempts to explain this phenomenon from existing science, physicists attracted dark energy and other exotic concepts whose physical meaning is a mystery. As shown in our publications, the cosmological acceleration can be clearly explained without uncertainties. The derivation of this explanation requires significant technical efforts described in our publications. The purpose of this article for the 2nd Inter- national Conference on Gravitation, Astrophysics and Cosmol- ogy (ICGAC 2026) is to explain our approach at the simplest possible level so that the basic ideas of our approach would be understandable to many physicists and astrophysicists. Keywords: irreducible representations; cosmological acceleration; de Sitter symmetry 1 Statement of the problem of cosmo- logical acceleration Let’s consider a system of macroscopic bodies that are located at large distances from each other so that all interactions between the bodies (gravitational, electromagnetic and others) can be neglected. Let us also assume that the sizes of these bodies are much smaller than the 1