2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/33944In present work the generalization of Einstein's special theory of relativity on 5-dimentional space is considered, in which as fifth coordinates we consider the interval s of a particle. 5-dimentional vectors in this space are isotropic both for mass, and for massless of particles. In extended space, offered by the authors, there is a possibility in addition with usual Lorentz transformations, to enter two new transformations, therefore massive and massless of a particle can reversible converted to each other.10 pages, PDF only,". submitted to the V International Conference on Gravitation and Astrophysics of Asian - Pacific Countries (ICGA-2001), Moscow, 1-7 October, 2001General Relativity and Quantum CosmologyAstrophysicstext