Physicists usually understand that physics cannot (and should not) derive that c ≈ 3·10 8 m/s andh ≈ 1.054·10 −34 kg·m 2 /s. At the same time they usually believe that physics should derive the value of the cosmological constant Λ. We first prove that three parameters defining transitions from more general theories to less general ones are (c,h, R) where R is the parameter defining contraction from the de Sitter (dS) or anti-de Sitter (AdS) algebra to the Poincare algebra. The quantity R is fundamental to the same extent as c andh. In particular, a question why R is as is does not arise, and the answer is simply that R has its value because people want to measure distances in meters. The quantity Λ has a physical meaning only on classical level and equals Λ = ±3/R 2 for dS and AdS spaces, respectively. As a consequence of the fact that quantum dS and AdS symmetries are more general than Poincare symmetry, the cosmological constant problem does not arise, Λ is necessarily not zero and there is no need to involve dark energy for explaining the cosmological acceleration. In the case of those symmetries all physical quantities are dimensionless and no system of units is needed. In particular, the quantities (c,h, s), which are the basic quantities in the modern system of units, are not so fundamental as in relativistic quantum theory, time is not strongly continuous and description of the inflationary stage of the Universe by times (10 −36 s, 10 −32 s) has no physical meaning. Following our previous publications, we consider a system of two free bodies in dS invariant quantum mechanics and show that in semiclassical approximation the dS repulsion is the same as in General Relativity. This result is obtained without using geometry of dS space, metric and connection but simply as a consequence of quantum dS symmetry.