Condensed matter analogs are useful when considering phenomena related to the quantum vacuum. This is because, in condensed matter, we know the physics both in the infrared and in the ultraviolet limits, while, in particle physics and gravity, the physics on the trans-Planckian scale are unknown. One of the cornerstones of the connections between nonrelativistic condensed matter and modern relativistic theories is the two-fluid hydrodynamics of superfluid helium, which was developed by Landau and Khalatnikov (Isaak Markovich Khalatnikov later founded and headed the Landau Institute). The dynamics and thermodynamics of the de Sitter state of the expansion of the Universe bear some features of the multi-fluid system. There are actually three components: the quantum vacuum, the gravitational component, and relativistic matter. The expanding de Sitter vacuum serves as a thermal bath with local temperature, which is twice the Gibbons—Hawking temperature related to the cosmological horizon. This local temperature leads to the heating of the matter component and the gravitational component, which behaves like Zel'dovich stiff matter and represents dark matter. In equilibrium and in the absence of conventional matter, the positive partial pressure of the dark matter compensates the negative partial pressure of the quantum vacuum. That is why, in full equilibrium, the total pressure is zero. This is rather similar to the correspondingly superfluid and normal components of superfluid liquid, which together produce a zero pressure of the liquid in the absence of environment. We propose the phenomenological theory, which describes the dynamics of dark energy and dark matter. If one assumes that, in the dynamics, gravitational dark matter behaves like real Zel'dovich stiff matter, it is shown that both components undergo power law decay due to the energy exchange between these components. It then follows that their values at the present time have the correct order of magnitude. We also consider other problems through the prism of condensed matter physics, including black holes and the Planck constant.