The current cosmological observations of distant supernovae type Ia suggest the existence of dark energy component with negative pressure. The most obvious candidate for this dark energy is the cosmological constant which raises several theoretical difficulties. The problem of dark energy, due to our Universe is accelerating at present in principle is open. We argue that this problem will dominate the cosmology in XXI century. From the philosophical point of view it is interesting to provide evidence and comments for the key issues related to the dark energy models just at the moment before scientific revolution.