Article - Advances in physical sciences, t. 171, No11, 2001. Recent observational studies of distant supernova explosions indicate the presence in the Universe of a cosmic vacuum whose energy density exceeds the density of all other forms of cosmic energy combined. Vacuum creates antigravity field that causes acceleration of cosmological expansion. This acceleration has been detected in observations. The discovery of the cosmic vacuum entails a radical revision of established ideas about the current state of the universe. It also poses a number of new fundamental problems in both cosmology and foundational physics. Why the density of the cosmic vacuum has exactly the same value, which is found in the observations? Why different components of the space environment have different, but still close in order of magnitude observed density values? However, this discovery, made at great cosmological distances (hundreds and thousands of megaparsecs), sheds light on the dynamics of our near neighborhood in the universe, on the motions of galaxies in a local volume with a radius of up to 10-20 Mpc, where the cosmological expansion was originally discovered.