  We point out that $\Lambda$CDM cosmology has an ignored assumption. That is,
the $\Lambda$ component of the universe moves synchronously with ordinary
matters on Hubble scales. If cosmological constant is vacuum energy, this
assumption may be very difficult to be understood.
  We then propose a new mechanism which can explain the accelerating recession
of super-novaes. That is, considering the pressures originating from the random
moving (including Hubble recession) of galaxy clusters and galaxies. We provide
an new analytical solution of Einstein equation which may describe a universe
whose pressures originating from the random moving of galaxy clusters and
galaxies are considered.
