  Most of the calculations done to obtain the value of the cosmological
constant use methods of quantum gravity, a theory that has not been established
as yet, and a variety of results are usually obtained. The numerical value of
the cosmological constant is then supposed to be inserted in the Einstein field
equations, hence the evolution of the Universe will depend on the calculated
value. Here we present a fundamental approach to the problem. The theory
presented here uses a Riemannian four-dimensional presentation of gravitation
in which the coordinates are those of Hubble, i.e. distances and velocity
rather than space and time. We solve these field equations and show that there
are three possibilities for the Universe to expand but only the accelerating
Universe is possible. From there we calculate the cosmological constant and
find that its value is given by 1.934x10^(-35)s^-2. This value is in excellent
agreement with the measurements obtained by the High-Z Supernova Team and the
Supernova Cosmology Project. Finally it is shown that the three-dimensional
space of the Universe is Euclidean, as the Boomerang experiment shows.
