  Using the relation proposed by Weinberg in 1972, combining quantum and
cosmological parameters, we prove that the self gravitational potential energy
of any fundamental particle is a quantum, with physical properties independent
of the mass of the particle. It is a universal quantum of gravitational energy,
and its physical properties depend only on the cosmological scale factor R and
the physical constants \hbar and c. We propose a modification of the Weinberg's
relation, keeping the same numerical value, but substituting the cosmological
parameter H/c by 1/R.
