Paul Dirac noticed that the ratio between the dimensions of the universe (visible size and age) and the protons (diameter, duration of the passage of light through the proton) constitutes a large number of about 10^40. And that the ratio of the gravitational force and the electromagnetic force between an electron and a proton is roughly the same. From this he deduced that the strength of gravity is inversely proportional to the age of the universe. He could only make a rough estimate, because of course he did not yet know the more precise value of 13.8 billion years world age assumed today. Especially the evaluation of the data from the Planck space telescope has produced this value in the last 10 years. So today we are in a position for a more detailed evaluation. We will show that gravity could result from an universal time-energy uncertainty relation if we assume that the universe's age is 13.8 billion years. Furthermore we will give by this approach a precise and straightforward formula for the gravitational constant G without magic factors, powers or roots. Finally, we want to describe an approach with which the gravity can be explained as an asymmetry of attractive and repulsive electromagnetic forces by the fact that in a finite universe with age T(u) there can be no electromagnetic interactions with frequencies smaller than the reciprocal of T(u).