What is gravity? What is its cause or source? Many minds have attempted to solve this ancient puzzle, but no one has yet been fully successful. For Newton, the force of gravity was merely a function of masses and the distance between them. For Einstein, gravity caused a deformation of the space-time continuum. On this basis, he developed a highly complex algebra that merely describes it geometrically. The majority of studies to date explain only the effects of gravity and not its nature. The unification of gravity with electricity has been a challenge for many great physicists of the last century. Einstein dedicated almost 35 years to the problem without success, while, in 1968, Dirac suggested that it would not be possible to unify the fundamental forces. There is now a large body of evidence to suggest a strong connection between - and perhaps a common fundamental origin of - electromagnetism and gravity, as exemplified by an innovative experiment presented at the recent meeting of the American Astronomical Society. Carried out by the University of Missouri - Columbia and the National Radioastronomy Observatory, it used precise measurements to show that gravity is propagated at the same velocity as light. The relationship between gravity and electricity is also demonstrated by the fact that both obey the inverse square law, despite the immense differences in their relative intensities and distances. In http://www.geocities.com/rolfguthmann/QTG/qtg.html we where demonstrates both the origin of this relationship and the reason for these differences. Further evidence is derived from Einstein's Theory of Relativity, and is based on the principle of the equivalence of inertial and gravitational mass, whereby both experience the same acceleration in a gravitational field, with immense precision. This theory shows that gravity and inertia are the same thing, because both act on a body in the same manner, with their forces proportional to the mass of the body. It can thus be acknowledged that gravity and inertia have a similar origin. It is important to remember that the latter results from a very common phenomenon: the application of a force to a massive body. The question of gravity can thus be answered through the two facts presented here: gravity is an inertia and is caused by an electromagnetic force of nuclear origin. The evidence also shows that the source or cause of gravity is the relative difference between the electrostatic and centripetal forces within atoms. We will see that the origin of these differences lies in the relativistic motion of electrons and the time reference they adopt. In order to understand the workings of gravity, we must understand the origin and workings of time and the connection between time and gravity. We must therefore find a physical interpretation that better matches observed phenomena, replacing the Uncertainty Principle with the Temporal Uncertainty Principle as the factor of imprecision in the behavior of subatomic particles. Under the Temporal Uncertainty Principle, a particle is always out of phase with the present or with its local time reference. For any observer at any moment, there will be a slight temporal dislocation either towards the past or towards the future, resembling a sine curve when visualized in two dimensions, or a spiral in three dimensions, in both cases centered on the x-axis, which represents the atom's local "present" or local time reference. Gravity is generated only when an atom is found in a gravitational field, without which there can be no temporal reference, this being defined by the presence of at least one other atom. The beginning of time thus occurred as of the existence of the second atom in the universe. The gravity generated also depends on the intensity of the gravitational field, hence the expression that "gravity gravitates". Time passes at different rates in different locations in the universe according to the intensity of local gravitational potential, a property exhaustively tested and demonstrated by the Theory of General Relativity. Adopting time as the factor of imprecision, the same atom under the influence of gravitational fields of different intensities will experience time passing at different rates: the sensation of the atom's mass or gravity will also be different in these different locations. This variation will be extremely small, to the point that it cannot be calculated with scientifically acceptable precision, but its existence is sufficient to explain a number of cosmic phenomena not previously understood, such as dark matter and the gravitational anomalies experienced by deep space probes. On the basis of the above, we can disregard the controversial Mach Principle, which establishes that the inertial and gravitational properties of matter are somehow linked to the existence of all of the matter in the universe. We can also disregard the influence of distant stars in the definition of an atom's local time reference: the behavior of the water in Newton's famous bucket experiment (How does the water know it is in rotation? In rotation with respect to what?) can be explained perfectly well if we consider that gravity is generated by the atoms. In this case, the reference will be the atom itself accelerated in relation to the others, because each atom is a source of gravity-time and therefore a temporal reference: a collection of such references defines a local time reference. All the intricate and complex philosophy surrounding the difficulty of explaining relative or absolute acceleration is resolved when we refer the present or local time reference to the nucleus of the atom. It is in the dependence of inertia and gravity on the local time reference that we find the explanation for the question of the inertial reference system: the rate of time experienced by the observer will define what is observed. In this way, we can regard gravity not as one of the four fundamental forces, but as a relative difference between known interactions: electromagnetism, the strong force and the weak force. In the following SITE http://www.geocities.com/rolfguthmann/ we will demonstrate how gravity can be found in atoms and the importance of time.