In 1928 Paul Dirac developed through complex mathematical calculations a theory that integrated quantum mechanics, used to describe the subatomic world, with Einstein’s Special Relativity, which says nothing travels faster than light.
However, he soon realized his equations not only worked for an electron with negative charge. It also worked for a particle that behaves like an electron with positive charge.
In other words, they predicted something entirely new to science – antiparticles.
100 Years of General Relativity 
In 1932, Carl Anderson a professor at California Tech experimental confirmed their existence when he observed cosmic rays in a cloud chamber leaving a track which could have only been created by something with a positively charged, and with the same mass as an electron."
However, even though the environment containing antimatter is defined only in terms of the abstract prosperities of mathematics its existence can tell us a great deal about the physical geometry of our universe.
For example, Einstein’s theories make very specific predictions based on the existence of a single spacetime environment that if found not to occur would invalidate it.
For example, his theory tells us that light should bend as it passes by a massive object.
If this was not observed his theory would have to be discarded.
However, 1919 Arthur Eddington lead an expedition to photograph the total eclipse of the Sun. The photographs revealed stars whose light had passed near sun had been bent exactly as Einstein had predicted. The experiment was repeated in 1922 with another eclipse with the same confirmation.
Additionally in past century, since he proposed his theory there has not been any observations of our macroscopic universe that disagree with any of its predictions.
Even so this does not mean that we should assume that our universe is physically made up of four dimensional spacetime because, as with all multidimensional theories when Einstein derived the geometric properties of a spacetime universe in terms of the constant velocity of light he also define another one with identical properties in terms of four *spatial* dimensions.
In other words, by defining the geometric properties of spacetime in terms of the constant velocity of light he provided a qualitative and quantitative means of redefining its time related properties in terms of only four *spatial* dimensions.
As was mentioned earlier the fact that light bends as it passes by massive objects does not mean our universe is made up of four dimensional spacetime because the symmetry of equations used to make that prediction also predicts one made up of only four *spatial* dimensions will do the same.
Therefore, the fact that light bends as it passes by a mass cannot be used to eliminate that possibility.
However, there is an experiment very similar to the one Arthur Eddington preformed that would resolve this ambiguity.
Einstein’s Theory of General Relativity tells us that objects that create gravitational field cause time to "move" slower. However, due to the symmetry of his equations one could also say that time slowing down results in the formation of a gravitational field. Therefore, one must assume that a gravitational field must always be attractive because observations indicate that the passage of time can only be slowed not accelerated.
However, the fact that one can use Einstein’s equations to qualitatively and quantitatively redefine the energy he associated with gravity in terms of four *spatial* dimensions means as was done in the article “Defining energy?” Nov 27, 2007 that it can be derived in terms of a spatial displacement in a "surface" of a threedimensional space manifold with respect to a fourth *spatial* dimension as well as one in a spacetime dimension.
However, unlike time, which is observed to only move in one direction forward observations tell us that we can move in spatially in two directions up down or backwards and forwards.
Therefore, if and only if the universe was made up of four *spatial* dimensions could there exist a form of mass that posses a negative gravitational potential.
One candidate for such a mass is antimatter. We know from observations that in it has an electrical charge that is oppositely directed from its matter counterpart. Therefore, it is possible that it has a gravitational field that is oppositely directed from that of ordinary matter.
An experiment has been proposed that could determine if this is indeed true.
As describe in the New Scientist article "Antimatter mysteries 3: Does antimatter fall up?" Apr 29, 2009, it involves using uncharged particles to prevent electromagnetic forces from drowning out gravitational effects. It will first build highly unstable pairings of electrons and positrons, known as positronium, then excite them with lasers to prevent them annihilating too quickly. Clouds of antiprotons will rip these pairs apart, stealing their positrons to create neutral antihydrogen atoms.
Pulses of these antiatoms shot horizontally through two grids of slits will create a fine pattern of impact and shadow on a detector screen. By measuring how the position of this pattern is displaced, the strength – and direction – of the gravitational force on antimatter can be measured.
In other words, there is an experiment that could determine if our universe is physically composed of four dimensional spacetime or four *spatial* dimensions because as was mentioned earlier a universe physically composed of four dimensional spacetime cannot support a negative gravitational potential while one made up of four *spatial* dimensions can.
Yet if found to be true it does not mean that Einstein’s theories are invalid because his theories and predictions were based on pure mathematics and as mentioned earlier a universe consisting of four dimensional spacetime and four *spatial* dimensional are mathematically are equivalent in every respect.
However, it would require us to rethink our understanding of the physical geometry of our universe and the causality of gravitational forces.
Later Jeff
Copyright Jeffrey O’Callaghan 2016
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