Can antigravity explain dark matter and dark energy?
Harry Goodhew Everything in the world is made of matter, which is itself made up of atoms. Atoms consist of a nucleus containing protons and neutrons, held together by a force known as the strong force and electrons, which are attracted to the nucleus by the electromagnetic force. Each of these particles has its own antimatter equivalent (or antiparticle), with identical properties in every respect other than charge, when a particle and its corresponding antiparticle meet they annihilate, releasing energy in the form of photons, the carriers of the electromagnetic force. This in a nutshell is the standard model which governs all of modern particle physics. However, it has nothing to say about gravity other than it is carried by the elusive graviton nor can it account for dark matter or dark energy, thought to make up 96% of the visible universe.
One of the many uncertainties about gravity is the gravitational interaction between matter and antimatter, some theories suggest that it is attractive, like opposite poles on a magnet, others that it is repulsive, like two south poles on a magnet. Despite the existence of several experiments attempting to resolve this uncertainty none have yet resulted in an answer. A conclusive answer to this question is keenly awaited as a repulsive gravitational interaction, antigravity, could have serious ramifications for cosmology by helping to explain dark matter and dark energy and further our understanding of the universe. The equivalence principle states that the mass causing the gravitational force (gravitational mass) is indistinguishable from the mass that resists an accelerating force (inertial mass). This is one theory that rejects the possibility of antigravity as this would represent a difference between these two masses. However, other theories predict a repulsive gravity, most convincingly an attempt to make Einstein’s theory of general relativity, our best theory of gravity, unaffected by the simultaneous replacement of all matter with antimatter, the reflection of space in a mirror and the reversal of time. 1 This is a significant result as it is currently thought all process in the universe are unchanged by such a transformation. This conflict between theories emphasizes that this proposal must be tested experimentally, however, this is far from simple. One way in which a conclusive result could be found is by comparing how cosmic particles are affected by their passage through the universe, if it were found that matter and Dark Energy, Dark Matter, Dark Force: Not Afraid Of The Dark http://physicsforme.com/2011/08/19/dark- energy-dark-matter-dark-force-not-afraid-of-the-dark/
1 M. Villata (2011). ‘CPT symmetry and antimatter gravity in general relativity’. Cornell University Library (Online)
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