Cloudscape

Antimatter particles, when combined with matter particles of the same sort, cause one hundred procent of energy conversion. However, when antimatter particles are combined with matter particles of another sort, the energy conversion is far less. Pointing a matter and an antimatter beam at a target focal point could cause full energy conversion, although air molecules could partly convert the antimatter before it reaches the antimatter. For this reason, it would be best to use negatively used antiparticles, such as antiprotons, which would be repelled by the electrons in the air molecules.

Dirac thought that the negative energy results of the Dirac equation could be explained by the existence of antimatter. However, the energy of antimatter is actually as positive as that of ordinary matter. This becomes evident when the two are combined to produce energy rather than destroy it: if matter was composed of energy and antimatter of anti-energy, they would simply disappear when combined, rather than being converted into photons. After all, the sum of both energies would be zero.
Moreover, antimatter can be produced by matter. Thus, in the process, not only antimatter, but also matter should be produced for energy to be conserved: negative energy cannot arise from positive energy unless more positive energy likewise arises from it.
According to Feynman, antiparticles are particles traveling back into time. He though this a solution to the paradox of negative energy: a particle with negative energy traveling forward in time would actually be a particle traveling backward in time. A particle moving back in time, however, when seen from the past, would travel forward in time, so that it is actually impossible for a particle to move back in time.
Feynman believed that a particle which combined with its antiparticle to create a photon was actually a particle which created a photon to become its antiparticle. But if the particle would travel forward in time and then become an antiparticle which would travel backwards in time, then where does the photon come from? After all, no energy should be lost or gained as it travels backwards in time. This therefore violates the law of conservation of energy, as the energy of the particle is smaller than the energy of the antiparticle plus the energy of the photon. Another problem with this is that it would be acausal.
Another possibility may be that anti-energy simply has anti-mass. The notion of anti-mass, however, is hypothetical: it has never been observed, and nothing seems to indicate that it should exist at all.
Maybe the problem of negative energy is actually a very simple one. Perhaps, we meet negative energy daily as well as positive energy, and they are as hard to tell apart as negative and positive charge. Rather than being a property only of some exotic particle, it can be a property of half the particles in the universe: negative energy may simply be energy which has an opposite direction relative to positive energy.

An excerpt from Tempest - The Transition (http://www.lulu.com/content/1929564)

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