Today, antimatter was one of our main energy sources. CERN had already produced 100 anti-hydrogen atoms in 1995, and in 2006 they could generate 10 million anti-hydrogen atoms per second. This isn't much, of course: with all the anti-matter they'd made by then, they could lit a light bulb for a few minutes. But for a decade, it's an enormous progress when one considers exponential growth.
Because anti-matter would react with any normal matter, it posed a problem to storing it, though this could easily be surmounted: the anti-matter was placed as an ionized solid in a vacuum, electromagnetically repelled from its charged container. To be safe, however, such antimatter reservoir had to be capable of resisting considerable force. The maximum force at which it could remain stable was equal to the force of the container's electromagnetic repulsion. However, this force could impossibly be sufficiently great to allow it to withstand terroristic attacks.
Now, to provide the population of an entire city, antimatter fuel tanks could contain several milligrams of antimatter. To me, this would seem minuscule, and indeed a milligram of twencen gasoline would yield only about fifty joules of energy. However, when combined with matter, this yields energy on the orders of 1011 J - hundred gigajoules. As one kilogram of TNT can be converted into 4,184 · 106 J, this is equivalent to a nuclear explosion of tens of megatons. Four milligrams of antimatter will yield as much energy as the Tsar Bomba, one of the most powerful atomic bombs ever constructed. Needless to say, this is dangerous: if such reservoir would fail, the entire city would perish with it. Such accident has already happened once, and that was enough to warn the world to be more leery with antimatter: no sane soul would still have the reckless temerity to store large amounts of antimatter in a single fuel tank.
That is why larger antimatter reservoirs were usually built in uninhabited areas, and their energy was transported by foglets, be it in the form of electricity (conducted through long chains of foglets) or directly in the form of antimatter. Each foglet needed to transport only very little antimatter, so that the electrical energy needed to repel the ionized antimatter was negligible.
Dangerous as antimatter was, it was present all around us: though foglets could easily be provided with energy by electricity, almost all of our foglets contained antimatter. When concentrated in a single fuel tank, antimatter was extremely dangerous, but it was virtually harmless when diffused: the antimatter contained within a single foglet was close to zero, so that there would be no harm in destroying them. Their antimatter was no more dangerous than oxygen.
Foglets were actually mostly powered by electricity, and not by antimatter: by forming invisible networks of minuscule wires, they could convey electrical energy throughout an entire space, permeating the air all around us. These webs could be omnipresent in the air the one moment, and disappear into nothingness the next moment as we walked onto them. This method was so efficient that the bulk of our foglets derived all their energy from it. Instead, their antimatter reservoirs were much rather a means to have immediate access to antimatter than to fuel the foglets.
Yet, if needed, antimatter could allow foglets - or anything else - to move at enormous speeds. If massive energy is converted into kinetic energy,
EP = Ek
⇔ ηmPc2 = ½mTv2
where mP is the mass of the propellant and η is the efficiency of conversion. For antimatter-matter combination, η is 50%, or ½. Thus,
½mPc2 = ½mTv2
⇔ mP/mT = v2/c2
Or, if we write the ratio v/c as ß and the ratio mP/mT as µ:
√µ = ß
Thus, if 25% of their mass consisted of matter-antimatter fuel, they could attain a speed half the speed of light (150.000 kilometers per second!) without friction. Note that this requires all fuel to be used at once.
