Physics of the Future: How Science Will Shape Human Destiny and Our Daily Lives by the Year 2100

Pennsylvania State University estimates that 4 milligrams of antimatter will take us to Mars, and perhaps a hundred grams will take us to the nearby stars. Pound for pound, it releases a billion times more energy than rocket fuel. An antimatter engine would look rather simple. You just drop a steady stream of antimatter particles down the rocket chamber, where it combines with ordinary matter and causes a titanic explosion. The explosive gas is then shot out one end of the chamber, creating thrust.
    We are still far from that dream. So far, physicists have been able to create antielectrons and antiprotons, as well as antihydrogen atoms, with antielectrons circulating around antiprotons. This was done at CERN and also at the Fermi National Accelerator Laboratory (Fermilab), outside Chicago, in its Tevatron, the second-largest atom smasher, or particle accelerator, in the world (second only to the Large Hadron Collider at CERN). Physicists at both labs slammed a beam of high-energy particles at a target, creating a shower of debris that contained antiprotons. Powerful magnets were usedto separate the antimatter from ordinary matter. These antiprotons were then slowed down and antielectrons were allowed to mix with them, creating antihydrogen atoms.
    One man who has thought long and hard about the practicalities of antimatter is Dave McGinnis, a physicist at Fermilab. While standing next to the Tevatron, he explained to me the daunting economics of antimatter. The only known way to produce steady quantities of antimatter, he emphasized to me, is to use an atom smasher like the Tevatron; these machines are extremely expensive and produce only minuscule amounts of antimatter. For example, in 2004, the atom smasher at CERN produced several trillionths of a gram of antimatter at a cost of $20 million. At that rate, it would bankrupt the entire economy of earth to produce enough antimatter to power a starship. Antimatter engines, he stressed to me, are not a farfetched concept. They are certainly within the laws of physics. But the cost of building one would be prohibitive for the near future.
    One reason antimatter is so prohibitively expensive is because the atom smashers necessary to produce it are notoriously expensive. However, these atom smashers are all-purpose machines, designed mainly to produce exotic subatomic particles, not the more common antimatter particles. They are research tools, not commercial machines. It is conceivable that costs could be brought down considerably if one designs a new type of atom smasher specifically to produce copious amounts of antimatter. Then, by mass-producing these machines, it might be possible to create sizable quantities of antimatter. Harold Gerrish of NASA believes that the cost of antimatter might eventually go down to $5,000 per microgram.
    Another possibility lies in finding an antimatter meteorite in outer space. If such an object were found, it could supply enough energy to power a starship. In fact, the European satellite PAMELA (Payload for Antimatter Matter Exploration and Light-Nuclei Astrophysics) was launched in 2006 specifically to look for naturally occurring antimatter in outer space.
    If large quantities of antimatter are found in space, one can envision using large electromagnetic nets to collect it.
    So although antimatter interstellar rockets are certainly within the laws of physics, it may take until the end of the century to drive down the cost. But if this can be done, then antimatter rockets would be on everyone’s short list of starships.
    NANOSHIPS
    When we are dazzled by the special effects in
Star Wars
or
Star Trek,
we immediately envision a huge, futuristic starship bristling with all the latest high-tech gadgets. Yet another possibility lies in using nanotechnology to create tiny starships, perhaps no larger than a thimble, a needle, or even smaller. We have this prejudice that a starship must be huge, like the
Enterprise,
and capable of supporting a crew of astronauts. But the essential functions of a starship may be miniaturized by nanotechnology so that perhaps millions of tiny nanoships might be launched to the nearby stars, only a fraction of which actually make it. Once they arrive on a nearby moon, they might create a factory to make unlimited copies of themselves.
    Vint Cerf, one of the original creators of the Internet, envisions tiny nanoships that can explore not just the solar system but eventually the stars themselves. He says, “