From the March 2005 issue

Bob Berman’s strange universe: Annihilate this

March 2005: If antimatter didn't exist, someone would have to make it up — it's that juicy.
By | Published: March 1, 2005
Bob Berman
If antimatter didn’t exist, someone would have to make it up — it’s that juicy. Predicted by the brilliant physicist Paul Dirac in 1928 — and first found by Carl D. Anderson of Caltech in 1935 — antimatter looks, smells, and acts exactly like ordinary matter. But let it touch anything, and both vanish in a maximum-energy explosion.

It’s easy to understand, because antimatter’s the same as regular matter, except all electrical charges are reversed. It’s as if some incompetent deity from another dimension accidentally wired it backwards. At the center of anti-atoms lurk antiprotons with negative instead of positive charges. Positive electrons — positrons — orbit the antiprotons.

When the most recent incarnation of the universe was born 13.7 billion years ago, equal amounts of matter and antimatter should have been created. Collisions happened all the time in that crowded, wild environment, and when the dust settled, everything should have evened out. It didn’t. Somehow, we ended up in a matter-dominated universe. Theorists still debate why that happened. Recent evidence suggests nature has a slight bias for matter instead of antimatter creation — that the two processes are not as symmetric as everyone thought.

Unlike the Earth-you, the anti-you neatly folds his clothes at night instead of tossing them on the floor.

Nevertheless, the cosmos could contain entire antimatter stars. The light emitted by such antisuns would be identical to the energy from normal stars. Looking into the night sky, there’s no way to know whether a star is matter or antimatter.

There could be antimatter planets, too. Maybe there’s an anti-Earth, with antirestaurants serving antipasto. There might even be an anti-me and an anti-you. Unlike the Earth-you, the anti-you neatly folds his clothes at night instead of tossing them on the floor.

The most dramatic thing about antimatter is what happens when it encounters ordinary materials. Remember E=mc2? Write down the weight of anything (in grams), multiply that by the square of lightspeed expressed in centimeters per second (roughly 30 billion times 30 billion) and voilà: That’s how much energy (in ergs) is in that lump of material. Every cigarette butt on the street is a cauldron of super-energy trapped in a dormant, disgusting form. Release it, and you could power your house for a thousand years. Well, your subwoofer anyway.

H-bombs and the solar core unleash energy with only a 0.007 efficiency. Seven-tenths of one percent. But when matter and antimatter meet, their masses convert to energy with 100 percent efficiency. And you could use anything at all — junk mail, corpses — any matter works.

But where to get the antimatter? Nobody’s selling any, not even on eBay. It’s made in particle accelerators like Fermilab, but it’s not cheap. Current annual global production is about 10 nanograms (billionths of a gram). The biggest chunks are whole anti-atoms, first created in 1995.

It’s hard to keep, too. Antimatter would annihilate the wall of any container you put it in. Like leftover Chinese food, the best storage solution is to keep it in a vacuum in the fridge. If chilled near absolute zero, it would scarcely move around. Then, if you manufactured only charged positrons or antiprotons, the antimatter could be suspended in a magnetic field.

A moving field, like those that levitate bullet trains, could guide such fuel to a rocket’s combustion chamber to meet bits of regular matter.

Such magnetic containment is the way to go, but you’d better be sure the field never wavers due to a power failure or technical problem. (“We’re losing containment!” shouted Scotty. The crew knew this wasn’t just a minor problem for the Enterprise’s to-do list. “Lost containment” meant the ship and crew would turn into pure energy, voiding their insurance.)

We know antimatter is out there because matter-antimatter annihilation produces photons with a recognizable signature of 511,000 electron volts. Geysers of such positronic debris erupt violently from our galaxy’s core, at right angles to the Milky Way’s plane.

Although these blazing fountains were discovered by the Compton Gamma Ray Observatory 8 years ago, their source is still a mystery. Massive star bursts? Black-hole antimatter factories? Nobody knows the origin of the Milky Way’s antimatter.

Someday, antimatter may help propel us to the galaxy’s core to see for ourselves. Odds are, the trip won’t be anticlimactic.