The real world of antimatter Physics: Astronomers have found evidence of a 'fountain' of antimatter spewing into space from the center of the Milky Way galaxy. What they aren't sure of is how the positrons are being created.

Writers love antimatter.

Star Trek screenwriters used it to fuel their TV starships and spike their plots. A screw shakes loose somewhere, threatening to free the antimatter fuel and annihilate our regular-matter heroes.

An editorial writer once used matter and antimatter as a simile for two apparently contradictory realities that nevertheless exist side by side -- specifically, a booming economy and the average American's money worries.

A TV critic used antimatter to power a metaphor for C-SPAN -- that cable TV channel devoted to long speeches no matter how long, or how few are watching. "Starless C-SPAN," he wrote, "is television's antimatter, traveling a unique orbit, with its own laws of space and time."

None of them got it quite right.

Antimatter, it turns out, is real, nonfiction stuff, but too rare to be used directly as rocket fuel. It can't exist for long side-by-side with regular matter. And, it does obey the standard "laws of space and time."

Astronomers from Northwestern University and the Naval Research Laboratory recently announced that they had found evidence of a "fountain" of antimatter spewing from the center of our Milky Way galaxy. Antimatter is also produced by radioactive decay. Medical researchers study growing tumors by injecting a radioactive substance and imaging the gamma rays produced by the annihilation of the antimatter it generates.

In fact, if it were not for a cosmological quirk, we -- people, blue crabs, stars and galaxies -- might easily have evolved from antimatter instead of regular matter.

Opposite of regular matter

Antimatter atoms, like regular atoms, are composed of protons, neutrons and electrons. It's just that antimatter's atomic particles carry electrical charges and magnetic "moment" (directional tendencies in a magnetic field) opposite those of regular matter.

Where regular electrons have a negative charge, antimatter "electrons" have a positive charge (called positrons).

Likewise, regular protons have a positive charge, but anti-protons are negative. Neutrons and anti-neutrons are both electrically neutral, but have opposite magnetic moment.

If these antimatter particles were combined, they would form atoms of recognizable chemical elements, with the same atomic weights as chemical behaviors as their regular matter counterparts. Laboratories in Europe and America have actually made a few atoms of anti-hydrogen.

The forbidden apple here, of course, is that we and travelers from antimatter worlds would meet at our mutual peril. Annihilation turns both us and the antimatter visitors into a handful of sub-atomic particles called pi mesons, and a lot of energy, chiefly gamma rays.

Here, it helps to recall the connection between energy and matter. Albert Einstein discovered that the amount of energy (E) locked up in a chunk of matter equals the mass of the chunk (m) times the speed of light (c) squared -- E=mc2.

The speed of light squared (multiplied by itself) is a very large number. Under the right conditions, physicists realized, a relatively small amount of matter could be converted into huge amounts of energy, like plutonium and the blast of a nuclear weapon.

More to the point here, Einstein's formula also works in reverse. In an environment of very high energy, such as the Big Bang, a particle accelerator or near a black hole, tiny particles of matter may pop spontaneously into existence. And, they appear in pairs -- one particle of matter and one of antimatter.

That, most cosmologists believe, is where all the matter in the dTC universe today came from. Some 14 billion or 15 billion years ago, the Big Bang erupted in a burst of pure energy. As the blast expanded and cooled, it began to produce equal amounts of subatomic particles called quarks and anti-quarks.

"Everything that's happened since then over 15 billion years has been the condensation of quarks into ... the form that we see matter in today," says Gerald A. Smith, a physics professor and antimatter expert at Pennsylvania State University. "The question is, what happened to all the anti-quarks?"

And all the antimatter? Everything around us appears to be made of regular matter.

One argument is that the particles of matter and antimatter began bumping into each other and annihilating. Everything would have disappeared if it weren't for a tiny imbalance in the amounts of matter and antimatter.

It's a complicated theory rooted in particle physics, Smith says. But "if we work out what the universe was 1-billionth of a second after it began, it turns out that for every billion anti-particle/particle pairs, there was one extra particle. To that ... we owe our existence."

Annihilation

There is probably no original antimatter left: Most scientists believe that in the very compact early universe, antimatter particles could not have sorted themselves out from matter fast enough to condense into antimatter hydrogen and helium, and from that into stars and galaxies. Annihilation probably got them all first.