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Sunday, June 12, 2011
Warp-drive quest for the Big Bang's 'lost' material
By ROWAN HOOPER
What do these three things have in common: a mysterious, donut-shaped belt of plasma wrapped around the Earth; the warp engines on the starship USS Enterprise; and a laboratory at the European Organization for Nuclear Research (CERN) outside Geneva, Switzerland?
The answer is that they all involve the most powerful energy source in the universe, something so familiar to us from science fiction that I've already felt the necessity to reference "Star Trek." But it is something that really does exist: antimatter.
In their laboratory, the CERN scientists have actually made this exotic stuff, which is the opposite of normal matter and is currently the world's most expensive form of energy. Last week, a collaboration of scientists, including Yasunori Yamazaki from the University of Tokyo, announced that they had created and trapped atoms of the antimatter form of hydrogen (antihydrogen) — and stored them for more than 15 minutes.
"We've trapped antihydrogen atoms for as long as 1,000 seconds, which is forever in the world of high-energy particle physics," said Joel Fajans of University of California, Berkeley, a member of the ALPHA (Antihydrogen Laser Physics Apparatus) team at CERN, whose results are published in the current issue of the journal Nature Physics.
Why, you might well ask, are these mad scientists making stuff that could destroy the world if it escaped their labs? After all, author Dan Brown had the bad guys in his 2000 best-seller "Angels and Demons" build an antimatter bomb and try to blow up the Vatican. And a thimblefull of the stuff could destroy Tokyo and Yokohama.
For starters, we have rather less than a thimblefull: The ALPHA team made and stored 309 antiatoms of hydrogen.
Sure, this stuff is powerful — with a billion times more calorific energy than rocket fuel. But it's not so powerful that one tiny slipup could spell the end of the world. In fact, one of the ways the ALPHA scientists detect it is to allow an atom of the stuff to escape and interact with normal matter: They annihilate each other and give off a tiny flash of light. Hardly an explosion to level the Swiss Alps.
Indeed, with current technology, it would take millions of years to create enough antimatter for a weapon that could do any damage. This not only puts the brakes on current bomb-making capability using antimatter, but it is also a serious problem for that application we are familiar with from "Star Trek" — using antimatter to power a starship. But more of that later.
The real reason why physicists are excited about producing and storing antimatter is that it is one of the greatest mysteries in the universe.
This is because, according to the baffling but highly successful branch of physics known as quantum mechanics, it should have been produced in equal quantities with normal matter during the Big Bang that created the universe 13.6 billion years ago — but we can't find it. So, if we can make even a tiny amount and store it, we can study it and learn about its properties.
"Our objective," said Makoto Fujiwara, a physicist at the University of Calgary and at Canada's National Laboratory for Particle and Nuclear Physics, "is to address one of the big mysteries in science: What happened to antimatter in the course of the evolution of the universe?"
The question is related to our own existence, Fujiwara told me, because if matter and antimatter were present in exactly equal amounts, they would have annihilated each other, producing only energy in the form of light.
"That means that humans, the Earth, the solar system, the galaxy — everything made of matter — would not have existed," Fujiwara said.
So how do they capture and store this almost-mythical stuff?
Hydrogen — the simplest of all the elements — comprises a proton and an electron, so antihydrogen is made from the opposite ingredients: an antiproton and a positron (an antielectron). Hence those scientists in Switzerland mix positrons with antiprotons from CERN's Antiproton Decelerator in a vacuum chamber, where they combine into antihydrogen atoms. These precious atoms of antimatter are then held in a kind of magnetic bottle, chilled to more than 272 degrees below zero.
Certainly it's a breakthrough to be able to store this stuff at all, but we are still very far from being able to make enough of it to use in a starship's engines.
Antimatter is made when matter is smashed together in a particle collider, but these atom-smashers, such as the Large Hadron Colllider at CERN, are not designed specifically to make antimatter. Perhaps if there were commercial antimatter colliders, it would be cheaper to make the stuff.
In the meantime, there are naturally occurring sources. Around both the Earth and Jupiter, there are belts of radioactive plasma that contain antimatter. Earth's is called the Van Allen Belt, and it could theoretically be a source of antimatter.
The stuff in the Van Allen Belt is created in a similar way to CERN's method. It's like a scaled-up particle collider, one that's formed when cosmic rays from outer space smash into the Earth's atmosphere. There may also be antimatter elsewhere in the universe, and a detector, the Alpha Magnetic Spectrometer, has just been delivered to the International Space Station to look for it — on the last flight of the Space Shuttle Endeavour that ended on June 1.
In the "Star Trek" universe, Google tells me that antimatter engines were invented in 2063, but it's hard to see us being able to produce enough to power a starship by then. Unless, that is, we manage to detect a meteor made of the stuff . . .
Follow Rowan Hooper @rowhoop on Twitter. The second volume of Natural Selections columns translated into Japanese is published by Shinchosha at ¥1,500. The title is "Hito wa Ima mo Shinka Shiteru (The Evolving Human)."