Search This Blog

Wednesday, September 10, 2008

New age in Physics

Switzerland -- It is the biggest machine ever built. Everyone says it looks like a movie set for a corny James Bond villain. They are correct. The machine is attended by brainiacs wearing hard hats and running around on catwalks. They are looking for the answer to the question: Where does everything in the universe come from? Price tag: $8 billion plus.

The world's largest particle accelerator is buried deep in the earth beneath herds of placid dairy cows grazing on the Swiss-French border. The thing has been under construction for years, like the pyramids. Its centerpiece is a circular 17-mile tunnel that contains a pipe swaddled in supermagnets refrigerated to crazy-low temperatures, colder than deep space.

The idea is to set two beams of protons traveling in opposite directions around the tunnel, redlining at the speed of light, generating wicked energy that will mimic the cataclysmic conditions at the beginning of time, then smashing into each other in a furious re-creation of the Big Bang -- this time recorded by giant digital cameras.

On Wednesday, they fired this sucker up
It will be months before the proton beams reach full power and produce the kinds of exotic collisions that may herald an age of "new physics." But if the machine works -- this most ambitious, expensive, technologically advanced civilian scientific experiment in history -- it would be a happening for humanity.

"I think we may have to rewrite our textbooks," said Fabiola Gianotti, a project leader for ATLAS, one of the four huge detectors that will record and analyze the collisions. "There must be something more than we have seen. There is something missing from the puzzle."

The Large Hadron Collider, as it is called by the 8,000 scientists, engineers and technicians from 85 countries who dote on it, will probe the most fundamental mysteries. From the fireballs, there might spring forth black holes and the elusive thing that gives matter its mass. Or not! There might be particles called "strangelets" and evidence of "dark matter" and signs of "supersymmetry" and maybe a little antimatter.

Oh, and they might find some extra dimensions. But this is the delicious part. They. Don't. Exactly. Know.

That accounts for the last-minute legal challenges by opponents who worry that the Large Hadron Collider -- hadrons, by the way, are collections of quarks, which are the particles inside protons and neutrons, which form the nucleus of the atom -- might spark a chain reaction of runaway events that could destroy the planet.

Their greatest concern is that the black holes, the stuff of a hundred "Star Trek" subplots, could grow and suck, grow and suck, which is what black holes do. A retired radiation safety expert in Hawaii sought a restraining order in a U.S. court but was denied. Another group filed its doomsday appeal with the European Court of Human Rights, which also declined to act.

To calm public anxiety, the proton smashers investigated safety concerns and said any black holes "would be entirely benign" and would decay almost instantly. They would be "mini black holes," just like the ones that occur (the theorists say) whenever a couple of cosmic rays collide in space. Nature has already conducted experiments just like this, the report concludes, "and the planet still exists."

The Large Hadron Collider was built by the European Organization for Nuclear Research, known as CERN, which on the surface looks like a slightly down-at-the-heels state college in the middle of a cow pasture in the dull suburbs of Geneva. CERN, however, is now the mecca for international physics, where the streets are named for Einstein, Newton and Curie. It is the place where they invented the World Wide Web. The cafeteria also serves wine with lunch.

After the United States stopped construction of the Superconducting Super Collider in 1993, after spending $2 billion and digging 14 miles of a 54-mile tunnel, the center of action for particle physics shifted to Europe.

To see what the excitement is about, you have to put on a hard hat and get into one of the elevator shafts and travel 300 feet below the Earth's surface to the tunnel, which was possible earlier this summer, before they closed the doors.

You drop into towering caverns lined with thick slabs of concrete that hold the detectors. The detectors look like building-size barrels, honeycombed with wafers of silicon and doughnut-shaped magnets. They are crawling, Medusa-like, with blue, red, green cables, like arteries and veins. They look muscular, beautiful, alive.

The tunnel itself is like a subterranean racetrack. Protons stripped from hydrogen atoms will be accelerated to high energies and whizzed around and around the tunnel, through an ordinary-looking blue pipe, which is not ordinary at all but quite extraordinary -- because it is coiled with thousands of superconducting magnets, which bend the proton beam so it can travel in circles. The magnets are superconducting because they are supercooled by superfluid helium, which is superstrange.

"A completely novel engineering material," is how Lyn Evans, the project manager of the collider, describes supercold helium. "For example, if you were to put it into a beaker? It could crawl out."

This is how they talk at CERN. If you stop them, and say, "What do you mean, crawl out?" They might go to a blackboard and begin with the math. You do not want them to do this.

Instead you say: Why underground?

"Cheaper," Evans said. It would cost a fortune to acquire the land in France and Switzerland to build the racetrack on the surface.

And why here? CERN was born in the rubble of postwar European physics. "Switzerland was neutral, and believe it or not, it was cheap," Evans said. "It is still neutral."

These protons whizzing through the pipe and around the track? They travel in bunches. These bunches are inches long and half the width of a human hair. Each bunch contains 100 billion protons, give or take a few. Each beam carries about 3,000 bunches. They travel at 99.9999991 percent the speed of light. So they are able to complete 11,245 laps a second. In 10 hours of operation, the beam could travel to Neptune and back.

At four major intersections along the way, the parallel beams will cross one another and collide. The crash sites are the business end of the machine. That is where they put the detectors.

"Think of oranges," Evans said. "You collide two oranges together, you get a lot of pulp. We're not so interested in the pulp. What we want to do is see what happens when the pips -- the seeds -- hit each other."

And how many times will these pips collide? That would be 600 million collisions a second. The good head-on-smashup will erupt into a cloud of scattering particles, and the detectors (and their computers) will attempt to record the trajectories, energies, speeds, decays.

That's a lot of data to record.

"Quite," Evans said.

In one of the very useful cartoon books produced by the CERN public relations staff, an illustration shows a stack of 3 million CDs that is equal to the data flow from a year's worth of collider experiments. It is 12 miles tall.

* * *

To understand, deeply, some of the things the scientists here are talking about is not really possible. "I don't understand, fully, the math involved in the string theories," confessed Robert Cousins, a physics professor from the University of California in Los Angeles, working at CERN on the Compact Muon Solenoid experiment.

But the general idea is this. "Humans have always asked, 'Where do we come from?' " Cousins said. "And this is the way that physicists ask that question."

For example, astrophysicists have observed that visible matter accounts for only 4 percent of the universe. By looking at gravitational effects -- for instance, how fast galaxies spin -- they can guess that there is more stuff out there than they can see. But what is this "dark matter?" Could dark matter be composed of "supersymmetric" particles, which might pop up in the collisions at CERN? For this reason, some people have called the Large Hadron Collider the "Hubble telescope of inner space."

And what about the mystery of antimatter? Antimatter is the identical-but-opposite twin of matter, except that for some unknown reason, nature prefers matter. As Cousins explained, if the universe and nature were neat and tidy, then equal amounts of matter and antimatter would be present at the Big Bang. But something is missing. The universe appears to be constructed entirely of matter. Where did all the antimatter go? "There is an imbalance," Cousins said. "So what gives?"

Physicists like balance, elegance and, believe it or not, simplicity, for instance E=mc{+2} -- energy equals mass times the square of the speed of light. The problem, theoretical physicist John Ellis says, "is mass. Where does it come from?"
Scientists' current understanding of the universe and all its particles and forces is called the Standard Model, and it is now 35 years old. It does not explain why some particles, such as protons, are relatively heavy, while others, like photons, have no mass at all. In a theory that dates to the early 1960s, a British physicist named Peter Higgs suggested that there was a mechanism -- alternatively described as a field, a boson, a particle, a whaddayacallit--that makes some things heavy and other things light.

Say what? Exactly.

Ellis, who has long white hair, a Gandalf vibe and a specialty in supersymmetry, lectures worldwide in four or five languages, including math. He expects the supercollider to detect the Higgs particle, but he hopes to see much, much more.

"Simply seeing the boring old Higgs? Or nothing at all?" He shuddered at the thought. "But then again, not seeing anything at all might be very interesting." Still, he bets they will uncover the nature of dark matter, and he has a lot riding on the wager.

For two decades, Ellis said, the Large Hadron Collider has been all about the builders. "For the engineers, the job is over," he said. "For the experimentalists, they're happy to find what they find.

"But for the theorists, for me, it is a bit different, because we have spent 40 years on a theory." He raised an eyebrow.

"There have been thousands of theoretical papers," he continued, "and I've written hundreds of them myself. What if it all turns out to be pile of garbage?"

The Large Hadron Collider will not operate at full intensity for a year, and so many variables could hold up its work. But the physicists at CERN have reached a milestone. Now that the machine has been turned on, Cousins said, "the trick for us is to be as full of wonder as we can be -- and simultaneously as skeptical as you can get."

No comments:

Find here

Home II Large Hadron Cillider News