To Shake Up Journey of Particle Physics, Toss the Map

It's funny how the most intimate dilemmas can mirror the largest scientific questions. For example: Should the U.S. spend $5 billion or more on a new particle accelerator? And if so, what kind?

The answer will turn, in part, on the same kind of considerations that go into deciding whether you should sign up for an experimental medical protocol, take a new job, make a pass at that girl.

How much risk are you willing to take and at what cost?

On the one hand, we are a society that puts the highest premium on safety: We want cars that can't crash, relationships that can't fail. At the same time, our communal cheer is: "Go for it!"

Scientists face a similar dichotomy. Many big discoveries come from precise measurement and plodding observations: the beaks of finches, the motions of galaxies, the subtle loss of energy in particle collisions each in turn provided the crucial evidence for evolution, dark matter and neutrinos.

Other discoveries, by contrast, involve expensive gambles: space missions, decoding the human genome and many findings of subatomic particles.

Of course, big leaps also ultimately rest on the exacting collection and analysis of data. But the approach as well as style of research differs: Measure well what you think is out there versus go for broke and see what you can find that may or may not be out there.

Accelerator physics is inherently about careful measurement. It involves pumping up subatomic particles to high energies, crashing them together and sifting through what comes out for clues to the fundamental nature of everything.

But even here, said UC Santa Barbara physicist Harry Nelson, "there are the control freaks versus the wonderment people."

Nelson was one of a dozen High-Minded Observers invited to a recent meeting on the future of particle physics in Snowmass, Colo., to keep their colleagues from getting too comfortable with conventional wisdom. So he was only doing his job last week when he bluntly told them: "I feel we've underperformed. . . . We're not as good as we used to be."

Just why that is, he admitted, is a hard problem. But he thinks it has something to do with granting too much power to the control freaks. "There's something lacking we once had. It [once] felt much more exhilarating."

Particle physics hasn't had a completely unexpected discovery in a long time--something really off the wall, such as the 1964 discovery that some particles prefer to be left-handed. "If you're in this for discovery, you feel a little disappointed," he said.

In some large part, that lack of surprise is testimony to the field's success. But it's also part of the pressure to "go where our theorist colleagues have already pointed us," said Nelson. "It feels like we're sort of monks copying things down from the books the theorists write for us."

That leaves the experimenters in the same position as someone looking for lost keys under a lamppost because it's the only place that's lit.

Of course, accelerators are expensive. Taxpayers (not to mention politicians) don't want to hear the scientists say: "We'd like to build a $5-billion accelerator, but we might not find anything new."

And some things can be guaranteed from virtually any new machine: better measurements that lead to new theories or validation of old ones; a whole rich range of technological spinoffs. But major discoveries are another matter entirely.

Guaranteed discovery is an oxymoron. Asking for guarantees, said Jonathan Dorfan, director of the Stanford Linear Accelerator, "is a recipe for failure. If you're going to ask for guarantees, you're never going to reach the frontier."

And yet, "there is a big pressure to play it safe from our government," said physicist Jonathan Bagger, co-leader of a panel charged with deciding the future of the field. "We're a very goal-oriented society."

Going for a known goal not only can preclude real discovery, it takes away much of the adventure--the reason for discovering in the first place.

The late physicist Frank Oppenheimer liked to tell of a mistake he made when first exploring the Colorado mountains. The first hike up a path, he'd take his time, perhaps stumbling upon a beautiful meadow or a waterfall before reaching the grand vista from the top. But when he came up again with friends, he'd rush them in such a hurry to the summit that they never had a chance to see the meadow or the waterfall, or discover something of their own.

Oppenheimer compared this to the way physics is often taught in schools, but there's also a lesson for discoverers: You can't find anything unexpected if you always know where you're going. Sometimes the shortest distance from A to B isn't the most interesting or fruitful.

The biggest risk may well be not to take risks at all.

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