In Physics, Discoveries Can Be in the Eye of the Beholder
The first time, it was a solo planet drifting around by itself in the vastness of space--the first ever seen untethered to a star.
The next time, it was “quark soup.” Then it was hypothetical “dark matter” particles known as WIMPS.
Each time, scientists were so sure of what they saw that they called a news conference to announce the results to the world.
And each time, other scientists chimed in to protest: It just ain’t so.
Why can’t the scientists agree on what they saw?
To be sure, it’s difficult to tell whether a dim point of light is a far-off star or a nearby planet. It’s even harder to know what “quark soup” looks like, or to catch a WIMP in an ordinary trap.
Quark soup is an exotic state of matter that made up the whole universe just after the Big Bang--a boiling blend of subatomic particles called quarks and the “gluons” that hold them together. Quark soup can’t exist in today’s cool universe any more than hot water exists in a freezer.
But earlier this year, physicists in Europe thought they had cooked up a soupcon of the stuff by smashing heavy particles at targets. Physicists on this side of the Atlantic weren’t buying that a bit. Even if the soup did make a brief appearance, they argued, no one yet had tools to know what they saw.
As for WIMPS, suffice it to say that if “dark matter” were easy to see, someone would have claimed this discovery long ago. And WIMPS aren’t named Weakly Interacting Massive Particles for nothing; they have so little contact with ordinary matter, in fact, that they pass right through most of it like ghosts.
Still, when an Italian group claimed to have found evidence for a dozen WIMPS a few months ago, seven major U.S. institutions put out a joint news release saying, in essence: no way. Better, more sensitive detectors had ruled out the very WIMPS the Italians said they saw.
These on-again, off-again discoveries can make scientists sound like a bunch of puffed-up kids battling over bragging rights. One group claims: Yes we did! The other insists: No you didn’t!
What’s the public to think?
The truth is, it’s not that easy to know when something has actually been discovered.
“You don’t always get things right the first time,” said physicist Roger Dixon of Fermi National Accelerator Laboratory in Batavia, Ill., one of the institutions that put out the news release doubting the discovery of WIMPS. “The public is seeing the actual process at work. Sometimes that’s confusing.”
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Last month, the apparent solo planet turned out to be a dim star after all. If the soup and the WIMPS evaporate under further scrutiny, as most physicists believe they will, the public won’t necessarily have caught the scientists with their pants down. It will just have caught them in the act of doing what physicists normally do: making guesses based on the best available information, then holding their hunches up to the harsh light of experiment.
Theorists, after all, routinely ride their equations into dangerous territory, like the heart of the fiery Big Bang; they dream up all manner of exotic particles, spin out universes that breed like rabbits and expand space and time into 11 dimensions. But these dreams come dressed in rules.
The roller-coaster of imagination comes equipped with built-in reality checks as brakes.
Like toddlers on tethers, the theorists are free to play in such dangerous ground precisely because at the end of the day, they’re still firmly attached to the long arm of experiment. If their ideas are just hot air, eventually, the experimenters will bring them down to earth.
When experiments prove hard to do, of course, it’s difficult to know when a theory has proved its worth. It’s embarrassing to be caught yelling “fire” when there’s nothing but a little bit of smoke. On the other hand, sometimes smoke is the only signal there is. But what if the smoke turns out to be ordinary dust kicked up by the experimenters’ shoes?
The call is never simple. An everyday neutron can look like a WIMP, just as a man reaching for his wallet can look the same as a man reaching for a gun. Especially if you’re expecting to see a gun. Or hoping to be the first human to glimpse the dark side of matter.
Experimenters are people, Dixon reminds us. “And some of them need to take credit [for perhaps premature discoveries] in order to survive.”
The good news is: Nature has the answer. The bad news is: Sometimes we have to wait longer than we’d like to find out what it is.
