Why Particle Physicists Need to Be Humble

Grand unified theory. Re-creating the big bang. Finding the “God particle.” Some days it seems as if particle physicists are on the verge of discovering the ultimate answer to life, the universe, and everything.

Which may or may not be 42.

With the recent stream of breakthroughs in dark matter, neutrinos, and the debut of the Large Hadron Collider, some folk are even asking whether the upcoming round of physics experiments will in fact find all the answers, effectively putting an end to particle physics as a field of study.

That’s nowhere close to true, according to Barry Barish, a Caltech physicist and current director of global design effort for the International Linear Collider, a proposed “straight line” companion to the circular LHC.

Particle physics “is suffering from overzealousness and the use of hyperbole by colleagues in my field,” Barish told the crowd during a lecture at the 2010 annual meeting of the American Association for the Advancement of Science in San Diego.

“We need to be more humble.”


Argonne National Lab director Albert Crewe explains the 1957 Zero Gradient Synchrotron

—Photo courtesy Argonne National Laboratory

According to Barish, part of the issue is that particle physics has changed from an observational science to an inquiry-based one.

In other words, it’s no longer about making colliders and watching what happens in order to make discoveries. It’s about asking questions and then building the experiments that have a shot at answering them.

And right now, it’s one looooong list of questions:

  • What’s the nature of dark energy?
  • Do extra dimensions exist?
  • Why are there so many types of particles?
  • What exactly is dark matter?
  • Where did the universe come from?
  • What’s the deal with antimatter imbalance in the early universe?
  • Why do neutrinos have so little mass?
  • Are there any undiscovered particles we haven’t even predicted yet?
  • Etc.

Within each of these broad questions is a subset of secondary questions waiting to be explored.

The LHC, for example, is constantly being hailed as THE machine that will find the Higgs boson, the predicted particle that should explain why matter has mass. Kinda funny that we don’t know that, right? But we don’t.

Trouble is, even if the LHC does find the Higgs, it won’t be able to study its properties, Barish said. That’s because when the LHC collides particles, it’s smashing up protons on protons, which are themselves made of several subparticles.

In a way that’s kind of the point, as physicists are hoping that the Higgs will be one of the short-lived pieces broken out of the protons and recorded by LHC detectors.

But all the other subparticles will get detected, too, so there’ll be a lot of “background noise” in there along with the Higgs signature.


What proton-proton collisions might look like to the LHC. Can anyone spot a Higgs?

—Image courtesy CERN via USCMS/NSF

That background will keep scientists from being able to really analyze the Higgs and determine some of its fundamental properties, such as how it couples to other particles.

It’d kinda be like if Bob Ballard had found the wreck of the Titanic but hadn’t had the equipment to go down there and take pictures, collect artifacts, or find Kate Winslet’s ginormous diamond necklace [kidding, of course, on that last one].

What’s the point of knowing the Higgs boson is there if we still don’t know how it works?

And all of that is assuming there even is a Higgs boson. It’s a best guess for now, but as Barish pointed out, Newtonian gravity worked great until Einstein came along and showed us how much we didn’t really know about why apples fall from trees.

“Right now, we can see the horizon, we know how to ask discrete questions, and we can build the instruments that might answer them,” Barish said.

“But decades from now, a lot of [these theories] will either be stale or just plain wrong.”

Now don’t get all depressed. In science, not having all the answers is actually pretty exciting, and getting things wrong is part of the process. What I think Barish was really saying is that there’s a ton of work left to do in particle physics.

Those doing the work simply need to take a step back now and then so they can help the public appreciate the small victories that come from doing Big Science.

Changing Planet