The Particle Physics Project Prioritization Panel (P5) has just met and determined that of the five most exciting new areas of particle physics research—dark energy, dark matter, the Higgs boson, neutrinos, and new particles—the United States needs to focus its considerable resources on neutrinos. And at face value that sounds a little dull, because we verified the existence of neutrinos more than four decades ago and already have a lot of widely-accepted theories about what they are and how they operate. So as laypersons, we might ask: what’s the deal? Where’s P5’s sense of adventure?
There are several reasons why focusing the U.S. research program on neutrinos is a good idea. The first, and biggest, reason is practical: while the United States doesn’t have a large hadron collider, and is subsequently not in a great position to analyze the Higgs boson or discover new particles, Fermilab is well-equipped to lead the way on neutrinos. If you’re feeling cynical, the story might begin and end there—but there are good reasons why neutrino research is a good idea.
The first is that particle physics isn’t supposed to be glamorous. It isn’t about adventures; it’s about experimentally confirming, or challenging, theoretical models of the universe. The P5 report says with respect to neutrinos that “the experimental picture is incomplete,” which is a delicate way of saying that our theoretical framework with respect to neutrinos looks really nice on paper but may or may not correspond with reality. This means somebody has to do the difficult work of either confirming the theoretical framework (which leads to a lot of unsexy “Scientists Discover Near-Universally-Held Theory is Accurate” headlines), or challenging it (which leads to a lot of unsexy “Scientists Discover They’ve Been Getting It Wrong for Years” headlines). This may sound boring to laypersons, but for particle physicists this is where the real work begins, not where it ends.
The second is that we’re actually discovering new things about neutrinos—that there are three types of neutrinos, that they oscillate and presumably have mass, and so forth. One study a couple of years ago even implied that neutrinos can travel faster than light, though particle physicists are backing away from that hypothesis. Obviously this is changing our understanding of what mass is, and what the speed of light is, so anything we can confirm and deny about neutrinos runs the risk of changing our entire model of the universe. That’s tremendously exciting.
But the main reason I’m psyched by the prospect of a U.S. research program that focuses on neutrinos is that the darn things keep surprising us. Just when we think we understand them, they do something we wouldn’t expect them to do and we’re right back at square one. I find that kind of unpredictability very appealing; it reminds us that we really don’t know very much about the universe at all, and it forces us to confront the possibility that much of what we think we do know is wrong. That’s right at the heart of what it means to live in a mysterious universe, and to know that you do.