Now that physicists are wrapping up the most expensive experiment ever done — the multibillon-dollar Large Hadron Collider — they are proposing something even bigger and more expensive. Taking a very unpopular stand against this step, physicist Sabine Hossenfelder wrote a New York Times commentary, arguing that the collider had failed to deliver on its promise. She suggested her colleagues could hold off on asking for $10 billion, or more, to do it again on a bigger scale.
Scientists aren’t quite finished with the Large Hadron Collider, a machine with a 16-mile circumference, which started running in 2009 at CERN, near Geneva. The machine is getting an upgrade, and will go quiet for the next several years, but physicists seem resigned that any big surprises should have shown up by now. And so the natural next step is to build something much bigger. CERN, the European Organization for Nuclear Research, is considering such a project. So is China.
Hossenfelder’s critique provoked a quick outcry from physicists, who defended the notion of a next supercollider in the letters section of the Times as well as other publications. Such an experiment has obvious appeal. It’s exciting that scientists can accelerate particles to unthinkable speeds and smash them together so hard they produce bursts of energy more concentrated than anything since the big bang.
There’s a chance that going up in energy will peel back a new layer of reality, revealing deeper patterns in matter, space and time. But there’s also a chance that researchers using a larger collider will come up empty-handed. The Large Hadron Collider results don’t bode well.
It worked exactly as planned, but the natural world proved something of a letdown. The machine did produce an entity called the Higgs boson, which led to a Nobel prize, but people once had much bigger expectations.
I looked up a story I wrote for Science back in 1991, when physicists were at a similar crossroads. Back then, there were two potential projects on the table — the Large Hadron Collider, to be built at CERN, and a somewhat larger U.S. proposal — the Superconducting Supercollider. (The supercollider was subsequently abandoned after workers had started digging tunnels near Waxahachie, Texas.)
Back then, the physicists knew that the next big machine would very likely produce the Higgs Boson, because the theory of matter, the Standard Model, didn’t work without it or something like it. But what got them really excited was the prospect that they’d find something surprising, which would have guided the field on the next experiment, or round of experiments.
There were lots of ideas. A speculative theory called supersymmetry predicted that all the known particles had as-yet-unseen partners that would be revealed in a large collider. Serious physicists proposed even stranger things, such as contact with parallel universes that lived in dimensions beyond the usual three of space and one of time. There was speculation about miniature black holes.
In the 1991 story, I quoted Nobel laureate Sheldon Glashow saying that the worst possible outcome would be that the Higgs boson would show up exactly as predicted and they’d see nothing else noteworthy. That’s essentially what happened.
When I talked to Hossenfelder, a research fellow at the Frankfurt Institute for Advanced Studies, she said she wanted to emphasize that the Higgs theory came about to solve a problem in the existing theory of matter, but the universe will work just fine without all those other more exotic entities. The theories that predict them, she said, were guided more by aesthetics than by science.
They tie things together more neatly than our current standard model, which is really something of a hodgepodge, with 17 particles whose masses and other properties seem arbitrary. Many people believe the explanations for these will fall naturally out of some as-yet-undiscovered overarching laws.
Hossenfelder is not advocating giving up, she said, but she argued that it might not be such a bad idea to take some time off to rethink the next big step, while saving money that could go to other scientific endeavors, including a few that might yet bring us clues about the fundamental nature of reality. And she wants to be transparent with the public about the next big collider’s risk of an empty haul.
One promising avenue, she said, would be to try to understand how gravity, which governs matter on large scales, meshes with quantum mechanics, which governs the world on small scales. In the past, objects small enough to demonstrate the rules of the quantum world weren’t heavy enough for anyone to measure the force of gravity. “Now several experimental groups have made progress bringing heavier and heavier systems into quantum states,” she said.
As an example, she sent a paper on building up test masses one atom at a time, which she explained in a blog post. She also sent a more general article in Nature on other new schemes for understanding whether gravity obeys the laws of quantum mechanics.
If only we could do it all. But in this kind of science, we don’t know whether the answer will be fascinating or boring. It’s not like sending people to Mars, where even if there’s no life and nothing useful up there, the public will be satisfied with the fact of getting there.
And perhaps there is a philosophical, emotional drive behind expensive physics that’s not so different from the space enthusiasts’ mantra that it is humanity’s destiny to go into space.
That mantra is often followed by the warning that Earth-destroying asteroids are eventually coming, and so we’d better have a second home if we want to survive. The physics enthusiasts, and I consider myself one, gravitate toward using our temporary existence here in this universe to understand as much about it as we can. That means pursuing the most promising avenues for research, which probably means building a bigger collider eventually — but with other intriguing possibilities on the table, it could wait. That asteroid probably isn’t coming any time soon.
Also read: Birthday tribute to Satyendra Nath Bose, the physicist after whom Higgs boson particle is named