Particle accelerator

A particle accelerator in Switzerland is shutting down for upgrades, but building a bigger, more powerful accelerator is controversial because of its cost, among other factors.

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.

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.

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.

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.

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.

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. 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.

Faye Flam is a Bloomberg Opinion columnist.