CERN, the physics laboratory near Geneva, Switzerland, is well known as the home of the world鈥檚 biggest particle smasher, the Large Hadron Collider (LHC). On Tuesday it revealed a design study for an even bigger machine, the Future Circular Collider (FCC).
Costs start at 鈧�9 billion for the least expensive version, going up to an eye-watering 鈧�21 billion for the grandest vision. Inside a 100-kilometre-long ring tunnel, particles would be smashed together at energies which dwarf those achievable in the LHC. The idea has created plenty of excitement. The problem is, it is not worth it.
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It is possible that in such a collider we will find new sub-atomic particles, in the same way as the LHC found the Higgs particle. But we have no good reason to think this will happen because the most reliable predictions say any new discoveries will require energies 14 orders of magnitude higher than those the FCC could achieve.
There is no reason that new discoveries, like the particles making up dark matter, would be accessible with this collider. The only thing it will reliably do is measure the properties of the particles we already know about in greater detail. The CERN report acknowledges this, but obfuscates the point.
It notes some hypothetical particles that could be ruled out with the FCC, such as dark matter candidates called WIMPs. But physicists have conjectured no end of new particles. Ruling out a few among millions of others offers little progress.
Time for a pause
Supporters of the FCC make the usual arguments that investing in a science project this size would benefit some industries as well as education and scientific networks. But any large-scale experiment would have such benefits.
The point is we might get more bang for the buck if we waited for better particle smashing technologies. One example is the plasma wakefield acceleration method, which may become a more efficient route to progress. And high temperature superconductors may reach a level where they become usable for the magnets in a more potent collider. Both may become available in a decade or two.
It would make more sense to put the hunt for new particles on hold for 20 years to see whether new technologies are available, or more concrete predictions for new physics have been made to justify costly new accelerators.
Other large-scale experiments, such as radio telescopes and dark matter investigations, would more reliably offer new insights into the foundations of physics. Medium and small-scale experiments that tend to fall off the table when big collaborations eat up money and attention would be less likely to suffer too. Not to mention that we might be better off investing in other areas of science entirely.
A large particle collider is one of the most expensive experiments you can think of, and we don鈥檛 currently have a reason to think it would discover anything new. That alone makes this super accelerator a non-starter.
Sabine Hossenfelder is a physicist at the Frankfurt Institute for Advanced Studies in Germany
