Which supercollider will be built?

After CERN announced the plans for its new supercollider, I was surprised no one wanted to address the elephant in the room: the supercollider's similarity to one announced by China a few months ago.

The Chinese machine is called CEPC (Circular Electron Proton Collider) and the CERN machine, FCC (Future Circular Collider). Both CEPC and FCC have a tunnel length – i.e. ring circumference – of 100 km, four phases of operation, with plans to study the same set of particles in the same time period.

Both Yifang Wang and Michael Benedikt, the respective heads of projects, told me that the similarities validate their respective decisions to go with this particular design, and both of them also evaded the question of which machine will ultimately be built.

To be clear, it's not likely that both machines will be built. Even if they are, they won't receive equal support – both in the press and among the world governments – during the initial phase. Physicists working on the projects are free to believe that having two supercolliders can only be a good thing because one will be able to validate the findings of the other. However, the world doesn't have enough money for both.

The CEPC is expected to cost over $5 billion and the FCC, $15 billion. Both China and CERN have said that their machines will be built with international collaboration, with multiple participating countries supplying the people, the technology and, crucially, the money. And no country in the world is going to want to cough up the moolah for two identical machines to be built at the same time. The counter-argument is simple: the Large Hadron Collider is doing just fine as the only one of its kind.

Now, which machine are you willing to bet will get built? It's not easy to decide.

CERN already has a working international collaboration and doesn't have to forge one anew. But the flip side of this is that it could be more bureaucratic at the outset, with the organisation having to clear multiple checks before it can begin construction.

On the other hand, if China isn't able to build a collaboration that could help fund the project, the CEPC will face all the more resistance than it currently does. Building a supercollider by yourself is a colossal undertaking for any country. But that said, if anyone can do it, it has to be China – we all know this. And if the government sets its mind to it, it won't even have to deal with the same amount of paperwork that CERN already faces.

In fact, further complications could arise depending on who builds a supercollider first. For example, if China gets a suitable head-start and builds the CEPC half a decade before the FCC, say, then funders of the European project may not be so keen to continue investing.

The only way to break this gridlock would be for one machine to offer something that the other can't. To my mind, CERN seems better placed to make this happen than its Chinese counterpart, the Institute of High-Energy Physics (IHEP) in Beijing. The European lab already has an array of accelerators and detectors studying different aspects of nuclear physics.

With a little more effort and money, the FCC can be integrated into a larger suite of experiments that can conduct experiments of wider scope. But even then, the possibility of the Chinese going it alone doesn't seem to go away. We're already seeing this happen in spaceflight.

I personally believe a CERN machine will be more useful for two reasons: access and diversity. CERN already has mechanisms in place to ensure scientists from developing nations don't find it harder to access its experiments. It has also undertaken to make papers published based on its findings freely accessible online.

Its workforce is more diverse thanks to its large, functional collaboration, and has demonstrated its commitment to protecting the rights of all those working there. In fact, it looks like CERN has already started advertising this via YouTube.

It will be harder to implement similar, if not the same, policies in China, with its closed-off nature and its problematic human rights record.

Update (1:30 pm, same day): A Vox explainer based on the opinions of a few scientists, including Sean Carroll and Sabine Hossenfelder, presents a few interesting perspectives:

  • As I mentioned before, CERN has to get a lot more greenlights on board before it can proceed than China does – that also means opening itself up to opposition from more quarters
  • The cost is proving to be a significant roadblock for both CERN and IHEP, but if at any time China believes itself ready to go it alone, then it will be able to – unlike CERN, and the CEPC will get built instead of the FCC
  • China could just build the supercollider while CERN uses its money to fund smaller science experiments; but the other way round may not work, if Carroll's caution is to be believed: that if governments don't have to give $5/15 billion to one physics experiment, they will "never" give it to other physicists for different experiments
  • CERN, according to Hossenfelder, has been overselling what the FCC will be able to actually achieve (more here)

In light of all this information, I think I would be inclined to bet on the CEPC. However, it still unclear whether it is a good idea to advertise the FCC or the CEPC in terms of potential spinoff technologies:

  1. They are unpredictable
  2. If you're going to throw $5/15 billion at a large group of scientists working on a bunch of experiments on a common subject over three decades, of course something is going to come of it; the question is whether that would be enough
  3. The idea that governments will not bite if "potential spinoffs" aren't in the offing should merit a reexamination of why we 'do' science, and whether spending more on an abstract physics experiment is likely to drive the wedge between science and society further down

As a human being, I believe that 'knowing' is the highest aspiration of all, and that we must fund science projects simply because they help us know things about the world, and the universe. The question is how much and when, and given the constraints described above, it shouldn't be hard to find a solution that everyone can agree with.

Featured image: LHC undergoing upgrades. Credit: CERN.