With this, the Large Hadron Collider (LHC) has demonstrated that arguments used by particle physicists for the existence of new particles beyond those in the standard model were wrong. With these arguments now falsified, there is no reason to think that a next larger particle collider will do anything besides measuring the parameters of the standard model to higher precision. And with the cost of a next larger collider estimated at $20 billion or so, that’s a tough sell.
Particle physicists have meanwhile largely given up spinning stories about discovering dark matter or recreating the origin of the universe, because it is clear to everyone now that this is marketing one cannot trust. Instead, they have a new tactic which works like this.
First, they will refuse to admit anything went wrong in the past. They predicted all these particles, none of which was seen, but now they won’t mention it. They hyped the LHC for two decades, but now they act like it didn’t happen. The people who previously made wrong predictions cannot be bothered to comment. Except for those like Gordon Kane and Howard Baer, who simply make new predictions and hope you have forgotten they ever said anything else.
Second, in case they cannot get away with outright denial, they will try to convince you it is somehow interesting they were wrong. Indeed, it is interesting – if you are a sociologist. A sociologist would be thrilled to see such an amazing example of groupthink, leading a community of thousands of intelligent people to believe that relying on beauty is a good method to make predictions. But as far as physics is concerned, there’s nothing to learn here, except that beauty isn’t a scientific criterion, which is hardly a groundbreaking insight.
Third, they will sure as hell not touch the question whether there might be better ways to invest the money, because that can only work to their disadvantage. So they will tell you vague tales about the need to explore nature, but not ever discuss whether other methods to explore nature would advance science more.
But fact is, building a large particle collider presently has a high cost for little expected benefit. This money would be better invested into less costly experiments with higher discovery potential, such as astrophysical searches for dark matter (I am not talking about direct detection experiments), table-top searches for quantum gravity, 21cm astronomy, gravitational wave interferometers, high-precision but low-energy measurements, just to mention a few.
And that is only considering the foundations of physics, leaving aside the overarching question of societal benefit. $20 billion that go into a particle collider are $20 billion that do not go into nuclear fusion, drug development, climate science, or data infrastructure, all of which can be reasonably expected to have a larger return on investment. At the very least it is a question one should discuss.
Add to this that the cost for a larger particle collider could dramatically go down in the next 20-30 years with future technological advances, such as wake-field acceleration or high-temperature superconductors. In the current situation, with colliders so extremely costly, it makes economically more sense to wait if one of these technologies reaches maturity. Who wants to spend some billions digging a 100km tunnel when that tunnel may no longer be necessary by the time the collider could be be in operation?
Anyone who talks about building a larger particle collider, but who does not mention the above named issues demonstrates that they neither care about progress in physics nor about social responsibility. They do not want to have a sincere discussion. Instead, they are presenting a one-sided view. They are merely lobbying.
If you encounter any such person, I recommend you ask them the following: Why were all these predictions wrong and what have particle physicists learned from it? Why is a larger particle collider a good way to invest such large amounts of money in the foundations of physics now? What is the benefit of such an investment for society?
And do not take as response arguments about benefiting collaborations, scientific infrastructure, or education, because such arguments can be made in favor of any large investment into science. Such generic arguments do not explain why a particle collider in particular is the thing to do. I have a handy list with responses to further nonsense arguments here.
A prediction. If you give particle physicists money for a next larger collider this is what will happen: This money will be used to hire more people who will tell you that particle physics is great. They will continue to invent new particles according to some new fad, and then claim they learned something when their expensive machine falsifies these inventions. In 40 years, we will still not know what dark matter is made of or how to quantize gravity. We will still not have a working fusion reactor, will still not have quantum computers, and will still have group-think in science. Particle physicists will then begin to argue they need a larger collider. Rinse and repeat.
Of course it is possible that a larger collider will find something new. The only way to find out with certainty is to build it and look. But the same “Just Look” argument can be made about any experiment that explores new frontiers. Point is: Particle physicists have so far failed to come up with any reason why going to higher energies is currently a promising route forward. The conservative expectation therefore is that the next larger collider would be much like the LHC, but for twice the price and without the Higgs.
Particle physics is a large and very influential community. Do not fall for their advertisements. Ask the hard questions.