Steven Weinberg has a new article in The New York Review of Books on The Crisis of Big Science, which is based on a talk he gave this past January at the American Astronomical Society meeting in Austin (for some discussion of this, see here and here).
Weinberg is rather gloomy about prospects for particle physics, seeing dim prospects for a new generation of particle accelerators, especially in the US. He goes over the sorry story of the SSC, which he was deeply involved in, and worries that the same thing is happening to the James Webb Space Telescope project. He argues that progress is particle physics will be difficult without going to higher energies:
The discovery of the Higgs boson would be a gratifying verification of present theory, but it will not point the way to a more comprehensive future theory. We can hope, as was the case with the Bevatron, that the most exciting thing to be discovered at the LHC will be something quite unexpected. Whatever it is, it’s hard to see how it could take us all the way to a final theory, including gravitation. So in the next decade, physicists are probably going to ask their governments for support for whatever new and more powerful accelerator we then think will be needed…
That is going to be a very hard sell. My pessimism comes partly from my experience in the 1980s and 1990s in trying to get funding for another large accelerator….
During the debate over the SSC, I was on the Larry King radio show with a congressman who opposed it. He said that he wasn’t against spending on science, but that we had to set priorities. I explained that the SSC was going to help us learn the laws of nature, and I asked if that didn’t deserve a high priority. I remember every word of his answer. It was “No.”…
All these problems will emerge again when physicists go to their governments for the next accelerator beyond the LHC. But it will be worse, because the next accelerator will probably have to be an international collaboration. We saw recently how a project to build a laboratory for the development of controlled thermonuclear power, ITER, was nearly killed by the competition between France and Japan to be the laboratory’s site.
There are things that can be done in fundamental physics without building a new generation of accelerators. We will go on looking for rare processes, like an extremely slow conjectured radioactive decay of protons. There is much to do in studying the properties of neutrinos. We get some useful information from astronomers. But I do not believe that we can make significant progress without also pushing back the frontier of high energy. So in the next decade we may see the search for the laws of nature slow to a halt, not to be resumed again in our lifetimes.
He has similar worries about cosmology:
But cosmology is in danger of becoming stuck, in much the same sense as elementary particle physics has been stuck for decades. The discovery in 1998 that the expansion of the universe is now accelerating can be accommodated in various theories, but we don’t have observations that would point to the right theory. The observations of microwave radiation left over from the early universe have confirmed the general idea of an early era of inflation, but do not give detailed information about the physical processes involved in the expansion. New satellite observatories will be needed, but will they be funded?
I’m not well-informed about what is going on with large projects in astronomy like the JWST, but do see news reports about cancellation or possible cancellation of important and valuable instruments which people have been working on for years. It’s likely Weinberg’s arguments are highly relevant in these cases. About particle physics though, I fear he neglects to mention the underlying scientific and technological difficulties of going to higher energies. A major reason why things look gloomy for another generation of colliders is that it’s not clear what to build. Electron-positron colliders like ILC/CLIC would be very expensive, and not necessarily get to energy levels above those reached by the LHC. They would be excellent tools for studying TeV-scale physics, but if the LHC has shown there’s no new physics there, the case for building them will be hard to make. Probably the best bet for going to higher energy is the HE-LHC, an LHC upgraded with higher field magnets. The technological limits on such magnets though will make it hard to go to dramatically higher energies. If no new physics besides the Higgs shows up at the LHC, there won’t be a good reason to expect it at HE-LHC energies. The case for the LHC was a slam-dunk, because we knew that the Higgs or something doing the same job had to be accessible at LHC energies. What there will be for an HE-LHC to study is less clear.
An HE-LHC would of course be built in Europe, so prospects for a new collider in the US are very dim indeed. Weinberg attributes the problem to a failure of the US to support scientific research, and the public good in general (please, take discussion of his political arguments elsewhere, I’m sick of this already, and November is a long ways away…). About support for science I think he’s a bit disingenuous though, arguing:
Funding is a problem for all fields of science. In the past decade, the National Science Foundation has seen the fraction of grant proposals that it can fund drop from 33 percent to 23 percent.
without noting that the NSF has seen sizable budget increases over the past decade. The fact that the number of Ph.Ds in the subject is increasing much faster than funding for them to do research is another problem…