The "Nightmare Scenario" For Fundamental Physics
During the 20th century the search for a theory of how the physical world works at its most fundamental level went from one success to another. The earliest years of the century saw revolutionary new ideas including Einstein's special relativity and the beginnings of quantum theory, while the decades that followed each were times of surprising new insights. By the mid-1970s all the elements of what is now called the Standard Model were in place, and the final decades of the century were ones dominated by endless experimental results confirming this theory's predictions. By the end of the millennium, we were left in an uncomfortable state: the Standard Model was not fully satisfactory, leaving various important questions unanswered, but no experimental results disagreeing with it. Physicists had little to nothing in the way of hints as to how to proceed.
The LHC was supposed to be the answer to this problem. It could produce Higgs particles, allowing study of a crucial and less than satisfactory part of the Standard Model that had never been tested. A raft of heavily promoted speculative and unconvincing schemes for "Beyond Standard Model" physics all promised exciting new phenomena to be found at LHC-accessible energies.
Results from the LHC have now started to come in, and these are carrying disturbing implications. Unsurprisingly, none of the promised "Beyond Standard Model" particles have put in an appearance. More worrisome though is the big LHC success: the discovery of the Higgs. Within the still large experimental uncertainties, now that we've finally seen Higgs particles they look all too much as if they're behaving just the way the Standard Model predicted they would. What physicists are facing now is a possibility that they always knew was there, but couldn't believe would really come to pass: the "Nightmare Scenario" of the LHC finding a Standard Model Higgs and nothing more.
For the experimentalists, this leaves the way forward unclear. The case for the LHC was obvious: the technology was available, and the Higgs or something else had to be there for it to discover. Going to higher energies though is extremely difficult, and there's now no good reason to expect to find anything especially new. A lower energy "Higgs Factory" special purpose machine designed for detailed study of the Higgs may be the best bet. In the longer term, technological breakthroughs may be needed to allow studies of physics at higher energies at affordable cost.
Theorists in principle are immune to the constraints imposed by technology, but they face the challenge of dealing with the unprecedented collapse of decades of speculative work, and no help from the experiment on the question of where to turn to for new ideas. The sociological structure of the field is ill-equipped to handle this situation. Already we have seen a turn away from confronting difficult problems and towards promoting fatalistic arguments that nothing can be done. Arguments are being made that because of random fluctuations, we live in a corner of a "multiverse" of possibilities, with no hope of ever answering some basic questions about why things are the way they are.
These worries are in some sense just those of a narrow group of scientists, but I think they may have much wider implications. After centuries of great progress, moving towards ever deeper understanding of the universe we live in, we may be entering a new kind of era. Will intellectual progress become just a memory, with an important aspect of human civilization increasingly characterized by an unfamiliar and disturbing stasis? This unfortunately seems to becoming something worth worrying about.
