Beliefs and proofs in particle physics March 21, 2007Posted by dorigo in italian blogs, personal, physics, science.
Today Jeff posted a reply to a long thread originated by my post on the new Tevatron average of the top quark mass , and I think he makes a few interesting points, which can be appreciated without reading all the thread.
It all started with my comment “whether or not we are able to detect a particle with our technology does not affect its existence.”… Jeff replied that “A modern scientific theory has an obligation to furnish observables. We are obliged to detect the particle, at least produce a very tight set of quantitative observations that point to it. Otherwise an outsider would say “these physicists are no better than those that believe in supernatural ectoplasms”.”
And then he left an analysis of the issue:
Tommaso. Avoid bad philosophy and bad relations with outsiders. Bad philosophy can and IS used as an excuse by hostile outsiders to argue the emptiness and hence uselessness of the scientific enterprise.
Regards evidence and existence [of the Higgs boson – TD] you guys can do better than that! Maybe most of you are too young and haven’t read enough history or have forgot it. How about the neutrino! Far more paradigmatic than the recent top quark. From the mid 30s to mid 50s, the neutrino seemed to elude direct detection, BUT it was leaving finger prints everywhere! The neutrino was an essential ingredient to allow physicist to make sense of weak interactions. It allowed them to be quantitative and scientifically creative: data could be accounted for and new ideas and experiments could be conceived to mount further evidence that the theory was on the right track. Ultimately these further experiments pointed to further subtle and deeper problems.
Consilience: a network of loose evidence collectively furnishes a tight argument. Single experiments are not water tight proofs for any theory; it is the network of experiments and accounted phenomena that make modern science. It is “detection of existence” in the broad sense of the word. Most physicists were convinced of the existence of the neutrino before the “direct” Reines and Cowan 1956 experiment. The top quark was a replay. After the discovery of the bottom quark the evidence for the top mounted in a anticlimatic crescendo. Is the Higgs story another example? A replay of a story alread told. Do you really think it is?
I have left HEP for some years now so I am not updated (was I ever? No, just cog in a big machine.). I personally believe that physicist formulate effective theories – the Fermi point theory of weak interactions with neutrinos was the first modern example. I mentioned above consilience. Let me add that quantitative and profound qualitative changes may occur: a theory evolves to become signicantly more solid and profound when new unexpected phenomena become available as when energy thresholds are crossed. Higher energies required the Fermi effective theory be transformed to incorporate the heavy W and Z bosons and the theoretical and experimental work eventually led to the Standard Model.
In the past 100 years energy thresholds have uncovered surprises: existence of nucleus, of nucleons and nuclear structure, of nucleon substructure (partons and quarks), heavy intermediate bosons, jets, gluons, etc… To my knowledge NONE of these were predicted in any water tight way and when they were observed there was a great hustle of theory building and killing. I do find it remarkable that a consistent Standard Model emerged. It truely is a magnificent showpiece of how modern science works and it should be taught to outsiders emphasizing the hard work, the wrong turns, the great insights, the good and the bad philosophy, hoping to learn from mistakes, the predictables (hard work) and the unpredictables (the unexpected discoveries), but absolutely leaving out the the “gee-whiz”. That can sound like hocus-pocus to hostile outsiders.
From this point of view the real risk of accelerator physics is that the energy thresholds for uncovering new and welcomed unexpected phenomena are out of reach. But that is not to argue that the LHC should not have been built. There is no gain without pain. There is no thrill with a risk. There is the possibility that the Higgs might not make a show. Now that would be a discovery!!! Astrophysics and ultimately cosmology are probably the best realms for finding unaccountable and new phenomena.
I can only say I agree with most of what he said, and that I have always thought that the absence of the Higgs would indeed be a great discovery.