Promises, Predictions and Progress in Particle Physics

April 19, 2019 Leave a comment

PROPOSITION: “Particle physicists have promised us many new discoveries in the last forty years, including at CERN’s Large Hadron Collider, and all of their predictions were wrong, and so there has been zero progress in particle physics all this time.”


1. NO PROMISES. There are thousands of particle physicists around the globe. I know of only a few who “promised” anything at the LHC. (Declarations of “shoulds” and bets by a few others are not dispositive — e.g., I bet on Germany winning the World Cup but I certainly didn’t think it was guaranteed to happen, or was even above 50-50 chance.)

2. MEANING OF PREDICTION. What is even meant by “prediction” in the proposition above? If it means “If I do A [run experiment] then B [exotic new phenomena] might happen” then the proposition above is manifestly wrong for the simple fact that if B does not happen the “prediction” cannot be wrong since it anticipated that possibility. If “prediction” instead means the stronger version “If I do A [e.g., LHC] then B [e.g., slepton] is guaranteed” the proposition has a chance of being correct, although it now has a burden that it cannot bear (see 3).

3. NO WRONG PREDICTIONS. Thus, given 2, I am not aware of a single “wrong prediction” in the sense of a stated guarantee by anyone in the entire field of particle physics except for maybe the few physicists in comment 1.  In other words, the vast, vast, overwhelming majority of physicists made no wrong predictions whatsoever. Furthermore, stating what is possible is not making predictions and it is not only good science but also responsible public relations, and that’s what more or less everyone has been and is doing. The proposition certainly fails by this account. But there is more to quibble with the proposition.

4. PHYSICISTS ARE TENTATIVE, BUT THEORIES ARE DOGMATIC TYRANTS. And even then, physicists don’t really ever predict in the way outsiders think. For example, a beyond the Standard Model theorist’s primary goal is to identify empirically adequate theories (i.e., consistent with all known experiment to date) that solve outstanding problems (dark matter, baryogenesis, experimental anomalies, proton stability, etc.) or explain more (unification, flavor hierarchies, scale hierarchies, etc.) and then analyzes the theories to see what possible new signals these empirically adequate theories could make at future facilities. For example, the Standard Model theory, not physicists, guaranteed a top quark. This distinction is important to recognize because the vast majority of physicists are tentative in their beliefs regarding forefront theories and their prospects for confirmation, but forefront theories are dogmatic tyrants regarding their predictions and never contemplate themselves as maybe being untrue. Now who is narrow-minded enough to totally dismiss any reasonable empirically adequate theory and ignore its possible implications for future experiment and try to bully others into not daring to speak of such possibilities? I hope no one.

5. FOREFRONT SCIENCE IS PSYCHOLOGICALLY TOUGH. Very rarely if ever are there guarantees for a particular facility. The Standard Model required the top quark but many colliders were built and didn’t find it, and then another collider was built and didn’t find it, etc., until Tevatron found it in 1995. Same goes for the Higgs boson. Finally LHC found the Higgs boson in 2012 after a multi-decade search spanning many colliders. No individual collider was guaranteed anything except the possibility it was within its range. That is typical, not atypical. It’s psychologically hard, and many can’t take it, but that’s the way it’s always been in truly forefront science. Look at your science textbooks. Dramatic, easy-to-understand discoveries are usually decades apart, but they rarely talk about the smaller victories and the sobbing, crying, and frustrated scientists in between that keep progress going.

6. SIGNIFICANT THEORY AND EXPT PROGRESS. Theory progress can be indexed partially by analysis and creative additions to the repertoire of many new empirically adequate theories that solve problems and explain more, which also have phenomenological implications for future experiment. Experimental progress can be indexed partially by how many of these theories face exclusions, confirmations, falsifications, etc. Tremendous progress on both fronts has taken place in the last four decades, along with important discoveries of neutrinos masses and mixings, top quark and Higgs boson. We know dramatically more about what could be the underlying laws of nature and what surely is not the underlying laws of nature now than we possibly ever could have guessed four decades ago, mainly due to vigorous theory work and vigorous experiment work ranging from high energy colliders to cosmological probes.

Screen shot of first page of Tristan’s doomed-but-couldn’t-know-it search for the top quark in the 1980’s.


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