Planning and Executing Credible Experiments. Robert J. Moffat

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СКАЧАТЬ (RH) first experimental mentor in aerodynamics was W.S. Saric. He told me the advantage our area had over other physics fields: in thermo‐fluid physics, researchers shared their techniques. His reasoning: since Ludwig Prandtl, an early pioneer in fluids, had not won a Nobel Prize, no one in our area of classical physics would expect to win. Classic thermo‐fluid physics was crucial to so many areas of science. The camaraderie of joint effort was inviting.

      Essentially every Nobel Prize in Chemistry recognizes experimental work. Likewise, essentially every Nobel Prize in Physiology or Medicine recognizes experimental tests. How about for Physics Nobel Prizes? An accounting (Quantum Coffee 2014) of the Nobel Prizes in Physics up to 2014 divided as such: theory, 30.75 prizes (28.7%); experiment, 76.25 prizes (71.3%). Nobel Prizes in Physics for technical innovations (reckoned as experiment) were 22.2%, almost as much as theory.

      The Higgs mechanism, theoretically predicted in 1962, eventually culminated in the announcement of the experimental discovery of the Higgs boson in 2012 at the Large Hadron Collider (LHC). The LHC employs thousands of scientists and engineers. F. Englert and P.W. Higgs received the 2013 Nobel Prize in Physics for their theoretical work. The Higgs Nobel Prize was a rare instance where theory preceded experiment. Einstein, like most theorists to win, won the prize for explaining an experiment.

      Einstein's Theory Always Invites Tests

      Einstein's theory of relativity is arguably of the most precisely tested theory in science, with experimental agreement to better than the 12th decimal place. The measurements allowing such fine precision and accuracy involved a binary pulsar (Antoniadis et al. 2013). Although it is so well tested, several times a decade we read about an experiment claiming to violate or refute Einstein's theory. The experimental results which appear to refute are expertly considered and critiqued. Invariably a flaw in technique or instrumentation is discovered, further confirming Einstein's theory rather than refuting it. Confidence in Einstein's theory increases with each test. In 2018 a test beyond our galaxy was reported and confirmed.

      We trust Einstein's theory as far as it has been experimentally tested, not due to its popularity.

      Observations of a Popular Theoretical Physics Field

      In the early 1980s, String Theory became a popular physics field. Our particular interest for this text is twofold: (i) its fashionability invites comparison with Ioannidis corollaries 5 and 6; (ii) Ioannidis evaluated medical research based on falsifiable predictions, called “PPV,” as discussed in Panel 2.1.

      During the peak years of String Theory popularity, its math techniques flourished. It garnered the majority of physics funding; its proponents placed the majority of professorships. We avidly read about it.

      Since String Theory is one of several competing theories, and outside our specialty, we continue to watch with interest all sides in the dispute.

String Theory notably depended on multiple spatial dimensions. E.A. Abbott's book Flatland: A Romance of Many Dimensions had already introduced us to imagining extra spatial dimensions. E. Witten was a top advocate of String Theory. A principal concern, stated by advocates and critics alike, was that String Theory lacked predictions that could be tested experimentally.

      Beginning in 2006, the warnings in Ioannidis corollaries 5 and 6 compared with String Theory. Theoretical physicist L. Smolin raised an alert in his book The Trouble with Physics: The Rise of String Theory, the Fall of a Science and What Comes Next (2006). Noting that physics was rich in alternative “promising new directions,” Smolin wrote to promote other areas of theoretical and experimental physics. Others noticed as well. P. Woit wrote his critique Not Even Wrong: The Failure of String Theory and the Continuing Challenge to Unify the Laws of Physics (2006).

Roger Penrose⁶ took on three popular areas of physics, expressing similar concerns. Penrose's recent book (2016) is Fashion, Faith, and Fantasy in the New Physics of the Universe. The chapter entitled “Fashion” covers String Theory, adding his perspective. The chapter covering quantum mechanics is entitled “Faith.” Techniques of quantum electrodynamics show success, the evidence being experimental validation to accuracies rivaling relativity. Penrose added an experimental test of macro‐quantum superposition. The chapter entitled “Fantasy” deals with cosmologies beyond the big bang. Penrose highlighted “The Phenomenal Precision in the Big Bang”; of particular interest to us in thermo‐fluids was the necessarily low entropy.

      Regardless of a theory's popularity, political or otherwise, we urge experimental tests.

      Sometimes an experiment planned for another purpose provides the answer. A prime example was the search for residual thermal evidence of the big bang. While a Princeton physics group was proposing to test the theory, a couple of astronomers at AT&T Bell Labs, Arno Penzias and Robert Wilson, were trying to eliminate noise which was contaminating the signal in their antenna. They even removed pigeon and bat residue. Failing to eliminate the noise, they spoke with Princeton professor Robert Dicke. They published “A Measurement of Excess Antenna Temperature at 4080 Mc/s” in the Astrophysical Journal (Penzias and Wilson 1965). In 1978, Penzias and Wilson won the Nobel Prize.

      Another Invitation from Feynman

      Richard Feynman was an experimentalist as well as a theoretician. CalTech once assigned him to teach introductory physics. His notes are immortalized in The Feynman Lectures on Physics, Volumes 1–3 (1963). He remarked about fluid physics in volume 1, chapter 3 of his lectures:

      There is a physical problem that is common to many fields, that is very old, and that has not been solved. It is not the problem of finding new fundamental particles, but something left over from a long time ago – over a hundred years. Nobody in physics has really been able to analyze it mathematically satisfactorily in spite of its importance to the sister sciences. It is the analysis of circulating or turbulent fluids.

      In volume 2, Feynman went into more depth in chapter 41 entitled “The Flow of Wet Water.”

In a personal letter, Feynman admitted “The theory of turbulence (I have spent several years on it without success).” Turbulence was an area of classical physics beyond even Feynman's ability to solve. To this day, basic turbulence remains unsolved. As an added incentive, one of the seven Millennial Problems awaits solution of the Navier–Stokes equations which govern fluid flows.

      Consider Feynman's challenge as an invitation to thermo‐fluids, experimental or theoretical. It is the most challenging area of classical physics. Turbulence becomes further complicated by heat transfer; yet more complicated by mass transfer; yet more by chemical reactions or combustion; yet more complicated by electromagnetic interactions. It is important for flight, for weather, for breath and blood, for life, for engines, for circulation within celestial stars. Flows of liquids, gases, and plasmas are found at the microscopic scale within living cells to the astronomic scales between galaxies.

      One of our colleagues, Professor Adrian Bejan, overlaps with us in the same field and the same publisher. Bejan's Constructal Theory has brought a fresh theoretical approach to thermo‐fluid systems, to urban planning, and to appreciating design in living creatures as well as other fields.

      Extra Invitations to Experiments

      At the time of the first edition, two popular TV shows featured experimental scientists. NCIS featured СКАЧАТЬ