"New data from old poop"

Don't you want to learn about changes to our microbiome over time, by examining paleofeces?  You do.  See the commentary by Andrew Curry from earlier this year.

Scientist biography series

Somewhat related to the theme of recent posts (here and here), let's look at a couple of scientific biography series from the two gigantic British academic presses, Cambridge and Oxford.  

Cambridge University Press has a Cambridge Science Biographies series.  At the time of writing, there are ten volumes listed in print on the website.  These are serious biographies running into the hundreds of pages.  There are three devoted to physicists:  Galileo, Newton, and Ampere.  There are three for chemists:  Lavoisier, Humphry Davy, and Justus von Liebig.  There are two for biologists:  Charles Darwin and Thomas Huxley.  Rounding out the set are Henry More and Mary Somerville.  I've always understood that Somerville was a mathematician, but the table of contents indicated she worked in physical and Earth sciences as well.  Henry More was a name unfamiliar to me.  Apparently he is primarily viewed as a philosopher, but he pursued experimental science as well, and was an influence on Newton.  Since these are substantial biographies, I would imagine no attempt is made to cover all the major figures in science.  Otherwise the choice of Ampere over Einstein would be most curious!

Oxford Portraits in Science are shorter biographies intended for young adult readers.  At the time of writing I see 17 volumes in print.  However, I own copies of the volumes on Faraday and Einstein, and they list additional volumes that may be out of print.  I will  include them here and group them collectively as follows:

Biologists & physiologists:  Charles Darwin, Gregor Mendel, William Harvey, Edward Jenner, Louis Pasteur, Crick & Watson (a single volume covering both).

Chemists: Marie Curie, Linus Pauling.

Physicists & astronomers:  Copernicus, Kepler, Galileo, Newton, Ben Franklin, Faraday, Joseph Henry, Curie, Rutherford, Fermi, Einstein

Inventors and technologists:  Alexander Graham Bell, Charles Babbage, Thomas A. Edison.

Behavioral scientists:  Pavlov, Freud.

Anthropologists:  Margaret Mead.

Paleontologists:  Othniel Charles March & Edward Drinker Cope (a single volume covering both).

In the above accounting, I've included the Curie volume under both physics and chemistry; it could be argued that Rutherford should also be so counted.

Here, we might have a greater expectation than with the Cambridge Science Biographies, that the most important, or at least most interesting, scientists be included.  However, none of the chemists in the Cambridge series appear in the Oxford series.  The selection of biologists/physiologists is an excellent one, but could certainly be expanded further.  Again I will focus mainly on the physicists/astronomers.   The Oxford series has an excellent list - all of them are deserving.  As I've stated before, volumes on Tesla and Feynman would probably sell as well, if only they existed.  The inclusion of Franklin and Henry, American contributors to electromagnetic science, raises the question of why non-Americans in this field have not been included (such as Ampere, Oersted, and above all Maxwell).  Again it seems to me that Niels Bohr might deserve a volume.  

Finally, as a dessert for this discussion, what about Princeton University Press's "The Quotable..." series?  These are books of quotations by various authors.  Three scientists are included:  Darwin, Einstein, and Feynman.  Maybe you might consider Jung as a behavioral scientist.  Others in the series include Niccolo Machiavelli, Thomas Jefferson, Henry David Thoreau, and Soren Kierkegaard.  I suppose this is the most subjective of all, since the person in question has to be very "quotable"!

Peer Review

Last week in the online magazine Physics, psychologist Simine Vizire published a call for peer review reform.  Hers is not the first, nor will it be the last.  My personal experience with peer review is mixed and I would support calls for reform.  In discussions with other scientists, I have heard appalling examples of abuse, such as the stealing of authors' work and credit by anonymous reviewers.

All the manuscripts I have submitted for peer review have benefitted from the process.  The published manuscripts are usually improved as a result of the vetting, and in most cases I prefer the published version over the initially submitted draft.  However, in two cases the published version is also shorter or more condensed than I would have preferred, and 19 and 12 years later, respectively, I'm still sore about that.  In one case, the peer review process extended for over a year, in my opinion needlessly, due to a single obstinate reviewer who added absolutely no value to the process.  In another case I eventually published a manuscript in unrefereed form (in a conference proceedings) because the journal rejected it for being "too simple".  (The talk corresponding to that paper won an award at the conference where I presented it!)  I have since pulled the same trick for a second paper, also rejected, though it gets lots of reads where I posted it (academia.edu).  I strongly believe that the taste of referees and editors does not necessarily correspond with that of readers.

As a referee, I also feel that I strongly improved every manuscript I have refereed.  However, I have seen other published research that should have been better vetted.  I have taken to posting critiques of such papers on PubPeer, a website for open, post-publication "peer review".  In my view, tools like PubPeer should be better integrated into the research culture.  Upon reading a paper that you think you may want to use, one of your first instincts should be to look it up in PubPeer.  And scientists should not hesitate to post their criticisms or discussion of published work on PubPeer.

Vazire makes some pertinent points.  We don't understand the performance of peer review because there is essentially no empirical research done on this (with the exception, she says, of medical journals) - a hypocrisy considering scientists pride themselves on being "evidence based".  She calls for giving peer review researchers access to now-confidential materials, the raw material of peer review, so as to better study the process.  (It would be a brave editor who agrees to such sharing!)

Other issues she complains about (status bias and bias due to the gender, institution, or ethnicity of authors) could be addressed by double blind peer review, a process I have participated in myself.  She calls for more diversity in recruiting referees, though the flip side of this is placing additional (unpaid) labor burden on minorities, who already bear an additional burden at their institutions in many cases.  I agree with her that mechanisms to hold editors accountable for their own abuses are nowhere near sufficient.  

I support Vazire's recommendation of disclosure of referee reports and decision letters; but such documents are taken out of context without the corresponding draft versions of manuscripts.  Thus the use of preprint servers and tools like GitHub could be used in conjunction with transparency of peer review.

Vazire also requests specialized review processes; statistical analysis is her example.  In principle this is a sound suggestion, but in practice I frankly believe statisticians might do both harm and good in this role.  Much of the damage to the research enterprise in the first place has been due to the influence of the statistical inferential framework, as I've written about previously.

Peer review is a broken process, but it should be reformed instead of discarded.  Statistical inference too is broken, but we've given statisticians a chance to reform it, to no avail.  Discarding it in most cases would be a step forward.

Scientists and Very Short Introductions

Continuing the parlor game from my last post, let's look at Oxford University Press's Very Short Introductions series, or VSIs, as well as its predecessor, the Past Masters series.  In contrast to the multi-authored Cambridge Companions, the VSIs are short, pocket-sized introductions to subjects (including famous individuals) by typically a single author.  However, like the Oxford Handbooks, the VSIs have respectable coverage of science topics, something the Cambridge Companions generally lack.  Again, the usual suspects (Descartes, Pascal, Leibniz, Bertrand Russell) all have volumes dedicated to them - they all did work in mathematics or physics, though that work is not what secured them their places in this series.  (Pascal's was a Past Masters that did not get transferred to the VSIs.)  There are no VSIs for individuals who were primarily mathematicians.

Again, in biology only Darwin has a volume, and I see no chemists represented.  Among physicists, we have Copernicus, Galileo, Newton, Michael Faraday, and Niels Bohr.  Strangely there is no VSI for Einstein!  C'mon now!!  By the same token, Cambridge Companions needs to catch up and issue volumes for Copernicus, Faraday, and Bohr.  And any list of great physicists must include James Clerk Maxwell, though I do not know whether his influence on the humanities has been as great as the others mentioned here.  

Turning to economics, there are VSIs for Adam Smith, Thomas Malthus, Karl Marx, and Lord Keynes, but Hayek is missing.  (As Malthus is missing from the Cambridge Companions.)  Past Masters had a single volume covering Smith, Malthus, and Keynes, but like Pascal's, this one did not get transferred to the VSIs.

Scientists and the Cambridge Companions

Today we veer a little from our usual terrain.  The Cambridge Companions book series consists of anthologies of articles meant to introduce and provide context for major writers and thinkers, topics, and historical periods.  The subjects covered are primarily in the humanities.  The major areas listed include American Studies, Ancient Worlds, Culture, Classical Literature, Law, Linguistics, Literature and Drama, Management, Music, Philosophy, and Religion.  The list of subtopics is quite detailed, with Philosophy of Science being the only one remotely related to science, engineering, and medicine.  Yet, I've noticed a few scientists end up having volumes dedicated to them.  It is interesting to dwell on those scientists whose work has had ripple effects on the humanities.

First, to dispose of the obvious, what crops up under "Philosophy of Science"?  Four volumes, on the following subjects:  Einstein, Piaget, Darwin's Origin of Species, and Philosophy of Biology.  Not mentioned there is that there is also a Cambridge Companion to Darwin, now in its second edition, as well as volumes for Bacon and Carnap.  When you click on the subject "General Science", the volumes for Darwin and Newton (also in second edition) join Philosophy of Biology.   As far as I know, Darwin is the only biologist with a volume dedicated to him, and I can't think of a single chemist who has one.

Let's turn to mathematics.  Clicking on this subject yields two volumes, Einstein and Frege.  However, we know that others to whom volumes are dedicated have done important work in mathematics:  Descartes, Pascal, Leibniz, and Bertrand Russell, for instance.  It is safe to say their mathematical work is probably not the principle reason they have volumes dedicated to them, however.

Let's sidestep a little and consider economics.  Two volumes pop up when you click on that subject:  Keynes and Hayek.  However, we know that there are also volumes on Adam Smith and Karl Marx.  There are also volumes dedicated to other thinkers who wrote about economics, but who might not primarily be considered "economists", such as John Locke, David Hume, and John Stuart Mill.

What I mainly wanted to write about here though is physics.  There are 3 volumes dedicated to physicists:  Galileo, Newton, and Einstein.  Obviously, some of the individuals mentioned above (Descartes, Pascal) and others (Thomas Hobbes) with Companions of their own, did work in physics as well, but Galileo, Newton, and Einstein are the ones that can be considered primarily physicists.  It is true that these three are revolutionary figures in the history of physics, and that their work did ripple out and influence philosophy and culture more broadly.  Each of them also worked in multiple areas of physics.

So, this raises an amusing question:  what other physicists might deserve a Cambridge Companion?  One hint is a set of books, not formally part of a series, published by Oxford University Press with a very similar format.  Three 19th century British physicists have such volumes dedicated to them:  Maxwell, Kelvin, and Stokes.  They are certainly deserving and were pivotal figures in the history of physics; however it might be argued that their impact on the humanities has not been as large as Galileo, Newton, and Einstein.  (Two obvious missing physicists from that 19th-century British set include Michael Faraday and Lord Rayleigh.)  Perhaps Niels Bohr might come closer to a good candidate.  At the more popular culture level, Nikola Tesla and Richard Feynman are obvious candidates (and such volumes would probably sell well), and Steven Weinberg certainly wrote prolifically for a general audience.  I will have to say though, the selection of Galileo, Newton, and Einstein are the most obvious choices to start with, and thus the series chose wisely.

The same parlor game could be played for biology, chemistry, and mathematics.  I don't know the history of these fields well enough to suggest candidates.  However, in logic (a field that overlaps with philosophy) an obvious and deserving figure would be Kurt Godel.  In economics, perhaps Herbert Simon or James M. Buchanan might be considered.  Among the geosciences, perhaps Alfred Wegener (of continental drift) and Edward N. Lorenz (of the butterfly effect) might be considered.

Of course, with Philosophy of Biology in the series, one could easily add volumes on the other major scientific disciplines, though these are frequently well served by other publishers (like the much more expensive Oxford Handbooks series, which generally has wider coverage than the Cambridge Companions). 

A tribute to Academic Press' Mathematics in Science and Engineering series

Almost a year ago, I wrote about Academic Press' acclaimed International Geophysics book series, which published a total of 104 volumes, the last one in 2014.  Though many volumes remain in print, it is unclear if any new volumes are anticipated.

Today I'd like to pay tribute to another Academic Press book series, Mathematics in Science and Engineering.  Academic Press is now part of Elsevier, and the latter's website shows that this series, apparently launched in 1961, is still going strong, with the latest volume published earlier this year.  Volume 1 was titled Concepts from Tensor Analysis and Differential Geometry, by Tracy Y. Thomas.  Sixty years later, the series published Luigi Berselli's Three-Dimensional Navier-Stokes Equations for Turbulence.  The website seems to suggest that the last numbered volume was #213, published in 2010, and at least 7 volumes have been published since then.  The longevity of a 60-year old series is truly impressive.

Scanning the list of titles and authors, there are indeed some impressive contributions.  Remarkably, I only own one of these volumes, Morton Gurtin's An Introduction to Continuum Mechanics (1981), volume 158 of the series.

Partisan Science in America

Last Tuesday's edition of the Wall Street Journal featured an op-ed by Gary Saul Morson titled "Partisan Science in America".  Among the topics discussed are the origins of COVID-19, Dr. Fauci's pronouncements about masks and "attacks...on science", and climate change.  While DTLR does not take a position on the "lab leak" theory, which is discussed at the center of Morson's piece, in my view the rest of the article is on point.  Though Morson is a professor of Slavic languages and literature, according to Wikipedia he is a graduate of the Bronx High School of Science and had a youthful interest in physics.  Much of what he writes here is accurate, though sadly not well understood even by scientists themselves.

Here are some of the best lines of the piece:

If science is treated as a solid block, each part of which is as indubitable as all the others, then science has been misunderstood.  Science always contains some propositions less firmly grounded than others:  on the frontier, newly discovered, based on experiments not readily replicated.

and,

Some scientific statements prove false:  that's how science works.  Those who claim that to doubt any part of the consensus is to be "antiscience" or "a denier" are themselves being antiscientific.

and,

To doubt a scientist is not to doubt science.  Quite the contrary, personal authority is precisely what science dispenses with, as much as possible....To be sure, nonscientists often have to trust scientists to inform them what the science has discovered.  But that is all the more reason that scientists bear the responsibility of not letting political or other nonscientific criteria affect their explication.

and finally,

If scientists expect their statements to be trusted, they must themselves be trustworthy in making them.  One had better be scrupulously honest before asking people to surrender their own judgment and simply believe what they are told.  Scientists should be especially careful not to misrepresent political or policy judgments as being scientific.  And they must protest vigorously and loudly when other influential people claim to speak in the name of science while misrepresenting it.

I've heard multiple politicians say "I believe in science".  Anyone who makes such a statement has no understanding of the scientific process, as the first quote above alludes to.  This kind of talk pollutes our collective ability to think critically about science and science policy.  

 

That famous painting of Lavoisier

Any scientist who visits the Metropolitan Museum of Art in New York City is brought to a halt by Jacque-Louis David's portrait of Antoine and Marie-Anne Lavoisier.  Chemistryworld has a post by Philip Ball this month about the discovery of what had been originally painted (and covered up).  Antoine Lavoisier was arguably the most pivotal figure in the history of chemistry.  Ball speculates that the painting was altered due to worries about Lavoisier's portrayal in light of the forthcoming French Revolution.  If so, the alterations were not sufficient to save Lavoisier's life--he was executed during the Revolution--though his wife did survive.  Check out Philip Ball's account.

An update on supersymmetry and competitors to string theory

About 12 years ago, I read Lee Smolin's The Trouble with Physics:  The Rise of String Theory, the Fall of a Science, and What Comes Next (Houghton Mifflin, 2007).  Like a few other physicists, Smolin was not pleased with the lack of evidential basis for string and M-theory, and the desire of some physicists to abandon the need for such empirical support.  Part III of the book looks at alternatives to string theory.  Though I am a physicist, I am as good as a layperson in this particular arena, and Smolin's book gave me a nontechnical discussion of string theory's competitors.

At the time Smolin wrote, the Large Hadron Collider at CERN was still under construction.  Smolin predicted that the LHC would find the Higgs boson (it did) and that its biggest task would be to find evidence for supersymmetry.  Last month, The Economist featured an article that essentially gives an update on all this ("Bye, bye, little Susy", Aug. 28, 2021).  It's a refreshing look at the situation as it stands today.

First, hopes of finding evidence for supersymmetry ("SUSY") are slipping quickly.  While SUSY hasn't been ruled out entirely, evidence has been lacking so far.  Without SUSY, string theory is also near a dead end.  Meanwhile, experimental anomalies with the standard model are beginning to accumulate.  

The article describes a number of competing "theories of everything" to string theory.  In some, the very notions of space, time, and causality are emergent phenomena.  I find it exhilarating to read that statistical physics and information theory may play a fundamental role in the standard model's successor. When I audited an undergraduate thermal physics class while in grad school, the professor introduced the topic by saying that thermodynamics was more general than either mechanics or electromagnetism.  From the Economist article, perhaps thermodynamics may be more general than we ever had a right to expect!

Experimental physicists discovered the Top Quark not long after I began studying physics; the discovery of the Higgs boson and gravitational waves have been more recent experimental breakthroughs.  However I remember in grad school seeing the high energy theory professors publishing about SUSY.  Theoretical physics may have indeed been in a rut, as Smolin would have you believe, during much of my professional lifetime.  The competitors to string theory discussed in the Economist article may be the first steps to a renaissance of theoretical physics.  If so, theoretical physics might get exciting again!

A tribute to McGraw-Hill's fluid mechanics books

Let's wrap up the current round of book publisher tributes with this look at McGraw-Hill's books on fluid mechanics.  Like Wiley discussed in the last post, McGraw-Hill published two widely used introductory fluid mechanics texts, the venerable one by Victor L. Streeter and coauthors, which seems to now be finally retired, and the more recent one by Frank M. White, just out in its 9th edition.  I have neither book, but their authors are represented in the following photo.

Some McGraw-Hill fluid mechanics books.

Streeter's Handbook of Fluid Dynamics was part of the publisher's Handbook series, which was quite prolific in its day.  It was joined in the series by McGraw-Hill's more recent Fluid Flow Handbook, edited by Jamal Saleh (2002), now also out of print.  White's Viscous Fluid Flow (2d edition above; the 4th edition came out this year) was part of McGraw-Hill's Series in Mechanical Engineering, as were the 7th edition of Schlichting (shown above), John D. Anderson's Modern Compressible Flow, Frank S. Sherman's Viscous Flow, and J. O. Hinze's Turbulence.  Also seen above is Katz & Plotkin's Low-Speed Aerodynamics, part of McGraw-Hill's Series in Aeronautical and Aerospace Engineering, which itself was once edited by Anderson.  Evidently a number of books in that series were cross-listed with the Mechanical Engineering Series.

The Brodkey & Hershey text seen on the right in the photo is a representative of McGraw-Hill's Chemical Engineering Series.  It must have been a flagship for the publisher, as the pre-title pages explain its history dating back to 1925.  It brags that the series "stands as a unique historical record of the development of chemical engineering education and practice.  In the series one finds the milestones of the subject's evolution:  industrial chemistry, stoichiometry, unit operations and processes, thermodynamics, kinetics, and transfer operations."  A few books in the series are still available from the publisher today.

The three books on the right illustrate the handsome livery of these engineering series, though Brodkey & Hershey's is hidden by the dust jacket.

A tribute to Wiley's fluid mechanics books

Let's now consider the fluid mechanics books published by John Wiley & Sons.  They are particularly strong in the markets for widely used engineering textbooks.  For instance, they publish the successors to both the Fox & McDonald and Munson, Young, & Okiishi introductory fluid mechanics texts, each on their 9th editions at the time of writing.  They also publish multiple texts in heat & mass transfer, including the classic Bird, Stewart, and Lightfoot, pictured below.

Representative Wiley fluid mechanics books in my personal collection.

The Handbook of Fluid Dynamics and Fluid Machinery seen on the left was published in 1996.  It seems unlikely such a behemoth will ever be published again, by any publisher.  Gulf's Encyclopedia of Fluid Mechanics was published between the mid 1980s and mid 1990s, for a total of 13 volumes, probably setting the record for largest fluid mechanics reference work.  The most recent such reference work I know of is CRC Press's Handbook of Fluid Dynamics (2016), which appears in a single volume.

Ronald Panton's Incompressible Flow is a favorite upper-level textbook, now in its fourth edition.  The red and white livery of the second edition, seen above, reminds me of the similar livery of its Wiley sibling, Jackson's Classical Electrodynamics 2/e, which you can see in this earlier post.  Also seen above is Lex Smits' introductory textbook, and the first of Hunter Rouse's 2-volume series of hydraulics texts.

Wiley keeps in print two classic monographs on waves:  J. J. Stoker's 1957 Water Waves:  The Mathematical Theory with Applications (currently available as a Wiley Classics Edition, but also in a much less expensive Dover reprint), and G. B. Whitham's 1974 Linear and Nonlinear Waves, published as part of Pure and Applied Mathematics: A Wiley Series of Texts, Monographs and Tracts.  Similarly, Wiley has several key books on gas dynamics, including Zucrow & Hoffman's two volume Gas Dynamics (1976), and the more modern Zucker & Biblarz, Fundamentals of Gas Dynamics, now in its 3d edition (2019).  Marcello Lappa has published two monographs with Wiley:  Thermal Convection (2010) and Rotating Thermal Flows in Natural and Industrial Processes (2012).

A tribute to Springer's fluid mechanics books

We're on a roll!  Let's now consider the fluid mechanics books published by Springer-Verlag.  They are a prolific publisher with footprints in nearly every subfield of fluid mechanics.  Let's start with some classics.  Today Springer publishes the current editions of some iconic books that originated with other publishers.  Ludwig Prandtl's Essentials of Fluid Dynamics was first published in English in 1952 by Blackie & Sons in the UK and Hafner in the U.S.; its original German publisher in 1931 was Vieweg, I believe.  The current (3d) English translation of the 12th German edition is published by Springer in its Applied Mathematical Sciences series (vol. 158).  Incidentally, vol. 5 of the same series is another classic, Fluid Dynamics by Richard von Mises and Kurt O. Friederichs (1971).  Finally, Boundary-Layer Theory, edited by Hermann Schlichting, was first published in 1954 in German by G. Braun; its English translation was previously published in the McGraw-Hill Series in Mechanical Engineering.  However the current (9th) edition (co-edited by K. Gersten) is published by Springer.

Of course, the monumental Handbuch der Physik, edited by S. Flugge, was also published by Springer.  Volume VIII was on fluid mechanics, while Vol. III covered classical and nonlinear continuum mechanics.

Here are a few other Springer fluids books in my personal collection.

A sample of Springer-Verlag fluid mechanics books in my personal collection.

Stanisic's book appeared in Springer's Universitext series, while Brekhovskikh & Goncharov's is Vol. 1 of the Springer Series in Wave Phenomena.  Chorin & Marsden's classic text appears as Vol. 4 in the series Texts in Applied Mathematics.  Constantinescu's book appears in Springer's Mechanical Engineering Series, while Rieutord's appears in the series Graduate Texts in Physics.  Other classics include Langlois' Slow Viscous Flow, Daniel D. Joseph's two-volume Stability of Fluid Motions (which appeared in the now-defunct series, Springer Tracts in Natural Philosophy), and Swinney & Gollub's edited Topics in Applied Physics volume, Hydrodynamic Instabilities and the Transition to Turbulence.  Students of hydrodynamic instability will also note Chossat & Iooss' The Couette-Taylor Problem, and Schmid & Hennigson's Stability and Transition in Shear Flows, both of which appeared in the aforementioned Applied Mathematical Sciences series as vols. 102 and 142, respectively.  The current (4th) edition of Marcel Lesieur's Turbulence in Fluids appears in Springer's Fluid Mechanics and its Applications series.

A tribute to Oxford University Press's fluid mechanics books

Here I will continue my series of tributes to book publishers in fluid dynamics with a look at Oxford University Press.  Their books in this field have an impressive pedigree, beginning with the 1938 publication of the 2-volume Modern Developments in Fluid Dynamics:  An Account of Theory and Experiment Relating to Boundary Layers, Turbulent Motion and Wakes.  This cornerstone in the history of fluid mechanics was written by the Fluid Motion Panel of the U.K.'s Aeronautical Research Committee, later renamed the Aeronautical Research Council of Great Britain, and collaborators, and edited by Sydney Goldstein.  These books were reprinted in 1965 by Dover.  In 1951, the Council saw the need to amplify the original volumes, and added Modern Developments in Fluid Dynamics:  High Speed Flow (1953), also in two volumes, written by the Council's Fluid Motion Subcommittee, and collaborators, and edited by Leslie Howarth.  Oxford published all four of these volumes in its Oxford Engineering Science series (which is confusing to me, because they apparently had another, later series of the same name, which I wrote about previously).

Instead of continuing in the Oxford Engineering Science series, a new series was then planned by the British Aeronautical Research Council: The Fluid Motion Memoirs, also published by Oxford's Clarendon Press.  As far as I know, two volumes were published:  Incompressible Aerodynamics:  An Account of the Theory and Observation of the Steady Flow of Incompressible Fluid past Aerofoils, Wings, and other Bodies (1960), edited by Brian Thwaites, and Laminar Boundary Layers:  An Account of the Development, Structure and Stability of Laminar Boundary Layers in Incompressible Fluids, together with a description of the Associated Experimental Techniques, edited by Louis Rosenhead (1963).  A volume on turbulence was commissioned, but I'm not sure if it was ever published.  I also don't know if the Fluid Motion Memoirs continued beyond these volumes.

Meanwhile, in 1961, Subramanyan Chandrasekhar's Hydrodynamic and Hydromagnetic Stability appeared in Oxford's International Series of Monographs in Physics.  This book was a landmark in the literature of hydrodynamic instability, and remains in print by Dover.  

With the superb foundation established by the publication of the above, Oxford has continued to contribute to the literature in this field up to the present.  I already mentioned McComb's turbulence monograph in an earlier post.   Oxford has another book on the subject of turbulence by P. A Davidson (whom we also met my post about the Cambridge Texts in Applied Mathematics).  Here are some other Oxford fluid mechanics books in my personal collection.

Some fluid mechanics books published by Oxford University Press.

The introductory texts by Acheson and Lighthill are classics, as is the monograph by Tritton, all pictured above. Acheson's text appears in the Oxford Applied Mathematics and Computing Science Series.  Tritton's and Lighthill's books feature the livery of Oxford Science Publications, though Lighthill's is also included in the Institute of Mathematics and It Applications Monograph Series as its Volume 2.  The text by Bruus shown above belongs to the Oxford Master Series in Condensed Matter Physics.

A tribute to Cambridge University Press's fluid dynamics books

Extending the theme from the last post, let's examine Cambridge University Press's books in fluid mechanics.  I daresay that nowadays, they are the foremost publisher in this field.  In addition to the books discussed below, they publish the foremost journal in the business, the Journal of Fluid Mechanics.  

Of course, many of Cambridge's fluid mechanics books have appeared in the "red" series Cambridge Texts in Applied Mathematics, already discussed in the last post.  Let's begin this one with a snapshot of some of their non-series books in my personal collection.

Cambridge University Press fluid mechanics books in my collection.

The books by Batchelor, Lamb, and Drazin & Reid pictured above are acknowledged classics.  To that list I should add George Batchelor's The Theory of Homogeneous Turbulence (1953, second edition 1970), C. C. Lin's The Theory of Hydrodynamic Stability (1955), and Waves in Fluids (1978) by James Lighthill.  In the more contemporary era, the turbulence texts by Stephen B. Pope (Turbulent Flows) and Mathieu & Scott (An Introduction to Turbulent Flow) are notable, as is the 2004 A Gallery of Fluid Motion, which features a selection of award-winning photos from the APS Division of Fluid Dynamics' so-named annual competition.  Cambridge also has multiple books in transport phenomena and astrophysical fluid dynamics.

Of particular note is their series, Cambridge Monographs on Mechanics and Applied Mathematics, which began in 1952.  Many of the entries are now long out of print, though the series continues to be active today, with the next volume scheduled for publication next year.  I'm not sure how many total books have appeared in the series, but the "Applied Mathematics" part of the series' title has been dropped for some time.  Like the Cambridge Texts in Applied Mathematics "red series" discussed in the last post, the titles and authors in this series are notable; in fact many are shared with that series.  Both series range beyond just fluid mechanics, but I'll focus on fluid mechanics in this post.  Here are the volumes from that series in my personal collection.

Family portrait of the Cambridge Monographs in Mechanics and Applied Mathematics in my personal collection.

Like the "red series", these books have a uniform livery:  dark blue hardcovers, with green dust jackets; the paperbacks have green covers mimicking the hardbacks' dust jackets.  For this reason I refer to them as the "green series" in contrast to the "red series".  Aside from those pictured, other notable entries include Buoyancy Effects in Fluids, by J. S. Turner, The Structure of Turbulent Shear Flow, by A. A. Townsend, The Fluid Mechanics of Large Blood Vessels, by Tim Pedley, and Magnetoconvection, by N. O. Weiss and M. R. E. Proctor.  The Drazin & Reid monograph, Hydrodynamic Stability, shown in the first photo above, originally appeared in the "green series" as well; sadly its reprints do not feature the green livery of its siblings.

A tribute to Cambridge Texts in Applied Mathematics

Last December DTLR had a series of posts in tribute to the publishers of classic physics and atmospheric science books, and followed up in April with a post on the Oxford Engineering Science series.  Today I'd like to honor a famous series in applied mathematics, the Cambridge Texts in Applied Mathematics.  As far as I can tell, the series began in December 1987 with Maximum and Minimum Principles by M. J. Sewell.  By the time I began grad school in 1995, there were barely over ten volumes in the series.  I am delighted to see from the publisher's website that there are now nearly 60 volumes in the series, and it is still going strong, with the most recent entry issued earlier this year.  Nearly all of them remain in print, though in one case a superseded first edition is only available in electronic form (specifically, P. A. Davidson's An Introduction to Magnetohydrodynamics).  The familiar red livery of the series has been maintained with minimal changes since its beginning.  

The list of titles and authors is supremely impressive, and it would be an honor to be published in this series.  Here I'll only mention some of the contributors of more than one volume.  Philip G. Drazin was one prolific contributor, with texts on Solitons (with R. S. Johnson), Nonlinear Systems, and Introduction to Hydrodynamic Stability.  Grigory I. Barenblatt contributed Scaling, Self Similarity, and Intermediate Asymptotics, a text named simply Scaling, and most recently Flow, Deformation, and Fracture.  Johnson also has a book on water waves, and E. J. Hinch has a pair of contributions:  Perturbation Methods and Think Before You Compute.  He is also a series editor, and other series editors have contributed themselves too.  For example, Mark J. Ablowitz has Complex Variables (now in second edition with co-author A. S. Fokas) and Nonlinear Dispersive Waves.  Editor John R. Ockendon contributed Viscous Flow (authored with his wife Hilary) and Applied Solid Mechanics (authored with Peter Howell and Gregory Kozyreff).

As a theoretical fluid dynamicist, my personal collection of books from this series is heavily weighted toward that topic, but I own only a fraction of the available texts even in that subtopic.  Unlike previous posts in this series, this is the first one where I can say I had the pleasure of asking some of the authors to sign my copy of their books - specifically the Ockendons' Viscous Flow (I met them both at the same conference) and Charlie Doering's Applied Analysis of the Navier-Stokes Equations (coauthored with J. D. Gibbon, whom I have not met).  Many years later, I was stunned to discover that Doering and his students cited one of my research papers in their work.  I first became aware of their interest when I attended an APS Division of Fluid Dynamics meeting, on a lark one year (I had long since ceased to be active in the field).  I had dropped in on a session related to my old stomping grounds, and midway listening to one of the students' talks, I realized he was discussing a paper I had coauthored!

A family portrait of Cambridge Texts in Applied Mathematics in my personal collection.

Some news on solar physics

This week's Physics magazine from the American Physical Society features an interesting article by Marric Stephens about an apparent anomaly - a contradiction between theoretical expectations and observational data regarding the sun's sodium D1 absorption line.  Stephens reports on a new paper by a Swiss/Spanish/German team that resolves the paradox by replacing a seemingly reasonable assumption:  that "the anisotropic radiation field that pumps the atoms of the solar atmosphere was assumed constant with wavelength over the very small spectral interval spanned by the nearby hyperfine structure components of both the sodium $D_1$ and $D_2$ lines."  The authors Ballester, Belluzi, and Bueno apply a theory of polarized radiative transfer that takes "into account the detailed spectral structure of the radiation, together with the effects of magnetic fields of arbitrary strength and elastic collisions in a realistic atomic model including [hyperfine structure]" .  There is a link to the paper itself, which is open source.  A nice tale of resolving an apparent conflict between theory and observation.

Reference

Ballester, Belluzi, and Bueno, 2021, Phys. Rev. Lett. 127:  081101.

Steven Weinberg 1933-2021

The world has lost one of its great theoretical physicists, Dr. Steven Weinberg, 1979 Nobel laureate.  Weinberg was also a great writer, authoring a series of influential textbooks, as well as works for the general public.  DTLR has always been admirer of his general writing.

The New York Review of Books, to which he was a longtime contributor, has made this 2001 essay by him available for reading in his honor.  I strongly recommend it.

The proton radius puzzle and the hazards of combining data from multiple studies

If journalism is a first draft of history, Physics World writer Edwin Cartlidge has done a superb job this month of reporting on the "Proton Radius Puzzle" and the pitfalls of combining data from multiple studies.  Cartlidge's piece is also a superb case study of a phenomenon described by David Bailey a few years ago.

Over time, a number of experiments around the world, using different physical principles, attempted to measure the radius of the proton.  An international group, CODATA, has the task of compiling all such data and basically reporting the community's best estimate.  This is done by first voting on which studies should be included; then the data are simply (weighted) averaged; presumably the weights are determined by the error bars reported by the individual studies.  The thus combined estimate, it is hoped, will have a more accurate point estimate, and narrow error bars, than any of the individual findings.  The former chair of the CODATA group working on the proton radius is quoted in Cartlidge's article arguing that this process incorporates all "individually credible results" but passes no judgment on whether each of those results is "right or wrong", a task that "would require superhuman powers".

Well, for about eight years, the measurement by the CREMA experiment, using a unique muon-based principle, was excluded from the average, as it was an outlier compared to other reports (in exactly the sense that Bailey has described).  However, in the interim, other groups using the more conventional approaches started to obtain results comparable to the lower value given by CREMA.  In 2018 CODATA finally incorporated the outlying results, though the stated error bars for the combined estimate had increased, unsurprisingly.  See Cartlidge's article for the twists and turns of the story.

DTLR's interest here is in the whole concept of combining data.  Something like this is widely practiced in statistics, under the name "meta-analysis".  I consider this poor practice, because it sweeps under the rug potential systematic errors in the individual results.  In the proton radius case, Cartlidge even seems to suggest that groupthink might have been at play in the CODATA decisions.

Here is DTLR's opinion about combinging data from multiple studies.  Don't do it.  Instead of meta-analysis, the individual study results, with their error bars, should simply be displayed together.  Users should be directed to critically review the study design, execution, analysis, and reporting of the individual studies, seeking out differences among them.  Authors of systematic reviews should use their judgment and discuss the similarities and differences, without blindly pooling all the data together.  Cartlidge writes, "the CREMA result was not really at odds with individual spectroscopy experiments – all but one differed by no more than 1.5 standard deviations, or σ. The only significant disparity – of at least 5 σ – arose when the conventional data were averaged and the error bars shrunk. But that disparity could only be maintained if the muon result itself was kept out of the fitting process – given how much it would otherwise shift the CODATA average towards itself."  My interpretation is that the artificial task of combining the data drove the source of confusion; this would have been avoided by simply presenting all the individual study results separately.  The field has clearly not reached sufficient maturity for a combined "best" estimate to be meaningful, in my opinion, and this is probably even more true of the meta-analyses often reported in the medical and public health literature.

Just days after Cartlidge's article came out, another one authored by him was published that also has combining data at its heart.  This one was about gravitational waves, but the story is complicated even further by the waveform modeling required to interpret gravitaitional wave signals.

Theory, computation, and machine learning in climate science

This month's Physics Today features an excellent article by Schneider, Jeevanjee, and Socolow, "Accelerating Progress in Climate Science".  In particular, its philosophical orientation with regard to the interacting roles of theory, computation, and machine learning is one of the best articulated I have seen, and more broadly relevant than just for climate science.  The emerging role of machine learning in the study of the atmosphere is a topic I've written about previously (here and here).

The authors write, "Researchers have made deductive inferences from fundamental physical laws with some success.  But deducing, say, a coarse-grained description of clouds form the underlying fundamental physical laws has remained elusive.  Similarly, brute-force computing will not resolve all relevant spatial scales anytime soon.  Resolving just the meter-scale turbulence in low clouds globally would require about a factor of 10^11 increase in copmuter performance.  Such a performance boost is implausible in the coming decades and would still not suffice to handle droplet and ice-crystal formation."

They continue, "Machine learning (ML) has undeniable potential for harnessing the exponentially growing volume of Earth observations that is available.  But purely data-driven approaches cannot fully constrain the vast number of coupled degrees of freedom in climate models.  Moreover, the future changed climate we want to predict has no observed analogue, which creates challenges for ML methods because they do not easily generalize beyond the training data."

The authors go on to describe a concept they call parametric sparsity while comparing Newtonian gravity (with a single free parameter) to Ptolemian epicycles and equants, "the deep learning approach of its time."  They note that Newtonian gravity theory has a remarkable track record of "out-of-sample predictions, uncertainty estimates, and causal explanations."  Ptolemy's theory, like deep learning, is a massively parameterized model of empirical data, overfitted to the training data, but providing little guidance on what to expect outside the training data, the authors seem to argue.  The analogy is interesting but imperfect. As I noted previously, deep learning has demonstrated, under some circumstances, an ability to generalize beyond the training data.  I wrote then, "We do not know under what circumstances such generalization can reliably occur, and I believe any such claims about these generalizations must be validated with independent data sets."  Thus, the authors' skepticism about such generalizability is a welcome pragmatic attitude.

The authors write, "Climate science needs to predict a climate that hasn't been observed, on which no model can be trained, and that will only emerge slowly.  Generalizability beyond the observed sample is essential for climate predictions, and interpretability is necessary to have trust in models.  Additionally, uncertainties need to be quantified for proactive and cost-effective climate adaptation."  They advocate for the use of theory to develop coarse-grained models for use in computational simulations.  "Where theory reaches its limits, data-driven approaches can harness the detailed Earth observations now available." The authors' advocacy of theory-first, empirical modeling second, might be seen as an answer to Kerry Emanuel's concern about computing too much and thinking too little (discussed here).

I might depart a little from the authors in expressing some skepticism about the quality of uncertainty quantification.  Any such quantification is likely to be done in the context of the model itself, and thus fail to account for model uncertainty, which can never be fully quantified.  See also my discussion of "Escape from Model-Land" here.

Nonetheless, readers interested in climate science, and more broadly the interacting roles of theory, computation, and machine learning in the scientific endeavor (which truly must be coupled with experiment and observation) should check out the Physics Today article and think about how its ideas might apply to their own work.

Reference

T. Schneider, N. Jeevanjee, and R. Socolow, 2021:  Accelerating progress in climate science.  Physics Today, 74 (6), 44-51.

The 200th Anniversary of the Navier-Stokes Equations

Earlier today, Nature Physics published a "Measure for Measure" note by Oxford professor Julia Yeomans about the Navier-Stokes Equations and the Reynolds Number.  She reminds us that next year, 2022, will be the 200th anniversary of the first appearance of these equations at the hand of Claude-Louis Navier in 1822.  Investigating further (Rouse & Ince, 1957; Darrigol, 2005; Eckert, 2006), it appears that Navier read his papers at the French Royal Academy of Sciences that year, but the written publication appeared later in 1827.  Navier's original formulation was based on a now-discredited molecular model.  Meanwhile also in 1822, A.L. Cauchy published his theory of stress in continua.  S. D. Poisson, Barre de Saint-Venant, and I. S. Gromeka are others who contributed to the theoretical development of the Navier-Stokes equations.  In most historians' view, the definitive derivation of the Navier-Stokes equations was given by George Gabriel Stokes in 1845.  Nonetheless it was indeed Navier in 1822 who first presented the equations.  Prof. Yeomans also discusses Osborne Reynolds' 1883 paper on the nondimensional parameter named in his honor.  

DTLR is grateful to Nature Physics and Prof. Yeomans for bringing these notions to the attention of the journal's readers.  As I've written before, fluid mechanics has been underrepresented in the U.S. physics curriculum, and it's nice to see pieces like this in physics journals.

References

O. Darrigol, 2005:  Worlds of Flow:  A History of Hydrodynamics from the Bernoullis to Prandtl.  Oxford University Press.

M. Eckert, 2006:  The Dawn of Fluid Dynamics:  A Discipline between Science and Technology.  Wiley-VCH.

H. Rouse and S. Ince, 1957:  History of Hydraulics.  Iowa Institute for Hydraulic Research.

J. M. Yeomans, 2021:  Fluid flows on many scales.  Nature Physics, 17:  756.

Ham radio and space weather

A superb example of "crowdsourced science" is described in this piece in this month's Eos. Check it out!

Reference

Collins, K., D. Kazdan, and N. A. Frissell (2021), Ham radio forms a planet-sized space weather sensor network, Eos, 102, https://doi.org/10.1029/2021EO154389. Published on 09 February 2021.

A tribute to the publishers of classic engineering science books: the Oxford Engineering Science Series

Back in December DTLR had a series of posts in tribute to the publishers of classic books in physics and atmospheric science.  I'd like to return to that theme by paying homage today to the Oxford Engineering Science Series.  As far as I know, the series began with the publication in 1974 of Synthesis of Planar Antenna Sources, by Donald R. Rhodes (Volume 1 of the series).  The last contributions I know of are Volume 51, Electromagnetic Waveguides and Transmission Lines, by Frank Olyslager, published in 1999, and a second edition of Volume 14, Engineering Rheology, by Roger I. Tanner, published in 2000.  

Here are a few members of the series in my personal book collection.

Volumes 2, 10, and 36 of the Oxford Engineering Science Series

As can be seen from the photo, these books were also branded as Oxford Science Publications.  Also illustrated in the photo, Peter Hagedorn's Non-Linear Oscillations (Volume 10) was another example of a member of the series that came out in a second edition (1988).  Unfortunately now even this edition appears to be out of print.  Other volumes with multiple editions include Collier & Thome's Convective Boiling and Condensation (3d edition, 1996) and Wesson's Tokamaks (4th edition, 2011), though this latter moved to the same publisher's International Series of Monographs in Physics (a series that continues to go strong today).  Other volumes actually appear in two-volume sets (collectively issued the same series number):  these include Jones' Methods in Electromagnetic Wave Propagation (1979) and Thornton's Science and Practice of Liquid-Liquid Extraction (1992).  Jones' book was issued in a second edition co-published by IEEE and Wiley (1994), in their Series on Electromagnetic Wave Theory.

In the photo, Hagedorn's book is flanked by Les Woods' 1975 book, The Thermodynamics of Fluid Systems (Vol. 2), and Beris & Edwards' 1994 contribution, Thermodynamics of Flowing Systems with Internal Microstructure (vol. 36).  (Woods was one of the series editors for many years as well.)  The Hagedorn and Beris & Edwards volumes illustrate the elegant blue and red livery of the paperback and hardback volumes of the series in its middle years.  The hardbacks even had gold trim on the covers; the photo does not do it justice.  Unfortunately, the paperback livery in the most recent years resembles that of other (less elegant) Oxford Science Publications.

Unfortunately I do not own a copy of Volume 25, The Physics of Fluid Turbulence, by W. David McComb (1990).  Interestingly, McComb later (2014) published a second work on turbulence, Homogeneous, Isotropic Turbulence:  Phenomonology, Renormalization and Statistical Closures, which appeared instead in Oxford's International Series of Monographs in Physics, where Wesson's Tokamaks also moved, as mentioned earlier.

As for the Oxford Engineering Science Series, like Academic Press's International Geophysics Series that I wrote about earlier, the publisher websites list them as active, but no new volumes have been published in a long time.  I do wonder if any of these series will continue (the McGraw-Hill and Addison-Wesley series I wrote about earlier seem to be long-defunct), given the dynamics of scientific publishing in recent years.

Hydrodynamics of the Ever Given's blockage of the Suez Canal

Readers of this blog ought to be following the news of the Taiwanese-operated cargo vessel Ever Given's blockage of the Suez Canal.  Earlier this week, the Financial Times' blog featured an article by Brendan Greeley, speculating on the hydrodynamics of how this event occurred.  Though his is not the final word on this episode, there is one passage in his piece worth memorializing here:

Sailors talk about hydrodynamics the way CEOs talk about macroeconomics: they either treat it with mystical reverence, or they claim to understand it and are wrong. Unlike with macroeconomics, though, if you know what you’re doing you can test the propositions of hydrodynamics on actual, physical models in a lab. As in: you build little boats and then you drag them through the water, in a towing tank. Hydrodynamics is what a five-year old would do, if a five-year old had a PhD. 

Bravo, Mr. Greeley!

 

Attention graduate students: try an internship while in school.

Last week, Nature published an excellent article by three Norwegian graduate students on their experiences doing summer internships in industry, while studying in the life sciences at Norwegian graduate schools. Graduate students in any STEM discipline should heed their advice.  I myself did two summer internships in industry while in graduate school.  They helped me try out different kinds of work and understand my strengths, weaknesses, and interests better.  They also allowed me to try out living in different parts of the country.

A few points made by each of the students resonated with me.  The second student, Kathleen, noted her surprise when the marketing team asked her how a new medical device would sell, and who the target was.  "I became aware that, for a product to hit the market properly, the product maker must understand the end user and their needs. A solution on paper might not always be a marketable one."  This is something I actually learned vividly while engaged in a lengthy conversation with a French post-doc I met in San Diego at a fluid dynamics conference.  He was working with a start-up company developing a new immunoassay.  Its engineering was innovative, but the product's value proposition for potential customers was unclear.  What do I gain by adopting the new technology over what I am doing now?  The existing technique was cheap, relatively fast, easy, and familiar to technicians.  The new product would improve the quality of measurement, but this improvement might be too marginal given the cost to adopt the new method and retrain the workforce.  

The third student, Nancy, described one of her lessons as "Quality Management is king" and I fully endorse this perspective as well.  She emphasizes the commercial and regulatory benefits, but I would argue further that there are scientific ones as well.  Quality Management is an attitude that more academic labs should adopt, because it contributes very directly to doing (and documenting) reproducible research.

The first student, Erik, listed one lesson as "Done is the new Perfect."  It is a lesson well earned and worthy.  Ironically, during my first internship, I learned an opposite lesson that I will have to tell on another occasion.  Suffice it to say that sometimes, a product must be absolutely bulletproof when it is ready to ship, especially when it has life-or-death consequences.

I learned other lessons as well.  One was, there is no such thing as a Physics problem, Math problem, or Computer Science problem.  The problems arrive unclassified, and you need to figure out, learn, and deploy whatever relevant knowledge is needed to solve it.

The two companies I worked for were a contrast.  The first one was a small company, and while they owned licenses to software such as Matlab and others, they were not always installed on all the computers in the office, in order to save memory.  Small companies often exist at the edge of survival; there is no largesse.  The second company I worked for was a Fortune 500 company, that provided subsidized housing and a shuttle van (occasionally a stretch limo when the van wasn't available) to take us interns to and from work.  On one evening they took us on a dinner cruise.  The intern manager had $4 million to spend on us interns (most were undergrads, but I was part of the graduate student cohort)  including pay...a situation which did not last in later years.

On the other hand, at a small company, all I had to do to get a decision made was to walk into the boss' office (when he was in town).  At the large company, often I had to fill out forms and collect multiple signatures.

I did end up working for the second company full-time, for about 7 years after I graduated.  But both internships gave me something concrete to talk about at job interviews when I was leaving school....not just academic research that might be of limited interest to employers.  I considered both my internships to be formative experiences that influenced the kind of scientist I am today.

Physicists and astronomers honored on US postage stamps

Today I received an order of US postage stamps, including a sheet of the new Forever stamp honoring Chinese-American nuclear physicist Chien-Shiung Wu.  Adrian Cho wrote about this stamp last month in Science.  The stamp was issued on the International Day of Women and Girls in Science.  As far as I know, Dr. Wu is the third woman physicist honored on a US postage stamp, and the first Chinese-American one.  The end of Cho's article talks about other physicists honored on US postage stamps -- there are many fewer of these than American Nobel Physics Laureates!  Cho mentions several, including some aerospace scientists, though he says the US Postal Service doesn't actually track how many there are.

This got me thinking about that very question.  How many physicists and astronomers are honored on US postage stamps?  There are just over a dozen, by my count. The overlap with mathematicians is considerable (since there are far fewer of those), so I'll include them too in this post.

The most honored American physicist on our nation's postage stamps is, of course, Benjamin Franklin.  It may be no coincidence that Franklin was also the nation's first Postmaster General.  I haven't even tried to count how many US stamps have honored Franklin.

At a distant second place is Albert Einstein, honored on two stamps:  an 8 cent stamp in the Prominent Americans series in 1966, and a 15 cent stamp in 1979 issued on the centenary of his birth. All other physicists on US stamps have a single stamp in their honor.  These include Robert Millikan, on a 37 cent stamp issued in 1982 as part of the Great Americans series, and Enrico Fermi on a 34 cent stamp issued in 2001.

The American Scientists series, which began in 2005, was a boon for physicists.  Josiah Willard Gibbs (a polymath claimed equally by mathematicians and chemists) and Richard P. Feynman were included in the first round (37 cents), while John Bardeen and astronomer Edwin Hubble appear in the 2008 second round (41 cents).  Maria Goeppert Mayer was honored in the third round (2011) with a Forever stamp.  Unfortunately, the series appears to have been discontinued after the third set.  (Did they just not sell well?)  The first round in 2005 also included mathematician John von Neumann, who made colossal contributions to physics, computer science, and meteorology, among other fields.  

The new stamp honoring C.-S. Wu is the second to honor a physicist in the decade since the last set of American Scientists was issued.  It follows the 2018 issue of a Forever stamp honoring Sally K. Ride, astronaut, physicist, and stamp collector.  Of the honored physicists mentioned, Einstein, Millikan, Feynman, and Mayer were Nobel laureates, with Bardeen being a double Nobel laureate in physics.  (Cho's article disucsses that many feel that Wu should have received a Nobel as well.)

Also worthy of note is Benjamin Bannker, honored in 1980 with a 15 cent stamp in the Black Heritage series.  Banneker was a surveyor, mathematician, and astronomer, who like Franklin, published his own almanacs.  A math teacher, Jaime Escalante, was honored with a Forever stamp in 2016.  Along with Wu, Banneker and Escalante are the only non-whites honored by stamps among those discussed in this post.

Since Cho's article mentions aerospace scientists and inventors, let's look at them too.  The Wright Brothers and their achievements were honored on the 25th, 46th, 75th, and 100th anniversaries of their first powered flight.  The first stamp (2 cents) was issued as one of a pair honoring of the 1928 International Civil Aeronautics Conference, in that year.  It featured the Wright Flyer.  Three airmail stamps honored both the Wrights and their aircraft, in 1949 (6 cents) and two in 1978 (31 cents).  Finally on the centenary of their first flight, another stamp featuring the Wright Flyer was issued in 2003 (37 cents).  Other aerospace pioneers include Robert Goddard (1964, 8 cents), Igor Sikorsky (1988, 36 cents airmail), and Theodore von Karman (1992, 29 cents).  As far as I know, von Karman is the only fluid dynamicist honored on a US postage stamp! 

Unfortunately, I cannot think of another American fluid dynamicist who should next be honored with a US postage stamp, for reasons similar to those I wrote about in an earlier post. But what about other American physicists, astronomers, and mathematicians?  Who would you nominate next?

I surmise that those known among the general public would have the best chance of being honored on a stamp, compared to those best known just within the physics community.  So, Nikola Tesla seems an obvious choice.  You can guarantee that such a stamp would sell well.  Perhaps W. Edwards Deming, though he is best known for his work in statistics and management consulting, or J. Robert Oppenheimer.  However, I am delighted that less publicly celebrated figures like Gibbs, Millikan, Fermi, Mayer, Bardeen, and Wu have been honored.  There are thus many worthy choices for the next postage stamp.  If only the American Scientists series could be revived!

Among astronomers, I'm surprised that Carl Sagan hasn't already been so honored.  Among mathematicians, perhaps Benoit Mandelbrot (the maestro of fractals), John Nash (Nobel in economics, subject of A Beautiful Mind), and Katherine Johnson (of Hidden Figures fame) might be considered.

I am grateful to the website of the Mystic Stamp Company, and Wikipedia, sources of the information I have provided above.

Excitement, self-deception, and retraction

Yesterday, Davide Castelvecchi reported in Nature on the retraction of a 2018 paper claiming detection of a signature suggesting the existence of a Majorana fermion state.  It's a good article, and includes a link to the report of an independent investigation which concluded that, while no fraud had occurred, the authors of the paper essentially fooled themselves, implying that they fooled everyone else too, by publishing.  There are a couple excerpts from the report (by "experts" P. Brouwer, K. Ensslin, D. Goldhaber-Gordon, and P. Lee) that are worthy of reading here.

First, from Section 3:

And finally, from the Conclusion:

It should be noted that the expert investigators were provided with unpublished data, available to the authors before they published, that would have cast doubt on the original authors' conclusions, and that even the published data had features that a sharp reader could have used to cast such doubt.

The Mars Rover's driver

This weekend's Wall Street Journal features an interview with Vandi Verma, a naturalized US citizen from Indian, whom the author Tunku Varadarajan describes as "arguably the world's most experienced Martian robot operator".  Verma worked with Curiosity previously, and serves as chief engineer of robotic operations for Perseverance and Ingenuity.  DTLR commends the piece to all its readers.

More on machine learning in weather and climate modeling

 My last post commented on the use of machine learning in Earth science modeling.  The Philosophical Transactions of the Royal Society, Series A, has just published a special issue on this topic, based on a workshop held at Oxford University in September 2019.  Here is a link to the introductory paper, and a link to one of the contributions, that deals with physically-aware machine learning models.  Ten case studies are discussed in the latter.

Physically aware machine learning models

My last post resurrected some Eos articles from a few years ago, but today I'd like to discuss a piece in this month's issue.  Maskey et al. write about "A Data Systems Perspective on Advancing AI", reporting on a NASA-sponsored workshop held in January.  They describe "traditional" Earth science modeling as "top down", starting with first principles (laws of physics), while the machine learning approach is "bottom up", having algorithms that learn relationships empirically from historical data.  An inherent limitation of empirical modeling, they recognize correctly, is the inability for a model trained on historical data to extrapolate into regimes never before seen in the training data.  Yet this is precisely what Earth science is called to do, when dealing with extreme weather events or climate change, for example.  The writers propose that "physically aware machine learning models" could overcome this limitation, suggesting a melding of the "top down" and "bottom up" approaches.  The authors mainly write about using physics to constrain the machine learning models or their cost functions during training, claiming promising results already.  It is less clear to me that placing constraints on an empirical model would allow it to creditably extrapolate, only that such constraints should improve interpolation capability.

On this blog, it was noted previously that there have been demonstrated cases of deep neural networks actually being capable of generalizing beyond the training data, though such cases are not well understood, and are not convincing unless validated in independent data.  From the context, it did not seem like these deep learning models were of the "physically aware" variety that Maskey et al. describe.

These are early days in the efforts to apply machine learning to physical problems.  We still have much to learn about what is possible, and what remains limited, with such efforts.

A couple of gems from EOS

I would like to direct readers to a couple of old Eos articles from 2016 that I found particularly engrossing.

The first is an article by JoAnna Wendel on dwarf planets.  I vaguely remember Pluto being dethroned from the status of planets some 15 years ago, and placed into the category of dwarf planets.  I remember agreeing with the reasoning, at the time, but didn't pay much attention to dwarf planets.  Wendel's article made me realize that dwarf planets constitute a rich set of objects, integral to our solar system, and as worthy of attention as their big siblings.

The second article by Jeffrey J. Love and Pierdavide Coisson, is about a cluster of geomagnetic storms triggered by solar activity in September 1941, and their effects on the earth during WWII.  There hasn't been such a cluster of geomagnetic within a single 14 hour period since then.  Our civilization would be much more vulnerable now to such an event than we were then, but the article tells of several examples of how life on Earth was disrupted.  It shows the importance of studying, and perhaps forecasting, space weather.

David Appell's "Ten Greatest Predictions in Physics"

Last week, physicist and science writer David Appell published his "Ten Greatest Predictions in Physics" in Physics World magazine.  Conceding that such a list of theoretical physics predictions is bound to be arbitrary, he invited discussion.  This is irresistible bait for DTLR!  However, instead of trying to propose a competing list, I will simply discuss what he has offered.

First, I would like to propose a taxonomy of theoretical physics predictions.  First, I make a distinction between retrospective and prospective predictions.  A retrospective prediction is a prediction of a previously observed phenomenon, perhaps lacking any theoretical explanation at the time.  A prospective prediction is a specific prediction that can then be experimentally or observationally verified, but does not correspond to a previously known phenomenon.  To borrow from Appell's list, Newton's prediction of Kepler's laws of planetary motion firmly belongs in the retrospective category, while Poisson's prediction of the "Arago spot" firmly belongs in the prospective category.

I contend that a prospective prediction lends greater credibility than a retrospective one, as in the latter, the theorist might have been influenced by knowledge of the known phenomenon in crafting his or her theory.  Thus, there may be a subtle "fitting" of the theory with the "facts", during the development of the theory.  This is of course understandable, as there is no point in developing a theory that contradicts known phenomena.  However, a prospective prediction is really going out on a limb - it's taking the ultimate risk for a theory, to predict something utterly new, and possibly wrong, and therefore far more convincing when verified.  Such a prediction most resembles the classic Popperian notion of a falsifiable theory, though in practice, in the face of a failure, theories could sometime be salvaged by later modifications.  Retrospective predictions that fail may often result in theories that never get published to begin with, and may never see the light of day.

However, retrospective predictions remain important and do provide some credibility to a theory.  The retrospective prediction may be made of a phenomenon directly related to a problem the theorist was trying to solve, or it may be to an unrelated physics problem; the latter seems more impressive and seems to provide corroboration along a different line of evidence than the one that inspired the theory.  Further examples are in order.  Max Planck used Boltzmann's energy quantization trick to produce a theory of blackbody radiation.  Planck was explicitly trying to find a theory of such radiation, and the resulting theory was quite consistent with known experimental data.  This is an example of a retrospective prediction concerning directly the problem the theorist was trying to solve.  However, when Einstein took the same hypothesis and used it to explain the photoelectric effect, he was taking a 'quantum leap' of sorts - elevating Planck's ad hoc quantization assumption to a principle of physics, and finding it could solve an apparently unrelated problem.  I surmise that this achievement, rather than Planck's original formulation, is what originally made the nascent quantum theory a serious player in theoretical physics.

So, now let's turn to Appell's list.  I would have to dispute the tenth prediction on the list, Rubin and Ford's prediction of dark matter, as I regard this as a discovery rather than a prediction, albeit a "theoretical" discovery.  Furthermore, it remains experimentally and observationally unknown what this dark matter is, so it is too early to assess.  

That leaves us with nine predictions, and I would categorize them as follows:

Retrospective:

• Newton's derivation of Kepler's laws from his theory of motion and theory of gravitation.
• Maxwell's prediction of the speed of light.
• Einstein's prediction of Mercury's anomalous perihelion precession.

Prospective:

• Poisson's and Fresnel's prediction of the Arago Spot, lending credibility to the wave theory of light.
• Goeppert Mayer's prediction of the second series of transuranic elements.
• Schwinger's prediction of the electron's anomalous magnetic moment.
• Hoyle's prediction of an excited state of carbon-12, a missing link in the theory of the nucleosynthesis of heavy elements.
• Lee and Yang's parity violation in the weak interaction.
• Josephson tunneling.

With the exception of Goeppert-Mayer's case, Appell tells us that the above prospective predictions were quickly verified experimentally.  I presume that the second series of transuranic elements required more time to experimentally discover, one by one; I wish Appell had said more about this.  For the purposes of this discussion I will assume that her predictions were indeed experimentally verified.

Of the prospective predictions, the Arago spot is the most impressive (and dramatic), as described by Appell.  Poisson was opposed to the wave theory, and confronted pro-wave Fresnel with his prediction, in an attempt to falsify the wave theory.  Fresnel admitted the correctness of the prediction, and Arago did the experiment, showing that the Arago spot did exist.  While this was not a decisive blow against the corpuscular theory (nor was Thomas Young's earlier double slit experiment), it certainly contributed to the accumulation of lines of evidence in favor of the wave theory.  

I can think of other consequential prospective predictions:  Dirac's prediction of the positron (confirmed) and magnetic monopole (unconfirmed); Einstein's prediction of length contraction and time dilation, from special relativity; and the prediction of Black Holes and the Higgs boson by multiple theorists.

Let's turn back to the retrospective predictions on Appell's list.  Newton was explicitly trying to solve celestial mechanics with this theory, so its ability to produce Kepler's laws was directly related to his motivation.  Nonetheless, this was likely the first time such a thing had been seen in the history of physics, so my comments should not detract from the towering achievement it represents.  The Maxwell and Einstein predictions were particularly interesting, as both theorists were after much bigger game than merely trying to predict the speed of light or Mercury's anomalous orbit.  Rather, both predictions are like interesting side effects of the resulting theories, yet definitely valuable in establishing their credence.

I will end with some predictions from my field, fluid mechanics.  Kolmogorov's phenomenological theory of turbulence ("K41") has been, to a large extent, experimentally corroborated within an extensive set of flow regimes, as discussed by Davidson (2015).  However, Davidson mentions that there is "anecdotal evidence" that Kolmogorov may have been aware of some 1935 measurements that would have supported one of the scaling laws Kolmogorov derived.  If so, K41 might have to be classified as retrospective rather than prospective, though this could certainly be open to historical dispute.

In Rayleigh-Benard convection, Schmidt & Milverton's 1935 experiments verified the predicted critical Rayleigh number for the onset of thermal convection proposed by Harold Jeffreys in 1928.  This as a prospective prediction.  However, that a critical Rayleigh number triggers the onset of convection in the first place, was first theoretically proposed by Rayleigh in 1916.  According to Koschmieder (1993), Benard himself essentially observed this feature in 1900, without realizing it, and was skeptical as late as 1930 about the critical temperature difference.  Rayleigh was well aware of and motivated by Benard's work.  The critical value of a control parameter at which a stable regime loses stability is now one of the basic pillars of hydrodynamic instability theory.

Reference

P. A. Davidson, 2015:  Turbulence:  An Introduction for Scientists and Engineers.  Second edition.  Oxford University Press, p. 218.

E. L. Koschmieder, 1993:  Benard Cells and Taylor Vortices.  Cambridge University Press.

Nobels Neglect Fluid Dynamics

This month's issue of Physics Today includes a letter to the editor from Rajan Menon, under the headline that I've reproduced as the title of this post.  Prompted by P. W. Anderson's obituary, Menon argues that "well-known physicists have worked in different aspects of fluid mechanics," mentioning Arnold Sommerfeld and Werner Heisenberg.  He then mentions three outstanding fluid dynamicists of the 20th century:  Ludwig Prandtl, Theodore von Karman, and G. I. Taylor.  Menon tells us that both Taylor and von Karman thought that Prandtl deserved a Nobel Prize in Physics.  Certainly all three of these illustrious individuals should have been strong candidates for the Nobel Prize, in my view.

Menon's letter nicely complements a post of mine from 2014, Nobel laureates and fluid dynamics research.  In that post I discuss the one Nobel Physics Prize that did seem to be awarded for research in fluid dynamics (H. Alfven, 1970) as well as the fluid dynamics activities of several other Nobel laureates, both in physics and chemistry, including Heisenberg.  I believe that Menon is essentially correct that "the field of mechanics, has been routinely neglected in considerations for the physics Nobel Prize."  However, aside from Prandtl, von Karman, and Taylor, all now long-dead, it is unclear to me who else should be a candidate.  The list of winners of the APS Fluid Dynamics Prize, for instance, features many outstanding researchers in this field, but what accomplishment would rise to the level of say, Prandtl's boundary layer theory, of such consequence to be honored by a Nobel Prize in physics?  To make the question more concrete, if the Nobel committee were to respond to Menon by selecting a Nobel Physics Prize for research in fluid dynamics next year, who would be the candidates among living fluid dynamicists? 

Menon proposes that if the Clay Mathematics Institute's Millenium Prize for proving the existence and smoothness of solutions to the 3-dimensional Navier-Stokes Equations is ever awarded, that person is deserving of a Nobel Physics Prize as well.  Though I sympathize greatly with Menon's letter, this is the one place I would part company with him.  The solution to this problem is rightly deserving of a top mathematics award, but I do not think it worthy of a Nobel Prize in Physics, simply because it is unclear a priori what physical insight would be gleaned from such a proof.

I would propose that the criteria for a Nobel Physics Prize to be awarded to fluid dynamics should be either for work of a total game-changing nature in the field, like Prandtl's boundary layer theory, or an advance in fluid dynamics that has colossal ripple effects in other areas of physics or technology, like Alfven's work in magnetohydrodynamics, including Alfven waves, which impact on plasma physics and astrophysics.

On the flip side, I do think Nobel physics laureates should continue to contribute their talents to fluid dynamics, as Rayleigh, Purcell, Landau, Onsager, and Chandrasekhar did.