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The Curious Wavefunction

The Curious Wavefunction

Musings on chemistry and the history and philosophy of science

Theorists, experimentalists and the bias in popular physics

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Most people have heard of Paul Dirac but few know about Carl Anderson who, by observing particle tracks in a cloud chamber, discovered the positron (Image: Annenberg Learner)

Most people with more than a passing interest in physics will tell you who came up with the idea of quarks - Murray Gell-Mann.

Now gather around the same crowd which knows about Gell-Mann and ask them who Henry Kendall, Jerome Friedman and Richard Taylor are. It’s very likely that you will draw mostly blank stares.

Yet “coming up with the idea” was as far as Gell-Mann went in 1964 when he and George Zweig independently developed the concept. Without the 1968 experiments of Kendall, Friedman and Taylor at the Stanford Linear Accelerator Center (SLAC), quarks would have remained a mere theory, a will-o-wisp whose existence was confidently postulated but never proven.

Similar themes proliferate throughout the popular view of physics. Everyone knows Paul Dirac who conjectured the existence of the positron, but how many know Carl Anderson and his collaborator Seth Neddermeyer who actually found it? People similarly know about Wolfgang Pauli and Enrico Fermi stating the requirement for a ghostly particle called the neutrino in the 30s, but ask popular science enthusiasts if they are aware of the dogged pursuit of the neutrino by Raymond Davis for over 30 years and you will likely see knitted brows. Finally, even today, a schoolchild would likely know Einstein’s prediction of the bending of starlight by the gravitational field of a star, but Arthur Eddington’s verification of this fact would be little known.

I started mulling over this vivid gap between the public’s appreciation of theorists vs experimentalists on reading a post by physics professor Chad Orzel who, taking a cue from my post about famous American physicists, makes the cogent point that while American theorists lagged behind their European counterparts until the post-war years, they were almost equal to the Europeans even in the 1920s. His point is that we often tend to overemphasize the role of theory over experiment.

Now there’s no doubt that physicists themselves would be the first ones to recognize the value of experimentalists; for instance Anderson, Davis and the Kendall-Friedman-Taylor trio were all recognized by Nobel Prizes. But their recognition in the public mind ranges from vague to non-existent. This gap in perception is especially startling given the singular importance of experiment in physics and all of science, a central paradigm that has been the centerpiece of the scientific method since Galileo (apocryphally) dropped iron balls from the leaning tower of Pisa. Richard Feynman paid a sparkling tribute to the supremacy of experiment when he said:

“In general we look for a new law by the following process. First we guess it. Then we compute the consequences of the guess to see what would be implied if this law that we guessed is right. Then we compare the result of the computation to nature, with experiment or experience, compare it directly with observation, to see if it works. If it disagrees with experiment it is wrong. In that simple statement is the key to science. It does not make any difference how beautiful your guess is. It does not make any difference how smart you are, who made the guess, or what his name is – if it disagrees with experiment it is wrong.”

An even more pointed and roaring tribute to experiment came from the utterly self-assured king of experimental physics, Ernest Rutherford. His opinion of theoreticians was that “they play games with their symbols, but we turn out the real facts of Nature”. And he is said to have admonished the capable students working under his tutelage - nine of whom won Nobel Prizes - to not “let me catch anyone talking about the Universe”.

Rutherford was the ultimate experimentalist and Feynman was the ultimate theorist but Feynman was well aware of how a well-conceived experiment is really the only thing that can make or break a theory. Ironically, the public devaluing of experimentalists applies to Feynman’s own work. The theory of quantum electrodynamics which he developed is perhaps the most accurate theory in physics. As one example, it can calculate the magnetic moment of the electron correctly to an unprecedented 15 decimal places. But we would never have known this if it weren’t for the experimentalists who devised increasingly ingenious experiments to measure the parameter. Yet everyone has heard of Feynman, but who has heard of Lamb, Kusch or Foley?

It seems to me that there are at least two important reasons why the public, in spite of tacitly appreciating the all-important role of experiment in physics, fails to give experimentalists their due. First is the sheer success of theoretical physics in uncovering the deepest mysteries of the universe through armchair speculation. Nobody can fail to gasp in awe at an Einstein or Bohr who, working with a few facts and pencil and paper, divine grand operating principles for the cosmos in short order.

Compared to their efforts based on pure thought, the corresponding efforts of experimentalists who get down on their knees, liberally coat their hands with grease and spend most of their time soldering electronic circuits and fashioning precision machine parts on a lathe sounds humdrum and boring. Yet this mundane work is an essential step toward the grand finale of hard factual discovery. Even the rare combination of theorist and experimentalist appreciates this; for instance, in spite of his pioneering contributions to theory, Fermi always said that his first love was experiment and he could often be found performing the most mundane of tasks.

To be fair though, it’s hard not to admire theorists when many experimentalists, as ingenious as their contraptions are, “simply” validate things which the theorists have already said. Anderson might have discovered the positron, but Dirac invented it first. Eddington might have observed deflected starlight, but Einstein simply plucked it out of thin air based on what seemed like magical speculation.

Firstly however, it’s very important to realize that all the awe for Einstein which we rightly feel comes only after the fact, after a thousand increasingly demanding tests of general relativity have established the veracity of the theory beyond any doubt. As Feynman said, no matter how pretty the theory looks and no matter how brilliant its creator sounds, it is no more than a hypothesis until it’s verified. Einstein unverified would have been a mystic. Fortunately the public seems to have gradually woken up to the straitjacket that ugly, grease-and-solder experiment imposes on elegant theory. This is most apparent in the decline of popular versions of string theory; after a period of breathless ascendancy by its proponents, the public seems to increasingly realize the gaping chasm between theory and experiment which the string theoretical framework constantly displays. String theory in fact is the perfect test of the ability of an informed public to distinguish between fact and speculation, and so far the signs seem promising.

Secondly, there are also outstanding example of discoveries made by experimenters which really had no theoretical precedent. That is what makes Rutherford and Faraday the two greatest experimental physicists in history. Rutherford discovered the atomic nucleus in 1908, but it took thirty years for physicists to develop a concrete theory of the nucleus. Similarly Faraday discovered the seamless relationship between electricity and magnetism - one of the very few examples of unification by experiment - but it took until after his death for Maxwell to come up with his pioneering theory of electromagnetism. Experimentalists often follow in the steps of theorists, but the instances in which they lead the way are as full of creativity and achievement as the work of an Einstein, Bohr or Feynman. And even when they follow, they are the ones who bridge the gap between idea and hard fact.

The other big reason why for the public seems to downplay the key role of experiments is the bias in physics popularization toward theory. And here at least part of the blame must be laid at the feet of experimentalists themselves. For instance if we ponder over who the leading physics popularizers in the last twenty years are, the names that come to our minds include Brian Greene, Lisa Randall, Leonard Susskind, Brian Cox and Sean Carroll. Almost no experimenter makes the list; Anil Ananthaswamy is one of those rare writers who has shined a light on the heroic efforts of experimenters in validating cutting-edge theories. In a previous post I mentioned how the public has been fed increasingly exotic and speculative physics fare that tends to influence their opinion about what they consider are the most important fields in physics. Cosmology and quantum theory rank high on their list, condensed matter physics and biophysics rank low. But condensed matter theory still ranks higher than condensed matter experiment. Observational cosmology still takes a backseat to speculations about the Big Bang. This has to change.

If we want to improve the public visibility of experimentalists and place experimentalists in their rightful place in the pantheon of popular physics, the main initiative would have to come from experimentalists themselves. There is no doubt that experimental physics has seen some amazing advances in the last two decades, so there's certainly no dearth of stories to tell. For instance just last year the Nobel Prize in physics went to Serge Haroche and David Weinland who have achieved amazing feats in trapping ions and atoms and verifying some of the most bizarre predictions of quantum mechanics. Yet where are the books which elaborate on these successes? Three years ago the physics Nobel again went to experimenters who used the simplest and most ingenious methods to create graphene. Still there are no vividly written books about these experiments. There are plenty of other motifs, from the observation of supernovae and x-ray astronomy to the manipulation of single DNA molecules using lasers, which can be productively captured in popular physics books. In addition the manipulation of these tools to plumb the depths of nature’s secrets is every bit as exciting to its practitioners as calculating the curvature of spacetime is to its own. It’s up to those who deftly wield this machinery to convey their personal pleasure of finding things out to the public.

Experiment is the ultimate arbiter of science and it’s a pity that the current popular physics literature does not reflect this all-important fact. Experimenters and their journalist friends need to now pick up the baton and run with it. They need to communicate to the public why ion traps are as engrossing as Lie groups, why even the most elegant mathematical edifice can crumble in the face of confounding experimental evidence, why, in Rutherford’s words, “the theorists play games with their symbols while they are the ones who turn out the real facts of nature”.

Update: Tom Swanson, Chad Orzel and ZapperZ all offer excellent perspectives of their own. I concur with their two main observations (Hat tip: Jennifer Ouellette); that experimenters always have to know at least some theory to make sense of their experiments (and Rutherford certainly did), and that temporal and spatial constraints may make it harder for experimentalists to make regular forays into popular science writing. Also, Brian Cox is an experimentalist, not a theorist.

The views expressed are those of the author and are not necessarily those of Scientific American.

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