Michael Faraday, Biological Physicist?

Last week in this blog I discussed the greatest physicist of all time, Isaac Newton. However, if we narrow consideration to only experimental physicists, I would argue that the greatest is Michael Faraday (with apologies to Ernest Rutherford, who is a close second). In Section 8.6 of the 4th edition of Intermediate Physics for Medicine and Biology, Russ Hobbie and I discuss Faraday’s greatest discovery: electromagnetic induction.

In 1831 Faraday discovered that a changing magnetic field causes an electric current to flow in a circuit. It does not matter whether the magnetic field is from a permanent magnet moving with respect to the circuit or from the changing current in another circuit. The results of many experiments can be summarized in the Faraday induction law.

I have always admired the 19th century Victorian physicists, such as Faraday, Maxwell and Kelvin. Michael Faraday, in particular, is a hero of mine (it is good to have heroes; they help you stay inspired when the mundane chores of life distract you). I had the pleasure of quoting from Faraday’s Experimental Researches in Electricity in an editorial I wrote in 2005 for the journal Heart Rhythm:  “Michael Faraday and Painless Defibrillation.” I tried to get a picture of Faraday included as part of the editorial, but alas the journal editor removed it. The article described a heart defibrillator having a design that included a type of Faraday cage.

Michael Faraday, arguably the greatest experimental physicist who ever lived, first demonstrated the shielding effect of a hollow conductor in 1836 by building a 12 ft × 12 ft × 12 ft cubic chamber out of metal. We would now call it a “Faraday cage.”

“I went into the cube and lived in it, and using lighted candles, electrometers, and all other tests of electrical states, I could not find the least influence upon them, or indication of anything particular given by them, though all the time the outside of the cube was powerfully charged, and large sparks and brushes were darting off from every part of its outer surface.” [Faraday M. Experimental Researches in Electricity. Paragraph 1174. Reprinted in: Hutchins RM, editor. Great Books of the Western World, Volume 45. Encyclopedia Britannica, Chicago, 1952.]

Faraday cages are used to shield sensitive electronic equipment. The metal skin of an airplane, acting as a Faraday cage, protects passengers from injury by lightning. Researchers perform electrophysiology experiments inside a Faraday cage to prevent external noise from contaminating the data. A rather spectacular example of shielding can be seen in the Boston Museum of Science, where a van de Graaff generator of over one million volts produces a dramatic display of lightning, while the operator stands nearby—safe inside a Faraday cage.

Why this little physics lesson? In this issue of Heart Rhythm, Jayam et al. [Jayam V, Zviman M, Jayanti V, Roguin A, Halperin H, Berger RD. “Internal Defibrillation with Minimal Skeletal Muscle Activation: A New Paradigm Toward Painless Defibrillation,” Heart Rhythm, Volume 2, Pages 1108–1113, 2005] describe a new electrode system for internal defibrillation that eliminates the skeletal muscle activation and pain associated with a shock. The central feature of their design is a Faraday cage: a conducting sock fitted over the epicardial surface of the heart…

In Section 8.7, Russ and I describe what may be the most important biomedical application of Faraday’s work: magnetic stimulation.

Since a changing magnetic field generates an induced electric field, it is possible to stimulate nerve or muscle cells without using electrodes. The advantage is that for a given induced current deep within the brain, the currents in the scalp that are induced by the magnetic field are far less than the currents that would be required for electrical stimulation. Therefore transcranial magnetic stimulation (TMS) is relatively painless. Magnetic stimulation can be used to diagnose central nervous system diseases that slow the conduction velocity in motor nerves without changing the conduction velocity in sensory nerves [Hallett and Cohen (1989)]. It could be used to monitor motor nerves during spinal cord surgery, and to map motor brain function. Because TMS is noninvasive and nearly painless, it can be used to study learning and plasticity (changes in brain organization over time). Recently, researchers have suggested that repetitive TMS might be useful for treating depression and other mood disorders.

I worked on magnetic stimulation for many years while at the National Institutes of Health in the 1990s. It was a pleasure to explore an application of Faraday induction; it is my kind of biological physics.

Faraday’s name can be found in a few other places in our book. It first appears in Chapter 3, when the Faraday constant is defined: F = 96,485 Coulombs per mole. It also appears in an abbreviated form in the unit of capacitance: a farad (F).

I suppose by now the reader realizes that I like Mike. But is he a biological physicist? Doubters might want to look at another physics blog: http://skullsinthestars.com/2010/05/15/shocking-michael-faraday-does-biology-1839. Faraday apparently did studies on the electrodynamics of electric fish. So, yes, I claim him as a biological physicist, and the question mark in the title of this blog post is unnecessary.

Isaac Newton, Biological Physicist?

Arguably the greatest physicist of all time (and probably the greatest scientist of all time) is Isaac Newton (1643–1727). Newton is so famous that the English put him on their one pound note (although I gather nowadays they use a coin instead of paper currency for one pound). Given Newton’s influence, it is fair to ask what his role is in the 4th edition of Intermediate Physics for Medicine and Biology. One way Newton (along with Leibniz) contributes to nearly every page of our book is through the invention of calculus (or, as I prefer, “the calculus”). Russ Hobbie states in the preface of our book that “calculus is used without apology.”

When I search the book for Newton’s name, I find quite a few references to Newton’s laws of motion, and in particular the second law, F = ma. Newton presented his three laws in his masterpiece, the Principia (1687). (Few people have read the Principia, including me, but a good place to learn about it is the book Newton’s Principia for the Common Reader by Subrahmanyan Chandrasekhar) Of course, the unit of force is the newton, so his name pops up often in that context. The only place where we talk about Newton the man is very briefly in the context of light.

A controversy over the nature of light existed for centuries. In the seventeenth century, Sir Isaac Newton explained many properties of light with a particle model. In the early nineteenth century, Thomas Young performed some interference experiments that could be explained only by assuming that light is a wave. By the end of the nineteenth century, nearly all known properties of light, including many of its interactions with matter, could be explained by assuming that light consists of an electromagnetic wave.

Newton’s name also arises when talking about Newtonian fluids (Chapter 1): a fluid in which the shear stress is proportional to the velocity gradient. Not all fluids are Newtonian, with blood being one example. Newton appears again when discussing Newton’s law of cooling (Chapter 3, Problem 45).

Some of Newton’s greatest discoveries are not addressed in our book. For instance, Newton’s universal law of gravity is never mentioned. Except for a few intrepid astronauts, animals live at the surface of the earth where gravity is simply a constant downward force and Newton’s inverse square law is not relevant. I suppose tides influence animals and plants that live near the ocean shore, and the behavior of tides is a classic application of Newtonian gravity, but we never discuss tides in our book. (By the way, harkening back to my vacation in France last summer, the tides at Mont Saint Michel are fascinating to watch. I really must plan a trip to the Bay of Fundy next.) Newton, in his book Optiks, made important contributions to our understanding of color, but Russ and I introduce that subject without referring to him. We don’t discuss telescopes in our book, and thus miss a chance to honor Newton for his invention of the reflecting telescope.

Never at Rest:
A Biography of Isaac Newton,
by Richard Westfall.

A wonderful biography of Newton is Never at Rest, by Richard Westfall. I must admit, Newton is a strange man. His argument with Leibniz about the invention of calculus is perhaps the classic example of an ugly priority dispute. He does not seem to be particularly kind or generous, despite his undeniable genius.

Was Newton a biological physicist? Well, that may be a stretch, but Colin Pennycuick has written a book titled Newton Rules Biology, so we cannot deny his influence. I would say that Newton’s contributions are so widespread and fundamental that they play an important role in all subfields of physics.

Jean Leonard Marie Poiseuille, Biological Physicist

Chapter 1 of the 4th edition of Intermediate Physics for Medicine and Biology contains an analysis of the flow of a viscous fluid through a pipe. Russ Hobbie and I show that the fluid flow is proportional to the fourth power of the pipe radius. We then state that

This relationship was determined experimentally in painstaking detail by a French physician, Jean Leonard Marie Poiseuille, in 1835. He wanted to understand the flow of blood through capillaries. His work and knowledge of blood circulation at that time have been described by Herrick (1942).

The paper by Herrick appeared in my favorite journal, the American Journal of Physics (J. F. Herrick, “Poiseuille’s Observations on Blood Flow Lead to a New Law in Hydrodynamics,” Volume 10, Pages 33–39, 1942). The key paragraph in the paper is quoted below.

The important role which the physical sciences have played in the progress of the biological sciences has eclipsed, more or less, the contributions which biologists have made to the physical sciences. Some of these contributions have become such an integral part of the physical sciences that their origin seems to have been forgotten. An outstanding example of such a contribution is that by Jean Leonard Marie Poiseuille (1799–1869). About 100 years ago Poiseuille brought a fundamental law to that division of physics known as hydrodynamics—which is a branch of rheology, according to more recent terminology. This law resulted indirectly from his observations on the capillary circulation of certain animals. Most physicists, chemists and mathematicians associate the name of Poiseuille with the phenomenon of viscosity because the cgs absolute unit for the viscosity coefficient has been named the poise in his honor. Few know the story leading up to the discovery of the law which bears his name. This law had more fundamental significance than Poiseuille himself realized. It established an excellent experimental method for the measurement of viscosity coefficients of liquids. The underlying principle of this method is in use today. Since Poiseuille’s law was based entirely on experiment, it was purely empirical. However, the law can be obtained theoretically. Those who are familiar with only the theoretical development are generally surprised to learn that the law was originally determined experimentally—and still more surprised to know that Poiseuille got his idea from studying the character of the flow of blood in the capillaries of certain animals.

More about Poiseuille and his law can be found in a paper by Pfitzner (“Poiseuille and His Law,” Anaesthesia, Volume 31, Pages 273–275, 1976)

Jean Leonard Marie Poiseuille (1791–1869) was born and died in Paris. Remarkably little seems to be known about his life. He studied medicine for a considerable time and submitted a thesis for his Doctorate in 1828 (aged 30–31 years). Where he carried out his early experiments studies, and how they were financed, is obscure.

His published work includes… “Experimental Studies on the Movement of Liquids in Tubes of Very Small Diameter” (his most famous paper, completed in 1842 and published in 1846). For his work “On the Causes of the Movement of the Blood in the Capillaries” he was awarded the Paris Academie des Sciences prize for experimental physiology. In later life he became a foundation member of the Academie de Medecine of Paris.

My biggest question about Poiseuille is the pronunciation of his name. I gather that it is pronounced pwah-zweez. The unit of the poiseuille has been proposed for a pascal second (or, newton second per square meter), but is not commonly used.

Steven Chu, Biological Physicist

Readers of the 4th edition of Intermediate Physics for Medicine and Biology may wish to see examples of physicists who have contributed to biology. One excellent example is Steven Chu, who until recently was professor of physics and professor of molecular and cellular biology at the University of California, Berkeley. Chu describes his biological physics research on his Berkeley website:

We apply single molecule techniques such as fluorescence resonance energy transfer, atomic force microscopy and optical tweezers, we study enzyme activity, and protein and RNA folding at the single bio-molecule level. Systems being studied include how the ribosome reads m-RNA and manufactures proteins, how vesicles fuse into the cell wall at the synapse of neurons, how cells adhere to each other via adhesive molecules, and how RNA molecules fold into active enzymes.

If you want to hear Chu talk about his biological physics research, watch this video on YouTube.

 Steven Chu asks What Can Physics Say About Life?
https://www.youtube.com/watch?v=lUR3WgVh-Hc

Some of his best known biological physics papers, published while on the faculty at Stanford, are:

• Zhuang XW, Bartley LE, Babcock HP, Russell R, Ha TJ, Herschlag D, Chu S (2000) “A Single-Molecule Study of RNA Catalysis and Folding,” Science, Volume 288, Pages 2048–2051.


• Zhuang XW, Kim H, Pereira MJB, Babcock HP, Walter NG, Chu S (2002) “Correlating structural dynamics and function in single ribozyme molecules,” Science, Volume 296, Pages 1473–1476.


• Ha T, Rasnik I, Cheng W, Babcock HP, Gauss GH, Lohman TM, Chu S (2002) “Initiation and re-initiation of DNA unwinding by the Escherichia coli Rep helicase,” Nature, Volume 419, Pages 638–641.


• Blanchard SC, Gonzalez RL, Kim HD, Chu S, Puglisi JD (2004) “tRNA selection and kinetic proofreading in translation,” Nature Structural and Molecular Biology, Volume 11, Pages 1008–1014.

Steven Chu exemplifies how physicists can contribute to our understanding of biology.


....Oh, did I forget to mention something? Chu is best known for his work on the “development of methods to cool and trap atoms with laser light,” for which he shared the Nobel Prize in Physics in 1997. He is currently Secretary of Energy in the Obama administration, and is leading the US effort to move away from fossil fuels and toward alternative energy sources, thereby combating global warming.

Who says we don’t have wonderful role models anymore?

Benjamin Franklin, Biological Physicist

The First American:
The Life and Times of
Benjamin Franklin,
by Henry Brands.

I recently finished reading H. W. Brands’ biography The First American: The Life and Times of Benjamin Franklin. (Actually, I listened to the book on tape while walking my dog Suki each evening.) I enjoy history and biography, but was not expecting to find any biological physics in the book.

Wrong. Late in Franklin’s life, during his years in France, he played a role in a bizarre episode related to biomagnetism. Brands writes

“Friedrich Anton Mesmer had studied medicine at Vienna during the period when Franklin’s electrical experiments were becoming known on the European continent. Like many of Franklin’s readers from the Poor Richard days, Mesmer believed in astrology; having learned from Franklin how lightning carried celestial energy to earth, he easily concluded that electricity provided an invisible but pervasive fluid that linked the stars to human lives. Unfortunately for both his scientific theory and his medical practice, electricity was unpleasant to patients, sometimes violently so. But Mesmer was resourceful, and substituting magnetism for electricity as the invisible transmitter, he developed a flourishing practice stroking patients with magnets. In time he dispensed with the magnets, replying simply on his own powers of persuasion to release the therapeutic effects of “animal magnetism”...

In March 1784 King Louis appointed a committee of the Paris faculty of medicine to investigate; the distinguished members included Joseph Ignace Guillotin, who would add a word to several languages by his advocacy of the use of a swift and thereby comparatively humane decapitation machine. The doctors decided they needed help from the Academy of Sciences, whereupon Louis added five members, including the great chemist Lavoisier—who would meet his end at the device endorsed by Dr. Guillotin—and the eminent American, Dr. Franklin...

Franklin and the commissioners filed their report [on Mesmer’s activities], with his name heading the list of signatures. A public version was hurried into print, and twenty thousand copies were snatched up. The report declared the claims of animal magnetism unproven; such mitigation of symptoms as appeared were due to the customary causes of self-delusion and ordinary remission.

Voodoo Science,
by Robert Park.

I am not too surprised that Mesmer was able to fool so many for so long in the 1700s, long before Faraday, Maxwell, and others provided a complete understanding of electricity and magnetism, and well before the importance of well controlled, double-blind medical studies was appreciated. What’s disturbing about this tale is that similar hoaxes go on today, at a time when we know so much more about bioelectricity and biomagnetism, and put much more effort into conducting careful clinical trials (for specific examples, see Bob Park’s book Voodoo Science). Such non-scientific activities have a striking similarity to Mesmer’s claims.

How do we combat such nonsense? Knowledge and education is the only way I know. Hopefully readers of the 4th edition of Intermediate Physics for Medicine and Biology will be in position to more effectively detect and expose non-scientific claims. Like Franklin, we must encourage educational and civic measures designed to separate exciting and important scientific developments from unfortunate and unsupportable scientific frauds.

Max Delbruck, Biological Physicist

Niels Bohr's Times:
In Physics, Philosophy, and Polity,
by Abraham Pais.

Last week, I discussed the book Niels Bohr's Times: In Physics, Philosophy, and Polity by Abraham Pais. In particular, I summarized Pais’s view that Bohr played a key role in the development of nuclear medicine through his collaboration with Georg Charles von Hevesy. This week, I address another contribution of Bohr to biological physics through his influence on Max Delbruck.

Bohr had some unorthodox views about biology that were motivated by his idea of “complementarity” in quantum mechanics. Even Pais admits Bohr’s “thoughts on biology have not borne fruit,” which is a polite way to put it. But Delbruck, then a young physicist, wrote “I am perhaps the only one of his associates of those days who took [Bohr] so seriously that it determined [my] career, changing over into biology to find out whether indeed there was anything to this point of view.” Pais writes

Delbruck’s professional switch was Bohr’s greatest contribution to biology. In an obituary of Delbruck it has been written: “Odd though these views [expressed in Bohr’s lecture ‘Light and Life’] may seem to us now, in retrospect, this lecture confirmed Max’s decision to turn to biology... It is fair to say that with Max, Bohr found his most influential philosophical disciple outside the domain of physics, in that through Max, Bohr provided one of the intellectual fountainheads for the development of 20th century biology...”

[Delbruck’s] celebrated work on bacteriophages (viruses that infect bacteria) began after his move to Cal Tech in 1937, where he became professor of biology in 1946. It is worthy of note that, in the 1963 meeting at Copenhagen commemorating the 50th anniversary of Bohr’s first papers on atomic constitution, only one paper on complementarity was presented—by Delbruck, on biology. He received the Nobel Prize in 1969.

Delbruck, a German native, spent the years during World War II with the Department of Physics at Vanderbilt University in Nashville, Tennessee (where I later obtained my PhD). While at Vanderbilt, Delbruck collaborated with Salvadore Luria on an experiment using bacteriophages to show that mutations in viruses are random rather than directed events. The American Physical Society has named its prize in biological physics the Max Delbruck Prize for his work on genetics.

Why do I discuss Bohr, Hevesy and Delbruck in a blog about the 4th edition of Intermediate Physics for Medicine and Biology? Because they represent classic examples of how physics and physicists can make fundamental and lasting contributions to medicine and biology. And that is the whole point of the book.