The mass intellectual emigration from continental Europe in the 1930s, which so stimulated physical science in the United States and England, also had profound consequences for biology, even though the men involved were fewer and younger, with their reputations still to make. They included [Max] Perutz, who left Austria for England in 1936, and [Erwin] Chargaff, also an Austrian, who emigrated to the United States in 1934. A less direct influence was the distinguished and passionately intelligent Hungarian physicist Leo Szilard, who in the 1930s had been the first to envision the possibility that sustained nuclear fission, a chain reaction, would work and cause an explosion, and the first to urge that the United States should try to make an atomic bomb. Szilard wrote the letter about the idea that [Albert] Einstein signed and that was read to [President Franklin] Roosevelt in 1939. Szilard worked on the atomic project at the University of Chicago through the war; afterwards, in reaction against the weapons and against the big-money, big-team physics he had been instrumental in creating, he turned to biology and also to campaigning within the international scientific community for disarmament—for example, through the Pugwash conferences, which he helped to found. In 1947, [University of Chicago chancellor Robert] Hutchins gave Szilard the physicist an appointment as professor of biology and sociology. In the early years of molecular biology, Szilard was an erratic if interesting experimenter and theorist, a cross-pollinator of ideas and an effective critic of others’ work, an intellectual and ethical inspiration to younger scientists.
The most important immigrant to biology, however, was Max Delbrück. Delbrück was German, born to the aristocracy of the intellect—his father was the professor of history and his uncle the professor of theology in the University of Berlin—and trained as a quantum physicist. His mind and style had been formed by Niels Bohr, the physicist, philosopher, poet, and incessant Socratic questioner who made Copenhagen one of the capital cities of science between the wars. Delbrück’s ideas about the physical properties of the gene, in a youthful paper of 1935, had led [Austrian physicist Erwin] Schrödinger to write [the influential book] What Is Life? Delbrück was perhaps the earliest of the theoretical physicists who have crossed over to biology; Szilard, [Francis] Crick, Maurice Wilkins were others, while Linus Pauling, arriving at biology from a different tangent, was a physical chemist whose strength was founded in quantum mechanics. The move from physics has been the intellectual immigration that has mattered most to biology [my italics].
Each of us who has emigrated from physics to biology has followed in the footsteps of giants such as Szilard and Delbrück. We each follow our own individual path, but share a common bond. Physicists have played key roles in biology, and will continue to do so.
Thomson, Roentgen, Becquerel, and Rutherford all received Nobel prizes for their work. But the most glamorous of all the Nobel laureates of the turn of the century was Marie Curie, born Marja Sklodowska in Poland in 1867. Marie went to Paris to get an education (at the Sorbonne), and there she met and married a French chemist, Pierre Curie.
Becquerel’s discovery of the radiations from uranium fascinated Marie; it was she who suggested the term “radioactivity.” With enthusiasm and imagination, she plunged into a career of investigating this phenomenon. Marie began by trying to measure the strength of radioactivity. As the instrument of measurement she used the phenomenon of piezoelectricity, involving the electrical behaviors of crystals, which had been discovered by Pierre Curie. Pierre, realizing perhaps that his wife was a greater scientist than he was, abandoned his own research and joined her.
As they measured the radioactivity of samples of uranium ore, they found to their surprise that some samples were many times more radioactive than could be accounted for by the uranium content. This could only mean that other radioactive elements also were present. But if so, the amount must be extremely small, because the Curies were unable to detect any by ordinary chemical analysis. So they decided they would have to collect huge quantities of the ore to get enough of the trace material to analyze. They managed to get tons of ore from the mines in Bohemia; the Austrian government had no use for it and was glad to give it away, provided the Curies paid for the transportation. This took almost all their life savings.
They set up shop in a little unheated shed and went to work on their mounds and mounds of uranium ore. Year after year they kept concentrating the radioactivity, discarding inactive material and working with the active. (Marie took time out to have a baby, Irene, who later turned out to be a great scientist on her own.) At last, in July 1898, they succeeded in boiling down their tons of ore to a highly radioactive residue. What they had was a pinch of black powder which was 400 times more radioactive than the same quantity of pure uranium would have been. In this bit of stuff they found a new element resembling tellurium. Mendeleev might have named it “eka-tellurium.” The Curies called it “polonium,” after Marie’s native land.
This element didn’t account for all the radioactivity, however. A still more active element must be hiding in their ore. Six months later they finally concentrated that element. Its properties were like those of barium. The element fitted into row IIa in the seventh period of Mendeleev’s table. It was the first new element discovered in the seventh period since Berzelius had found thorium 60 years before.
The Curies called the new element “radium,” because of its powerful radioactivity.
Pierre Curie died in 1906 as the result of a traffic accident (involving a horse-drawn cab, not one of the new-fangled motor cars). Marie took over his professorship at the Sorbonne and carried on alone. She was the first woman professor in the history of that proud institution. Moreover, she was the only scientist in history to receive two Nobel prizes—one in physics (shared with her husband and Becquerel) for their accurate measurements of radioactivity, and one in chemistry for the discovery of polonium and radium.
International Organization of Medical Physics President Message on the International Day of Medical Physics 2022.
The behavior of a sphere moving through a fluid illustrates how flow behavior depends on Reynolds number... At very high Reynolds number, viscosity is
small but still plays a role because of the no-slip boundary condition at the sphere surface. A thin layer of fluid, called
the boundary layer, sticks to the solid surface, causing a
large velocity gradient and therefore significant viscous drag.
For readers who want to know more about the boundary layer, let me quote the start of Chapter 8 of Steven Vogel’s masterpiece Life in Moving Fluids.
At the interface between a stationary solid and a moving fluid, the velocity of the fluid is zero. This, of course, defines the no-slip condition… The immediate corollary of the no-slip condition is that near every such surface is a gradient in the speed of flow. Entirely within the fluid, speed changes from that of the solid to what we call the “free stream” velocity some distance away. Shearing motion is inescapably associated with a gradient in speed, so in these gradients near surfaces, viscosity, fluids’ antipathy to shear, works its mischief, giving rise to skin friction and consequent power consumption. The gradient region is associated with the term “boundary layer”…
The boundary layer… wasn’t so much discovered as it was invented, in the early part of this century, as a great stroke of genius of Ludwig Prandtl. Recognizing the origin of this notion is crucial. In the basic differential equations for moving fluids, the Navier-Stokes equations, some terms result from the inertia of fluids and some from their viscosity… The Reynolds number gives an indication of the relative importance of inertia and viscosity… At Reynolds numbers below unity, inertia can be ignored and nicely predictive rules nonetheless derived—[such as] Stokes’ law for the drag of a sphere… At high Reynolds number, one might expect to get away with neglecting viscosity… It may sound neat, but it all too commonly gets us in trouble—results diverge from physical reality, drag vanishes, and d’Alembert has his paradox.
Prandtl reconciled practical and theoretical fluid mechanics at high Reynolds numbers by recognizing that viscosity could never be totally ignored. What changes with Reynolds number was where it had to be taken into account; initially it mattered everywhere, but as the Reynolds number increased well above unity, viscosity made a difference only in the gradient regions near surfaces. These regions might be small, and they might get ever smaller… as the Reynolds number increased; but as long as the no-slip condition held, a place had to exist where shear rates were high and viscosity was significant. Prandtl called the place in question… the “boundary layer.” In general, a higher Reynolds number implies a thinner boundary layer but a higher shear rate in that boundary layer.
To learn more about the biological significance of the boundary layer see the Chapter 9 in Life in Moving Fluids, which is all about “Life in Velocity Gradients.”
If you want a more rigorous and mathematical analysis of boundary layers, I recommend Boundary Layer Theory by Hermann Schlichting and his student Klaus Gersten. The eighth edition of this book (2000) is cited in IPMB; a revised and updated ninth edition was published in 2017. Schlichting and Gersten write
At the end of the 19th century, fluid mechanics had split into two different directions which hardly had anything more in common. On one side was the science of theoretical hydrodynamics, emanating from Euler’s equations of motion and which had been developed to great perfection. However this had very little practical importance, since the results of this so-called classical hydrodynamics were in glaring contradiction to everyday experience. This was particularly true in the very important case of pressure loss in tubes and channels, as well as that of the drag experienced by a body moved through a fluid. For this reason, engineers, on the other side, confronted by the practical problems of fluid mechanics, developed their own strongly empirical science, hydraulics. This relied upon a large amount of experimental data and differed greatly from theoretical hydrodynamics in both methods and goals.
It is the great achievement of [German scientist] Ludwig Prandtl [1875–1953] which, at the beginning of this century, set forth the way in which these two diverging directions of fluid mechanics could be unified. He achieved a high degree of correlation between theory and experiment, which, in the first half of this century, has led to unimagined successes in modern fluid mechanics. It was already known then that the great discrepancy between the results in classical hydrodynamics and reality was, in many cases, due to neglecting the viscosity effects in the theory. Now the complete equations of motion of viscous flows (the Navier Stokes equations) had been known for some time. However, due to the great mathematical difficulty of these equations, no approach had been found to the mathematical treatment of viscous flows (except in a few special cases). For technically important fluids such as water and air, the viscosity is very small, and thus the resulting viscous forces are small compared to the remaining forces (gravitational force, pressure force). For this reason it took a long time to see why the viscous forces ignored in the classical theory should have an important effect on the motion of the flow.
In his lecture on “Über Flüssigkeitbewegung bei sehr kleiner Reibung” (On Fluid Motion with Very Small Friction) at the Heidelberg mathematical congress in 1904, L. Prandtl... showed how a theoretical treatment could be used on viscous flows in cases of great practical importance. Using theoretical considerations together with some simple experiments, Prandtl showed that the flow past a body can be divided into two regions: a very thin layer close to the body (boundary layer) where the viscosity is important, and the remaining region outside this layer where the viscosity can be neglected. With the help of this concept, not only was a physically convincing explanation of the importance of the viscosity in the drag problem given, but simultaneously, by hugely reducing the mathematical difficulty, a path was set for the theoretical treatment of viscous flows. Prandtl supported his theoretical work by some very simple experiments in a small, self–built water channel, and in doing this reinitiated the lost connection between theory and practice. The theory of the Prandtl boundary layer or the frictional layer has proved to be exceptionally useful and has given considerable stimulation to research into fluid mechanics since the beginning of this century. Under the influence of a thriving flight technology, the new theory developed quickly and soon became, along with other important advances—airfoil theory and gas dynamics—a keystone of modern fluid mechanics.
Introductory Fluid Mechanics L19 p2 — The Boundary Layer Concept.
If you shine x-rays through a material and measure the number absorbed by it, you create an x-ray absorption spectrum. The absorption is related to the cross section; the bigger the cross section, the more the x-rays are absorbed. Figure 15.2 from Intermediate Physics for Medicine and Biology is shown below, where the cross section for carbon is plotted as a function of the x-ray energy. I’ve drawn an oval around what’s the most interesting feature of the plot, the jump in the cross section at an energy of about 0.28 keV. This abrupt rise is known as the K edge, and is an example of an absorption edge.
The cross section jumps up when the photon’s energy rises above the binding energy of a K-shell electron [an electron in the innermost energy level]. It’s not a small effect; the cross section increases by more than a factor of ten at the K edge (note that this is a log-log plot).
When I see such a dramatic effect, I imagine how surprising it must have been for the person who observed it first. Who was the person who discovered the K edge? Maurice de Broglie.
Maurice de Broglie in 1932.
Maurice was the elder brother of the more-famous Louis de Broglie, who Russ Hobbie and I mention when talking about electron waves and the electron microscope. Maurice was born in Paris in 1875. After more than a decade in the French navy, he left the military to study physics. He was interested in x-rays, which were discovered by Wilhelm Röntgen in 1895. In 1913, Maurice published the first observation of an absorption edge (Comptes Rendus, Volume 157, Pages 924–926). When World War I began, he went back to the navy to do research on detecting U-boats (German submarines). After a long career in science, including being awarded the Hughes Medal by the Royal Society of London, he died in 1960 at the age of 85.
Although Röntgen represents the beginning of X-ray science, the remarkable de Broglie royal family has been significant in both the world of science and the history of France. It has been said that if Maurice did nothing more than convince his younger brother, Louis, to drop his study of history and begin a career in science, he should be memorialized for that alone. But he did considerably more than that. His work in X-ray and atomic physics was innovative and important. Maurice had begun a career as a naval officer, but became interested in the exciting new world of X-rays and physics and resigned his commission. Beginning in the laboratory of Paul Langevin working on the ionization of gases by X-rays, he later built his own laboratory in his personal mansion on rue Châteaubriand. There he became the first in France to work with X-ray diffraction. During these experiments he invented X-ray spectroscopy. The experimental innovation came about when he mounted a single crystal on the cylinder of a recording barometer where the clockwork mechanism rotated it around its vertical axis at 2° h−1. As the crystal rotated, all angles between the incident beam and the diffraction planes (hence, all X-ray energies) were recorded on a photographic plate. In this way he obtained an X-ray line spectrum from the tube with sharp and diffuse lines, bands etc. Two of the absorption bands proved to be the K edges of Ag and Br in the photographic emulsion. This was the first observation of an absorption edge (de Broglie, 1913). It took a few more experiments to reach the correct interpretation of the absorption edges. After the end of the First World War, Maurice gathered a large group of young scientists, all working on X-ray diffraction or X-ray spectroscopy, at the laboratory in his home. Joining him in his work were, among others, Alexandre Dauvillier, Jean Thibaud, Jean-Jacques Trillat, Louis Leprince-Ringuet (all were major contributors to the field of X-ray science) and his young brother, Louis. Maurice’s scientific work and his social position soon made him a major player in the science world.
Apparently it took a while to figure out that the absorption edges belonged to materials in the photographic film and not the x-ray tube or the crystal, but eventually it was all sorted out. A German scientist, Julius Hedwig (1879–1936), independently studied x-ray spectroscopy, and may have observed an x-ray absorption edge before Maurice, but he soon abandoned the work while Maurice pursued it further, becoming the father of x-ray spectroscopy.
Recently, I stumbled upon a delightful YouTube video of an interview with Paul Horowitz, explaining how The Art of Electronics began. I’ll keep this post brief, so you’ll have time to watch the video. The host is Limor Fried, who goes by the moniker Ladyada in honor of computer programing pioneer Ada Lovelace. Fried owns the electronics company Adafruit Industries, which is a cross between a business and an educational organization. Notice that during the interview Fried wears a “transistor man” tee shirt; I remember reading about transistor man in The Art of Electronics when I was designing a circuit in John Wikswo’s lab during graduate school.
Enjoy the video, and make The Art of Electronics your go-to book for designing circuits; or, just read it for fun.
Young (1773–1829) went to medical school and was a practicing physician. How did he learn enough math and physics to become a biological physicist? In Young’s case, it was easy. He was a child prodigy and a polymath who learned more through private study than in a classroom. As an adolescent he was studying optics and building telescopes and microscopes. As a teenager he taught himself calculus. By the age of 17 was reading Newton’s Principia. By 21 he was a Fellow of the Royal Society.
Some of his most significant contributions to biological physics were his investigations into physiological optics, including accommodation and astigmatism. In Intermediate Physics for Medicine and Biology, Russ Hobbie and I state that the “ability of the lens to change shape and provide additional converging power is called accommodation.” Robinson describes Young’s experiments that proved the changing shape of the lens of the eye is the mechanism for accommodation. For instance, he was able to rule out a mechanism based on changes in the length of the eyeball by making careful and somewhat gruesome measurements on his own eye as he changed his focus. He showed that patients whose lens had been removed, perhaps because of a cataract, could no longer adjust their focus. He also was one of the first to identify astigmatism, which Russ and I describe as “images of objects oriented at different angles… form at different distances from the lens.”
Young’s name is mentioned in IPMB once, when analyzing the wave nature of light: “Thomas Young performed some interference experiments that could be explained only by assuming that light is a wave.” The Last Man Who Knew Everything describes Young’s initial experiment, where he split a beam of light by letting it pass on each side of a thin card, with the beams recombining to form an interference pattern on a screen. Young presents his famous double-slit experiment in his book A Course of Lectures on Natural Philosophy and the Mechanical Arts. Robinson debates if Young actually performed the double-slit experiment or if for him it was just a thought experiment. In any case, Young’s hypothesis about interference fringes was correct. I’ve performed Young’s double-slit experiment many times in front of introductory physics classes. It establishes that light is a wave and allows students to measure its wavelength. Interference underlies an important technique in medical and biological physics described in IPMB: Optical Coherence Tomography.
A green laser passing through two slits 0.1 mm apart produces an interference pattern. Photo by Graham Beards, published in Wikipedia.
Was Young a better biological physicist than Helmholtz? Probably not. Was Young a better scientist? It’s a close call, but I would say yes (Helmholtz had nothing as influential as the double slit experiment). Was Young a better scholar? Almost certainly. In addition to his scientific contributions, he had an extensive knowledge of languages and helped decipher the Rosetta Stone that allowed us to understand Egyptian hieroglyphics. He really was a man who knew everything.
Importance Concerns over radiofrequency radiation (RFR) and carcinogenesis have long existed, and the advent of 5G mobile technology has seen a deluge of claims asserting that the new standard and RFR in general may be carcinogenic. For clinicians and researchers in the field, it is critical to address patient concerns on the topic and to be familiar with the existent evidence base.
Observations This review considers potential biophysical mechanisms of cancer induction, elucidating mechanisms of electromagnetically induced DNA damage and placing RFR in appropriate context on the electromagnetic spectrum. The existent epidemiological evidence in humans and laboratory animals to date on the topic is also reviewed and discussed.
Conclusions and Relevance The evidence from these combined strands strongly indicates that claims of an RFR–cancer link are not supported by the current evidence base. Much of the research to date, however, has been undermined by methodological shortcomings, and there is a need for higher-quality future research endeavors. Finally, the role of fringe science and unsubstantiated claims in patient and public perception on this topic is highly relevant and must be carefully considered.
Public perception is also an important consideration, especially
in the context of addressing patient fears. Given the combined
biophysical and epidemiological evidence base to date against
the proposition that RFR is carcinogenic, it might seem surprising
that this belief is so widely evangelized and propagated relentlessly.
A major and unedifying part of the reason for this is the noxious
influence of fringe science on confounding public understanding; the
BioInitiative Report, a nonscholarly [non-peer reviewed] work that insists that RFR causes
many harms from cancer to autism, has been widely circulated since
2007. Despite its popularity, it has been repeatedly debunked by
health bodies worldwide, and the attempts to treat its unsubstantiated
assertions as equivalent to the weight of peer-reviewed weight
of scientific evidence are archetypical false balance.
Tellingly perhaps, the recent misinformation propagated around
5G is not even new—the same grave claims were made about prior
mobile technologies for decades and were equally unsupported.
Their renaissance now is underpinned by disinformation perpetuated
across social media and a microcosm of a greater problem with
online disinformation. There is, for example, a thriving online market
for dubious devices that promise to protect consumers from RFR,
furthering a likely misguided perception of harm. Cancer is an emotive
topic, which undoubtedly increases the virulence of misguided
assertions. It is accordingly important to be cognizant of the fact that
while the issue may be strictly academic to researchers, it is a source
of anxiety and apprehension to patients and the general public, and
there is an onus on scientists to both convey the scientific consensus
and to ensure that future work is conducted to a high standard.
The International Agency for Research on Cancer designation of RFR as a group 2B agent (a possible carcinogen) in 2011 is also frequently
misunderstood as implying evidence of harm. However, such
an interpretation is incorrect, as reiterated in the most recent International
Agency for Research on Cancer communication in 2020,
which stated that “despite considerable research efforts, no mechanism
relevant for carcinogenesis has been consistently identified to
date. In the past 5 years, epidemiological research on mobile phone
use and tumours occurring in the head has slowed down compared
with the previous decade. Most new and previous case-control studies
do not indicate an association between mobile phone use and
risk of glioma, meningioma, acoustic neuroma, pituitary tumours,
or salivary gland tumours.”
It is worthwhile too to acknowledge a potentially political dimension
to the propagation of falsehoods on 5G in particular; a New
York Times investigation found that Russian state forces were complicit
in spreading falsehoods, with the European Commission finding
the fingerprints of both Russian and Chinese health disinformation
rising with the advent of COVID-19, including false claims
linking cancer to RFR. All of this undermines collective understanding and makesit imperative that scientists be at the vanguard of communicating the evidence to prevent detrimental misconceptions [my italics].
Grimes has taken much criticism for his article, all of which, in my opinion, is undeserved. See, for example, this website containing an attack titled “Why did JAMA Oncology publish a paper written by a Telecom industry spokesperson?” by Joel Moskowitz (JAMAOncology did no such thing). Several groups called for JAMA Oncology to retract Grimes’s article, but the journal refused (I’m proud of them). My advice for Grimes is to just be happy that people are paying attention to his work. Are Electromagnetic Fields Making Me Ill?, which covers much of the same ground and comes to similar conclusions, has not been similarly criticized, apparently because the critics are either unaware of it or don’t think it’s important enough to bother with.
Problem 24. The differential form of Ampere’s law,
Eq. 8.24, provides a relationship between the current density
j and the magnetic field B that allows you to measure
biological current with magnetic resonance imaging (see, for
example, Scott et al. (1991)). Suppose you use MRI and find
the distribution of magnetic field to be
Bx = C(yz2 − yx2)
By = C(xz2 − xy2)
Bz = C4xyz
where C is a constant with the units of T m−3. Determine
the current density. Assume the current varies slowly enough
that the displacement current can be neglected.
To solve this homework problem, calculate the curl of the magnetic field to get, within a proportionality constant, the current density.
By the way, the problem doesn’t ask you to do this, but you might want to verify that the divergence of B is zero as it must be according to Maxwell’s equations, and that the divergence of j is zero (conservation of current).
Using MRI to measure current density was one of those ideas I wish I’d thought of, but I didn’t. When Peter Basser and I wrote a paper analyzing an alternative (and less successful) method to detect action currents using MRI, we cited four of Joy’s articles in our very first sentence! I first met Joy when we co-chaired a session at the 2009 IEEE Engineering in Medicine and Biology Society Conference in Minneapolis. I had the honor of being the external examiner for one of Joy’s graduate students, Nahla Elsaid, at her 2016 dissertation defense. Joy was a delightful guy, and a joy to work with.
I’ll miss him.
MICHAEL LAWRENCE GRAHAME JOY (July 31, 1940–July 5, 2020) was born in Toronto and died at Drynoch Farm in Caledon, on his own terms, in his own time. He was predeceased by his wife Jane (née Andras) and will be dearly missed by his wife Carol Fanning, his son Rob, his daughters Gwen and Ellen, their partners, his grandchildren (Asha, Nel, Tallulah, Freya, Kelvin, and Skyler) and generations of nieces, nephews, cousins, former students, friends and colleagues.
Mike was professor emeritus at the University of Toronto; Institute of Biomaterials & Biomedical Engineering; Department of Electrical & Computer Engineering. He was a pioneer in the development of Magnetic Resonance and Electric Current Density Imaging and earned numerous significant grants, awards and citations.
Mike, (Muncle Ike, Zeepa) was truly a unique individual. He was a man of many interests who always had time for the numerous children who would follow him like shadows as he puttered on his latest amazing project. He could turn the most mundane chore into both an adventure and a learning experience. He imparted his love of nature, enquiry and adventure on his young assistants, whether tinkering on his jet boat Feeble, constructing a zip line, building model rockets, fishing, or going on long walks where “getting lost” was all part of the fun.
Mike enjoyed being surrounded by those he loved. His birthday parties at the Bay were the highlight of the summer while the Christmas tree parties at the Farm kicked off the festive season. Whether at summer picnics, Church, dinners, gatherings, bridge games, visiting family at Nares Inlet or summer afternoons on the side porch, he was always at the center of things with his distinctive laugh and quick sense of humour.
Mike left his imprint on so many. His was a life well lived and well loved. In lieu of flowers, please consider a donation to the Georgian Bay Land Trust, one of the many conservation projects Mike supported.
This blog is about physics applied to medicine and biology, but if we don’t solve the climate crisis there’s no use developing fancier ways to do medical imaging or radiation therapy; we’ll all be dead. So today I’m going to tell you about a book I just read, titled Drawdown: The Most Comprehensive Plan Ever Proposed to Reverse Global Warming. It’s the book I’ve been looking for. It analyzes all the different ways we can address global warming, and ranks them by impact and importance. Here’s how the editor Paul Hawken begins Drawdown.
The genesis of Project Drawdown was curiosity, not fear. In 2001 I began asking experts in climate and environmental fields a question: Do we know what we need to do in order to arrest and reverse global warming? I thought they could provide a shopping list. I wanted to know the most effective solutions that were already in place, and the impact they could have if scaled. I also wanted to know the price tag. My contacts replied that such an inventory did not exist, but all agreed it would be a great checklist to have, though creating one was not within their individual expertise. After several years, I stopped asking because it was not within my expertise either.
Then came 2013. Several articles were published that were so alarming that one began to hear whispers of the unthinkable: It was game over. But was that true, or might it possibly be game on? Where did we actually stand? It was then that I decided to create Project Drawdown. In atmospheric terms drawdown is that point in time at which greenhouse gases peak and begin to decline on a year-to-year basis. I decided that the goal of the project would be to identify, measure, and model one hundred substantive solutions to determine how much we could accomplish within three decades towards that end.
Many solutions are presented in Drawdown, but here I count down the top ten, ranked according to their total atmospheric carbon dioxide reduction, with a brief quote from Drawdown accompanying each.
10. Rooftop Solar
As households adopt rooftop solar… they transform generation [of electricity] and its ownership, shifting away from utility monopolies and making power production their own.
9. Silvopasture
Silvopasture is… the integration of trees and pasture or forage into a single system for raising livestock… Trees create cooler microclimates and more protective environments, and can moderate water availability. Therein lies the climatic win-win of silvopasture: As it averts further greenhouse emissions from one of the world’s most polluting sectors, it also protects against changes that are now inevitable.
8. Solar Farms
Any scenario for reversing global warming includes a massive ramp-up of solar power by mid-century. It simply makes sense: the sun shines every day, providing a virtually unlimited, clean, and free fuel at a price that never changes. Small, distributed clusters of rooftop panels are the most conspicuous evidence of the renewables revolution powered by solar photovoltaics (PV). The other, less obvious iteration of the PV phenomenon is large-scale arrays of hundreds, thousands, or in some cases millions of panels [solar farms] that achieve generating capacity in the tens or hundreds of megawatts.
7. Family Planning
Increased adoption of reproductive healthcare and family planning is an essential component to achieve the United Nations’ 2015 medium global population projection of 9.7 billion people by 2050. If investment in family planning, particularly in low-income countries, does not materialize, the world’s population could come closer to the high projection, adding another 1 billion people to the planet.
6. Educating Girls
Girls education, it turns out, has a dramatic bearing on global warming. Women with more years of education have fewer, healthier children and actively manage their reproductive health… Synchronizing investments in girls’ education with those in family planning would be complementary and mutually reinforcing. Education is grounded in the belief that every life bubbles with innate potential. When it comes to climate change, nurturing the promise of each girl can shape the future for all.
5. Tropical Forests
In recent decades, tropical forests... have suffered extensive clearing, fragmentation, degradation, and depletion of flora and fauna… One of the dominant storylines of the nineteenth and twentieth centuries was the vast loss of forestland. Its restoration and re-wilding could be the twenty-first-century story.
Whether on the farm, near the fork, or somewhere in between, efforts to reduce food waste can address emissions and ease pressure on resources of all kinds, while enabling society more effectively to supply future food demand.
2. Wind Turbines
Ongoing cost reduction will soon make wind energy the least expensive source of installed electricity capacity, perhaps within a decade.
1. Refrigerant Management
As temperatures rise, so does reliance on air conditioners. The use of refrigerators, in kitchens of all sizes and throughout “cold chains” of food production and supply, is seeing similar expansion. As technologies for cooling proliferate, evolution in refrigerants and their management is imperative.
While reading Intermediate Physics for Medicine and Biology, let’s turn up the thermostat a bit during warm days. Between chapters, let’s ditch the hamburger and eat a salad instead (and if you can’t finish it, save the rest for leftovers). Let’s make sure girls in particular are encouraged to read IPMB (or whatever else that will help with their education). And let’s write our congressional representatives and encourage them to support solar and wind energy sources.
If you don’t have the time to read Drawdown, or don’t have easy access to it, then visit the website drawdown.org or watch the videos below, which summarize the plan to reverse global warming.
“Earth teems with sights and textures, sounds and vibrations, smells and tastes, electric and magnetic fields. But every animal can only tap into a small fraction of reality’s fullness. Each is enclosed within its own unique sensory bubble, perceiving but a tiny sliver of our immense world.”
An Immense World sometimes overlaps with Intermediate Physics for Medicine and Biology. For example, both books discuss vision. Yong points out the human eye has better visual acuity than most other animals. He writes “we assume that if we can see it, they [other animals] can, and that if it’s eye-catching to us, it’s grabbing their attention… That’s not the case.” Throughout his book, Yong returns to this idea of how sensory perception differs among animals, and how misleading it can be for us to interpret animal perceptions from our own point of view.
Like IPMB, An Immense World examines color vision. Yong speculates about what a bee would think of the color red, if bees could think like humans.
Imagine what a bee might say. They are trichromats, with opsins that are most sensitive to green, blue, and ultraviolet. If bees were scientists, they might marvel at the color we know as red, which they cannot see and which they might call “ultrayellow” [I would have thought “infrayellow”]. They might assert at first that other creatures can’t see ultrayellow, and then later wonder why so many do. They might ask if it is special. They might photograph roses through ultrayellow cameras and rhapsodize about how different they look. They might wonder whether the large bipedal animals that see this color exchange secret messages through their flushed cheeks. They might eventually realize that it is just another color, special mainly in its absence from their vision.
Both An Immense World and IPMB also analyze hearing. Yong says
Human hearing typically bottoms out at around 20 Hz. Below those frequencies, sounds are known as infrasound, and they’re mostly inaudible to us unless they’re very loud. Infrasounds can travel over incredibly long distances, especially in water. Knowing that fin whales also produce infrasound, [scientist Roger] Payne calculated, to his shock, that their calls could conceivably travel for 13,000 miles. No ocean is that wide.…
Like infrasound, the term ultrasound… refers to sound waves with frequencies higher than 20 kHz, which marks the upper limit of the average human ear. It seems special—ultra, even—because we can’t hear it. But the vast majority of mammals actually hear very well into that range, and it’s likely that the ancestors of our group did, too. Even our closest relatives, chimpanzees, can hear close to 30 kHz. A dog can hear 45 kHz; a cat, 85 kHz; a mouse, 100 kHz; and a bottlenose dolphin, 150 kHz. For all of these creatures, ultrasound is just sound.
In IPMB, Russ Hobbie and I introduce the decibel scale for measuring sound intensity, or how loud a sound is. Yong uses this concept when discussing bats.
The sonar call of the big brown bat can leave its mouth at 138 decibels—roughly as loud as a siren or jet engine. Even the so-called whispering bats, which are meant to be quiet, will emit 110-decibel shrieks, comparable to chainsaws and leaf blowers. These are among the loudest sounds of any land animal, and it’s a huge mercy that they’re too high-pitched for us to hear.
Yong examines senses that Russ and I never consider, such as smell, taste, surface vibrations, contact, and flow. He wonders about the relative value of nociception [a reflex action to avoid a noxious stimulus] and the sensation of pain [a subjective feeling created by the brain].
The evolutionary benefit of nociception is abundantly clear. It’s an alarm system that allows animals to detect things that might harm or kill them, and take steps to protect themselves. But the origin of pain, on top of that, is less obvious. What is the adaptive value of suffering?
On the continuum ranging from life’s unity to diversity, Yong excels at celebrating the diverse, while Russ and I focus on how physics reveals unifying principles. I’m sometimes frustrated that Yong doesn’t delve into the physics of these topics more, but I am in awe of how he highlights so many strange and wonderful animals. There’s a saying that “nothing in biology makes sense except in light of evolution.” That’s true for An Immense World, which is a survey of how the evolution of sensory perception shapes they way animals interact, mate, hunt their prey, and avoid their predators.
Two chapters of An Immense World I found especially interesting were about sensing electric and magnetic fields. When discussing the black ghost knifefish’s ability to sense electric fields, Yong writes
Just as sighted people create images of the world from patterns of light shining onto their retinas, an electric fish creates electric images of its surroundings from patterns of voltage dancing across its skin. Conductors shine brightly upon it. Insulators cast electric shadows.
Then he notes that
Fish use electric fields not just to sense their environment but also to communicate. They court mates, claim territory, and settle fights with electric signals in the same way other animals might use colors or songs.
Although flowers are negatively charged, they grow into the positively charged air. Their very presence greatly strengthens the electric fields around them, and this effect is especially pronounced at points and edges, like leaf tips, petal rims, stigmas, and anthers. Based on its shape and size, every flower is surrounded by its own distinctive electric field. As [scientist Daniel] Robert pondered these fields, “suddenly the question came: Do bees know about this?” he recalls. “And the answer was yes.”
The chapter on sensing magnetic fields is different from the others, because we don’t yet know how animals sense these fields.
Magnetoreception research has been polluted by fierce rivalries and confusing errors, and the sense itself is famously difficult both to study and to comprehend. There are open questions about all the senses, but at least with vision, smell, or even electroreception, researchers know roughly how they work and which sense organs are involved. Neither is true for magnetoreception. It remains the sense that we know least about, even though its existence was confirmed decades ago.
If you want to read a beautifully written book that explores how much of the physics in Intermediate Physics for Medicine and Biology can be used by species throughout the animal kingdom to sense their environment, I recommend An Immense World. You’ll love it.
Umwelt: The hidden sensory world of animals. By Ed Yong.
I am an emeritus professor of physics at Oakland University, and coauthor of the textbook Intermediate Physics for Medicine and Biology. The purpose of this blog is specifically to support and promote my textbook, and in general to illustrate applications of physics to medicine and biology.
