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This post is a review of Mr. Tompkins in Wonderland by George Gamow . Though first published in 1940, it still remains a classic of science popularization and I often give out copies of it to the undergraduates who top my modern physics/quantum physics courses. A pdf is available online for free. The book is largely related through the adventures of Mr. Tompkins, a bank clerk, who is interested in science. Gamow explains three areas of modern science by exaggerating their effects through a clever device. (He calls his book science fantasy, not science fiction). In his fantasy, he keeps the laws of physics the same and only changes the values of some constants of nature. For example, by exploring what would happen if light were to move very slowly Gamow makes the consequences of special relativity very prominent and easy to understand. Similarly, he chooses a large gravitational constant (in our universe this is a small number) to highlight the nature of gravity; and a large Planck's constant to exaggerate the effects of quantum mechanics. All this makes the physics easier to understand. Vis-a-vis Mr. Tompkins, the effects are also amusing. Relativity : The speed of light in real life is 186,000 miles per second. Gamow reduces it to about ten miles per hour in Mr. Tompkins' dream when he falls asleep during a popular relativity lecture. This makes the police lazy about catching speeders , since everybody is going slow anyway. Folks who travel for business age more slowly than their relatives who stay at home. A murder case is solved using the effects of causality and the relativistic notion of simultaneity. Gravity : Gamow considers a situation in which the strength of gravity (which in our universe is so weak, its effects are prominent only when large masses are involved) is increased greatly. The large value of gravity makes space curve on itself in a diameter of five miles (a stone thrown by you would come back in about an hour, so you have to watch out or you'll be hit by it), and allows Mr. Tompkins to stand upside down on a floating rock. Quantum Mechanics : Making Planck's constant (which is very small in our universe, making quantum effects subtle to detect) large, Mr. Tompkins sees billiard balls on a table spread out like waves after being struck ('quantum elephantism' as per Gamow; s-wave scattering for the experts); then goes to a 'quantum jungle' where the elephant he is riding on is attacked by 'multiple' tigers, which all 'collapse' into one when Tompkins manages to fire a bullet into the right place. Although Gamow uses fantasy, he does not shy away from technical expositions in his book. There are figures and (numbered!) equations in the text. But the illustrations are helpful and artistic and the equations are simple and revealing. There are also arias set to music, but since I do not read staff notation, only the words made sense to me (some of it is nonsense verse). At some points the fantasy may seem a bit forced, for example in the conversation between the scientist Dirac and a dolphin, and in the Luiz Alvarez liquid hydrogen Bath Tub. But these can be taken with a grain of salt. Summary Overall, the book is a minor classic, and I did not find anything which has been proved wrong since then, though of course a lot of new information has been found. I had first read it in college (25 years ago); I found it to be a good and entertaining re-read more recently. Afterword There is an educational film on YouTube with the same name.

A favorite pastime of physicists - like that of sports fans or politics enthusiasts - is comparing prominent figures in their discipline to each other: was Einstein's contribution bigger than Newton's? Was Faraday as important as Maxwell? Are the best mathematicians of today as good as Euler or Lagrange? As may be expected, the debate is ultimately inconclusive, but the discussion sharpens our knowledge of how knowledge is appraised, how major contributions are made, and what we need to be careful about when delivering judgements on such comparisons. Some thoughts about the matter follow. Who showed up first is often a crucial ingredient in the discussion. On the one hand the first person to discover or invent something has sometimes little prior art (in the language of patenting) to rely on. For example, when Newton and Leibniz discovered calculus, it was a major step (although Newton said he stood on the shoulders of giants; for example, the analytic geometry of Descartes influenced him greatly). And it is surely true that this advance facilitated many discoveries down the line (e.g. Maxwell's laws of electromagnetism). At the same time, I think chronological priority makes subsequent discoveries of the same order of magnitude difficult: calculus can only be invented once. Indeed, when Newton discovered the universal law of gravitation, Lagrange famously said that " Newton was the greatest genius that ever existed, and the most fortunate, for we cannot find more than once a system of the world to establish." It took Einstein to find another system. Who was greater? (Einstein gave his own vote to Newton). From the perspective of experimental discoveries, time again plays an interesting role. For example, there can be no doubt that the discovery of electromagnetic induction by Faraday was a stunning advance, facilitating, among other things, the motors that are now so indispensable to present day technology. However, it is very hard to make again a discovery of that level, since the laws of physics seem to be so few - there aren't too many of that class remaining to be discovered (at least so it seems). Perhaps the next major step in electromagnetism was the discovery of superconductivity by Kammerlingh Onnes. Should we put him in the same class as Faraday? Maybe not, as Faraday was more prolific and versatile; but then Onnes marshalled much more complex technology (for the liquification of Helium). The argument can be wound back to Einstein who phrased special relativity using not even calculus, just high school algebra - can anyone make such a fundamental advance today using such a simple theoretical tool? In fact Newton was a mathematical genius who created new mathematics; Einstein was not a mathematical genius (he described himself modestly as a mathematical ignoramus), but he upended Newton's universe with his physics. Who, then, we ask again, was greater? The debate is inconclusive, but in the process we learn more about Newton and Lagrange and Faraday and Maxwell and Einstein and Kammerlingh Onnes. Afterword At some point I will do a post on current ranking systems such as the h-index , proposed by Jorge Hirsch who has been controversial as a physicist (he was previously banned from the arxiv for using unprofessional language), although the index he proposed has become very popular.

This is a review of the book Elon Musk by Walter Isaacson . Some readers might find the subject contentious, especially given the current political environment. I should probably therefore declare at the outset that I am neither an unqualified fan nor an abject hater of Musk. Overall, I do find him to be a fascinating character. Many aspects of Musk's life are described in the 670-page book; in this review I will focus on the scientific and engineering aspects, and also some of the managerial philosophies. From my perspective the contents of the book may be described by basically stating Musk's agenda plus algorithm and his various ventures. The Musk Manifesto Start with a grand motive. Focus on making this mission succeed, rather than on making profit. Obtain and maintain individual control of the project. Have a superaggressive sense of urgency. Set impossible deadlines. This drives people to accomplish tasks they thought were outside their reach. Remove all that is not necessary from the path. One of Musk's favorite words is 'delete'. He believes only the laws of physics are fundamentally binding on any enterprise; everything else is a recommendation. If at least 10% of what was deleted was not reinstated then not enough deletion had been made in the first place. Trust that a few capable - Musk's preferred word is 'hardcore' - people are more effective than a big inertial task force. Hence his tendency to fire employees, often using the phrase in the title of this post. Companies i) Zip2 : Combined business directories with maps in the early days of the internet. This was the first company started by Musk. It was later acquired by Compaq. ii) PayPal : Allowed online financial transactions. This was set up in collaboration with Peter Thiel and others. iii) SpaceX : Made spaceflight commercial. Musk believes human consciousness to be precious and wants it to survive any planetary disasters Earth might face. The most immediate aim is to get to Mars (preferably before Musk dies). The subsidiary Starlink provides internet connectivity via a satellite network. This service has featured recently in the war in Ukraine. iv) Tesla : Made electric vehicles commercially mainstream. This was done, at least initially, in collaboration with Martin Eberhard and Marc Tarpenning. Later, Tesla diversified into clean energy, acquiring SolarCity which makes solar panels, etc. v) OpenAI : This company focuses on the uses of artificial intelligence. The negotiations in the book feature now well-known characters like Demis Hassabis (Nobel Prize in Chemistry 2024) and Sam Altman. See here for a video of Optimus the humanoid robot. Musk eventually left the company. vi) The Boring Company : Provides infrastructure (such as tunnels) aimed at solving transport problems. vii) Neuralink : Interfaces human intelligence with AI, by putting chips in our brains. See this video of a monkey playing electronic ping-pong mentally. viii) Twitter/X: As everybody knows. Summary In my opinion Isaacson has done a really good job of conveying Musk's thinking, his commercialization of disruptive technologies, his thirst for constant innovation, and his avid risk taking. The aspects of Musk's life that I did not cover - his childhood, family and romantic life, business and personal relations - are quite dramatic and combined with its technological highlights and sociological relevance - make the book unputdownable.

This post is a short review of the book Einstein's Universe by Nigel Calder . The book came out in 1979, celebrating the 100th anniversary of Einstein's birth, and had the same title as the BBC film released on that occasion (whose script Calder wrote). Although the book is almost 45 years old, it is interesting because Einstein's science is still good; also I found the subtitle on the cover - "Relativity Made Plain" - alluring. The book mainly covers special and general relativity (black holes, pulsars, gravitational waves), though it mentions the phenomena of the photoelectric effect and stimulated emission as well. Over 21 short chapters (the book is 154 pages long) interesting descriptions are provided for how to weigh a black hole (from the dynamics of the nearby stars), why a pressing iron is heavier when hot (because energy equals mass), how Dicke's theory of relativity (which assumes the gravitational constant changes with space and time) compares with Einstein's. I found the speculation about finding gravitational waves interesting, because the book dates back to way before they were first observed in 2016. The author definitely has a sense of humor. The book has several amusing observations - as to why relativity is a bad name for the theory, how we can satisfy all our energy needs by dumping our trash into a black hole, how if you travel fast you will age slowly, but gain more weight. I found a couple of statements somewhat confusing - for example, the book associates light (because it has energy) with mass (but photons are massless!). Some statements of course need to be updated - the book acknowledges that the universe is expanding, but that the rate of expansion is accelerated (driven by dark energy) was established much after the book was published. Still, it is quite amazing how much of the book's content is still pretty much valid today. The book ends with a treatment of Einstein's discomfort with quantum mechanics, and a good summary of the qualities made Einstein great as a scientist - scepticism, childlike wonder, good intuition, introversion and persistence. Not, as the book notes, great mathematical dexterity. It reminded me of one of Einstein's quotes that I really like: "Most people say that it is the intellect which makes a great scientist. They are wrong: it is character." Summary The book is written with verve and makes for good reading even today. Calder's experience in communicating with lay audiences shines through. A number of very distinguished scientists are acknowledged for help - Dennis Sciama, Irwin Shapiro, Roger Penrose, Wheeler, Sydney Drell, etc. Maybe the number of chapters could have been condensed. There's a good number of diagrams and photos (e.g. of rockets etc.). Worth reading if only to gauge how the world was responding to a hundred years of Einstein's work.

This post is a review of The Zoologist's Guide to the Galaxy: What Animals on Earth Reveal About Aliens and Ourselves by Arik Kershenbaum . The author's basic idea is to propose that some aspects of life are universal - applicable throughout the Universe - and these principles can be used to make educated guesses about the nature of life on places other than Earth. Motivation The subject of the book has become topical especially in the last few years, as a large number (thousands) of exoplanets - planets that orbit stars other than our Sun - have been discovered and have raised the prospect of the discovery of life in the universe out there. Discussion of what that kind of life could look like is useful as it would help in its discovery, in communicating with it, and in coexisting with it. Assumptions We have a lot of confidence that the laws of physics and chemistry are universal. The author sets out to state those principles of biology (life) that are likewise universal. He assumes that: i) If there is life there has to be death (I disagree with all three reasons he gives for this later in the book; for example, he says otherwise we would run out of space - Hey the universe is infinite as far as we can see! There's plenty of space out there - please bring on the immortality!). ii) Living beings will need to eat, reproduce, compete, and cooperate (and hence communicate). iii) If life and death are present there must be mutation and natural selection (independent of any specific biochemistry, e.g. DNA). Characteristics With such assumptions, the book says that evolution anywhere will generate similar solutions for similar problems, though the mechanisms might be different, as on Earth. Some examples of interesting aspects treated in detail are i) Motion : This is necessitated by the need to find food, or avoid becoming food. The modes of motion developed by aliens will depend on what their planet is made of (has to be liquid solid or gas) and which forces it is dominated by (gravity, liquid viscosity, magnetic fields, etc.). Thus, if the aliens live at the interface of a solid and a fluid (as humans do), they will probably have legs (which efficiently solve the necessity of having some frictional contact but not so much as to be a total drag -:)). They will probably also have bilateral symmetry (which evolved as it is more efficient than its absence - easier to walk/run than hop on one leg). ii) Sex : The Universe is a hostile place and in order to survive, life needs to become complex and diverse; also, cooperation or sociality emerges from the unequal sharing of traits (blood is thicker than water). But asexual reproduction leads to very little diversity as characteristic (genes for us) are generally not exchanged; and this kind of cloning basically leads to equal trait sharing for everybody. Hence aliens, if they are advanced, must be having sex. iii) Communication: This is required for cooperation. The prediction here is that the physics of the planet will select the modality. In our own case, since light is blocked more easily by obstacles than sound, our preferred mode of communication is aural. If the alien planet has an atmosphere that absorbs sound, but allows light, their preferred mode might be visual. There is a very interesting discussion in the book in this context about the attribute most scientists agree humans possess in the greatest degree compared to other animals - language. The book asks what language is, how can it be identified algorithmically (see Zipf's Law ), and consequently how to detect signals from alien civilizations. iv) Intelligence: Possibly an even more contentious topic than communication. The book tries to characterize intelligence (as a prediction machine useful for survival, as the ability to learn, as a means of inducing flexible behavior and hence Darwinian fitness, etc.). There is a discussion about AI (the book came out in 2020), alien intelligence, personhood and whether aliens could be considered human in any sense. My favorite part: Alex the speaking African Gray parrot of Prof. Irene Pepperberg. Conclusion I found the book quite stimulating and informative. As might be expected, consideration of such a topic leads to deep meditations about what makes us alive and human, even more than it leads to realistic conclusions about the nature of alien beings. Because we know so little about the rest of the (especially far-away parts of) universe, and because we only have a single example of a living planet, it is only possible to speculate about aliens. Thus the book's real accomplishment, in my opinion is to sharpen the questions, rather than to provide answers. The writing is generally clear and tight, though some repetition could have been avoided, in my opinion. One of the things I really liked is the explicit mention of booktitles in the footnotes, which helped me mark several of them down for further reading (there is also a bibliography/suggested reading at the end). Afterword One of my favorite quotes from Arthur C. Clarke: It's not a UFO until you see the Mars registration plate!

This post is about James Sylvester Gates, Jr. , who visited our campus earlier this week . Jim, as he likes to be called, is a distinguished string theorist and a popularizer of science, with a bunch of popular science books (see below), and lots of YouTube videos of his talks and interviews (I enjoyed particularly the extensive one with Lex Fridman ). Early Life Jim is a very interesting character. He is an African-American. But as an army kid, he managed to reach the age of 13 without experiencing segregation, since the US army had integrated in 1948 following President Truman's executive order. Once he stepped out into the civilian world, however, he had 'to learn how to be black'. As an ironical offshoot of racial policies, he came under the influence of an outstanding physics teacher at the segregated Jones High School in Orlando, Freeman Coney, who in desegregated times would likely have been teaching at a university or working in industry. Higher Education His interests motivated by Coney (and Marvel comics, as he showed in his talk), Jim then attended MIT (BS in physics and math) and PhD (Physics; he told me his thesis was based on the work of Nobel prize winner Abdus Salam who later invited Jim to give a talk at the ICTP in Trieste), moving on to a postdoc at CalTech (mentored by Richard Feynman and Murray Gell-Mann, both Nobelists), and then faculty positions at MIT, Brown, Howard and now Maryland. Gates has also worked at the interface of STEM education and science policy, and was honored with a National Medal of Science by President Obama in 2013. Research Jim's physics work is highly mathematical and technical. He works in an area of string theory which considers bosons and fermions to be symmetric partners - in lay language this means in the theory the equations for force and matter have the same form. Jim is a pioneer and authority in his field and a co-author of Superspace, or One thousand and one lessons in supersymmetry (1984 ) . A free version can be found here . The Universe as Simulation Gates' work has a powerful appeal for lay people. With collaborators, he found he could express the equations of supersymmetry pictorially in terms of diagrams that he called adinkras (after patterns from West Africa which express aphorisms or concepts). These diagrams are beautiful and fascinating by themselves. However, using them Gates further figured out that the equations of supersymmetry (which attempt to describe the cosmos at its most fundamental level) contain error-correction codes, of the same type as invented by Hamming and others and which are routinely used in our browsers, etc. These codes ensure that our messages do not turn into gibberish due to the imperfect nature of our computers, transmission wires, etc. Therefore finding them built into the fundamental equations of the cosmos implies suggestively that the universe is a simulation [although the error-correction is clearly not working in my case -:)] as implied in the popular movie the Matrix. Here is an accessible popular article by Jim about this work. Conclusion Added to my reading queue, the popular science books written by Gates: [1] Superstring Theory: The DNA of Reality [2] Reality in the Shadows [3] Proving Einstein Right

Historically, students with advanced degrees in physics (i.e. a PhD) have rarely had the financial world in their sights. This changed in the last two decades of the 20th century when physicists began to get involved in the finance industry. The end product of this exercise was the emergence of financial engineers who use mathematical tools to model money. These professionals are called quants for short. This post is a review of the book My Life as a Quant  by Emanuel Derman . Derman came to the US from South Africa, obtained a PhD in particle physics from Columbia, rose to upper levels at Goldman Sachs, and now teaches financial engineering at Columbia. He worked closely with Black (of Black-Scholes equation fame) and has an interest rate model (the Black-Derman-Toy model) named after him. The book is a quite detailed and revealing account of how physicists (can) transition into finance. As someone who knows practically nothing about the finance industry, I found it fascinating. Early Years Derman does not say too much about his initial years in South Africa; the book really gains meat once he lands in the US. It provides a substantial description of American physics graduate schools in the 70's (they haven't changed too much, perhaps). Derman describes the almost religious devotion to fundamental physics with which he joined the PhD program at Columbia, the star faculty at the time in the department (Rabi was still around, but the emergent personality was T. D. Lee, both were Nobelists), his brilliant classmates, the loneliness that seems to be the lot of (especially) international students who are introverts, the long haul of coursework, the dog years of finding an advisor and solving a research problem whose impact on the field is not quite earth-shaking, the seven years (which he estimates as ten percent of his life span) taken to finally complete the PhD. He describes three postdoctoral positions he then holds, at UPenn, Oxford and Rockefeller, marked by the not unusual travails of living separately from his wife, his mother's gradual lapse into Lou-Gehrig's disease, the lack of close friends, the pressure of generating results much faster than during the PhD, the low salary, the competition from highly gifted and driven physicists, the conflicts with postdoctoral advisors, and uncertainty about future employment. Finally, he finds a physics faculty position in Boulder, which he quits after one year, disliking the intense solitude the work forces upon him (interactions with faculty were sparse; those with students are not mentioned; his wife and now son were still living in New York). The narrative until now repeats Derman's profound dissatisfaction with the academic process, loneliness and uncertainty, and the deepening realization that he will never do anything great (at the level of Einstein, Feynman, or T. D. Lee). During these years, Derman flirts with various Western philosophies, eastern (Buddhist) practices, and the idea of becoming a doctor. Middle Years After quitting academia Derman moves to Bell Labs. Here he discovers his love of computing (C and Unix had been invented at Bell recently) and his distaste for big bureaucracy. Almost from the beginning of his 5 years there, he looks for an exit strategy. At this time, Wall Street is headhunting for software types since they need someone to model stocks and (more so) bonds, etc. Derman joins the Financial Strategies Group and is mentored by Ravi Dattatreya, himself an engineer who had quit Bell earlier. Here Derman flourishes. Good physicists are versatile, capable and interested in learning new things; the mathematics required to model securities is familiar to physicists as stochastic calculus; also physicists are used to writing their own code. All these qualities helped Derman excel at GS. Quants, like physicists, read papers and build models. The most famous financial model is named the Black-Scholes-Merton (Scholes and Merton got the economics Nobel in 1997; Black had died earlier) equation. Fischer Black worked at GS and Derman soon got to collaborate with him; the book has many professional and personal recollections about Black, including how Derman was rehired by Black after a brief hiatus working at Salomon Brothers . Later Years In 2002 Derman retires from GS and starts teaching financial engineering at Columbia. This part of the book has interesting discussions about how his background in physics helped him flourish in finance. The kind of physics he was trained on is called phenomenology : here you don't come up with fundamentally new laws or even an exact microscopic description using known laws, for a system you are trying to understand. You just build a model which replicates the phenomena displayed by the system. This approach works nicely for modeling a complicated financial system, where the microscopic variables are not well characterized, and can take random values. Summary There is a lot of technical detail in the book about the details of the financial instruments Derman worked to model, the technology used by the industry (one of his first tasks was to build a GUI for traders), etc. As I am not an expert on these, I have largely left them out of the review. For me, the interesting parts were how some physicists are not turned on by the agenda of academic physics which can feel like slaving away in a corner by yourself (I kind of enjoy that, actually); and also how the training of a physicist can be useful for tasks that one might not initially expect. All in all a good read, giving us a window into an important physics-related development in the finance industry.

Concrete In physics-teaching we try to make the subject relatable by giving concrete examples to illustrate the principles at hand. For example, in an introductory mechanics course, we show the students a ball rolling down a slope (rather than general spheres and inclines), cannonballs and divers jumping from cliffs (rather than abstract projectile motion), hockey pucks on ice (representing frictionless motion), etc. In a more advanced course, like electromagnetism or quantum mechanics, this becomes challenging, because a realistic situation is complicated, but we need to 'learn the ropes' of the subject by first looking at somewhat artificial but simple examples (such as charges located at the corners of a square in electromagnetism, or a particle in an infinite well). Nonetheless, each model system being studied needs to be motivated clearly (students must be told why that model is important - 'why do we need to study this?'). Preferably, even before we get into the details of the model, the relevant outcomes (a list of objectives that we expect to learn) of the study should be outlined (e.g. 'this will help us understand how radioactivity occurs'), and the list needs to be checked off at the end of the exercise, for full customer satisfaction. Abstract All this is well and good. However, those who are looking to make original contributions to the subject may want to consider this kind of thinking (clarified and predictable) carefully and understand it for what it is. Because in physics research, advances both great and small often result from just `playing around' without any clear aim or agenda in mind. The history of physics is filled with discoveries which were made by alert minds but motivated by obscure reasons, and certainly not by following any kind of 'scientific method' or declared aim (Roentgen was not trying to pioneer imaging techniques in medicine when he discovered X-rays; Hertz was not trying to build a radio when he found radio waves). In fact, many scientists have famously wrongly predicted the development of science (Rutherford didn't think nuclear physics would be of much use; the head of IBM said computers were not going to be very important). In pure science, often such a discovery reveals secrets which were not even suspected to exist (Dirac's equation introduced the concept of anti-matter). Even in technology, often previously unconnected advances come together to enable life-changing utilities (mobile phones combined microprocessors, touchscreens, GPS, cameras, batteries, wifi, internet...) Certainly in my own bread-and-butter research, we are excited by what is proposed in the grant proposal that funds the research; but we are just as (and sometimes more) excited by things which we discover along the way whose discovery we could not have predicted. (That such discoveries are made is not entirely a surprise - it is only their specific nature that cannot be predicted). Indeed, review articles which summarize a subfield of physics often end with the hope that progress in the mirror (crystal ball?) may be rendered nearer by fortuitous discoveries which, however, cannot be found by fiat or agenda. Conclusions Making such advances requires being willing to play with the theoretical framework or experimental apparatus, without a rigid framework of motivation or expectation. It is when we drop our preconceived notions, when we remove our imagination from a strait jacket, that we become able to discover new things. So while it is important while initially being trained in the subject to have a clear aim, as we advance to the frontiers of physics research, I believe it is also very important to start regarding the activity of subject study as rewarding and interesting for its own sake. Such an activity, as I mentioned in my previous post, is autotelic, and optimal for creativity.

This is a review of the book Creativity: Flow and the Psychology of Discovery and Invention by Mihaly Csikszentmihalyi , the psychologist famous for labeling ' flow ', the state of mind best suited for productivity, and thus for giving us some of our lives' most rewarding moments. Creativity is a subject that fascinates me, and on which I have written before . The book is based on the interviews of 91 highly creative people, including 14 Nobel laureates. [Some of the people who refused to be interviewed are quoted; management guru Peter Drucker's reply was to the tune of 'there is no such thing as creativity, but there is productivity, which consists of throwing into the waste basket requests for such interviews' (this is not a literal quote)]. The interview questions are listed in Appendix B. The Elements of Creativity : According to the book, three things need to exist for creativity to occur. i) A domain : This is a system of symbolic rules. General examples of domains are poetry, science, politics; more specific examples are algebraic geometry, basketball and impressionist painting. Creative people typically spend a lot of time mastering the rules of their domain(s) of interest. The demand for creativity within a domain can be set by customers and patrons (e.g. the Borgias during the Renaissance). Domains that exist at the interface of two social/musical/intellectual cultures (e.g. biotech and public policy) are especially fertile, as they suggest novelty more easily. If the systemic rules can be enunciated clearly (e.g. in mathematics or physics) then young people can jump in and be creative (and hence we say that mathematical talent peaks early). If the rules are vague and complex (politics, philosophy) then it takes a while to make contributions and be recognized. ii) A c reator : This is a person who innovates in a domain (Michael Jordan in basketball). Creative people can also innovate new domains (Galileo initiated, in some sense, experimental physics; Freud started psychoanalysis). Creative works, says the book, are cultural innovations (memes) analogous to mutations in genes. iii) A field : This consists of experts who certify the innovation. Their certification dictates which memes will persist; only a few (compared to the many that are put forward) do (there are about a million booktitles published in the US each year - how many stay in our collective memory?). Experts can cause reputations to wax and wane with time: examples are J. S Bach the musician (rescued from obscurity by Mendelssohn) and John Donne the poet (resurrected by T. S. Eliot), etc. Creative Types Creative people, the author finds, do not do something just to earn a living. They think of their work as a higher calling, as a way of systematizing their experience, of extending available knowledge or power, and of having an effect on humankind that is not curtailed by their personal death. Regardless of its explicit purpose, they intrinsically love their work for itself: i.e. the work becomes autotelic . After an extensive discussion the book observes that creative people seem to combine a number of opposite qualities: convergent (solving well-defined problems) with divergent (playing around with ideas) thinking; playfulness with responsibility; introversion (producing and processing ideas) with extroversion (talking shop with colleagues/subjects); aggression with sensitivity; periods of extreme business with intervals of total idleness; naivete with penetrating wisdom, etc. Conclusion The book then goes through the common features in the lifecycle of the creators interviewed, discussing their nurture, peak performance years, and creative old age. Then it suggests what we should focus on in order to live creative lives, should we wish to. I found the book to be a detailed but lucid and penetrating analysis of the phenomenon of creativity, flush with specific illuminating examples, and ringing with quotes in the original voices of the interviewees. A recommended read for anyone interested in creativity, a phenomenon which is crucial to the advance of our species.

This post is a review of the book The Science of Spin by Roland Ennos. The book is about the role played by physical rotation in the universe and in our lives. This is a favorite topic of mine - I am fascinated by things that rotate . The Galaxies : The book discusses the effect of rotation on the shapes of the galaxies (spiral galaxies have more and elliptical galaxies have less rotation). The Solar System : The book begins with explaining the role of rotation behind the fact that all the planets go around the sun in the same direction and in the same plane, and the same for the moons of any planet. It discusses how the Sun's rotation is slowing down due to the angular momentum carried away by the radiation it emits. The Earth : There is a very engaging discussion of the tides, which are caused by the Earth's rotation with respect to the moon and the sun. The movement of water causes friction relative to the Earth's rotation, leading to the length of days increasing by a couple of milliseconds per century. This effect, in reverse, can be seen on the moon, because it is tidally locked, and always shows the same side to the earth. There are also illuminating explanations of how the earth is stabilized by rotation about its own axis and about the moon; how the planet's rotation-induced magnetic field protects it from radiation from space; and how planetary rotation creates days and nights, seasons, wind patterns. Technology : This part of the book covers many of the technological applications of rotation over the course of history: drills, spindles, the wheel, rollers, the Archimedes' screw, windmills, spinning jennies, flywheel, paddle wheels, propellers, turbines, etc. Automation and flying are covered quite extensively. The Human body : Balance, gait, force transmission (throwing, hitting, etc.) by human beings are addressed here. There is a long chapter on the role of body part rotation in sports. The author's expertise as a biomechanics person seems most directly relevant here. Evaluation The book is well written, with no equations but a good many diagrams. The technical material is well explained. One of the themes of the book is a sustained complaint against physicists who have 'delayed' the progress in the understanding of rotational science by an 'over-dependence' generally on mathematical analysis and specifically on equations. The author supports this allegation e.g. by quoting several instances of claims by scientists who ended up being wrong about rotational systems. But of course this is the usual course of science. Scientists often come to wrong conclusions - but science eventually self-corrects. The story becomes a bit clearer when the author reveals that he found physics so mathematical he switched to zoology at university; so there's nothing wrong (and in fact everything right) with the math - it just so happens that our scientist author is not mathematically inclined (there are many). This perhaps explains why some of the more fundamental advances in our knowledge of rotational science not mentioned or emphasized in the book, e.g.: i) the spin-statistics theorem which relates the spin of particles to their statistics ii) the Stern-Gerlach experiment , which discovered quantum spin ii) the existence of bosons and fermions, and perhaps anyons iii) how the Pauli exclusion principle determines the stability and structure of matter iv) how Regge showed angular momentum can be considered to be complex (rather than real) with benefits to particle scattering analysis v) Light can carry more angular momentum than (polarization-related) spin. ... Appreciating these advances might require a bit more sophisticated mathematics than described in the book. Still, it's quite readable.

This post is in response to questions from various students about the typical steps in the career of an academic physicist (employed at a university). Below, I will summarize the experience at each stage. These comments only hold in general; of course there will be special exceptions. High school : Many (but not all) of the students who end up becoming physicists become interested in the subject at this stage. This may be due to the enthusiasm imparted by a very good teacher, a supportive environment at home (books, radio or electronics sets, etc.), exposure to professional science (through programs run by nearby universities or research institutes). The requirements at this stage are basically doing well in coursework, showing some excellence in science subjects (physics, mathematics, maybe chemistry). College : Many institutions worldwide require incoming undergraduates to declare a major upon entry, although this is changing, especially in the US. Nonetheless, at some point, interested students have to pick physics as a major (sometimes accompanied by a double major, usually in engineering; or a minor, such as in mathematics). This stage definitely requires a student to absorb many aspects of physics, including basic (e.g. mechanics and electromagnetism), intermediate (e.g. quantum physics) as well as advanced (e.g. solid state physics/astronomy) courses. There is nowadays an increasing emphasis on research experience for undergraduates and it is not unusual to have a 'senior thesis' requirement for the bachelor's degree or even undergraduate students as co-authors in articles published in peer-reviewed journals. For this to happen, students need to work with a professor in the department. University: Students who are interested in an academic career apply to graduate school for a PhD. Masters degrees are considered terminal (for those who are going to leave the academic line) and do not count for much for those who are continuing. This is a long haul project (~ 5 years or more), testing the ability, persistence, and sometimes teamworking capacities of the students. After some initial coursework, they join a research group. At the end of the PhD they should have published a good number of papers (some of them in high impact factor journals), become trained in the techniques of the field, and capable of solving problems that cannot be solved in a day, week or month. It is a journey of intellectual, emotional and social growth. Postdoctoral experience: Almost all academic physics jobs require post-PhD experience. This consists of 1-3 short term (2-3 years) appointments where physicists have to learn a new (sub)field and become productive in the area rather quickly. The idea of postdoctoral training is to demonstrate the ability to scientifically succeed at a place other than the PhD; and to add tools to the toolbox which the physicist will use when they finally set up shop at their own permanent position. The work can involve supervision of graduate and undergraduate students, basically running the group for the hiring professor. Assistant Professor : This job is not permanent. About 5 years are allowed in which the physicist has to secure research funding, publish papers, supervise students, teach courses and serve the department. This is an intense time in the career of a professor, with a lot at stake. When this pressure cooker timer rings, the university decides whether to grant permanent tenure and (usually) concomitant promotion to associate professorship. Associate Professor: The professor typically extends their research interests, expands collaborations, writes books, effects teaching changes at the curricular level, and serves the community at a higher level than before. Typically this phase lasts for 5 years, after which the 'associate' is up for promotion to 'full'. (Full) Professor : Those who are inclined to stay in research mainly now start on the track towards becoming true authorities in their field; they may become heads of centers and institutes. Those who are administratively inclined become department heads, then deans of colleges, then presidents of universities. Retirement (or not): There is no official retirement age for faculty in the US; in countries where the retirement age is relatively early (~60-65) faculty often move from government to private institutes and prolong their careers. Some professors truly retire and give their time to family and/or hobbies and pursuits. Interestingly, many professors work till they die (because physics is so interesting!). I am reminded in this context of a joke that Nobel laureate Bill Phillips often tells in his popular talks. He quotes the example of the two twins, one of whom stays on earth, while the other travels at relativistic speeds in a rocket. Since, according to special relativity, clocks run slower for objects that moved faster, when the traveler returns, he finds his twin has aged more than he has. In Phillips' joke, the twins are both physicists, and when the traveler comes back he finds his twin is older, but still working, "Because," says Phillips, "That's what physicists do."

This is a review of the book DNA: The Story of the Genetic Revolution by James Watson with Andrew Berry and Kevin Davies. When I saw the 2017 copyright under Watson's name the first question that came to mind was if he is still alive, given his Nobel-prize winning co-discovery of the structure of the DNA molecule was quite a while ago (1953). Watson is actually alive and 94. As a physicist with almost no knowledge of biology, I found this book extensive, accessible, and fascinating. Background : This is a quick recap of the basic biology I seemed to require for launching into the book: cells contain nuclei, which contain chromosomes, which are strands of DNA. Sections of a DNA strand constitute genes. There is ongoing debate about function of the material in between the genes - sometimes it is called junk DNA, sometimes dark matter. Prehistory : The book begins by reminding us that humankind has been running genetics experiments for many thousands of years by breeding plants and animals; and by tracking the hereditary transmission of diseases. History : Modern genetics proper starts with Mendel's paper in 1866, followed by Walter Sutton's indication of the role of chromosomes, and then the monumental work of T.H. Morgan on fruitflies at Columbia, where he observed gene recombination via separation of linked traits. The book then discusses Galton (who pushed eugenics), Goddard (who introduced IQ tests to the US from Europe) and Madison Grant (whose book on racial eugenicist policies was declared by Hitler to be his bible.) DNA : Watson describes his undergraduate days at University of Chicago and the influence of What is Life? , the book in which Schrodinger suggested life could be understood in terms of transmission of genetic information. The chapter condenses the story of the discovery, by Watson and Crick, of the structure of DNA, and told earlier and in more detail in The Double Helix . Much of the rest of the book is about advances in the study of genes. 5. Genes produce enzymes : This was established by the pioneering experiments of Beadle and Tatum on mold. Genes produce proteins : (Not all proteins are enzymes). This was established by Francis Crick, involved an understanding of RNA as the intermediary, and is now known as the Central Dogma of Molecular Biology . Genes express themselves: Genes switch on at different times and in different cells so an entire organism (e.g. a human) can develop from a single cell (the fertilized egg for humans). These studies were started by Jacob, Monod and Lwoff, followed by many other researchers. 8. Recombinant DNA : The story moves on to the development of cutting (e.g. with restriction enzymes), copying (e.g. with polymerase chain reactions) and pasting (e.g. with DNA ligase) sections of DNA (e.g. genes). These were seminal advances, eventually giving rise to the field of biotechnology evolving into powerful technologies like CRISPR ( Clustered Regularly Interspaced Short Palindromic Repeats ) which can edit the genes of living organisms. Biotechnology : Human genes were harvested to produce valuable proteins such as insulin (related to the start of Genentech, the world's first biotech company), tPA (used for treating strokes), and bovine growth hormone (which gives more milk yield), etc. The book naturally moves on to GMOs (genetically modified organisms) such as crop plants with better pest resistance. Human Genome Project : A big movement was the sequencing of the human genome (complete set of genes) which was completed in 2003. This involved personalities like Bill Clinton, Watson himself, and Craig Venter (who started Celera Genomics). Genes and disease : The ability to sequence our genomes allows us to identify which diseases our genes predispose us to (e.g. APOE on chromosome 19, which correlates with Alzheimer's). Not unexpectedly, the search for cancer cures has dominated the biotech industry, focusing on genes which mutate to cause cancer (oncogenes); the book devotes an entire chapter to this topic. Genes and our Past : DNA contains information allowing us to identify species (Neanderthals vs. humans; an interesting gene in this context is FOXP2, which affects speech), our ancestry (this is molecular anthropology; some amusing paternity suits are mentioned in the book, as well as the company Ancestry.com ), and the traces we leave behind at historical or crime scenes (some sensational cases are included). Some trivia collected from the book : African elephants stay fertile until they die (~90 years); human chromosomes are numbered in order of decreasing size (chromosome 1 is the largest, with a quarter billion base pairs), except for the sex chromosomes which are labeled X or Y; the mustard plant has more genes (27,000) than us (21,000); cytogenetics is the study of chromosomes; the Flynn effect says worldwide IQ is increasing. Summary The material is well arranged, the writing is taut, the technicalities are explained well. Watson has been reasonably frank about his opinions on politics, religion, eugenics and the future of biotechnology. His panoramic view of the field is impressive. I would say this book is a resource for a nonexpert in biology (like me) as a useful introduction to as well as survey of a fundamental, vast and profound field of scientific research which is indubitably going to affect our lives in the past (ancestry), present (healthcare), as well as the future (longevity).