Search Results

Clocks play an incredibly important role in our lives. This post is about a recent development, based on nuclear physics , which promises the most accurate clock ever [1]. A Short History of Clocks To measure time, we need an event that repeats. Thus the earliest clocks were made of pendulums, hour glasses, etc. The relatively recent advent of electronics brought clocks made of quartz crystals and transistors. These timepieces each present some problems. For one, their accuracy is limited: even a good quartz clock, for example, goes off time by about half a second every day. Also, each one, due to manufacturing differences, is unique: no two quartz crystals lose exactly the same amount of time. This poses problems for synchronization. Clocks go Atomic Interestingly, Nature gives us clocks that are identical copies of each other: atoms. A Cesium atom from China is indistinguishable from a Cesium atom from India, or from anywhere else in the universe for that matter. How can an atom be used as a clock? Roughly speaking, by driving one of its electrons periodically between two well-defined energy levels. This repeating action, which is carried out by using a laser which puts out photons with the same energy as the difference between the atomic energy levels, gives us a clock. Using these ideas, ' atomic clocks ' have made fantastic progress; Cesium clocks lose about a a second in 1.4 million years; the best atomic clocks lose one second in 30 billion years (more than twice the age of the universe)! One might ask at this point if this isn't overkill now - why even bother building better clocks? The answer is that a precise measurement of time can be translated into a measurement of other quantities. For example, a good clock can be used to measure distances accurately: this is why atomic clocks form the basis of the GPS: the more accurate the clock, the better you can localize your car in the parking lot. Super-accurate atomic clocks are also used to look for very slow changes, such as predicted by some scientists, in the fundamental constants in the universe. (These look like constants right now, but may in fact be changing slowly with time - but this is yet to be confirmed). So we do need better clocks. Problems with Atomic clocks A major limitation of atomic clocks is that the atomic energy levels are very sensitive to noise, and background electric and magnetic fields, which are usually present in the apparatus. So the atoms have to be levitated in space (using electromagnetic fields which we need to know well), away from as many things as possible so the 'clock levels' are not affected. This makes most atomic clocks quite bulky - though some chip-scale designs have emerged lately. Why would you need a chip-scale clock, when GPS gives us access to the time? There might be situations where GPS is not available (down in an oil well, or in outer space, for example). Clocks go Nuclear Interestingly, the problems faced by clocks based on atomic electrons can be tackled by clocks based on atomic nuclei. Because atomic nuclei (protons and neutrons) are (five orders of magnitude) smaller than electron orbits, they are relatively more insensitive to background electromagnetic fields and chemical environments. They are therefore expected to be highly accurate, sensitive and portable. The problem is that the nuclear energy levels are usually too energetic to be driven by the lasers we presently have (they typically need gamma rays - so that's a motivation for you to build a gamma ray laser, in case you are itching to make one). However, there is a freak pair of energy levels in the Thorium 229 nucleus, which were being hunted for for more than 25 years, and have recently finally been identified using a laser at 148nm [2]. This is the first time an atomic nucleus has been excited using a laser! Among other things (see below) this is expected to lead to a clock which loses 1 second in 300 billion years - so you don't have to worry about being late for work anymore. Bonus i) The energy levels in Thorium could also be used to make a 'nuclear laser'. Don't ask me what that is. ii) The nuclear clock is sensitive to dark matter . Since no one has ever detected dark matter, this new clock is an exciting development in the context of ongoing dark matter searches. [1] A Brief History of Timekeeping by C. Orczel. (I have not read it; I will probably review it when I do). [2] J. Tiedau et. al, PHYSICAL REVIEW LETTERS 132 , 182501 (2024) .

The Problem A question I receive very frequently from students is: what do I need to know or what courses do I need to take, to join your research group? I answer that no specific coursework is required, only a willingness to pick up whatever is specifically demanded by the research project I give them. In fact, I tell them, that one can never study everything required for doing research ahead of time, and the point of doing research is to actually learn new things. This strategy has turned out to be quite practicable in my experience of supervising students for about 15 years. What I do not tell the students is that it would be wonderful if they could put in a couple years of service in the military - or equivalent - before they join my research program. This is not because I am a proponent of war - I am not. This is because most of the typical problems I see with students would have already been taken care of if they had such a qualification on their resume. In fact, I am slowly coming to the belief that not only students specifically interested in research, but those interested in education as well, would benefit from the kind of military service that some countries require and others offer as a choice. I have had some students who had this type of experience prior to working with me, or were on active military duty while they worked with me, and I found their preparation in terms of maturity, mindset and discipline to be exceptionally productive. Some Possible Solutions: A List of Ten As I see it, military- or equivalent - service inculcates the following (sometimes interconnected) virtues very useful to students/researchers (if not to all human beings): i) Maturity : This I define as the willingness to submit to a process as a result of having made up one's mind to accomplish an aim. In the absence of maturity, the student's mind wanders, they are distracted by many things, it is difficult for them to keep focus, they create unrest in class, etc. The military, by teaching them to focus on tasks, inculcates maturity. ii) Responsibility : This is related to the previous point; I would define it as the willingness to do what it takes to finish a task. A responsible person understands what a task is and is willing to be answerable for its execution. An awareness of responsibility results in steady progress in education as well as research; a lack of it puts the onus of the progress solely on the teacher or supervisor. iii) Discipline : Even some very bright students are unnecessarily chaotic in their work. A touch of military discipline would make them much more efficient and productive. iv) Collaboration and Teamwork : Research as well as classroom instruction are performed as teamwork. Recognizing that other people are depending on you to function as a dynamic and personable unit is an important aspect of a professional career. An awareness that the whole world is not designed for our own convenience, and that we are part of an organization with many - often moving - parts is essential for smooth operation of the whole enterprise. v) Chain-of-command awareness : In order to function efficiently, it is necessary to know what a command is, whom to take it from and whom to give it to. A lot of confusion and chaos is caused by students who - unknowingly or even with good intentions - either cross borders of authority or do not enforce their own. (An example of the former is when a student writes to a research competitor for clarifications without informing the professor). The military develops in an individual an instinct for when to take decisions and when to defer them to other, appropriate, agencies. vi) Punctuality and Promptness : These ones I leave as too obvious to explicate. vii) Respect : This involves both giving and taking of respect. Behaving in a dignified manner makes for very pleasant dealings and as well as productive professional exchange. viii) Courage: Performing research (say advancing a new idea or tackling a hard calculation) or taking exams can both be daunting and having cultivated courage as a virtue is undoubtedly helpful. ix) Patience : This most helpful of virtues is something most of us need to cultivate, especially given that we live in an age of instant gratification. x) Strategy : Very important in research and also in education as in learning or test-taking strategies. Having a strategic mind often helps in solving problems. Postscript Of course, there are many good students who are already on to these virtues and practice them during their interactions with me. But there are a good many - I know I lacked several of these elements when I was a student - who could usefully add items from the list presented above to their skillset and maximize their education and opportunities. Postpostscript Some qualities valuable for research are likely not taught in the military, such as creativity and originality.

What is fashion? Many human beings seem to love what is new and get bored of whatever is old. New and old are of course relative terms. What is new may in fact be a reinvention; what is old may have hardly exhausted its possibilities. But it is undeniable that fashion trends (that go from being in to being out) are a phenomenon in many fields of human endeavor: clothing, art, films, literature, investment and even science. Some examples from physics Right now 'quantum' is rather fashionable. 'Nano' is still somewhat fashionable, but was perhaps more so about five-to-ten years ago. A strong trend that came by a few years ago, and that still has an afterglow is 'topology'. A trend that is still growing involves 'non-Hermitian' physics. How to identify these trends Easy - look at the top journals and try to find recurring buzzwords (such as those presented in quotes above) in the titles of the papers. In practical terms, papers on fashionable topics are easier to publish (especially in high impact factor journals) and more likely to accrue citations, funding is easier to obtain, the relevant sessions in the conferences are better attended, and recent faculty hires in physics departments are more likely to be in that area. How and Why do they arise? Someone needs to perform a more rigorous study of the origin of scientific fashions (I can't remember if Thomas Kuhn said something about them in his famous book The Structure of Scientific Revolutions , which I read a long time ago), but in my experience they typically arise from breakthroughs of some kind (major or minor) which open up a new area (large or small) in physics research. A substantial number of people then tend to follow up on the initial discovery based on motivations like i) the excitement of becoming the pioneers of a newly accessible frontier (a kind of a scientific wild west) ii) the possibility of picking 'low-lying fruit' (i.e. results which are technically relatively easy to obtain and rely more on the novelty of the topic for their appeal), and iii) the opportunity of moving away from already crowded areas of research. What are some of the good effects of such trends? Fashion trends ensure that i) new scientific discoveries are fleshed out extensively ii) that certain topics receive a lot of attention and vetting, and iii) that certain lines of thought are taken towards their logical limit (i.e. upto the point where another breakthrough is required to generate a fresh paradigm). The strength and relevance of the original discovery improves as a result and applications come into view (for certain areas). Particularly fruitful is the fact that fashion trends often attract people from different corner of physics research (e.g. optomechanics attracts gravitational wave astronomers, fluid dynamicists and quantum information scientists, to name a few types). These scientists, each with their own specialties, give their own takes on the breakthrough and work out its manifestations from different perspectives. This fleshes out the original physics in a manner which is powerful and fertile. What are some of the bad effects? Oscar Wilde said that fashion is a form of ugliness so intolerable that we have to alter it every six months. Fashion trends in physics promote i) unoriginal work (e.g. same physics is presented but for a different system, a value proposition which can be abused), ii) 'hit-and-run' physics (published by people who may not have a deep association with the area but manage to make a quick connection to their own expertise just to get into the fray; but they leave the fray as soon as the next trend comes along) iii) generate a substantial number of papers which will be forgotten in a generation or so, if not as soon as the next trend comes along iv) high citation numbers (read h-indices) for those scientists who are 'trend-coasters' (there are quite a few of them) as opposed to being 'trendsetters' (these are fewer in number). v) the enlistment of gradate students in fashionable areas of physics research, which unfortunately, may not continue to be fashionable by the time they finish their PhDs. This will reduce their employability vi) taking attention away from less glamorous or less topical but otherwise substantial areas, which might be equally investment-worthy in the long run. What should I do? Should I work in a fashionable area or not? This is, of course, a personal choice, and one which in fact need not be made. Meaning - at least as a professor - that one can work in both types of areas. I don't like making choices if I don't have to.

This post is about a book I stumbled upon while cleaning my room: Physics and Music by Gleb Anfilov, translated from the Russian by Boris Kuznetsov, now also available online for free . Mir Publishers issued the book in 1966, and that was part of what intrigued me - what was known about the topic in that era? How much of it has stood the test of time? How much of it has been lost from the subject, in more recent books? These questions still remain to be answered but here are some of the interesting things I found along the way: Membranes The book declares drums to be the oldest musical instruments, but does not say much about them, except briefly to indicate that they have no musical pitch and simply produce noise. I suspect this is due to the book limiting itself largely to Western music. There are drums with musical pitch in other musical traditions (e.g. Indian and Latin American). Wind The book declares that the simplest musical instrument is the conductor's baton - an abstract but pleasing identification. Then it launches into the description of what it calls the next simplest instrument - the flute. A long chapter traces the development of the flute and its variations such as the horn, oboe, clarinet (apparently the mouthpieces of older clarinets are missing since they used to be buried with the player), and saxophone (developed by the Belgian Adolphe Sax ). Finally it comes to the biggest instrument of all - the organ (the black and white keys of the piano first appeared on the organ). Strings String instruments are tackled next, starting with the harp, followed by the lute, mandolin and guitar. Finally we arrive at the violin, with a large section on Stradivarius and the efforts of scientists to uncover the secrets which enabled him to make amazing instruments (progress along this direction had been partial until 1966 at least; there did not seem to be a manufacturing formula since every instrument seemed to be unique; the verdict is that the Stradivarius violins were amazing not due to their individual parts but due to how they were combined). Then the discussion moves to the monochord, followed by the clavichord and harpsichord (mentioning that Mozart wrote his Rondo alla Turca for it), finally landing largely on the piano. Physics The next part of the book launches into a description of the physics of music, though in a way accessible to nonscientists. I found the physicist's definition of a musical instrument interesting - a vibrator (e.g. a clamped string) plus a resonator (e.g. a shell). Sometimes the resonator also vibrates: the French horn's sound is apparently a combination of the vibrations of its air column and its metal. There is an interesting discussion of how Helmholtz was the first to 'take music apart' into its constituent sounds by using various resonators to detect the notes being produced by any instrument. He could, in a reverse of this process, 'assemble' sounds - e.g. with a combination of tuning forks he could recreate the vowels of human speech. Voice The chapter on human voice and hearing, going by the definition presented above, says that the human voice is also a musical instrument. Naively speaking, its vibrators are elastic tendons and its resonators are the cavities of the throat and the mouth. In practice, the tendons can also be vibrated by electric signals from the brain. In fact when a singer listens to music without singing, the vocal chords follow along. This can be used to test a person's ear for music: play her a note and detect if the chords follow; it can also be used to identify voices as baritone, tenor, etc. The book also discusses which voices carry the furthest (an important consideration before microphones and amplification were available), and how the ear perceives and even adds its own frequencies to the sound. Electronic Music This was already a big topic when book was published. The chapter has an interesting historical tidbit about Theremin demonstrating his instrument before Lenin (Lenin apparently stepped in and finished the piece himself after Theremin showed him the technique). An interesting fact I learnt was that instruments are identified by the beginning, or attack, of a note they produce. That is, if we erase its beginning, it can be hard to say whether the note comes from a flute or a piano. This is one reason why electronic sound finds it difficult to replicate real instruments - maybe a problem for AI? Postscript The book ends with an account of computer-generated music. I won't go into all the details, except to share from the book that already in the 18th century people were generating music by throwing dice and reading phrases off precomposed tables (written by Mozart, e.g.). This is one sort of idea to start with in computer music - randomly combining phrases which nonetheless contain some musical order.

Many - if not most - people think that the life of a professor is relatively boring. As a counterexample, I will try to offer in this post, an account of the type of adventure as mundane a task as a speaking engagement can generate. Without loss of generality (a bit funny, since this is a phrase commonly used in physics papers), I will give an account of a generic experience (any resemblance to existing institutions or people is purely coincidental - haha). Getting Invited I was interested in speaking at and visiting a certain research institute in a certain country. So I made sure I ran into and introduced myself to one of the friendly senior professors from that institute at a conference elsewhere. Then later I emailed him, a few months in advance of my intended visit, asking if I could come. He replied with a generous invitation, but without specifying the precise dates. When my dates of choice were about a month away, I wrote to him suggesting those specific dates. He in turn introduced a junior colleague who would handle my details. The visit dates were finalized and I had already booked the flight tickets, when we realized that since I was not a citizen, and the institute was under the Department of Space (a bit funny, since scientific institutions are notoriously and perennially short of space), I needed special permission for campus access from higher ups in the government. I filled out the form they sent me, but did not hear back from the junior professor. Two days before my flight, I wrote him saying if I did not receive permission by the day before the flight, I would consider my talk canceled. I did not hear back from him or from anybody else. But I took the flight any way, since I had touristic interests: I had never been to that city before; a major politician was reputed to have made it especially modern, clean and safe; the memorial home, near the riverfront, of a historical national figure was also an attraction. I booked a hotel close to the biggest - and much vaunted - mall in the city; rather than one close to campus, as planned originally. Considering myself freed from my academic duties, I began looking online for interesting places to visit. Traveling The flight stayed on the ground for an hour after boarding us. Apparently the air conditioning would only work when the plane was airborne. So the passengers started getting roasted on the tarmac. Somehow, from my aisle seat, I was catching a draft from another fan, so the heat did not bother me that much. But the couple in the middle and window seats in my row were getting tortured as the fans (the small ones overhead) in our row were not working. They fanned themselves with the airlines magazines, requested the flight attendants repeatedly to fix the problem, turned to me accusingly after a while and asked how come I wasn't feeling hot, eventually lost their tempers, made on the spot and posted on Twitter a video about their predicament suggesting train travel as an urgent alternative to flying in this oven, and were finally rescued by two young men from the rear of the plane who agreed to swap seats with them. One of these fine young men took the window seat; the other one asked me to move to the middle, so he could take the aisle seat. I refused without explaining that I was claustrophobic; the middle seat would give me breathing problems, the window seat would have me gasping for air. I felt the heat of his displeasure - although the AC came on once the plane took off - for the remainder of the flight. Arrival When we landed after about an hour I took a prepaid taxi from the airport. The friendly and loquacious driver, upon learning that I was a new visitor, gave me a de facto tour of the city. I reached the hotel at about 4:30pm and as I opened my phone while waiting in line to check in, I saw a message from the junior professor: not only had permission been granted to me, my talk had been preponed to 5pm that same day as the next day happened to be a government holiday. The campus was about 45 minutes from the hotel - I called back and had the talk postponed to 5:30pm. I threw my luggage into the hotel room, rushed out with my laptop, and had the hotel call me a cab. The apologetic junior professor met me at the campus gate, which was being marshalled by sten-gun-toting army troopers. They looked dubiously at the paperwork which the professor showed them, sat both of us down inside their cabin, and progressively engaged increasingly higher levels of command on the phone, while the clock ticked past 5:30pm. I humorously remarked to my host that he should call to make sure the students were locked up in the seminar room until I could show up for my talk. Incredibly, that did the trick. The sergeant immediately changed his tone to his superior on the phone, and suggested that I could be admitted based on the available paperwork, since the talk was likely to be beneficial for the students. I made it to the seminar room at 5:40pm. But we waited for another 10 minutes to start as tea had been brought in - I suspect as a substitute for the locking the seminar room doors - for the surprisingly substantial (about 30 people) audience. Postscript The adventure did not stop with that day. The next day, I was invited back to the campus for discussions (a bit funny, since physicists like to always work, never mind holidays). The cab from the hotel took me ten miles in the direction opposite to that required before I realized there was another campus belonging to the same institute which had come up on the taxi driver's navigator. We turned around. This time I was an hour late on reaching the right campus, but did not feel sorry at all, after what they had put me through the day before. Overall, it was fun.

A statement of the problem This post is about a specific management problem that I often encounter while supervising students and postdocs: with the benign intention of being helpful, they start telling me what to do. This causes some interference at the very least, and often total havoc. It requires me to give a long explanation of why this is not appropriate behavior. If I do not provide this explanation and supply an instant correction, the student begins to assume more and more that (s)he needs to take the lead in our professional relationship. This post is an attempt at crystallizing my thoughts on the topic and creating a ready reference that I can send my students/postdocs to when the occasion arises. A specific example Imagine I have a student (could be an undergraduate or graduate) working with me on a project. I inform him that I could be hiring a postdoc whom I might involve in that project. The student writes to me: " I look forward to working with this new collaborator, please share my write up and contact information with him if you decide to involve him in this project. " The student means well and is actually trying to be helpful. His thought process is this: if I (the advisor) end up involving this new postdoc I’d be reaching out to him (the student) to give a heads up that I'd be sharing his work/contact information. He is simply trying to save me this hypothetical heads up email by letting me know that he understands involving him may involve the exchange of his work and contact info. He means this only as a courtesy. Nonetheless, he is issuing me instructions. Why is this a problem? This is a problem, because what the student proposed is only one of a countable infinity of possibilities, all of which are dynamically, but not deterministically, changing in time . Let me try to explain. At the moment I could be in the process of 'postdoc-hunting' , i.e. meeting/being contacted by/recruiting electronically a number of candidates. By the time I am done (maybe by early winter, maybe not) I will typically be considering 10 candidates (maybe more, maybe less). There is typically a wide distribution in their abilities and experiences, and this will dictate partially whether and how I engage them with the student. For example, one applicant could be an absolutely brilliant mathematical physicist who has written 26 papers during her PhD with minimal guidance from her two advisors in two completely different fields, and is currently touring Europe giving talks as a grad student. If I make her an offer (likely) and she accepts (less likely) , I might actually not tell her about the student at all (initially), because I want to see what her original thoughts on the subject are. In the process I may (or may not) uncover, using her, a totally new way of thinking about the subject, and entirely new mathematical tools. If she takes a completely different path than the one the student took I may never  even introduce the two of them and just publish separate papers with them (not unusual; currently I am collaborating with three different groups separately on - different aspects of - the same topic). Another candidate is competent, but not as brilliant as the one described above. I suspect this topic is too mathematically sophisticated for him. I might flash the student's pdf at him (without giving him a copy) and see what his response is. Likely, I would then put him on a different topic: the student might then never get to meet him (although the postdoc gets to see the student's material). A third scenario is the one the student mentioned, but I might give that postdoc the student's contact information (for which I would ask his permission, of course) only, and leave the write-up-sharing to the two of them.  By no means are the above three are only possibilities that can arise; I could come up with many more scenarios, but I hope I have conveyed my point. The point is that we are all part of a big machine and have to be cognizant of the existence of other parts of the machine. The best way for the student to help me is to actually fall in line with my requests and always check if they are ending up issuing me instructions (i.e. delete those from the email). I have considerably more experience than the student/postdoc and have dynamically changing plans in my mind which they cannot guess (nobody can). The bigger picture It's human to empathize with others, but it is good to recognize what is best for people may not be what we think is the best for them, and in fact may be interpreted as an unwarranted intrusion into their affairs. We may think we are being very nice presenting candy to a friend, but she may be diabetic (I did that to somebody). So the candy is actually not good for her. In fact there is a joke about this kind of situation, which states: "I am not afraid of my enemies; I am afraid of the good intentions of my friends."

Introduction This post is about the heavy demand, for the past few years, for popular physics books that purport to answer or tackle the biggest questions: why are we here in the universe? Is there a multiverse? How is there something from nothing? What is the future of the planet, of the universe? What is the meaning of life? While these are of course important questions about which physics has a bunch of interesting things to say (not too many of them definitive), in the author's opinion they are cornering an excessive amount of the market share in popular physics writing. They leave little room for other interesting topics, other amazing things from areas of physics other than astronomy or high energy physics: condensed matter physics, or optics, or fluid dynamics, for example. Some examples of Big Picture books/podcasts/articles: i) The Big Picture : On the Origins of Life, Meaning, and the Universe Itself ii) The Big Picture : Reflections on Science, Humanity, and a Quickly Changing Planet iii) Big Picture Science (podcast) iv) The Fabric of Reality : The Science of Parallel Universes - and Its Implications v) The Dawn of a Mindful Universe : A Manifesto for Humanity’s Future vi) Existential Physics : A Scientist's Guide to Life's Biggest Questions vii) Reality Is Not What It Seems : The Journey to Quantum Gravity viii) The True Science of Parallel Universes; Are We Living in a Simulation; Does Time Exist? (Topics from the site TedEd with tens of millions of reads) ... This preponderance is not a coincidence; for example, several editors I spoke to at the big publishing houses told me they had explicitly been told to try and publish such titles. Some examples of neglected topics: i) Turbulence : This is one of the biggest unsolved problems in physics, one of the remaining grand challenges in classical physics (quantum turbulence is actually also now a hot research topic). There is no popular science book on it; not even a popular biography of the great Kolmogorov . ii) Cybernetics : There are few contemporary popular books on cybernetics, the science of communication, especially with machines; no popular biography of its originator, the famous and idiosyncratic mathematician Norbert Wiener . Would seem timely in the age of AI. iii) Metamaterials : There is hardly any popular book on the revolution introduced by these amazing new materials, some of which have a negative refractive index; the only exception I know is the book on cloaking and invisibility by Greg Gbur. iv) Large scale atmospheric motion : The discoveries of the jet stream, Rossby waves, and polar fronts, the contributions of the Bergen School of Meteorology ; these are crucial to air travel, weather forecasting, and agriculture. v) Hi-fi stereo : The revolution in acoustics introduced by Amar Bose , which all of us enjoy today. The man himself is fascinating and needs a popular biography too. Incidentally, one of his thesis advisors was Norbert Wiener. Bose talks about himself and Wiener in this talk . ... Conclusions: Big questions are natural and fascinating to ask. We see this even among the physics students, who mostly want to work in high energy physics or astronomy. (The professors are well aware of this, of course - I once suggested hiring a string theorist in the department to even out the disciplines a bit, and was met with instant opposition from several colleagues who said we will lose all our students if we did that). But the answers to the big questions are far from settled - for the most part they are rather speculative. It's important, I think, to cultivate the taste of the public with more concrete, but no less wonderful, examples of stories from the rest of science, about discoveries that are related to the big, though not the biggest, questions. So I don't think the public can be blamed for its appetite; but maybe as science educators and popularizers, we can can try to prescribe them a balanced diet.

A topic I promised to write about earlier, and a source of frequent discussion in academic circles. Specifically, I would like to address the point, often made by a variety of people (including some eminent scientists) that older scientists should retire soon, although they are not legally required to (in the United States), because they are less creative and innovative than younger scientists. This would help make it easier for younger scientists to find jobs and flourish, and for science to advance more rapidly. Of course, the flip side of this question is related also to those countries which enforce retirement ages on their scientists - are they missing out on some serious 'senior scientist' creativity? (Some background: in the US the retirement age for academics was 65 until 1982, and 70 until 1994, when Congress removed mandatory retirement altogether). I do not pretend to have a definitive solution to this issue; so what follows is designed to sharpen the questions, rather than provide answers. Questions, Questions i) How do you define creativity? Any definition I can come up with seems susceptible to counterexamples. Should we define creativity by the number of patents? Feynman had none. By number of publications? Feynman had about 40, 20 less than I do right now. By the number of citations? I know of entering assistant professors in astronomy who already have as large an h -index as Feynman (62). Are they really that creative? ii) Is it true that physics is a young person's game? I have specialized this question to the science I am most familiar with. The question is often answered in the affirmative using the examples of Newton (who proposed his theory of gravitation at 23 years of age), Clerk Maxwell (electromagnetic theory at 31), Einstein (relativity etc. at 26), etc. But if we look at the entire population of contributing scientists and over a long period of time, the conclusions might differ - one study, for example, finds middle-aged scientists to be the most productive [1]. Others have found that scientists who made outstanding contributions at a younger age make important discoveries even later in their careers. I think there are several factors which feed into this. For one, life expectancy was lower, for example, in the earlier part of the twentieth century, for example, when the Nobel prizes came on; it is said often as a half joke, that the two conditions for receiving a Nobel are a) to do great work when you are young and then b) try and survive as long as possible. If you made a discovery later in life, the odds would be stacked against you receiving the prize before you died (indeed it is sometimes suspected that the Nobel Committee waits for some scientists to pass, so it can stick to its rules of no more than 3 sharers and no posthumous prizes). Now that the life expectancy has gone up, scientists creative at older ages succeed in snagging Nobels as well. Two recent nonagenarian prize recipients include Arthur Ashkin (at 96) and John Goodenough (at 97) both of who did their prize-winning work in their late forties. A second factor is that the amount of physics (and presumably any other science) to be mastered before one can enter research has gone up over the years as knowledge has advanced.   So it takes longer to make a creative contribution - some amount of mastery over the existing principles seems to be necessary for this. iii) What does my experience of my own field suggest? About 25 years spent doing atomic, molecular and optical physics seems to suggest that there is a distribution in creativity. Certainly some young superstars have burst into the field with early contributions that were spectacular (one of my favorite examples is Shina Tan ). However, typically it takes time to evolve a deep look into a theoretical problem, or build a machine which can execute cutting edge experiments, not to speak of large collaborations which may be necessary for achieving ambitious results. Most scientists seem to begin contributing deeply when they hit middle age. In fact, I know several prominent cases where the concerned scientists only began to hit their stride once they reached 60! Then there are also those projects that only senior scientists can be trusted with, typically big science-type undertakings. It would be difficult to think of a 30-year old leading LIGO , for example: Barry Barish , who shared the Nobel prize for the detection of gravitational waves in 2017, was past 60 when he became director of LIGO in 1997. Should we have retired him? Conclusion In my own case, I feel in my middle age I am doing work I could not have even imagined tackling in my twenties and thirties, and that there is still so much more to learn, improve on, and be creative about. One of the advantages of aging is that once the barriers of tenure and promotion have been crossed, one can become more ambitious, and open to risk-taking by striking out in new directions. Since one has built some cachet by this time, colleagues are also inclined to take one seriously. These privileges were not available to me as a young scientist, to say the least. So my tentative conclusion is that abolishing the mandatory retirement age for scientists in the US was a wise decision. And that retirement should be a personal decision. Nonetheless, it would be good to see some quantitative data addressing the issues raised in this post. [1] Is Science Really a Young Man's Game? K. Brad Wray, Social Studies of Science, Vol. 33, No. 1 (Feb., 2003), pp. 137-149.

My last two posts have been about biographies of scientists (Roy Glauber and Srinivas Ramanujan). While writing these, I began looking around in the scientific biography space and noticed a number of gaps. Below is a short list of missing biographies that I thought would be nice to have - authors/biographers, please take note! The List In no particular order (the only qualification is that the subjects should not be alive), they are: i) Lagrange : One of the greatest mathematicians of all time. His - Lagrangian - formulation of Newtonian mechanics has been very influential. He is one of pioneers of the calculus of variations. There's plenty to write about: his Italian birth and his French citizenship, his latecoming to mathematics (at 17), his mathematical service to artillery and ballistics, his exchanges with Euler, his two decades of service at the court of King Frederick of Prussia, his life during the French revolution. ii) J. M. Charcot: Sometimes considered to be the father of neurology; famous for his investigations of hysteria and hypnosis, he was the first to describe multiple sclerosis. He taught: Freud, Binet, William James, de la Tourette (after whom Tourette's syndrome is named). iii) Lars Onsager: Nobel prize in Chemistry 1968. A great theoretical physicist who famously solved the two-dimensional Ising model (because 'he had a lot of time' during World War II), among other things. Things to write about: his early childhood in Norway, his first degree in chemical engineering, his confrontation of Debye to inform him of the mistake in his theory of electrolytes (Debye was impressed enough to hire Onsager as an assistant), his dismissal from Johns Hopkins for poor teaching, his move to Brown (where his course on Statistical Mechanics was dubbed Sadistical Mechanics by his students), then to Yale and finally to Miami. iv) A. K. Raychaudhuri: A general relativist whose 'Raychaudhuri Equation' is a crucial component of Penrose-Hawking singularity theorems (for which Penrose received his Nobel). Things to write about: His mathematician father, his four years of experimental research which convinced him to move to theory, the refusal of S. N. Bose to discuss Raychaudhuri's work with him, how he worked essentially by himself to arrive at his pioneering research. v) Harish Chandra: A great mathematician who contributed, among other topics, to group theory. Facts of biographical interest: His PhD under Dirac, his switch from physics to math (famously memorialized by his conversation with Freeman Dyson, who was switching the other way); his interactions with Borel and Weil; the fact that many of his papers are exactly 33 or 66 printed pages long (from his 50 or 100 handwritten pages). vi) Freeman Dyson: A famous mathematician with numerous scientific contributions (including some fun ones, like the idea of self-replicating spacecraft, or Astrochicken). The son of a social worker mother and a musician father, a mathematical prodigy, Dyson became a professor at Cornell without ever getting a PhD, was controversial for his opposition to theories of climate change, his support of ESP, and his general scientific iconoclasm. He has an autobiography, but it is epistolary; I would like to see a proper biography. vii) Kenneth Wilson: Nobel Prize in Physics 1982. A physicist who made deep contributions to the theory of phase transitions (how water turns to steam, to give a simple example). Bio highlights: His father, who was a chemist at Harvard, and who tried to teach him, unsuccessfully, group theory; his thesis under Murray Gell-Mann; his preference for a faculty position at Cornell because it had a good folk-dancing group; his achievement of tenure without publishing a single paper (surely a feat even more unique than the Nobel prize); his seminal work on the renormalization group (nothing to do with the folk-dancing group). viii) Michael Atiyah : Fields medal 1966. One of the greatest geometers of the last hundred years. Interest: Early childhood in Sudan, PhD under Hodge at Cambridge, many collaborations with other famous mathematicians. Most of his work is too sophisticated for my understanding. Would be nice if someone wrote an accessible biography. ix) John Pople: Chemistry Nobel prize 1998. A pioneer of computational methods in chemistry. Facts worth writing about: He picked up calculus from a book discarded in the wastepaper basket; often injected artificial mistakes in his homework at school to avoid coming off as too clever; but was discovered after he succumbed to the temptation of winning a math competition; ended up at Cambridge; claims that his attempts at piano led to his neighbor (the philosopher Wittgenstein) leaving the university; his movement from pure to applied mathematics, from physics eventually to chemistry. x) J.W. Gibbs: One of the fathers of statistical mechanics and of physical chemistry, and a pioneer of vector calculus. Highlights: was one of the earliest PhDs in the US, a doctorate from Yale, he taught Latin as well as Natural Philosophy, never married, was a good horseman; Einstein said he would not have written some his papers had he been aware of Gibbs' work (it was so good); the Chair created in his name at Yale was at one time occupied by Onsager. Afterword The total absence of women from this list might be a good sign - biographies have been written of all the female scientists I could think of. Would be happy to learn of any gaps - that would make for a separate post.

This post is a review of Srinivasa Ramanujan by Suresh Ram, a fine introductory book of ~85 pages (as opposed to the much more comprehensive The Man Who Knew Infinity by Robert Kanigel, ~450 pages). The Book Ram's book, apart from covering the relevant logistical details, reminded me of several highlights of Ramanujan's life: i) The fact that the schedule for his high school of 30 teachers and 1500 students was so complex that only he could draw it up (this in his teenage years). ii) In the 'fourth form' (form=grade?) he solved all of Loney's Trigonometry (I tried to go through the volumes, many years later in my own career, and with far less success; I am sure some of you have seen, if not read, it). iii) In his teen years, Carr's Synopsis of Elementary Results in Pure and Applied Mathematics fell into his hands; this is what sparked his genius. He worked out the more than six thousand theorems by himself... iv) He eventually became so engrossed in mathematics that he kept filling his Notebooks, and failed several exams aimed at gaining employment. Proofs were often omitted in his writings, as being either obvious or a waste of times (the ideas were coming too fast!). v) His letters were returned without comment by Profs. Baker and Hobson, at Cambridge. It was only then, that he wrote, successfully, to Hardy. vi) His family's opposition to his going to England - and the accruing loss of caste - was removed by the goddess Namagiri who appeared in his mother's dream and commanded her to withdraw her objections. vii) Most of the math professors at Cambridge with whom Ramanujan would have interacted were called away by war duties when he arrived. The bonus was that he got more time with Hardy; the downside was that he was restricted to Hardy's expertise and interests. viii) The high point of Ramanujan's stay in England, in addition to the papers he published, and the comparisons to Euler and Jacobi he earned, was arguably his election as Fellow of the Royal Society in 1918. ix) Apparently he loved oddities and curiosities, and had a select library of articles by mathematical crackpots. x) He passed away after his return to India; in a brief life of 32 years, he proved more than 3000 theorems. There is an informative last chapter on his wife, who lived to be 94, with whom he shared a touching mutual devotion, but no children. Conclusion This is a sprightly and informative read. The text flows well, garnished with many quotes: Hardy speaks on many occasions; Freeman Dyson describes how he chose Ramanujan's Collected Works for the second mathematical prize he ever received; Bruce Berndt, who edited and compiled the three Notebooks of Ramanujan, lends his voice to the book at several places. Afterword There are several movies and videos on Ramanujan on YouTube, in various languages (e.g. Hindi, English). I have watched two of them, but not the longest one. I'm also currently looking to get my hands on the famous monograph [1] on Ramanujan by the prominent psychologist Ashis Nandy, whom I had the privilege of meeting some time ago - but somehow we never got to discussing Ramanujan (Einstein took precedence). [1] Alternative Sciences: Creativity and Authenticity in Two Indian Scientists

This post is a review of the book The Last Voice: Roy Glauber and the Dawn of the Atomic Age. The book covers the two main reasons Roy Glauber was an important person. First, he was (likely) the youngest theoretical physicist to participate in the making of the atomic bomb. Second, he was crucially responsible for the development of quantum optics, especially an understanding of the laser and of new kinds of stellar interferometry. For this, he was awarded a third of the Nobel prize for physics in 2005. The Bomb The book covers - not in sequence - Glauber's childhood, his early education and life as a prodigy, and his recruitment into the Manhattan Project while still at college in Harvard. Two notes about his childhood: first, as a child he played around with telescopes and other machines quite a bit, and even after he had won the Nobel prize for his achievements in theoretical physics, mused if he would not have been 'more successful' as an experimentalist (maybe he was thinking two Nobel prizes?). Second, his father was a traveling salesman, and since he wanted to be understood by everybody he was selling to, put a premium on clarity of language. This was reflected, ultimately in the lucidity of Glauber's scientific papers, which played a major role in his academic success, as we will see below. This power of concise expression is amply evidenced in Glauber's talks and interviews on YouTube. The book records Glauber's insightful, and sometimes trenchant, opinions about the people he crossed at Los Alamos: Oppenheimer [who had chosen the site for the bomb construction as he had spent time there as a boy, and later bought a cabin there he called Perro Caliente (Hot Dog)], Feynman (whose charismatic performances Glauber found unsettling), Bethe (for whom he had great respect), von Neumann (who traveled with him, though incognito, when Glauber first took the trip to Los Alamos), Teller, and General Leslie Groves, among other people. Glauber's career after the war continued to intersect with physicists like Oppenheimer (who sent him to CalTech as a replacement for Feynman, who had taken off to Brazil), Pauli (Glauber took a famous photo of Pauli kicking a football into his camera), and Ramsey (his colleague at Harvard, who also won a Nobel). (Trivia: Norman Ramsey once beat me to the last muffin at a conference tea table; I don't think he realized it, though). The Nobel prize Glauber showed how quantum physics was essential to optics, especially emphasizing the concept of 'coherence', basically how waves from light sources like lasers and stars sync up with each other. The book covers, briefly, the scientific dispute between Glauber and two professors at the University of Rochester: Len Mandel (I missed taking a course from him, but crossed him often in the hallway) and Emil Wolf (he taught me complex analysis) regarding the role of coherence. Glauber won that argument, and the Nobel prize, on the basis of his lucid exposition of his physics arguments in his papers. I heard from one of Wolf's graduate students that he would often prod them to write clearly, citing Glauber's example: a graceful response. The IgNobel Prize For many years, Roy Glauber was the Keeper of the Broom at the IgNobel prizes. This is the person who cleans up the paper planes customarily launched at the stage. The subject is referred to lightly in the book. Verdict For 125 pages, the books is a quick and compact read. A lot of the descriptions have a flesh and blood quality about them. Glauber's wit and wisdom shine through. There are some useful tables in the appendices, including a description of the team structure at Los Alamos. Bonus Throughout the book, and in his interviews online, Glauber displays a quiet but permeating sense of humor. It's clear he liked to have a chuckle now and then. I got to experience Roy Glauber's chuckle first hand when I was a postdoc at the University of Arizona (circa 2006-9; he had recently won the Nobel). He held an adjunct position there and would come to visit once in a while. My then boss, Pierre Meystre, would take him around campus (here's a nice talk by Pierre about Glauber's contributions). So it came to pass that I found myself alone with Roy in Pierre's office when Pierre, after making the introductions, had to step out for a second for some reason. Roy then asked me what I was working on. I said I was trying to solve a problem in molecular physics. "Oh," he chuckled, with a twinkle in his eye, "I couldn't tell a molecule from a hole in the ground!" I knew he was joking of course - every competent physicist knows some molecular physics - but I didn't get to press him on the topic as Pierre stepped back in. But in hindsight, it was quite cool that even with his exalted status, he wasn't above messing around with a humble postdoc.

The Topic Today is the last day of the workshop in Spain that I mentioned in last week's post. One of the interesting aspects of this workshop was that, apart from the talks with technical focus, there were panel discussions about larger scientific issues. One such discussion addressed the important topic: How much scientific research should be curiosity-based and how much focused on well-defined applications? The Panel The distinguished panel consisted of i) Anthony Leggett: Nobel prize in physics (2003). Professor at Urbana-Champaign; widely considered a leading authority on low-temperature and quantum physics. ii) Mario Rasetti: Majorana Prize (2011). A distinguished physicist now working on artificial intelligence and complex systems. iii) Natan Andrei: Lars Onsager prize (2017). Professor at Rutgers; works on string theory and highly correlated electronic systems (e.g. superconductivity) iv) Charles Clark: Gold Medal, U.S. Department of Commerce (2011 and 2004). Ex-Director, Joint Quantum Institute, University of Maryland. v) Jose Ignacio Lattore: Director of Center of Quantum Technologies in Singapore. Author of the books Quantum, your future at stake (Ariel, 2017) and Ethics for machines (Ariel, 2019). The audience had about 30 people out of all the attendees at the conference. The discussion was moderated by the conference leader, Prof. Luigi Amico, executive director of the Technology Innovation Institute, Abu Dhabi. The Discussion A number of interesting and sometimes differing perspectives emerged from the opinions of the panelists and the audience. Here's a few: i) There is a false dichotomy between basic and applied research; in reality they go hand in hand. Someone mentioned, as an example, the case of Planck, who was hired by an energy company to optimize their light bulbs and went on to shake the world with the discovery of quantum physics. However, I later found this may be a myth - Planck was apparently never hired by any company; he considered blackbody radiation purely as an academic problem. Stay tuned for clarifications. A second example - whose veracity I do believe - involved the development of laser cooling of atoms, which was initially funded by the navy as a technology for making more precise clocks, eventually became a platform for many fundamental studies, and was awarded the Nobel prize for physics. Actually this theme still persists, as a mix of curiosity-driven many body physics being explored (using concepts like entanglement) for making better clocks. You can get a sense for this from the interview with Ana Maria Rey, one of the stars of the field. To this list maybe we could add the ongoing search for high temperature superconductivity, which will undoubtedly have pointed economic effects once realized, but in the meantime is generating very subtle physics concepts and sophisticated mathematical models. ii) Nowadays it is difficult for a scientist to obtain government funding unless they promise an application. In my experience, as long as there are no precise deliverables (perhaps these are more suitable for engineering projects), there's usually enough flexibility - if not pressing need - to carry out both curious exploration and pointed realization as part of the grant. The funding agencies, of course, determine the ratio of the two types of research, and the program managers (at least in the United States) are usually good at picking the projects with appropriate combinations. Having said that, there is a distribution of course - some agencies keep a tight leash on the research, requiring frequent reports of concrete advances, while others provide a longer leash (mine require yearly reports). iii) There should always be some funding explicitly allocated for blue-sky research. There is a saying that in order to produce useful research you should give money to some intelligent and creative people and leave them alone. This may be difficult to achieve in the letter, with resources being finite, but I think the spirit of it is correct. In this context I'm reminded of Abraham Flexner's essay on the Usefulness of Useless Knowledge. Flexner was the founder-director of the Institute of Advanced Study in Princeton, where Einstein lived out his last years. His point was that research that initially seems abstruse and pointless at first sometimes turns out to be powerfully life-changing. The question, skeptics ask, is how many times. iv) Nowadays, all the good students are being lured away by big money tech jobs, leaving the universities without an essential core of researchers in basic physics. I can identify with this. Certainly in my experience, hiring capable postdocs and getting them to stay in academia has become more difficult in the last 5 years. I hear this from colleagues worldwide as well. As we have only just started a physics PhD program at RIT, I guess it will take some time to figure out what the dynamic of graduate admission is going to be like. The Conclusion The assembly decided that the topic was crucially important and scientists ought to keep an eye on it, especially in the rapidly changing technology - read quantum and AI - scenario. Would, someone asked, AI be eventually able to do basic research? Not before I retire, I hope [and in case you did not catch my earlier post, I intend to never retire -:)].