{"id":68268,"date":"2025-07-16T22:23:16","date_gmt":"2025-07-16T22:23:16","guid":{"rendered":"https:\/\/www.europesays.com\/us\/68268\/"},"modified":"2025-07-16T22:23:16","modified_gmt":"2025-07-16T22:23:16","slug":"professor-emeritus-daniel-kleppner-highly-influential-atomic-physicist-dies-at-92-mit-news","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/us\/68268\/","title":{"rendered":"Professor Emeritus Daniel Kleppner, highly influential atomic physicist, dies at 92 | MIT News"},"content":{"rendered":"

Daniel Kleppner<\/a>, the Lester Wolfe Professor Emeritus of Physics at MIT whose work in experimental atomic physics made an immense mark on the field, died on June 16 at the age of 92, in Palo Alto, California.<\/p>\n

Kleppner\u2019s\u00a0varied research examined the interactions of atoms with static electric and magnetic fields and radiation.\u00a0His work included creating precision measurements with hydrogen masers, including\u00a0the co-invention of the hydrogen maser atomic clock; his research into\u00a0the physics of Rydberg atoms and cavity quantum electrodynamics; and his pioneering work in Bose-Einstein condensation (BEC).<\/p>\n

Kleppner, who retired in 2003 after 37 years at MIT, was a highly literate and articulate scientist whose exacting research and communication skills helped set the direction of modern atomic, molecular, and optical (AMO) physics. From 1987 to 2000, he was associate director\u00a0of the\u00a0MIT Research Laboratory of Electronics<\/a> (RLE), and served as interim director in 2001.\u00a0He also co-founded the\u00a0MIT-Harvard Center for Ultracold Atoms<\/a> (CUA) in 2000, where he was co-director until 2006.<\/p>\n

While he was never awarded a Nobel Prize, Kleppner’s impact on the field of atomic physics and quantum optics, and his generous mentorship, enabled the Nobel achievements of many others. His patient and exacting pursuit of discovery led to basic research insights that led to major achievements. His extensive research into the tiny atom provided the fundamental knowledge necessary for the huge: the eventual development of groundbreaking technologies such as the global positioning system (GPS), magnetic resonance imaging (MRI), and quantum computing.<\/p>\n

\u201cHe was a leader in the department, and a leader in the American Physical Society,\u201d says\u00a0Wolfgang Ketterle<\/a>, the John D. MacArthur Professor of Physics at MIT and a 2001\u00a0Nobel laureate. \u201cHe was a statesman of science. He was this eloquent person, this master of words who could express things in memorable ways, and at the same time he has this sense of humility.\u201d<\/p>\n

\u201cDan Kleppner was a giant in the area of AMO physics, and in science more broadly,\u201d says\u00a0John Doyle PhD \u201991, Harvard Quantum Initiative co-director and Kleppner advisee who helped Kleppner create the Bose-Einstein condensate from atomic hydrogen. \u201cPerhaps his most impactful legacy is leading a culture of respect and supportive community actions that all scientists in the area of AMO physics enjoy today. Not only did his science lay the path for current research directions, his kindness, erudition, and commitment to community \u2014 and community service \u2014 are now ever-expanding waves that guide AMO physics. He was a mentor and friend to me.”<\/p>\n

Kleppner\u2019s daughter Sofie Kleppner notes: \u201cPeople who worked on early lasers never imagined we would be scanning groceries at the checkout counter. When they developed the hydrogen maser, they were a bunch of nerdy people who really wanted to understand Einstein\u2019s theory of relativity. This was the basis for GPS, this is how our flights run on time. Our dad was convinced that basic research today could lead to all sorts of valuable things down the road.\u201d<\/p>\n

Early life and career<\/strong><\/p>\n

Born in Manhattan on Dec. 16, 1932, Kleppner was the son of Vienna native and advertising agency founder\u00a0Otto Kleppner,<\/a> who wrote the best-selling book \u201cAdvertising Procedure.\u201d His mother, Beatrice (Taub) Kleppner, grew up in New Jersey and was a graduate of Barnard College. She helped with Otto\u2019s manuscripts. Daniel Kleppner was the second of three siblings; his brother, the late Adam Kleppner, was a professor of mathematics at the University of Maryland, and his sister, Susan Folkman, was a research psychologist at the University of California at Berkeley.<\/p>\n

\u201cAs a teenager, I just liked building things,\u201d Kleppner once said. \u201cAnd that turned out to be very useful when I went on to become an experimental physicist. I had a crystal radio, so I could listen to the radio over earphones. And the thought that the signals were just coming out of the atmosphere, I remember thinking: totally remarkable. And actually, I still do. In fact, the idea of the electromagnetic field, although it\u2019s very well understood in physics, always seems like a miracle to me.\u201d<\/p>\n

In high school, he was inspired by his physics teacher, Arthur Hussey, who allowed Kleppner to work all hours in the labs. \u201cThere was one time when the whole school was having a pep rally, and I wasn\u2019t that interested in cheering football, so I stayed up and worked in the lab, and the high school principal noticed that I was in there and called me in and gave me a dressing down for lack of school spirit.\u201d<\/p>\n

He didn\u2019t care. Hussey talked with Kleppner about quantum mechanics, and \u201cthat sort of put a bee in my bonnet on that,\u201d and taught him a little calculus. \u201cIn those years, physics was extremely fashionable. These were the post-war years, and physicists were considered heroes for having brought the war to conclusion with the atom bomb, and \u2026 the development of radar.\u201d<\/p>\n

He knew by then that he was \u201cdestined to spend a life in physics,\u201d he said in a\u00a0video interview for InfiniteMIT<\/a>. \u201cIt was an easy era to become delighted by physics, and I was.\u201d<\/p>\n

Studying physics at Williams College, he was drawn to Albert Einstein\u2019s theory of general relativity. He built a programmable machine that he called a forerunner of cybernetics. Williams also instilled in him a lifelong love of literature, and he almost became an English major. However, he didn\u2019t appreciate what he called the\u00a0school fraternities\u2019 \u201cplayboy\u201d and \u201canti-intellectual\u201d atmosphere, and worked to graduate quickly within three years, in 1953.<\/p>\n

He deferred his acceptance to Harvard University with a Fulbright Fellowship to Cambridge University, where he\u00a0met the young physicist Kenneth Smith, whose research was with\u00a0atomic beam resonance.\u00a0Smith introduced him to the book \u201cNuclear Moments,\u201d by Harvard professor Norman Ramsey, and presented\u00a0a proposal by Ramsey\u2019s advisor I.I. Rabi, who invented a technique that could make an atomic clock so precise \u201cthat you could see the effect of gravity on time that Einstein predicted,\u201d said Kleppner.<\/p>\n

\u201cI found that utterly astonishing,\u201d Kleppner noted. \u201cThe thought that gravity affects time: I had a hard time just visualizing that.\u201d<\/p>\n

When Kleppner wandered Harvard\u2019s halls in 1955, he was excited to see a door with Ramsey\u2019s name on it. He was interested in Ramsey\u2019s research on molecular beam magnetic resonance, atomic clocks, and precision measurements. \u201cFortunately, I came along at a time when he had an opening in his research group,\u201d Kleppner recalled.<\/p>\n

A new atomic clock<\/strong><\/p>\n

As Kleppner\u2019s advisor, Ramsey encouraged him to create a new type of atomic clock, believing that cesium and ammonia masers, a technology of amplified microwaves, were not precise enough to measure the effect of gravity on time.<\/p>\n

Kleppner\u2019s thesis was on using\u00a0the concepts behind an\u00a0ammonia maser<\/a>\u00a0to advance toward a\u00a0hydrogen maser<\/a>,\u00a0which uses the natural microwave frequency of hydrogen atoms and amplifies it through stimulated emission of radiation.\u00a0Kleppner discovered that coherent cesium atoms can bounce from properly prepared surfaces without losing their coherence.<\/p>\n

After\u00a0his 1959 PhD, Kleppner\u00a0stayed on at Harvard, becoming an assistant professor in 1962.<\/p>\n

Kleppner\u2019s research on hydrogen led to a method to keep hydrogen atoms locked in a glass container for study over a longer period of time. The result,\u00a0featuring hydrogen atoms bouncing within a microwave cavity, is used to stabilize the frequency of a clock to a precision better than one microsecond in a year.<\/p>\n

In 1960, he and Ramsey successfully created a new atomic clock whose significant stability could confirm the minute effects of gravity on time, as predicted by Einstein\u2019s theory of general relativity.<\/p>\n

The current generation of optical clocks \u201care good enough to see the gravitational red shift for a few centimeters in height, so that\u2019s quite extraordinary, and it\u2019s had an extraordinary result,\u201d said Kleppner. \u201cWe got to rethink just what we mean by time.\u201d<\/p>\n

While the hydrogen maser did verify Einstein\u2019s conjecture about time and gravity, it took more than a decade before being widely used, at first by radio astronomers.\u00a0Today,\u00a0atomic clocks such as the hydrogen maser are used in\u00a0applications requiring high short-term stability, such as\u00a0the synchronization of ground-based timing systems that track global positioning satellites, for\u00a0timekeeping and communication by naval observatories\u00a0to maintain a precise and stable time reference known as UTC (USNO);\u00a0very long-baseline microwave interferometry (VLBI) that enables astronomers to achieve very high resolution and study distant radio sources, including black holes;\u00a0and, indirectly, in magnetic resonance imaging.<\/p>\n

\u201cWhen we first set out to make these atomic clocks, our goals were about the least practical you can think of,\u201d Kleppner said in an interview with the MIT Physics Department. \u201cFrom being a rather abstract idea that you\u2019d like to somehow witness, it becomes a very urgent thing for the conduct of human affairs.\u201d<\/p>\n

Ramsey went on to win the Nobel Prize in Physics in 1989 for his\u00a0work on the\u00a0separated oscillatory fields method<\/a> and its application in the hydrogen maser and atomic clocks.<\/p>\n

MIT, ultracold gases, and BEC advancements<\/strong><\/p>\n

Kleppner figured he wouldn\u2019t get tenure at Harvard, \u201cbecause no matter how generous and good-spirited Norman was, he casts a long shadow, and it was good for me to be at just the right distance. When I came to MIT, I had a pallet of experiments that I wanted to pursue, and some ideas about teaching that I wanted to pursue, and the transition was very simple.\u201d<\/p>\n

Kleppner\u00a0joined the Institute in 1966, and his\u00a0Harvard PhD student (and current MIT professor post-tenure)\u00a0David Pritchard<\/a> followed him, to work on scattering experiments: Kleppner worked with pulsed lasers, and Pritchard with continuous-wave (CW) lasers.<\/p>\n

\u201cHe was young, he was verbal, and he seemed to have new ideas about what to do,\u201d says Pritchard. \u201cWe foresaw how important lasers would become. For a long time, it was just Dan and myself. That was actually the era in which lasers took over. Dan and I started off, we both got into lasers, and he did Rydberg atoms, and I did collisions and spectroscopy of weakly bound molecules and two-photon spectroscopy.\u201d<\/p>\n

Kleppner led the tiny MIT Atomic Physics Group to eventually become the US News and World Report\u2019s No. 1 nationally ranked atomic physics group in 2012. \u201cDan was the leader on this,\u201d recalled Pritchard. \u201cTo start from non-tenure and build it into the number-one ranked department in your subfield, that\u2019s a lifetime achievement.\u201d<\/p>\n

The group became what Pritchard called \u201cthe supergroup\u201d of laser developers that included Charles Townes, who won the Nobel for his work; Ali Javan,\u00a0who established a major laser research center at MIT; and Dolly Shibles. Pritchard joined the faculty in 1970, and\u00a0<\/a>Ketterle joined in 1990 as his postdoc. \u201cWe were pioneers, and the result was of course that our total group had a bigger impact.\u201d<\/p>\n

\u201cHe\u2019s not just the father figure of the field, he is my scientific father,\u201d says Pritchard. \u201cWhen I\u2019m writing something and it\u2019s not going very well, I would sort of think to myself, \u2018What would Dan say? What would he advise you?\u201d<\/p>\n

With MIT low-temperature physicist\u00a0Tom Greytak<\/a> \u201963, PhD \u201967, Kleppner developed two revolutionary techniques \u2014 magnetic trapping and evaporative cooling. When the scientific community combined these techniques with laser cooling, atomic physics went into a major new direction.<\/p>\n

In 1995, a group of researchers, led by Kleppner’s former students\u00a0Eric Cornell PhD \u201990 and Carl Weiman \u201973, made a BEC using rubidium atoms, and Ketterle succeeded with sodium atoms. For this achievement, they received the\u00a02001 Nobel Prize in Physics<\/a>.\u00a0Kleppner called BEC\u00a0\u201cthe most exciting advance in atomic physics for decades.\u201d\u00a0<\/p>\n

At a conference on BEC in 1996, Ketterle recalls Kleppner describing his own contributions: \u201c’I feel like Moses, who showed his people the Holy Land, but he never reached it himself.’ This was exactly what Dan did. He showed us the Holy Land of Bose-Einstein condensation. He showed us what is possible \u2026\u00a0He was\u00a0the godfather of Bose-Einstein condensation.\u201d<\/p>\n

But he did reach the Holy Land. In 1998, when only a few groups had been able to create BECs, Kleppner and Greytak realized a\u00a0hydrogen BEC.\u00a0When he presented their work at the summer school in Varenna soon afterward, he received a long-lasting standing ovation \u2014 after 20 years of hard work, he had reached his goal.<\/p>\n

\u201cIt is an irony that when Dan started this work, hydrogen was the only choice to reach the low temperatures for BEC,\u201d says Ketterle. But in the end, it turned out that hydrogen has special properties that made it much harder to reach BEC than with other atoms.\u00a0<\/p>\n

Rydberg atoms<\/strong><\/p>\n

In 1976, Kleppner pioneered the field of Rydberg atoms, a highly excited atom that shares the simple properties that characterize hydrogen.\u00a0Kleppner\u00a0showed that these states could be excited by a tunable laser and easily detected with field ionization. He then mapped out their response in high electric and magnetic fields, which he used to provide new physical insights into the connections between quantum mechanics and classical chaos.<\/p>\n

In 1989, his research into atomic energy levels, under conditions where the corresponding classical motion is chaotic, mapped out the positions of thousands of quantum levels as a function of laser frequency and applied field using high-resolution laser spectroscopy. His observations gave new physical insight into the implications of classical chaos on quantum systems.<\/p>\n

\u201cI see Dan as being the inventor of Rydberg atoms,\u201d says Dan\u2019s former student\u00a0William Phillips<\/a>\u00a0PhD \u201976,\u00a0physicist at the Institute of Standards and Technology (NIST). \u201cOf course, Rydberg atoms is something that nature gives you, but Dan was the one who really understood this was something that you could use to do really new and wonderful things.\u201d<\/p>\n

Such atoms have proved to be useful for studying the transition between quantum mechanics and classical chaos. Kleppner\u2019s 1976 paper<\/a> on Rydberg atoms\u2019 strong interactions, long lifetimes, and sensitivity to external fields has led to current scientific research and multimillion-dollar startups interested in developing the promising Rydberg quantum computer; highly accurate measurements of electric and magnetic fields; and in quantum optics experiments.<\/p>\n

\u201cLargely due to Dan\u2019s seminal roadmap, Rydberg atoms have become atomic physics\u2019 E. coli for investigating the interaction of radiation with matter,\u201d wrote Ketterle in his nomination for Kleppner\u2019s\u00a02017 APS Medal for Exceptional Achievement in Research. \u201cThey are being used by others in quests for experimental systems to realize Schr\u00f6dinger\u2019s cat, as well as for making a quantum computer.\u201d<\/p>\n

In 1981, Kleppner suggested in a\u00a0theoretical paper<\/a>\u00a0the possibility of suppressing spontaneous emission with a cavity: excited atoms cannot decay when the cavity lacks\u00a0the oscillatory modes to receive their emissions. This was\u00a0followed by his demonstration of this effect, and launched the field of\u00a0cavity quantum electrodynamics (cQED),\u00a0the study of how light confined within a reflective cavity interacts with atoms or other particles. This field has\u00a0led to the creation of new lasers and photonic devices.<\/p>\n

\u201cThis work fundamentally changed the way physicists regard the process of spontaneous emission by showing that it is not a fixed property of a quantum state, but can be modified and controlled,\u201d said Ketterle. \u201cCurrent applications of these principles, which Dan terms \u2018wrecking the vacuum,\u2019 include thresholdless lasers and the construction of photonic bandgap materials in which light propagation is forbidden at certain frequencies.\u201d<\/p>\n

MIT-Harvard Center for Ultracold Atoms<\/strong><\/p>\n

In 2000, Kleppner secured\u00a0National Science Foundation funding to co-found the Center for Ultracold Atoms (CUA), an MIT-Harvard collaboration that linked\u00a0RLE with the Harvard Department of Physics\u00a0to explore the physics of ultracold atoms and quantum gases. Kleppner served as its first director until 2006, and was a member of a group that included MIT professors Ketterle, Pritchard,\u00a0Vladan Vuletic<\/a>,\u00a0Martin W. Zwierlein<\/a>,\u00a0Paola Cappellaro<\/a> PhD \u201906, and\u00a0Isaac Chuang<\/a> \u201990.<\/p>\n

\u201cMany centers disappear after 10 to 20 years; sometimes their mission is fulfilled,\u201d says Ketterle, the CUA director from 2006 to 2023. \u201cBut given the excitement and the rapid evolution in atomic physics, the CUA is a super-active center brimming with excitement, and we just recently got renewed. That\u2019s partially due to the efforts of Dan. He created the tradition of atomic physics at MIT. We are one of the best atomic physics groups in the world. And we are really a family.\u201d<\/p>\n

Boost-phase intercept report<\/strong><\/p>\n

Kleppner co-authored a highly influential\u00a02003 report<\/a>\u00a0that\u00a0examined the technical feasibility of boost-phase intercept, a concept central to President George H.W. Bush\u2019s proposed controversial Strategic Defense Initiative (SDI), nicknamed “Star Wars,\u201d which purportedly would render nuclear weapons obsolete. The focus of the\u00a0APS Study on Boost-Phase Intercept for National Missile Defense<\/a>,\u00a0published as a special supplement to\u00a0Reviews of Modern Physics,\u00a0was on the physics and engineering challenges of intercepting a missile during its boost phase.<\/p>\n

\u201cThis was a subject on which I had no technical background at all,\u201d Kleppner recalled, so he expressed gratitude for the skills of co-chair Fred Lamb of the University of Illinois. \u201cBut the APS [American Physical Society] felt that it was important to have information for the public \u2026 and no one knew anything about it. It was the point in my life where I could do that. And I feel that you have an obligation when the need arises and you can do it, to do that.\u201d<\/p>\n

The result? \u201cTechnically, it really would not succeed, except in very limited circumstances,\u201d Kleppner said. Added Pritchard, \u201cIt vastly changed the path of the nation.\u201d<\/p>\n

\u201cHe was the perfect person to chair the committee,\u201d says Ketterle. \u201cHe excelled in being neutral and unbiased, and to create a no-nonsense report. I think the APS was very proud of this report. It shows how physicists analyze something which was at that moment of immense political and societal importance. This report helped to understand what laser weapons cannot do and what they can do. The fact that (SDI) eventually, slowly, disappeared, the report may have contributed to that.\u201d<\/p>\n

Dedicated educator<\/strong><\/p>\n

Kleppner trained generations of physicists, including\u00a0as advisor to\u00a023\u00a0PhD students who have gone on to attain positions in major universities and achieve major scientific awards.<\/p>\n

He was awarded the\u00a0Oersted Medal<\/a> of the American Association of Physics Teachers in 1997, and\u00a0earned the Institute\u2019s prestigious\u00a01995-1996 James R. Killian, Jr. Faculty Achievement Award<\/a>\u00a0for his service to MIT and society on behalf of atomic physics.\u00a0\u201cHe has given generously of his time and effort to the formation of national science policy, and he has served the Institute with distinction as teacher, administrator and counselor,\u201d the Killian committee wrote.<\/p>\n

Kleppner and Ramsey wrote the widely used text\u00a0\u201cQuick Calculus<\/a>\u201d\u00a0in 1972 \u2014 the third edition of the book was updated in\u00a02022 edition with MIT Department of Physics\u2019\u00a0Peter Dourmashkin<\/a>. With\u00a0Robert J. Kolenkow<\/a>, Kleppner also wrote\u00a0\u201cAn Introduction to Mechanics<\/a>\u201d\u00a0in 1973, and its second edition in 2013.\u00a0Physics department head\u00a0Deepto Chakrabarty<\/a> \u201988\u00a0called it \u201ca masterpiece:\u201d \u201cIt has formed the foundation of our freshman 8.012 course for potential physics majors for over 50 years and has provided a deep, elegant, and mathematically sophisticated introduction to classical mechanics of physics majors across the U.S. It was my own introduction to serious physics as an MIT freshman in 1984.\u201d<\/p>\n

Recently, while Kleppner was being wheeled into surgery, one of the medical personnel noticed that his patient was the author of that book and blurted out, \u201cOh my God, I still am wondering about one of those problems that I found so difficult,\u201d recalls his wife, Bea, laughing.<\/p>\n

Kleppner called his method of teaching\u00a0\u201can\u00a0engagement with the students and with the subject.\u201d He said that his role model for teaching was his wife, who taught psychology at Beaver Country Day High School. \u201cFortunately, at MIT, the students are so great. There\u2019s nothing tough about teaching here, except trying to stay ahead of the students.\u201d<\/p>\n

He leaves a legacy of grateful physicists impacted by his generous teaching style.<\/p>\n

\u201cI\u2019ve always felt that I\u2019ve just been incredibly lucky to be part of Dan\u2019s group,\u201d says Phillips, who was at Princeton when his research into magnetic resonance caught Kleppner\u2019s attention, and invited him to MIT. \u201cDan extended this idea to putting this hydrogen maser in a much higher magnetic field. Not that many people are trained by somebody like Dan Kleppner in the art of precision measurement.\u201d<\/p>\n

Kleppner also gifted Phillips an apparatus he built for his thesis, which shaved years off the laser cooling experiments that led to Phillips\u2019 Nobel.<\/p>\n

Ketterle credited Kleppner\u2019s mentorship for his career at MIT. \u201cHe was an older, experienced person who believed in me. He had more trust in me than I had initially myself. I felt whenever I was at a crossroads, I could go to Dan and ask him for advice. When I gave him a paper to edit \u2026 there was red ink all over it, but he was absolutely right on almost everything.\u2019\u201d<\/p>\n

In 2003, Kleppner was dismayed at the statistic that over 60 percent of middle and high school teachers teaching physics have no background in the subject. He started the CUA\u2019s\u00a0Teaching Opportunities in Physical Science<\/a> summer program with his then-postdoc Ted Ducas to train physics majors to\u00a0prepare and teach physics material to middle and high school students. In its 14-year run, they worked with 112 students.<\/p>\n

According to Ducas, one survey \u201cindicates over 60 percent of our undergraduates have gone into, or plan to go into, pre-college teaching \u2014 a higher percentage than expected, because physics majors have so many other career opportunities often paying significantly more. The potential positive impact of that number of highly qualified and motivated teachers is dramatic.\u201d<\/p>\n

Kleppner also partnered with Japanese mathematician Heisuke Hironaka on the mentoring program Japanese Association for Mathematical Sciences (JAMS), which connected American college science students with their Japanese counterparts.\u00a0\u201cHis interest in ensuring that future generations also see the value of international communities was reflected in JAMS,\u201d says Sofie Kleppner.<\/p>\n

Recognitions and public service<\/strong><\/p>\n

Kleppner was promoted to professor in 1974 and headed the physics department\u2019s\u00a0Division of Atomic, Plasma and Condensed Matter Physics from 1976 to 1979. He was named the Lester Wolfe Professor of Physics in 1985.<\/p>\n

Active in the interface between physics and public policy, he served on more than 30 committees. For the APS, he was on the Panel on Public Affairs (POPA),\u00a0chaired the Physics Planning Committee and\u00a0the Division of Atomic, Molecular and Optical Physics,\u00a0and\u00a0contributed to a study on the growth and mentorship of young physics professors. He\u00a0chaired a report for the National Academy of Sciences on atomic physics that he presented on various congressional committees, served on the National Research Council’s Physics Survey Committee, and was chair\u00a0of the International Union of Pure and Applied Physics\u2019 Commission on Atomic and Molecular Physics. At\u00a0MIT, he was also an ombuds of the Physics Department.<\/p>\n

Kleppner was a fellow of the American Academy of Arts and Sciences, American Association for the Advancement of Science, OSA (now Optica),\u00a0French Academy of Sciences, and the\u00a0American Philosophical Society<\/a>; a member of the National Academy of Sciences; and a Phi Beta Kappa lecturer.<\/p>\n

His interest in literature at Williams bloomed into a secondary career as a writer, including decades of writing witty and insightful, yet accessible, pieces for\u00a0Physics Today<\/a>, including his \u201cReference Frame\u201d columns on physics history and policy.<\/p>\n

Kleppner was a recipient of many awards, including the prestigious\u00a0Wolf Prize<\/a>\u00a0in 2005 \u201cfor groundbreaking work in atomic physics of hydrogenic systems, including research on the hydrogen maser, Rydberg atoms, and Bose-Einstein condensation.\u201d Other accolades include a\u00a02014\u00a0Benjamin Franklin Medal<\/a> and a 2006\u00a0National Medal of Science<\/a>, presented by U.S. President George W. Bush. He also received the\u00a0Frederic Ives Medal<\/a> (2007),\u00a0the William F. Meggers Award (1991),\u00a0the Lilienfeld Prize (1991), and\u00a0the Davisson-Germer Prize (1986).<\/p>\n

His articles, congressional testimony, and advocating on behalf of physicists around the world at one point inspired his\u00a0Physics Planning Committee colleagues\u00a0to present him with a Little League trophy of a golden baseball player, with the inscription \u201cDan Kleppner \u2014 Who Went to Bat for Atomic Physics.\u201d<\/p>\n

Kleppner said that he was inspired by his mentor, Ramsey, to get involved in the scientific community. \u201cIt\u2019s a privilege to be a scientist in this country,\u201d said Kleppner. \u201cAnd I think that one has some obligation to pay for the privilege, when you can.\u201d<\/p>\n

He wrote, \u201cAny scenario for a decent future of our nation and the world must include a reasonable component of science that is devoted to the search for new knowledge. We cannot afford to abandon this vision under a barrage of criticism, no matter how eloquent or powerful the critics.\u201d<\/p>\n

Family and retired life<\/strong><\/p>\n

Kleppner met his future wife, Beatrice Spencer, in 1954 on the USS United States, when both were England-bound and in their second year of studying at Cambridge. They began as friends, and eventually\u00a0married in 1958<\/a>,\u00a0in Ipswich, Massachusetts. They\u00a0raised their\u00a0three children, Sofie, Paul, and Andrew,\u00a0at their home in Belmont, Massachusetts, and their vacation home in Vermont.<\/p>\n

Kleppner\u2019s family described him as an optimist who didn\u2019t believe in lying, worrying, or unethical behavior. He and Bea generously invited into their home anyone in need. \u201cWhen we were growing up, we had the international community in our house,\u201d recalls Sofie. \u201cHe was just a tremendously generous person. At my father\u2019s 80th birthday celebration at MIT, there were three hours of five-minute reminiscences. It was really moving to hear the number of people who felt that just having the open door at my parents\u2019 house meant the difference to them as they went through difficult times.\u201d<\/p>\n

In his retirement, Kleppner continued with his woodworking projects, including building beds, lamps, cabinets, a beautiful spiral staircase, a cradle curved like the hull of a boat, and bookcases featuring super ellipses,\u00a0a closed curve that blends elements of an ellipse and a rectangle.<\/p>\n

\u201cI enjoy designing,\u201d he said\u00a0in one video<\/a>. \u201cIt\u2019s the same instinct for making things work in experimental physics. It\u2019s lovely to make a piece of apparatus that starts functioning, and even if the experiment doesn\u2019t do what you want it to do. There\u2019s always a lot of jubilation when the apparatus is first turned on and first works.\u201d<\/p>\n

His\u00a0last article<\/a> for\u00a0Physics Today was in 2020.\u00a0In his later years, he kept in touch with his colleagues, swapping book ideas with Ketterle\u2019s wife, Michele Plott, and, since the Covid-19 pandemic, maintained\u00a0regular Zoom meetings with a group of his former students, hosted by Mike Kash; and another, what they called \u201cThe Famous Physicists,\u201d that included Phillips and\u00a0 their Brazilian colleague Vanderlei Bagnato.<\/p>\n

\u201cIn recent years, I would still go to Dan for advice about difficult questions,\u201d says Phillips, \u201csometimes about physics, sometimes just about life and public policy, because maybe I always felt that if there was anything you wanted done in which physics or science was part of the question that Dan would be the best person to do it.\u201d<\/p>\n

His family says that Kleppner suddenly fell ill at a Father\u2019s Day dinner. According to his wife, his last words before being rushed to the hospital were a toast to his grandson, who recently graduated high school: \u201cTo Darwin and all youth who have new and exciting ideas.\u201d<\/p>\n

Says Bea, \u201c\u200b\u200bHe always said that you have to be optimistic to be a scientist, because you have to be patient. Things don\u2019t work out and they\u2019re fiddly, and there are lots of things that go wrong. His last words were ones that make you feel there\u2019s hope for the future.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"Daniel Kleppner, the Lester Wolfe Professor Emeritus of Physics at MIT whose work in experimental atomic physics made…\n","protected":false},"author":3,"featured_media":68269,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[25],"tags":[48363,48362,48361,48364,48366,48358,48357,48359,48360,492,159,67,132,68,48365],"class_list":{"0":"post-68268","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-physics","8":"tag-amo-physics","9":"tag-atomic-clocks","10":"tag-bose-einstein-condensates","11":"tag-daniel-kleppner","12":"tag-john-doyle","13":"tag-mit-faculty-obituary","14":"tag-mit-physics","15":"tag-mit-rle","16":"tag-mit-harvard-center-for-ultracold-atoms-cua","17":"tag-physics","18":"tag-science","19":"tag-united-states","20":"tag-unitedstates","21":"tag-us","22":"tag-wolfgang-ketterle"},"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@us\/114865255394839619","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/68268","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/comments?post=68268"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/posts\/68268\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media\/68269"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/media?parent=68268"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/categories?post=68268"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/us\/wp-json\/wp\/v2\/tags?post=68268"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}