Sunday, March 18, 2007

Guest Post: Yidun Wan

[Preface: Dear Readers of the Inspiration Series,

I realized that most of the guest contributions are too long to be read comfortably on screen. I have therefore put them together in a pdf-file, that you can download here. A nice Sunday evening to all of you,

Sabine ]

Why did I become a physicist? This, as normally a question for successful people, appears to be really hard for someone like me, who is still a PhD candidate with no splendid past. This is a hard question also because one can hardly answer it objectively and mathematically. However, being invited by Sabine Hossenfelder to write my answer as a guest post on her famous blog, it is my pleasure to try my best to say something, which may not be an satisfactory answer as expected by the host.

Prior to my story, I would like to spend some time on the word "physicist". Why? In English, one refers to physicists as those who do research in physics, including professors, researchers, postdocs, graduate students. However, the Chinese translation of a "physicist" (and more generally, a scientist) is not merely someone, who researches in physics, but one who has contributed to physics noticeably. The Chinese counterpart of a "physicist" in English should be a "physics researcher". Therefore, considering my situation, the question I am to answer should be better understood as "why did I become a physics researcher".

If I say that I simply have followed my destiny to become a physicist, you may laugh and think I am perfunctory, since this does not sound like what a physicist should say. Nevertheless, I am just telling the truth in an efficient way. To tell more details, it is better to first outline my history. Fourteen years ago, I began my undergraduate study in China. After four years, I obtained my first Bachelor's degree in Computer Science. One year later, I got my second one in Economics. Then I started to work in some Chinese company. Six years ago, I landed on the U.S.A. and continued my study in Computer Science as a graduate student. After one year and a half, I had the opportunity to switch to physics. Hence, I took a master's degree in Computer Science and quit. In the next two years, I had been doing research in applied physics (though theoretical calculation) in Canada, which brought me a master's degree in physics. Right after this, my world line extended to doing theoretical physics at the Perimeter Institute; now I still move on in the same direction—to explore the physical nature till the singularity of my life. Having read my brief history, you may take off now if not interested in any more detail.

So ladies and gentlemen, let us begin a time travel along my world line back to the past. In the summer of 2002, I often wandered around in the campus of the University of Pennsylvania, because a critical junction of my life came to me, which put me in front of two choices: to do research in Neural Networks towards a Ph.D. in Electrical Engineering, and to move to the University of Ottawa in Canada and begin my academic career as a physicist. Although the former option might be able to bring me a good life with stable job and income, I chose the latter one, as you already knew. There were two reasons. The first reason, obviously, was that I could then start to realize my dream of being a physicist. (I haven't explained why I love physics, but it is coming, just be a little bit more patient in the time travel. ) The second reason was related to my personal life; my girlfriend, who became my wife in that August, was to do her master's study at the University of Ottawa, so the only way for me to keep us together should be getting into the same university. The only shortcoming of going to the University of Ottawa was that I could not do pure theoretical physics but the so-called "theoretical" Fiber Optics, since the physics department there had only research groups in applied physics. Therefore, I decided to be enrolled in the master's program only in order to move to some other place where I can do theoretical physics later. Luckily, after two years stay in Ottawa, I successfully obtained my master's degree in physics and was admitted by the University of Waterloo, and joined the Perimeter Institute to pursue research in Quantum Gravity under the supervision of Prof. Lee Smolin. Since then I have been on the right track and become what I am now: a physicist.

Life is very unpredictable and is thus fascinating; a decision, which is apparently not perfect at the moment of being made, may turn out to be perfect at a later time. Take my decision of going to Ottawa as an example; it was not perfect for sure at that time because what I truly wanted to do was theoretical and fundamental physics. However, as soon as I entered Perimeter Institute, I realized that decision was so right. Why? Before I came to Ottawa, I actually had no any real background in physics and advanced mathematics; all I knew about physics and math was what I learned from my first year undergraduate physics course, some Electromagnetism I learned by myself, calculus and some complex analysis. With such a weak background, I would easily wash out quickly if I directly jump on some graduate program of pure theoretical physics. During the 2-year stay in Ottawa, I took graduate courses like "Quantum Mechanics", "Mathematical Methods in Physics", "Statistical Mechanics", and "General Relativity", and did a great job. Interestingly, I had no any problem of understanding Quantum Mechanics. The reason, I guess, was that I never learned Classical Dynamics systematically before I encountered the quantum one. Besides taking courses, I spent a lot time on learning useful math and physics by myself. Moreover, I also did some experimental physics, which input some concrete cognition of physics to my brain. In summary, having worked hard in that two years established me a relatively ok background in physics, which was of great help to me in my first year at PI. Every time when I look back, I am grateful to my experience in Ottawa, and hence to my decision made in the summer of 2002.

Our itinerary of time travel may be mis-programmed in the computer of our spacecraft; we now stop at my childhood. Anyway, let us accept this and turn around our craft to continue our trip from here to its future. I am not very confident of my memory about very early years in my life. So we would better to start from my second year in elementary school. I remember in that year every student in my class was asked to write an essay about his/her ideal. My essay looked like a science fiction, in which I imagined the world of twenty years later, and more importantly I was a scientist, but not a physicist in particular. Frankly speaking, this does not mean that I really wanted to be a scientist at the moment. Part of the reason was that I might be too young to understand what a scientist exactly is. The other part was that "being a scientist" was a common ideal of many Chinese children at that time, since we were taught to believe that making scientific contribution to our country and even the whole world is a sublime and holy career. However, I knew that I was definitely attracted by two mysterious entities: the universe and the being. I just had been able to tell which one, the universe or the being, I was more interested in until I met a book, "the First Three Minutes" by Steven Weinberg, which influenced my life to a large extent. I clearly remember it was in some day during my first year in junior high school when I borrowed the book (certainly the Chinese version) from the civic library of my hometown. "The first Three Minutes" vividly elaborated the story within the first three minutes of our universe, from which I first got to know that our universe originates from a singularity through a Big Bang in about 1.3 billion years ago. In fact, I was not able to understand the physics in the book and did not even know who Weinberg was; nonetheless, I was completely captivated by the splendid and gorgeous scene of the early universe illustrated by the book. At the time of reading the book, astonishment, doubt, and excitement had been always possessed me; strong eagerness to fully understand everything in the book in some day spurred me to take to be a physicist decoding the universe as my life-long ideal.

Irony of ironies, I did not appear to be very talented in physics when I was a child, and even when I was a teenager. My talent in literature (of course the Chinese one) and arts seemed much better than that in physics. This situation drastically changed only after I went to university, the South China University of Technology. The consequence was that I did not choose physics, but rather computer science as my undergraduate major, although to be a physicist had always been a dream hovering in my head. Another factor caused me to major in computer science was my parents, who made the decision for me; this was pretty natural in China, at least at that time.

During my undergraduate study, China was experiencing a rapid increase of her national economy; various enterprises, domestic or multinational, emerged; people became richer and richer. This big tide of economy also impacted me; I felt that to be a good businessman sounds not bad at all. Interestingly, to be adapted to the development of the our country, my university offered a new program, which allowed excellent engineering students to also major in International trade towards a Bachelor's degree in Economics. I, one ridiculously forgot his ideal at the moment, joined the new program. After graduation, I successfully found a job and planned to establish my own business in the near future. Nevertheless, soon I realized that was not the life I really liked and wanted. Watching the night sky decorated with shiny stars, the ideal to be a physicist woke up in my mind; I decided to go abroad to look for my dream. Therefore, after having worked for about half a year, I resigned and went back home to prepare for TOEFL and GRE, which are required by most American and Canadian graduate schools. I had to choose computer science again so that I could successfully be admitted by American universities, because applying for graduate study in physics in the States from China without a physics background was hopeless and it ought to be easier to switch major after getting an American degree. Unfortunately, at the end of 1999, my visa application was rejected by the US Consulate in Guangzhou, China; I tried another two times in sequence, but they were all rejected. In the next year, I had to re-apply for universities and also took some time to refresh my memory on advanced calculus and geometry, and general physics. After had painfully waited for almost a year, I finally got my US visa in the end of 2000. I then went to UPenn and began my life in North America.

Since we have already read my past related to physics after 2000, our time craft should directly fly back to our current time. Thanks everyone who joined our time travel! I would like to talk about why I selected quantum gravity, in particular Loop Quantum Gravity as my research area; however, this is not a short story, which can be clearly narrated within such a guest post. Anyway, what I wrote above should be sufficient to answer the question "why did I become a physicist".

I think my world line behaves like a damping oscillator along time, which although turns aside often from the way to be a physicist, eventually converges at being a physicist. So again, I have to say: "I simply followed my destiny."

Yidun Wan is a Ph.D. candidate affiliated with the University of Waterloo. He works on Quantum Gravity at the Perimeter Institute for Theoretical Physics, under the supervision of Prof. Lee Smolin. He blogs at Road to Unification and also maintains a personal webpage here. He is currently working on unifying matter with Loop Quantum Gravity.

See also the previous contributions to the inspiration-series by


  1. That's an interesting story - thank you for telling it!

    I am impressed by your persistence to beome a physicist! And the to and fro along your timeline mirrors very nicely your swithicng from computer science to business to computer science to physics, eventually.

    From reading through the other posts of this series, and this one, it seems to me that reading good popular science books as a teen is a very important incentive to become a physicist later in life. Maybe this is something that could encouraged mote in schools?

  2. Hi Yidun,

    That's an interesting story! I think we share at least two things in common. First, I also have an undergraduate degree in computing (apart from my B.S. in astronomy). I was somewhat driven to computing, because of some uncontrollable (at that time) external influences, but it was never something I really wanted to work on. Second, I wasn't very talented in physics/maths in high school as well. But my grades started to improve at the second half of my undergraduate studies and then my grades were all excellent (A+) in graduate school. I don't know why my grades evolved like that (well, better than the other way around), since I have been interested in physics from an early age, but... Perhaps with time I finally came to understand the essencials of studying physics and maths more appropriately.

    Best regards,

  3. Yes, thanks for sharing Yidun.

    I have been enjoying reading the profiles you all have been willing to offer of yourselves here in backreaction.

    This is a wonderful service even though I do not comment on all of the profiles, I still read them. I think this brings the public closer to the pople who are doing our science for us. As well as, your compatriots in the business.

    Thanks again Yidun

  4. the anonymous:

    Thanks! I agree with you on that reading good popular science book at the right time is very important. I think a good polular science book should aim not only at spreading scientific knowledge but also at telling people the scientific way of doing research, i.e. the methodology of science.

    Hi Christine,

    Thanks! It is interesting that we have some similarities. I think for those young genius, their IQ in math/physics becomes very mature during their childhood, whereas for those like us, the math IQ probably grows slower but gradually, and gets to a much faster increase rate after a critical age. Another possibility is that our talent in math simply just hid somewhere in our brain, or was suppressed by talents in other areas.

    Hi Plato,

    Thanks! I do agree with you that researchers should try to get closer to the general public. We'd thank Sabine for initiating this inspiration series, and even thank the one who invented webblog! :-)

    Have a great day,

  5. All these bios are quite interesting and we thank Bee for making it happen. Even for a retired physicist like me.

    Thanks Yidun for the story. But of course, doing fundamental physics has quite unique challenges. In business all you need to do is make money. In computer science (today) there's really not much to do - it has matured to become largely a commodity business. In physics, once you finished studying other people's stuff, you're immediately called upon to make stuff your peers would want to read. Or you don't get a job. Sorry to put a monkey wrench in the fun. All the very best.

  6. Hi All,

    Thanks for the feedback. I just love to hear other people's stories, this is why I initiated this series. I am happy to hear you find these stories as interesting as I do.

    Another remark: maybe some of you have noticed that I hardly ever comment on the guest posts. The reason is not that I have nothing to say (ha, now that would be news) but that most often I have commented on the story in an prior email exchange - so leave the stage here for you. Very special thanks also to Yidun, who has so skillfully time-travelled us along.



  7. Thanks Yidun for a fascinating journey! What strikes me as so impressive is your persistence and bravery in pursuing your dream of physics. And that you were so self-motivated to learn many things along the way. I so appreciate Bee's sharing these diverse and inspirational stories. You might think yours isn't a "splendid past" but to someone like me it very much so. Thanks again for sharing your story!

  8. Great post! I am impressed by your persistence and bravery! People like you should be respected! As a Chinese, I am proud of you! Good luck with your future journey!

  9. Its been pointed out to me that the magazine 'Focus' mentioned in the comment that I just deleted does indeed exist. In case you are interested in running the above post, please contact me by email (sabine[@] For obvious reasons, I will not give copyright to an anonymous commenter. Thanks,



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