The Straight Dope: advice for aspiring string theorists

This essay is intended for high school students and less experienced undergraduates considering a career in string theory.

First steps

String theory is a part of theoretical physics that has wiggled its way into the popular consciousness recently. Enthusiasm for string theory among the general public, and among students, may have been sparked or influenced by Brian Greene's books and the associated NOVA TV documentaries, and other sources. String theory is a subject full of buzz: it encompasses many cool concepts including quantum mechanics, relativity, extra dimensions of space, the arrow of time, the origin of our universe, branes, and so forth. I think it great that so many students are interested, but I am a string theorist so of course I am a tad biased. :-)

The next step in studying string theory, after reading popular books and websites, is to embark on a university degree. For the journey towards string theory expertise, the best route to take is a bachelors degree in physics with as much mathematics as possible. The reason a strong physics background is needed is to enable understanding the twin pillars of 20th century physics on top of which string theory is built: quantum mechanics and general relativity. (Quantum mechanics is introduced here at UofT in second year and continued into third and fourth year, while general relativity - which comes after special relativity - is introduced in fourth year.) The reason lots of math is advisable is that mathematics is the language of theoretical physics.

Getting advice

One important thing to consider is that there is so much more to physics than string theory. Even if you start a physics degree because you are interested in string theory, make sure you take a really good look around. There are tons of other really exciting areas of physics; e.g. here in our department we do research in earth atmospheric and planetary physics, condensed matter physics, quantum optics, high energy physics, astrophysics, biological physics, and physics education. It is noteworthy that there is an extraordinarily wide range of jobs that can be obtained after earning a bachelors degree in physics; see e.g. the CAP careers site.

A word about getting advice. Any particular advisor (e.g. high school careers counselor, family member, friend) may not be able to steer you in the right direction, academically or otherwise. Sometimes this can happen because of limited experience, or outdated information. The smartest thing to do is seek advice from a range of people; no one person can be expected to know everything and dispense accurate advice all the time. (Obviously, this applies to me as well!). To put it another way: it is wise to maintain a portfolio of mentors, a.k.a. a composite mentor.

Getting a Ph.D.

If you are interested in string theory as a long-term career, then you are aiming to become a physics professor researching and teaching in a university - which is where [almost] all string theorists work. This always requires a Ph.D. The trek to academic string theory as a profession is not an easy one. Like most things in life worth doing, building a sustainable career in the field is hard work. I put this page on the web so that students keen on string theory can get an accurate (non-sugar-coated) portrayal of what the path to a career in string theory might look like. This advice is intended to be encouraging while also being honestly informative.

If you are a senior undergrad, how do you embark on the trek towards becoming a string theorist? First, you apply to Ph.D. programs. As an undergraduate, think about how to present a strong application to graduate schools. Your application will typically consist of three or four components: your undergraduate transcript, GRE scores, recommendation letters, and (usually) a statement of what you are interested in.

Your application package

To maximize your chances, you want to present the strongest application you possibly can. Excellent grades really help; so does evidence of grade improvement over time. For string theory and other areas of theoretical physics, it also helps to have demonstrated aptitude for mathematics as well as general physics ability - and high initiative.

Always be honest about presenting yourself in your graduate school applications. For example, do not pretend that you are interested in condensed matter experiment if you plan to do a string theory Ph.D. (No kidding, some students tried this lie and ended up high and dry.) Emphasize your good points, for example any external or internal scholarships you have won. It is also important to think about what to leave out. Your triumph in Grade 10 Debating, your Cat Shelter activism, etc., are not relevant to a Physics graduate school application. Neither is your marital or family status, unless the university's application form says so explicitly.

The GRE is an easy place to slip up, by the way. You have to study and do lots of timed practice exams in order to do well, because the tests are very time pressured. For example, in the Physics exam you typically do not have time to derive equations (like the period of some kind of simple pendulum); you have to memorize them!

It is unfortunate but true that U.S. Physics Departments take the GRE seriously, particularly the most competitive places, and places with strict rules determined by the university administration rather than the department. This is obnoxious: social scientists have found evidence that the GRE is biased against historically underrepresented groups. Why do universities still take GRE scores seriously? They have tons of smart students applying; there is tough competition for supervisors, especially in fields the general public has heard of. Evaluators have to pick out the students most likely to succeed in their competitive atmospheres. If they see bad GRE scores, they may not take that application so seriously, because they will have loads of other applications with better GRE scores to look at. Your physics score is more important than your general test score.

Application strategy

Apply to a range of places. Apply to a few which are your small-probability fantasy places, then several where you think you have a very good probability of getting in, and lastly a few backup places. You never quite know how people will read your application. Think ahead: do not wait to apply to backup places until you have been rejected from the others. And if you are worried about fees for more than a handful of places, borrow money if you can. A few hundred bucks in application fees to good universities is a very good investment in your future.

You want to go to the very best place you can get into - and feel comfortable at. You benefit not only from the brand name degree, but also because the better places can typically attract stronger students, and you can learn a huge amount from your fellow students in graduate school. That is one of the little secrets of the Ph.D. story - you learn not only from the professors, but also their postdocs and other students.

About countries. Most students begin the academic trek thinking that they will be able to come home for a professorial job. I advise thinking much more broadly. The academic job market these days is unequivocally global. For example I thought I would go home to New Zealand because I grew up and did an undergraduate degree there. But I did a Ph.D. and two postdocs in the U.S. and got a faculty position here in Canada (!).

If you cannot face the idea of leaving your home province/state/country, either temporarily or permanently, then you should definitely have a plan B for employment, and probably a Plan C as well. Especially so if you are set on doing string theory, or any other topic for which academic expertise is not straightforwardly applicable in the commercial sector. My plan B was in the education sector; other mathematical physicists have gone into finance, computing, etc. Overall: there is real competition for postdoc jobs, and fierce competition for faculty positions; too much so to put your life on hold for 5+ years to do a Ph.D. and perhaps a postdoc before finding out that you may not have a long-term future in the profession because of your geographic restrictions.


About marketability. My advice is not to blindly take on board the reports which make prognostications like over the next decade we are going to have a giant shortage of people to fill professorial positions in Canada. The prediction may not come to pass - the demand bulge may be significantly smaller than predicted. For one thing, there may be insufficient taxpayer funding and/or political will to provide for universities/colleges to replace retiring professors.

In any case, that is not the most important point about intepreting the demand bulge predictions. The point is that the general is not necessarily the specific. It is probable that only a few big internationally competitive research-intensive universities will be supporting string theory and related research, whereas most of the increase in demand for professors will be at smaller, teaching-intensive colleges and universities.

Do think hard about your choice of subject within physics as compared to future marketability. String theory is a bit of a ... well, a crapshoot. A well-known American professor in my field once said that {the chance of a bright undergrad who thinks string theory is cool ending up a string theory professor at a research-intensive U.S. university} is as slim as {the chance of a high-school all-star basketball player ending up in the NBA}. It is much the same in Canada - think high school hockey vs. the NHL... Of course, that is no reason not to try! But you need to go into it with your eyes open.

I do not know much about employability prospects in other areas of physics. You should also ask your own professors what their view is on this matter. And look at the CAP and APS job prospects webpages; also AIP's employment trends data. Or take a peek at the "Job information" section on my main advice page.


Here is the most important advice of all: The only reason to do a Ph.D. in any field - string theory or otherwise - is a deep love of your subject, i.e. you cannot imagine doing anything else with your life. If you can imagine doing something else, then go and do that. But if you cannot, then welcome to this gnarly fun challenge, get your physics Ph.D., and keep your eyes and ears open regarding employment options as you go along your academic trek.

Be sure to check out all the options for what kind of physics to study. Even if your interest in physics was sparked by quantum mechanics, relativity, string theory, etc, that does not mean you are committed or condemned to chasing string (or particle) theory for the rest of your life. Here at the University of Toronto we give incoming M.Sc. students the opportunity to look around before getting an advisor for the Ph.D.; I think this is an excellent policy. Hey - if, after looking around, string theory is still the subject that grabs you, then go for it! :-)

Finally: please remember this advice was not offered in order to get anyone depressed. All I try to do in this essay is (a) to save time in repetitively replying to student queries, and (b) to give the straight dope to students who are curious to know how the grad school application business really works. You have to go into this with your eyes wide open. If you often spend a wee bit of your CPU thinking carefully about the steps beyond the ones you are currently taking, then it is highly likely that you will naturally take the right route. Gut instinct is more powerful and wise than many of us imagine. Knowledgeable advice from people you trust is also really important to seek. Maintain that Mentor Portfolio.

Work hard, and good luck!!