thesis defense

Your Physics Thesis Defense Guide

Estimated Read Time: 6 minute(s)
Common Topics: defense, graduate, thesis, adviser, work



At this point, you have completed writing your thesis, your adviser has approved of it, and you have distributed it to all the members of your thesis committee. It is now time for you to do your thesis defense. Officially, this is the final obstacle standing in your way between you and your Ph.D. degree. Needless to say, adequate preparations are necessary.

What exactly is a thesis defense? This is where you demonstrate your mastery of the subject matter that you have been researching during your years as a Ph.D. candidate. To put it bluntly, since you are producing an original, new work to be added to the body of knowledge of physics, you have to prove that (i) you understand the physics inside out and (ii) you are the world expert on this particular area. In fact, in certain parts of your thesis, even your adviser may not know as much, or as in detail, like you. This is where you have to establish yourself as someone who knows a lot about this particular topic. You must know every single thing that you wrote in your thesis, and maybe even some beyond that, especially if you make specific reference to other theories or experiments. Your thesis committee will try to judge if you are an expert in such a field.

The most important person that should prepare you for your defense (other than yourself) is your adviser. Your adviser would have guided you in the beginning into a research subject that would satisfy the graduate school/departmental requirement that your work is new, original, and something significant that contributes to the body of knowledge. Publishing in respected peer-reviewed journals would be a major indication that your work is accepted as being new and significant. So in preparation for your defense, he/she should try to impress upon you on making sure that you mention somewhere during your thesis defense that such-and-such work that you did was published in a so-and-so journal. More importantly, though, is that your adviser might know certain “quirkiness” of certain members of your committee that might help you to prepare for. If a particular professor always likes to ask about the “historical significance” of certain things, or maybe he/she likes to always try to include his/her own research area, then these are the things you should prepare for. It is ALWAYS a good strategy that if you happen to have used or cited the work of one or more of the committee members, then you should make sure you mention this clearly. You’d be surprised how well those kinds of acknowledgments can go down. This should be a common practice throughout your career. In any case, in preparing for your defense, talk to your adviser and ask him/her for his opinion. It may be that your adviser would like you to do a trial run at doing your defense. JUMP at such an opportunity. Such practice is always a good idea. Do this in front of your adviser and other graduate students (who should already be keen on seeing what it should look like since they have to go through the same thing soon enough). Such practice should allow for last-minute kinks to be worked out and to prevent major disasters.

How long your defense should take place depends very much on your adviser and the procedure enacted at your school. Most schools leave it entirely to your adviser. In turn, most advisers would prefer a defense that is between an hour to two hours. However, I have seen a defense that took place over a span of 2 days! It wasn’t pretty. So in your practice, make sure you pay attention to how long you are presenting your defense. You do not want your audience, or worse yet, your committee members, to fall asleep.

Most thesis defenses are usually announced to the public via the usual seminar/colloquium announcement made by your department. So everyone is usually welcome to attend your defense. Typically, the first part of your defense is similar to you giving a seminar. At the end of your presentation, everyone in attendance is invited to ask questions. The committee members usually would not ask anything during this time, but they will pay attention to how you respond to the questions being asked. So do not trivialize a question, even though it came from one of your buddies in attendance. After this question and answer session, the rest of the audience will be asked to leave, and the closed session will be just between you and the committee members. This is where usually the difficult questions will come up. They will dissect your presentation and the content of your written thesis. Pay careful attention to what they ask, answer as thoroughly as you can, and acknowledge any comment or suggestion that they give. Sometimes, a question can really come out from a left field that you simply did not expect, and you find yourself stumbling along. More often than not, if you have a good adviser, he/she might offer a reply to try to guide you on the right path. So pay attention and try to see if you can get any hints there. Just keep in mind that just because you are unable to answer something which might not be central to your work, this does not mean that they will fail you. So whatever you do, do not panic.

After the committee is done with this session, you will be asked to leave and they will deliberate your fate. My anecdotal account of my defense goes like this: they decided to stay in their deliberation for about 10 minutes longer JUST to make me squirm and sweat. At this stage, there’s nothing else you can do. Just exhale, relax, and try not to stress out. Unless something really disastrous happened during your defense, you can almost be assured that you have accomplished your goal. After the committee’s deliberation, your adviser will officially inform you if you have passed through your defense. He/she will also inform you of any changes that are necessary to your thesis based on suggestions from the committee members. These are the changes that you need to make before getting the final approval from all of them for you to submit to the thesis examiner/graduate school.

Other than that, it is time to rejoice. You have done a significant accomplishment that was not easy and took years of hard work and sacrifice. In the eyes of many, you are now a Physicist!

However, is that all there is? You can go out now and work as a Physicist? If only life is that simple and straightforward. In the next chapter, we will go back in time to approximately one year from your joyous occasion at completing your studies. Your journey on becoming a physicist isn’t done yet just because they are handing you your Ph.D. degree.

8 replies
  1. gleem says:

    One can say that preparing for your defense begins the day you enter the graduate program. In particular you do not want a faculty member on your board with whom you have crossed swords at some time. In reflecting on my defense and @DEvens post I may have dodged a bullet ( or a snake) having made a more or less public criticism of the teaching ability of a faculty member in my first year. Luckily he was either not selected, never got wind of it, forgot about it or was a mensch about it for he did not sit in on my defense.

  2. DEvens says:

    There are old stories passed around among grad students about the monster PhD oral defense. The nice one is from Cliff Stoll, the author of this. his PhD defense they asked him to explain why the sky was blue. And they kept asking him "can you be more specific?" until he had led his committee through a very long explanation of scattering and molecular energies and cross sections and visible light and optics and the character of the human eye. Which was really all on topic for a visible light astronomer. After he was done he was exhausted but very happy. And he passed.The not nice story involves a candidate being asked to estimate the number of barbers in Canada. There are multiple endings to that story. In one ending the candidate refused on the basis it had nothing to do with his thesis. Part A has him being failed for refusing. Part B has him being passed because it was unrelated to his thesis. Part C has him making an estimate, which was wildly wrong but showed a reasonable attempt to get an order of magnitude, and the candidate passing.So you should be sure you understand the rules for your defense. And these are different from one school to the next.

  3. ShayanJ says:

    Does your university not require you to fight a snake in order to graduate? o_O

    it's a jokeOhh…I thought its a metaphor for some actual phenomenon. I'm an undergrad.

  4. Ygggdrasil says:

    Could you explain which part of the thesis defense that's supposed to refer to?Does your university not require you to fight a snake in order to graduate? o_O

    it's a joke

  5. ShayanJ says:

    Don't forget to prep for the snake fight portion of your PhD defense. That's the part that often comes back to bite you :wink:Could you explain which part of the thesis defense that's supposed to refer to?

    Thanks for the good advices Zapper.

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