PhD Vivas

Awhile back, I posted some advice from my own experiences on doing a PhD.  Since then, several people have asked me for advice about the viva voce (or oral) examination, which most PhD programs require at the end of the degree.    Here are some notes I wrote for a candidate recently.
It is helpful to think about the goals of the examiners.   In my opinion, they are trying to achieve the following goals:
1. First, they simply want to understand what your dissertation says.   This means they will usually ask you to clarify or explain things which are not clear to them.
2.  Then, they want to understand the context of the work.  This refers to the previous academic literature on the subject or on related subjects, so they will generally ask about that literature.  They may consider some topic to be related to your work which you did not cover; in that case, you would normally be asked to add some text on that topic.
3.  They want to assess if the work makes a contribution to the related literature.    So they will ask what is new or original in your dissertation, and why it is different from the past work of others.  They will also want to be able to separate what is original from what came before (which is sometimes hard to do in some dissertations, due to the writing style of the candidate or the structure of the document).   To the extent that Computer Science is an engineering discipline, and thus involves design, originality is usually not a problem:  few other people will be working in the same area as you, and none of them would have made precisely the same sequences of design choices in the same order for the same reasons as you did.
4.  They will usually want to assess if the new parts in the dissertation are significant or important.  They will ask you about the strengths and weaknesses of your research, relative to the past work of others.   They will usually ask about potential future work, the new questions that arise from your work, or the research that your work or your techniques make possible.  Research or research techniques which open up new research vistas or new application domains are usually looked upon favourably.
5.  Goals #3 and #4 will help the examiners decide if the written dissertation is worth receiving a PhD award, since most university regulations require PhD dissertations to present an original and significant contribution to knowledge.
6.  The examiners will also want to assess if YOU yourself wrote the document.  They will therefore ask you about the document, what your definitions are, where things are, why you have done certain things and not others, why you have made certain design choices and not others,  etc.     Some examiners will even give the impression that they have not read your dissertation, precisely to find out if you have!
7.  Every dissertation makes some claims (your “theses”).  The examiners will generally approach these claims with great scepticism, questioning and challenging you, contesting your responses and arguments, and generally trying to argue you down.   They want to see if you can argue in favour of your claims, to see if you are able to justify and support your claims, and how you handle criticism.   After all, if you can’t support your claims, no one else will, since you are the one proposing them.
The viva is not a test of memory, so you can take a copy of your thesis with you and refer to it as you wish.  Likewise, you can take any notes you want.    The viva is also not a test of speed-thinking, so you can take your time to answer questions or to respond to comments.    You can ask the examiners to explain any question or any comment which you don’t understand.   It is OK to argue with the examiners (in some sense, it is expected), but not to get personal in argument or to lose your temper.
The viva is one of the few occasions in a research career when you can have an extended discussion about your research with people interested in the topic who have actually read your work.   Look forward to it, and enjoy it!


Do we each have a soul that incarnates in different bodies over time?  Most scientists in my experience dismiss any such idea, like they do most everything they cannot yet explain.  But a true scientist would (a) keep an open mind on the question, while (b) devising a scientific test of the claim.   And here’s where things become difficult – and interesting.  Exactly how would one test the hypothesis of reincarnation?

If reincarnation occurs, then there is a connection between bodies in different historical time zones.  Yet there seems to be no way that such bodies could communicate their special connectedness to one another.  In the case that reincarnation occurs, is there some way for instance that I could communicate a message with my future self (or selves), and only that person (or people), in a way that they could recognize the message as coming from me (their own past incarnation) and from no one else?  Thus far, I have not been able to imagine such a communication channel or message.  It may be possible to design a message that is public and seen by all, yet is only understood correctly by a particular recipient, as with the signal sent by the USSR’s Strategic Missile Command to the leadership of the USA during the August 1991 coup.

It would seem that no such inter-carnate communication is possible between incarnations of the same soul.   Yet all the scientific tests of  the hypothesis of reincarnation I can imagine would require some form of direct communications between separate human incarnations of the same soul, in the case there was reincarnation.   Suggestions for experiments most welcome.

Music and Physics on the Strand

The Music Shop at no. 436 Strand

Monday 22 October 2012, 6.00pm-7.30pm
Venue: King’s College London
Strand Building 2:39 (English Seminar Room)
Introduced by Clare Pettitt
“From the age of fourteen until his late teens, Charles Wheatstone worked in his uncle’s musical instrument shop on the Strand, modifying instruments and conducting experiments in acoustics at the back of the shop until he left to take up a scientific career, later moving down the road to become Professor of Experimental Philosophy at King’s College London and inventing the stereoscope, improving the concertina (Wheatstone’s musical instrument makers is still a going concern and makes concertinas) and inventing, with Cooke, the telegraph. When he was only 19 years old in September 1821, Wheatstone caused quite a sensation by inventing and exhibiting the ‘Enchanted Lyre or Aconcryptophone’ at his father’s music school/shop on Pall Mall and subsequently at the Adelaide Gallery of Practical Science on the Strand.
This session will concentrate on the crossover between musical, commercial and scientific culture and will ask whether it is possible to map the multiple utility of spaces on the Strand (shops which are schools which are galleries which are scientific workshops etc.) onto the radical rearrangement of the senses in this period which made new technologies of seeing, hearing and communication possible.”
[Text from here, where references and suggestions for further reading may also be found.]

The sociology of cosmology

Physicist Per Bak:

“I once raised this issue among a group of cosmologists at a high table dinner at the Churchill College at Cambridge. “Why is that you guys are so conservative in your views, in the face of the almost complete lack of understanding of what is going on in your field?” I asked. The answer was as simple as it was surprising. “If we don’t accept some common picture of the universe, however unsupported by facts, there would be nothing to bind us together as a scientific community. Since it is unlikely that any picture that we use will be falsified in our lifetime, one theory is as good as any other.” The explanation was social, not scientific.” (Bak, page 86)

Per Bak [1999]: How Nature Works: The Science of Self-Organized Criticality. (New York, USA: Copernicus)

Resilient capitalism

Yesterday began with a meeting at an investment bank in Paternoster Square, London, which turned out to be inaccessible to visitors and the public.   The owners of the Square had asked the police to close public access to prevent its occupation by the anti-capitalism (OWS) protesters, encamped between the Square and St Paul’s Cathedral.  So our meeting took place in a cafe beside the square.

The day ended with a debate at the Royal Society, organized by The Foundation for Science and Technology, on developing adaptation policy in response to climate change.     The speakers were Dr Rupert Lewis of DEFRA, Sir Graham Wynne of the Sub-Committee on Adaptation, UK Committee on Climate Change, and Tom Bolt, Director of Performance Management at LLoyd’s of London.  (Their presentations will eventually be posted here.) As Bolt remarked, insurance companies have to imagine potential global futures in which climate change has wrecked social and economic havoc, and so are major consumers of scientific prognoses.   One commentator from the audience suggested that insurers, particularly, may have a vested short-term financial interest in us all being pessimistic about the long term future, although this inference was not obvious to me:  one human reaction to a belief in a certainly-ruinous future is not to save or insure for it, but rather to spend today.
A very interesting issue raised by some audience members is just how do we engineer and build infrastructure for adaptability?  What would a well-adapted society look like?     One imagines that the floating houses built in the Netherlands to survive floods would fit any such description.  Computer scientists have some experience in creating and managing robust, designing resilient and adaptive systems, and so it may be useful to examine that experience for lessons for design and engineering efforts for other infrastructure.

Evolutionary psychology

In his Little Red Book, Mao Tse Tung said:   “Learn to play the piano.” [Fn #1]  However,  I don’t recall ever seeing a single piano in an African village, although I certainly saw (and heard) piano accordians in the villages and along the mountain paths of Lesotho (along with various hand-drums and mamokhorongs).  And settlements larger than traditional villages – Zimbabwe’s Growth Points, for example – sometimes had pianos in their churches or newly-built school halls.  Of course, the earliest of these pianos could only have been made in these last 300 years.

It seems to me that the historical absence of village pianos in Africa causes a problem for evolutionary psychology, since clearly a daily compulsion to play the piano is not something that has a long-standing evolutionary basis – at least, not for those of us descended from the peoples of the African savannah.  So if evo-psych cannot explain this very real human characteristic, what business does it have explaining any other human characteristic?  Why are some attitudes or characteristics to be explained by evolutionary means yet not others?  What distinguishes the one class of characteristics from the other? And what credence can we possibly give to any evolutionary explanation of phenomena which is not, prima facie, explainable in this way?   Surely, this limitation of the scope of evolutionary explanations completely undermines such arguments, since either all higher-level human characteristics have evolutionary explanations or none at all do.

1. In: Chapter 10:  Leadership of Party CommitteesQuotations from Mao Tse-Tung.  Peking, PRC:  Foreign Languages Press, 1966.

Reliable Knowledge

How little scientists know who only know science!  Thanks again to Norm, I learn about some statements by a retired professor of chemistry, Peter Atkins, about how we know what we know.   Atkins is quoted as saying:

The scientific method is the only reliable method of achieving knowledge.”

Well, first, it is worth saying that the scientific method does not produce reliable knowledge.  One of the two defining features of science is that scientific claims are defeasible:  they may be contested, questioned, challenged, and even overthrown, if the evidence warrants.   There is nothing inherently reliable about any scientific claim or theory, since new evidence may be found at any time to overthrow it.  The history of science is littered with examples.   (The second key feature is that anyone may do this contesting; science is not, or rather should  not be, a priesthood.)
Continue reading ‘Reliable Knowledge’

Let Newton Be!

Belately, I want to record a play seen at the headquarters of The Royal Society in London last month, Let Newton Be, written by Craig Baxter, but using only Isaac Newton’s own words.     The play was interesting although the energy of the play sagged at times, particularly in the first half.   The story only barely mentioned Newton’s interest in alchemy, and seemed to overlook his brutal, deadly campaigns against money forgers later in life (or did I nap through that scene?)
The play comprised three actors, two men and a woman, who played Newton at different ages – as a child, as a young-ish Cambridge academic, and as an old man.  As a work of drama, the conceit worked well, although it was best when one of the actors was playing another person interacting with Newton (eg, Halley, and later Leibniz, who spoke in an amusing cod-German accent).  Perhaps the real Newton was not sufficiently schizoid for three actors to play him, at least not when constrained to only use the man’s written words.    As I have remarked before, Newton’s personality was all of a piece:  it is only modern westerners who cannot imagine a religious motivation for activities such as scientific research, for example, or who find alchemy and calculus incoherent.
The performance was followed by a panel discussion by the Great and the Good – two historians and two scientists.  One of the scientists was the Astronomer Royal, Sir Martin Rees, who has subsequently won this year’s Templeton Prize for Science and Religion.  The discussion was interesting, so it is a pity it was not recorded for posterity.
A review of another play about a member of the matherati, Kurt Godel, is here.

Please post your apology here, Dr.

I have mentioned before the long-standing medical trope of first blaming the victim of an illness before identifying  its real causes.      To cholera (blamed on loose morals), drug addictions (blamed on weakness of will), stomach ulcers (blamed on a personal inability to handle stress), chronic fatigue syndrome (blamed on laziness), and repetitive strain injury (blamed on deception, or even self-deception), we may soon be able to add obesity and schizophrenia.
The contemporary developed world obesity epidemic has always struck me as being too widespread and occurring too fast to be due simply to a lack of self-discipline by lots of individuals.   Current medical advice is for individuals to eat less and exercise more, advice given despite the experimental evidence showing that increasing exercise actually may increase weight (on average), rather than reducing it.    And advice given despite the fact – known for at least 150 years, since the work of Claude Bertrand – that our bodies are complex adaptive systems, whose properties do not conform to simple linear models; for example, eating less may lead the body to retain more of the nutrients of the food ingested, because of a body-weight set-point effect, and thus not lead to much weight loss at all.   We already have evidence that appetite may have  genetic determinants.  Now, it seems that the obesity epidemic may have environmental or social causes, since as well as humans in the developed world putting on weight, so too have animals.  The animal species studied include not only pets and zoo animals (whose diets may have been influenced directly by human feeding), but also wild animals living near humans.
And schizophrenia, which once was blamed on poor parenting by the mothers of patients, and later on the patient’s genes (and who, Mothers, gave them those?), may in fact be caused by a virus – a retrovirus, present in our and our ancestors’ DNA for some 60 million years.  It turns out this is the same retrovirus that is believed by some scientists to cause Multiple Sclerosis.  A virus as cause could explain why there is a persistent, and statistically significant, effect on the incidence of schizophrenia arising from the season of birth of the patient.  Neither genes nor a mother’s parenting style would be expected to be influenced by the season of birth, but virus lifecycles, activations, durations and diffusions, certainly are.
The standard line initially of the medical panjandrums on RSI was that this medical condition only seemed to affect office workers, and not others who worked a lot with their hands, such as musicians.    The implication of such a statement was that the causes of RSI could not be some objective condition, outside of the patient, and so must be internal, either psychosomatic or actually knowingly invented.  Yet, musicians for at least a couple of centuries have been suffering from RSI (or closely-related conditions), as anyone who asked them would know.
When the medical profession is ready to apologize to us all for wrongly accusing us of moral failings, weakness of will, or malfeasance, I’ll be here ready and waiting.  I’m not, however, holding my breath.

Dyson on string theory

Physicist and mathematician Freeman Dyson on string theory:

But when I am at home at the Institute for Advanced Study in Princeton, I am surrounded by string theorists, and I sometimes listen to their conversations. Occasionally I understand a little of what they are saying. Three things are clear.  First, what they are doing is first-rate mathematics. The leading pure mathematicians, people like Michael Atiyah and Isadore Singer, love it. It has opened up a whole new branch of mathematics, with new ideas and new problems. Most remarkably,  it gave the mathematicians new methods to solve old problems that were previously unsolvable.  Second, the string theorists think of themselves as physicists rather than mathematicians. They believe that their theory describes something real in the physical world. And third, there is not yet any proof that the theory is relevant to physics.  The  theory is not yet testable by experiment. The theory remains in a world of its own, detached from the rest of physics. String theorists make strenuous efforts to deduce consequences of the theory that might be testable in the real world, so far without success.
. . .
Finally, I give you my own guess for the future of string theory. My guess is probably wrong. I have no illusion that I can predict the future. I tell [page-break] you my guess, just to give you something to think about. I consider it unlikely that string theory will turn out to be either totally successful or totally useless. By totally successful I mean that it is a complete theory of physics, explaining all the details of particles and their interactions. By totally useless I mean that it remains a beautiful piece of pure mathematics. My guess is that string theory will end somewhere between complete success and failure. I guess that it will be like the theory of Lie groups, which Sophus Lie created in the nineteenth century as a mathematical framework for classical physics. So long as physics remained classical, Lie groups remained a failure. They were a solution looking for a problem. But then, fifty years later, the quantum revolution transformed physics, and Lie algebras found their proper place. They became the key to understanding the central role of symmetries in the quantum world. I expect that fifty or a hundred years from now another revolution in physics will happen, introducing new concepts of which we now have no inkling, and the new concepts will give string theory a new meaning. After that, string theory will suddenly find its proper place in the universe, making testable statements about the real world. I warn you that this guess about the future is probably wrong. It has the virtue of being falsifiable, which according to Karl Popper is the hallmark of a scientific statement. It may be demolished tomorrow by some discovery coming out of the Large Hadron Collider in Geneva.” (page 221-222)

POSTSCRIPT (2012-12-27):  Physicist Jim Al-Khalili interviewed in The New Statesman (21 December 2012 – 3 January 2013, page 57):

Theoretical physics in the past hundred years has sometimes bordered on metaphysics and philosophy, especially when we come up with ideas that we can’t see a way of testing experimentally.   For me, science is empirical – it is about gathering evidence.  It’s debatable whether something like superstring theory, which is at the forefront of theoretical physics, is proper science because we still haven’t designed an experiment to test it.”

The link to metaphysics should come as no surprise, since all scientific investigations eventually end there, as Boulton argued.
Freeman Dyson [2009]:  Birds and frogs.  Notices of the American Mathematical Society, 56 (2): 212-223, February 2009.   Available here.