30 September 2015

Hierarchy of topics in physics

It seems to me that the prestige of the various subfields of physics depends on the nature of the objects under study as follows (in descending order):
  1. Bosons
  2. Fermions
  3. Atoms
  4. Everything else
Cold atoms (when they exhibit bosonic behaviour) go in the first category, with photons and the Higgs boson.

27 September 2015

Ontological gaps

The easiest solution to an ontological separation is via a middle term, e.g. the spirit as intermediary between body and soul.

Sometimes this can take exotic forms, like the gnostic hierarchy of emanations, which is much more complicated than other ways of bridging the distance between God and creation (such as the uncreated energies in Orthodox doctrine) but also psychologically more acceptable: naively, it is easier to understand a higher essence that becomes progressively diluted into creation (which does preserve a divine spark) than two completely separate orders where the first one conveniently has an aspect that can interact with the second.

22 September 2015

The bluebell curve

One of the reasons put forward for men's domination of both science and art is the spread of their IQ distribution: supposedly, there are more men than women at both extremes of the scales.
Novalis held the same point of view, but in reverse: "Doesn't it speak for the superiority of women that the extremes in their education are much more striking than in ours?" (II, 616). I cannot find an English translation of the fragment, but here is the relevant phrase in the original German, with discussion.

20 September 2015


I think I finally "get" Popper. He has a mathematician's outlook: every statement has (at most) one meaning, which can be either true or false. The truth value is constant and uncontroversial: the same for all people, at any point in history. He is a good Cartesian in this respect.
Unfortunately, the consequence is that anything other than pure mathematics is either meaningless or false. Scientific theories may well be useful, but they are (or will be) falsified; that is all we can say about them. This is not to demean Popper's contribution, which is foundational, but the foundation by itself is not very useful. In particular, there's no place in his system for a new theory that improves upon an old one without merely displacing it.
The same tendency is apparent when he discusses philosophy (and philosophers) in The Open Society. Popper feels no empathy for Plato and does not try to "inhabit" his thought, nor does he try to place the old Greek in the historical context, unless to better condemn him, as in the final section of the first volume. I suppose that if a contemporary author were to hold now Plato's position we would criticize her for her social views (and decide she is a quite poor logician). Should we do the same with Plato himself?
Marx receives the same treatment. Contrast Popper's description with Isaiah Berlin's life of Marx, which shows much more historical and even personal insight, although Berlin was far from being a Marxist.

11 September 2015

Presentation slides - what to avoid

About two years ago, I wrote a post on how to style a presentation. I was at a conference this week and I would like to highlight some easily avoidable mistakes that people made.
  • Do not put important information at the edge of the slide. In particular, the reference to the paper you are advertising should not be at the very bottom, where it can be cut off if, for instance, the beamer is not perfectly aligned with the screen. This happened to at least three speakers out of the approximately fifty I listened to.
  • Enhance the contrast of the images you intend to show. If you insist on showing the raw images, have an enhanced set on backup slides you can use if the audience cannot see the first ones. Alternatively, use light text on dark background and ask the organizers to dim the lights in the room (if possible.) It works for biologists.
  • Do not rely on color contrast between text and background: there should always be an intensity contrast between them. One speaker used blue and red text on green background. It was jarring and, for some colorblind people, probably illegible. I'm a big fan of solid black text on white backgroud, with color only used for highlighting.
Note that the first two points fall under the general principle: "do not expect things to look on the projection screen as they do on your computer."

6 September 2015

Reproducible experiments (again)

Last year I discussed a psychologist's essay on "the emptiness of failed replications". I'm returning to the status of experiment replication because a few days ago Science published a paper of the Open Science Collaboration, which was only able to confirm less than half of the 100 psychological studies it replicated. The study is very interesting in itself, but I'll only comment here on the reaction of psychology professor Lisa Feldman Barrett in a New York Times op-ed. She makes the point that attempting to replicate an experiment in different conditions can lead to different results and, by that fact, point to the importance of previously neglected parameters: context is important.

She illustrates her position by three examples, one of them taken from physics :

[...] when physicists discovered that subatomic particles didn’t obey Newton’s laws of motion, they didn’t cry out that Newton’s laws had “failed to replicate.”

Prof. Feldman Barrett confuses here the epistemological function of experiment and theory. A physical theory cannot be replicated, but it can be tested using (hopefully, reproducible) experiments. Obviously, performing an experiment with elementary particles cannot be seen as replicating one that uses macroscopic objects.

There is, however, a more alarming problem with her position, summarized by the phrase :

Much of science still assumes that phenomena can be explained with universal laws and therefore context should not matter.

There are very few completely general natural laws. Scientific results are "universal" precisely in the sense that the necessary context should be fully specified : A occurs every time conditions B, C, and D are fulfilled, irrespective of parameters E, F and G that are not mentioned.

Of course, the more general the applicability, the more interesting the result, as the psychologists very well know : they say "X correlates with Y and Z in adult humans", and not "X correlates with Y and Z in this set of 58 adults" that they used to infer that particular correlation. The latter finding will not be published in high-profile journals.

Fully specifying the context is certainly more difficult in the social sciences than in physics, but the solution is adding more rigour, not claiming for psychologists the right to generalize their results arbitrarily (what holds for a few dozen psychology undergraduates in an American research university may not apply to all mankind). If the generalisation is shown to be incorrect, this is not proof of a new and exciting result, but simply a sign that the original authors oversold their findings.