Over the limits!

"Croyez que vous pouvez courir plus longtemps ou plus rapidement. Croyez que vous êtes assez jeune, assez vieux, assez fort pour accomplir tout ce que vous voulez faire. Ne laissez pas les vieilles croyances vous empêcher de vous dépasser au-delà de vous-même."

John Bingham, cité par Martin Lussier et Pierre-Mary Toussaint dans Mythes et réalités sur la course à pied.

Time and the freedom to think

The other day, I was complaining to a colleague that the academic system, with its constant pressure to publish or perish, did not encourage real breakthroughs to be made in science, because it encourages scientists to tackle the easiest problems that will allow them to publish fast. I have just stumbled upon this quotation, which perfectly supports my point (see also this quotation by Einstein).

"Julian Barbour is known to many who follow science as the author of The End of Time, in which he argues that time is an illusion. He is an unusual physicist, who, since receiving his doctorate in 1968 from the University of Cologne, has never held an academic job. But he has been highly influencial among the small group of people who think seriously about quantum gravity, for it was he who taught us what it means to make a background-independent theory.
As Barbour tells it, on a climbing trip during graduate school, he was seized by a vision that time might be an illusion. This led him to investigate the roots of our understanding of time, contained in the general theory of relativity. He realized that he could not make a conventional academic career worrying about the nature of time. He also realized that if he was going to work on that problem, he would have to concentrate on it fully, without being distracted by the pressures of a normal career in physics. So he bought an old farmhouse in a little village half an hour from Oxford, brought his new wife there, and settled down to think about time. It was ten years or so before he had something to report back to his colleagues. During that period, he and his wife had four children, and he worked part-time as a translator to support them. The translating took him no more than twenty hours a week, leaving him as much time for thinking as most academic scientists have after the responsabilities of teaching and administration are taken into account.
To get a bearing on the meaning ot time in general relativity, Barbour read deeply into the subject, working his way back through the history of physics and philosophy. He finally was able to invent a new kind of theory, in which space and time are nothing but a system of relationships. His papers on this subject slowly began to be noticed, and eventually he became an honored member of the quantum-gravity community. His reinterpretation of Einstein's general theory of relativity as a relational theory is now the way we in the field understand it.
This is not nearly all that Barbour has done, but it's enough to show how the career of a successful seer differs from that of a conventional academic scientist. Such a person does not follow fashion — in fact, probably does not even follow a field well enough to know what the fashion is. People like this are driven by nothing except a conviction, gained early, that everyone else is missing something crucial. Their approach is more scholarly, in that to think clearly they have to read through the whole history of the question that obsesses them. Their work is intensely focused, yet it takes them a long time to get somewhere. In furtherance of an academic career there is no output whatsoever. Julian Barbour, when he was ready, changed science more than most academic scientists have, but at an age when most academic physicists are up for tenure, he had absolutely nothing to show for his work.
Barbour's career resembles that of other seers, like Charles Darwin, who also retreated to the English countryside to find the room to think through an idea that obsessed him. Einstein spent ten years thinking about the ideas that became special relativity, and then spent the next ten inventing general relativity. Time and the freedom to think, then, are all that a seer needs to find that unexamined assumption. The rest they do themselves."

Lee Smolin, "The trouble with physics" (p. 321-322).

The scientists quest

"[...] how difficult it is to try to wrest precious, fundamental secrets from nature. That quest can be compared to climbing a mountain, and when reaching the peak, seeing another higher mountain that tempts us to ascend to even greater heights. And when we do reach the higher peak, we discover as we look across the valley yet another peak that calls. In the end, it is the wonderful experience of scaling the mountain — of attempting to understand the secrets of nature — that motivates us as scientists. There is of course the additional thrill, upon reaching the top of a mountain, to ram in the flagpole announcing one's victory. But that is only a momentary emotion soon superseded by the new challenges presented by the higher peak on the horizon.
[...] I believe that with the ascent of each mountain — each theory, each paradigm — we reach a new truth, but that no mountain peak can ever represent the ultimate theory of nature."

John W. Moffat, "Reinventing gravity" (p. 222).

De la nécessité morale de bien communiquer

« Une mauvaise écriture est une des formes du mépris qu’on a pour autrui; car elle prouve qu’on attache plus de prix à son propre temps qu’à celui des autres. »

Hugo de Groot

Make sure you have data first

"I have no data yet. It is a capital mistake to theorize before one has data. Insensibly, one begins to twist facts to suit theories instead of theories to suit facts."

Sir Arthur Conan Doyle (Sherlock Holmes), as quoted by John W. Moffat in "Reinventing gravity" (p. 156).

This statement means the same thing as that one from Feynman.

Hymne à l'hiver

"Qu'ils ont de la chance les peuples qui vivent l'hiver ! Ces quelques mois trop courts pour les uns, trop longs pour les autres, obligent à une adaptation sans cesse renouvelée, année après année. Changement de rythme, de vêtements, de loisirs, de nourriture, ces mois de blancheur proposent l'alternance. Cette périodicité est vitale. L'auteur blotti au fond d'un café griffonne et rafistole les mots qui seront chantés l'été prochain. Chacun doit user d'imagination pour faire face aux rigueurs de l'hiver, fréquemment perçu comme un obstacle... On entend souvent dire: «Il est âgé, passera-t-il l'hiver ?». Une frontière vers l'inconnu. Vouloir améliorer son sort, vivre plus facilement, voilà le propre de tout être intelligent et l'hiver contribue particulièrement bien à cette recherche de solutions. À nous de profiter de cette occasion. Plusieurs sociétés modernes ne cherchent pas à s'adapter, mais plutôt à éliminer les obstacles, les embûches. Quel dommage !

On veut éradiquer cette saison, standardiser nos vies. Les villes repoussent et pelletent l'hiver... mais l'hiver s'accroche. Il orne les balcons et dissimule les imperfections. Les enfants glissent, les joues rose saumon.

L'hiver est long pour celui qui lui tourne le dos. L'hiver est froid pour celui qui ne le touche pas."

Bernard Voyer, explorateur, "Aniu", chapitre "Neige".

Est-il légitime de poser n'importe quelle question?

J'ai un jour entendu un de mes professeurs dire, pour encourager ses élèves à poser des questions en classe : "Il n'y a pas de question idiote. Il ne peut y avoir d'idiot que la réponse." Cette phrase m'a marqué et m'a libéré de la peur de poser une question qui pourrait être jugée idiote par un professeur. Kant vient de rétablir en moi cette peur écartée :

"C'est déjà une grande et nécessaire preuve de sagesse ou d'intelligence que de savoir quelles questions on peut raisonnablement poser. Car si la question est en soi absurde et appelle des réponses vaines, elle a pour inconvénient, outre qu'elle humilie celui qui la soulève, parfois aussi d'égarer dans des réponses absurdes celui qui l'entend sans faire preuve de précautions et de produire le ridicule spectacle de deux individus dont l'un trait le bouc (comme disaient les anciens), alors que l'autre tient au-dessous un tamis."

Emmanuel Kant, critique de la raison pure, section "De la division de la logique générale en analytique et dialectique".

Critique du scepticisme?

Nous avons l'habitude en science de cultiver un certain scepticisme à l'égard de tout résultat scientifique, ce que nous considérons comme une attitude saine pour ne pas tomber dans le dogmatisme. Je suis donc un peu surpris de lire ce qui m'apparaît comme une critique du scepticisme venant du philosophe allemand Emmanuel Kant:

"La critique de la raison conduit donc nécessairement, en fin de compte, à la science ; l'usage dogmatique de la raison, sans critique, conduit au contraire à des affirmations sans fondement, auxquelles on peut opposer d'autres affirmations tout aussi spécieuses, par conséquent au scepticisme."

Emmanuel Kant, Critique de la raison pure, Introduction.

Peut-être Kant n'utilise-t'il pas le terme "scepticisme" sous le même sens que nous lui donnons de nos jours...

It is all about perseverance

"It's not that I'm so smart. It's just that I stay with problems longer."

Albert Einstein, quoted by Lee Smolin (The trouble with physics, p. 309).

What is a good scientist?

"Good scientists expect that their students will exceed them. Although the academic system gives a successful scientist many reasons to believe in his or her own authority, any good scientist knows that the minute you succumb to believing that you know more than your best students, you cease to be a scientist."

Lee Smolin, "The trouble with physics" (p. 304).

May I always remember this!

Force-carrying particles

I always have had a hard time understanding the concept of force-carrying particles : the idea I had understood was that you can describe the interaction between two particles either by the action of the forces created by the fields associated with each particle, or by new particles that each original particle exchanged with the other, therefore transferring momentum from one particle to the other, hence altering their trajectories. I could make sense of this as long as the interaction was repulsive, as such a momentum transfer would push the particles away from each other. But how could particles get attracted to each other with such a process? This does not make sense to me.

Then, I read the following passage in Lee Smolin book "The trouble with physics" (p. 85): "[...]each gravitational wave could be seen quantum mechanically, as a particle called the graviton - analogous to the photon, which is the quantum of the electromagnetic field."

I thought I had finally understood the concept of force-carrying particle : according to general relativity, the gravitational force is nothing but the deformation of space-time by the presence of mass, which causes objects to move otherwise than in uniform rectilinear motion, hence making us invoke a force, gravity, to explain their motion according to Newton's Second Law. Now, assume that a mass is suddenly placed somewhere in space-time. Its deformation of space-time will propagate at a finite speed, that of light, making its effect felt at greater and greater distances. These are gravitational waves. In analogy with electro-magnetic waves, which are quantized in photons, gravitational waves are quantized in gravitons, which are therefore the particles "carrying" the gravitational force, i.e., making its effects felt at distance.

This at last made sense to me. But then I watched the DVD version of Brian Greene's book "The elegant universe", in which there is an animation showing two persons throwing small balls at each other, and getting attracted toward each other as they throw the balls harder and harder. So we are back to this idea of momentum exchange, and this does not make sense to me for explaining attractive forces such as gravity!

Is there a theoretical physicist around who could help me understand this better?

What kind of scientist are you?

"As I reflect on the scientific careers of the people I have known these last thirty years, it seems to me more and more that these career decisions hinge on character. Some people will happily jump on the next big thing, give it all they've got, and in this way make important contributions to fast-moving fields. Others just don't have the temperament to do this. Some people need to think through everything very carefully, and this takes time, as they get easily confused. It's not hard to feel superior to such people, until you remember that Einstein was one of them. In my experience, the truly shocking new ideas and innovations tend to come from such people. Still others — and I belong to this third group — just have to go their own way, and will flee fields for no better reason than that it offends them that some people are joining in because it feels good to be on the winning side. So I no longer get bothered when I disagree with what other people are doing, because I see that temperament pretty much determines what kind of science they will do. Luckily for science, the contributions of the whole range of types are needed. Those who do good science, I've come to think, do so because they choose problems that are suited to them."

Lee Smolin, "The trouble with physics" (p. 95).

I think I belong to the second group of scientists who need to think through everything very carefully and get easily confused, although don't expect shocking new ideas and innovations to come out of me! What about you, dear reader?

How do you know whether you have really understood something?

"The physicist Ernest Rutherford once said, in essence, that if you can't explain a result in simple, nontechnical terms, then you don't really understand it. He wasn't saying that this means your result is wrong; rather, he was saying that it means you do not fully understand its origin, meaning, or implications."

Brian Greene, "The elegant universe" (p. 203).

This rejoins this famous French quotation:

"Ce que l'on conçoit bien s'énonce clairement,
Et les mots pour le dire arrivent aisément."

Nicolas Boileau, "L'Art poétique".

The secret of immortality

"You don't stop running because you get old. You get old because you stop running."

Jack Kirk, still running races at age 96 when quoted in Christopher McDougall's book "Born to run".

May I also be able to run all my life!

La dignité sera le rempart contre tous les extrêmes

A tous ceux qui auraient peur d'une montée de l'Islamisme à la suite des événements récents et en cours dans le monde arabe, écoutez donc la réponse de Béchir Labidi, Tunisien:

"Je comprends que la peur de l’Islam est un vrai problème. Mais derrière cette peur se cache surtout la peur du fanatisme et de l’extrémisme.  Ce fanatisme et cet extrémisme ne sont que le résidu de la frustration et du mépris de l’Homme. La dignité sera le rempart contre tous les extrêmes.
Voila pourquoi, à mon sens, la révolution tunisienne remet les pendules à l’heure : c’est la liberté qui sera le garant de la stabilité et  non la dictature."

Des motivations

"[...] qui leur fera faire par goût et par passion ce qu'on ne fait jamais assez bien quand on ne le fait que par devoir ou par intérêt."

Jean-Jacques Rousseau, "Les considérations sur le gouvernement de Pologne et sur sa réformation projetée", Ecrits politiques.
Rapporté dans "Manière de voir", Le Monde diplomatique, no 112 (août-septembre 2010, p. 30).

L'eau n'est pas un bien mercantile

"Quel est le premier objet de la société? C'est de maintenir les droits imprescriptibles de l'homme. Quel est le premier de ces droits? Celui d'exister. La première loi sociale est donc celle qui garantit à tous les membres de la société les moyens d'exister. Toutes les autres sont subordonnées à celle-là; la propriété n'a été instituée ou garantie que pour la cimenter...

Les aliments nécessaires à l'homme sont aussi sacrés que la vie elle-même. Tout ce qui est indispensable à la conserver est une propriété commune à la société entière. Il n'y a que l'excédent qui soit une propriété individuelle, et qui soit abandonnée à l'industrie des commerçants... Toute spéculation mercantile que je fais aux dépens de la vie de mon semblable n'est point un trafic, c'est un brigandage, un fratricide. La liberté du commerce est nécessaire jusqu'au point où la cupidité homicide commence à en abuser."

Maximilien de Robespierre, "Discours sur les subsistances", Discours et rapports à la Convention.
Rapporté dans l'article "Remunicipaliser l'eau", Manière de voir, Le Monde diplomatique, no 112 (août-septembre 2010).

A quoi sert l'utopie?

"Elle est à l'horizon, dit Fernando Birri. Je me rapproche de deux pas, elle s'éloigne de deux pas. Je chemine de dix pas et l'horizon s'enfuit dix pas plus loin. Pour autant que je chemine, jamais je ne l'atteindrai. A quoi sert l'utopie? Elle sert à cela: cheminer."

Eduardo Galeano, Las Palabras andantes, cité par Dominique Vidal dans l'éditorial de Manière de voir, Le Monde diplomatique, no 112 (août-septembre 2010).

L'important

"Mais les évènements importants restent toujours ignorés du monde - comme cet enfant qui a pu regarder, émerveillé, un papillon voler, sans le tuer."

Iouri Norstein, Courrier International no 784.

Le premier pas

"Oser refuser l'immobilisme face à l'injustice, la souffrance, et décider de s'engager en faisant le premier pas là où l'on est. Quant à savoir là où il mènera, cela n'appartient à personne. Mais le seul fait de s'engager et de se mettre en marche ouvre un "champ du possible". [...]
En témoignant de l'impact du premier pas, nos pionniers révèlent une valeur majeure pour l'individu: celle de l'engagement. Ils puisent leur capacité à s'engager dans une révolte personnelle contre l'injustice, la dignité bafouée. Cette révolte génère en eux la force et la volonté de dépasser leurs nombreuses peurs - peur des obstacles, d'être incompétent, trop "petit", inadapté, de ne pas avoir la force... - pour agir."

Marie-Hélène et Laurent de Cherisey, Passeurs d'Espoir (vol. II).

Je relis cette citation au moins un an (peut-être même deux?) après l'avoir lue pour la première fois, et je me rends compte que je n'ai toujours pas fait ce premier pas...