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William had a good razor!

Guillaume d’Ockham
William of Ockham, sketch from manuscript Summa Logicae (William of Ockham, 1323) – public domain image via Wikimedia Commons.

The law of parsimony – sometimes called Ockham’s razor after the English Franciscan monk William of Ockham (circa 1285 – 1347), a pioneer in logic – is a principle common to philosophy and science. In fact, it has been stated before, the oldest occurrence that I have found is due to Aristotle1Ἀριστοτέλης, Φυσικὴ ἀκρόασις. Available on-line. An English translation by Robin Waterfield: David Bostock (editor), 1999. Physics, Oxford University Press. Available on-line. (384 – 322 BC), who attributes it to Empedocles (circa 490 – about 435 BC). However, Proclus (412 AD – 485) traces it back to Pythagoras (about 580 – about 495 BC)2The only version I know of the work in question is this German edition, which appears to be considered the reference: Manitius, C. (éditor et translator), 1909. Procli Diadochi hypotyposis astronomicarum positionum (Bibliotheca scriptorum Graecorum et Romanorum Teubneriana), Teubner, Leipzig. Reprinted in 1974: Teubner, Stuttgart..

This principle is not always well understood, as it is sometimes used in a manner denoting a misunderstanding about what it actually means. I propose you to see a brief history of this law before commenting on what it means. This article is therefore one of the series on history of science and popularisation I started with a view from here.

No, I have not yet specified what states this law. This is a barely honest process that aims to create an almost unbearable suspense to make you captive of my prose, so that you will read this whole article. However, do not worry: the explanation comes in a few lines!

Continue reading William had a good razor!

Notes

Notes
1 Ἀριστοτέλης, Φυσικὴ ἀκρόασις. Available on-line. An English translation by Robin Waterfield: David Bostock (editor), 1999. Physics, Oxford University Press. Available on-line.
2 The only version I know of the work in question is this German edition, which appears to be considered the reference: Manitius, C. (éditor et translator), 1909. Procli Diadochi hypotyposis astronomicarum positionum (Bibliotheca scriptorum Graecorum et Romanorum Teubneriana), Teubner, Leipzig. Reprinted in 1974: Teubner, Stuttgart.

Statistical analysis of the law on intelligence

Edward Sowden in 2013
Edward Snowden in 2013 – screen shot from the movie Citizenfour (2014, Laura Poitras, Praxis Films) under licence Creative Commons BY 3.0 via Wikimedia Commons.

You probably have notice that the public debate has been recently dominated by security issues – at least, it has been the case in France. The attacks in Paris on November 13, 2015 participated in putting this subject as one of the most debated. Yet, if the need to take some measures, probably real, is often stressed out, my impression, indeed not supported by a comprehensive study, is that the question of the effectiveness of these measures generally do not arise. However, even if it takes a bit to have the necessary perspective to assess the question of effectiveness, it is generally possible to carry out an a priori study.

Let take as an example the law on intelligence, promulgated in France on July 24, 2015 and which I have assess repeatedly, with a vue from here. Though we have to wait to judge its proven effects, a first assessment can been done using some simple statistics. This article was inspired by another one, published in the journal La Recherche in November 20151Claude Castelluccia and Daniel Le Métayer, 2015. Les failles de la loi sur le renseignement, La Recherche n° 505, pp. 61 – 65.. Our conclusions are compatible.

Continue reading Statistical analysis of the law on intelligence

Notes

Notes
1 Claude Castelluccia and Daniel Le Métayer, 2015. Les failles de la loi sur le renseignement, La Recherche n° 505, pp. 61 – 65.

A Vue From the Attic: the Space Opera, first part

At the time of Chasseurs de rêves (this link leads to a French speaking website), part of my work was to write overviews of chosen subjects: I was looking for and presenting works fitting with these subjects. I tried to present both the most well known works and less known jewels. I must admit: I liked making these overviews, it made me rummaging in bookshops, media libraries, and find something to surprise readers. Besides, I miss it a bit.

So I decided to start this series, A Vue From the Attic, which will explore the links between fantasy culture on the one hand, and classical and avant-garde cultures on the other hand. This will also allow me to emphasise connections between science and other cultural forms. For a start, I chose a subject that brings me back to the origins of science fiction: space opera. As I have to present works from various media, the most relevant and attractive seemed to do it on video. As web accessibility is essential to me, for the visually impaired, I tried to ensure that the audio track allows getting the essentials. For the hearing impaired, as well as those troubled with my accent, subtitles are available.

Continue reading A Vue From the Attic: the Space Opera, first part

E-Luminesciences: the blog of Jean-Pierre Luminet

Jean-Pierre Luminet
© Jean-Pierre Luminet.

Jean-Pierre Luminet is the author of the blog e-Luminesciences. But not only: he is also an astrophysicist, cnrs research director at the Laboratoire d’astrophysique de Marseille, as well as at the Laboratoire Univers et théorie. But not only: he also has scientific popularisation and cultural activities. His blog presents all of these activities. This blog has an English version.

Among his notable works, he is a pioneer in black holes realistic representations. As early as 19791Jean-Pierre Luminet, 1979. Image of a Spherical Black Hole with Thin Accretion Disk, Astronomy and Astrophysics, n° 75, pp. 228 – 235. Available on line., he proposed a more realistic and accurate one than the one presented in Interstellar2Christopher Nolan, 2014. Interstellar, Syncopy Films and Lynda Obst Productions.. He also worked on the form – actually, its topology – of the Universe, which led him to introduce the concept of Wraparound Universe3Jean-Pierre Luminet, 2008. The Wraparound Universe, AK Peters Ltd..

Continue reading E-Luminesciences: the blog of Jean-Pierre Luminet

Notes

Notes
1 Jean-Pierre Luminet, 1979. Image of a Spherical Black Hole with Thin Accretion Disk, Astronomy and Astrophysics, n° 75, pp. 228 – 235. Available on line.
2 Christopher Nolan, 2014. Interstellar, Syncopy Films and Lynda Obst Productions.
3 Jean-Pierre Luminet, 2008. The Wraparound Universe, AK Peters Ltd.

Presentation of e-Penser

Logo of e-Penser
Logo of e-Penser – © Bruce Benamran, via Wikimedia Common.

Since the creation of this website, I intended to give a selection of links that I find interesting. Therefore, I have created the “links” section. As I do not want to give a list without more element, each link will be published along with a presentation article. This article being the first one to present a link. Also, as while I write this my first video review is being shot, this gives me the opportunity to clearly show that the website is not at all abandoned.

The first link I propose leads to Bruce Benamran’s e-Penser, which proposes videos of general scientific popularisation. Though they are French speaking videos, several of them have English subtitles.

Continue reading Presentation of e-Penser

Everything is relative, my dear Bruno!

Giordano Bruno
Portrait of Giordano Bruno (nineteenth century, after an engraving published in the Book of the President, 1578) – image in public domain via Wikimedia Commons.

Even if special1A. Einstein, 1905. Zur Elektrodynamik bewegter Körper, Annalen der Physik, n° 17, pp. 891 – 921. It can be read on line. An English version translated by George Barker Jeffery is available on line. and general relativity2A. Einstein, 1916. Die Grundlage der allgemeinen Relativitätstheorie, Annalen der Physik, n° 49, pp. 769 – 822. It can be read on line. An English version translated by Alfred Engel can be read on line. theories were introduced by Albert Einstein (1879 – 1955), the principle of relativity were introduced in Physics much earlier. It is called Galilean relativity and were introduced by … Giordano Bruno (1548 – 1600).

Of course, if this first form of physical relativity is qualified “Galilean,” it is because Galileo had something to do in its formulation. The introduction of this principle is one of the main elements of the epistemological revolution to which I referred earlier. This article is therefore a continuation of the series on the history of science that I started. It will also be the occasion, once again, to introduce some concepts that will be useful for future popularisation articles to come.

Continue reading Everything is relative, my dear Bruno!

Notes

Notes
1 A. Einstein, 1905. Zur Elektrodynamik bewegter Körper, Annalen der Physik, n° 17, pp. 891 – 921. It can be read on line. An English version translated by George Barker Jeffery is available on line.
2 A. Einstein, 1916. Die Grundlage der allgemeinen Relativitätstheorie, Annalen der Physik, n° 49, pp. 769 – 822. It can be read on line. An English version translated by Alfred Engel can be read on line.

Praise the long time

An example of a simulation of an experiment to be done with the LHC
An example of a simulation of an experiment to be done with the LHC – © 1997 – 2015 CERN under licence CC-BY-SA-4.0.

On July 4, 2012, Atlas and cms experiments of the Large Hadron Collider (lhc) announced that they had identified the beh boson. This led to award 2013 Nobel Prize in Physics to François Englert and Peter Higgs. As I write this, LHC experiments are continuing, while it is rising in energy levels. On August 6, 2014, the space probe Rosetta joined comet 67P/Churyumov-Gerasimenko, dropping a module called Philae on it, among other experiments. This mission is at present still ongoing.

What is the common point between a particle physics experiment and a space science mission? They are both long time experiments: the first articles theorising the beh boson were published in 19641F. Englert and Brout, R., 1964. Broken symmetry and the mass of gauge vector mesons, Physical Review Letters, vol 13, n° 9,‎ pp 321 – 323. doi: 10.1103/PhysRevLett.13.321, available on line.2P.W. Higgs, 1964. Broken symmetries and the masses of gauge bosons, Physical Review Letters, vol 13, n° 16,‎ pp 508 – 509. doi: 10.1103/PhysRevLett.13.508, available on line. and the design of the lhc began in 1994. Concerning the Rosetta mission, its starting point were in 1984 with the validation of the Horizon 2000 project.

Continue reading Praise the long time

Notes

Notes
1 F. Englert and Brout, R., 1964. Broken symmetry and the mass of gauge vector mesons, Physical Review Letters, vol 13, n° 9,‎ pp 321 – 323. doi: 10.1103/PhysRevLett.13.321, available on line.
2 P.W. Higgs, 1964. Broken symmetries and the masses of gauge bosons, Physical Review Letters, vol 13, n° 16,‎ pp 508 – 509. doi: 10.1103/PhysRevLett.13.508, available on line.

How I extended Galileo’s work!

Spring tide in Wimereux
Spring tide in Wimereux (Pas-de-Calais, France) – photo by Marc Ryckaert under licence CC BY 3.0 via Wikimedia Commons.

I have already mentioned it: it is about time that I present the topics that I am interested in my work. As I have indicated on this site home page and as can be deduced from my resume, my areas of expertise are applied mathematics and theoretical computer science. My scope is physical oceanography. Specifically, I am reproducing ocean dynamics on computers.

However, though being a still evolving discipline, the study of ocean dynamics has a long history. The oldest references I have found were written during the antique times. The main topic on ocean dynamics they address is tide. I intend to present this story here. Much of the information you will find in the following comes from Bernard Simon’s La Marée océanique côtière1B. Simon, 2007. La Marée océanique côtière, collection “Synthèses”, Institut océanographique éditeur.. The following is an extract from the introduction of my Ph.D. thesis2Y. Le Bars, 2010. Modélisation de la dynamique océanique barotrope dans l’estuaire et le plateau amazoniens, Ph.D. thesis, Université de Toulouse III – Paul Sabatier.. This thesis focused on the development of an ocean model and its application to the estuary of the Amazon, so I do not claim to have achieved a definitive historical study: the following is a summary, albeit detailed, but with all the limitations of this exercise.

Continue reading How I extended Galileo’s work!

Notes

Notes
1 B. Simon, 2007. La Marée océanique côtière, collection “Synthèses”, Institut océanographique éditeur.
2 Y. Le Bars, 2010. Modélisation de la dynamique océanique barotrope dans l’estuaire et le plateau amazoniens, Ph.D. thesis, Université de Toulouse III – Paul Sabatier.

Nights of the stars 2015

Apparent movements of stars around Polaris
Apparent movements of stars around Polaris – by Steve Ryan under licence CC BY-SA 2.0, via Wikimedia Commons.

From August 7 to 9, these are the Nights of the Stars. This August, several interesting phenomena will be observable. It takes place during a year rich in astronomical events, including Rosetta and New Horizons missions.

If you are in France, the French Association for Astronomy offers a list of events that take place this weekend in the territory. If you are in France these days, do not hesitate!