An encyclopedic treatise of light

By using the distinction between Saint Bonaventure "lumen" (light radiated or exempt) and "lux" (light source) (introduced on p. 909 of the book) and moving in a scientific context, one could say that the exciting book of the astrophysicist Trinh Xuan Thuan constitutes "Summa lumine luceque". This is indeed a sum, mainly scientific, on light, light sources and light phenomena, which, moreover, very cleverly and happily combines historical and systematic perspectives. The clarity of the presentation and the teaching style of presentation (the latter, a virtue, of course) make the work accessible to a wide variety of readers and readers.

Here's how to organize this treaty.

The first two chapters offer us a historical overview of the concepts of light of Greek antiquity to the introduction of modern science in the 16th and 17th centuries.

The author continues the historical narrative in the third chapter, this time by tracing the path of modern science in its current design of light: according to the latter, light is of dual nature, being both wave and particle. It is also the same matter. In this chapter we find the electromagnetic theory and contemporary physics of the infinitely large (the macrocosm) and the infinitely small (the microcosm) respectively, the theory of relativity and quantum mechanics. The beginning of Chapter 4 will give us a glimpse of another part of the microcosm physics, namely string theory, which is still in a state of development and needs to be supported. This is a design of the elementary particles from which the latter are not entities in form of points, but the vibrations of "strings" infinitely small (of a size of 10 power least 33 cm). This will be one of the theories to be tested to the new CERN accelerator (the Large Hadron Collider Large Hadron Collider protons; see page 408.).

Visible light is one of the components of the electromagnetic spectrum. The spectrum in its entirety, from radio waves to gamma waves, consists of different kinds of light, and the light that our eyes reveal is white or visible light itself, as Newton has demonstrated the first, composed of various colored lights that makes, for example, highlight the rainbow sky. The mechanism that generates a rainbow sky is that of diffraction: fine droplets of water split up white light into its colored components. Can produce the same effect using a glass prism.

The fourth chapter "dress [e] an inventory of all the sources of light and energy of the universe and tells their history and evolution of the most distant past to the most distant future" (p. 480). The cosmic theory of the big bang provides the theoretical background of this extraordinary narrative. The big bang theory has emerged in 1965 following the discovery of the microwave background (p. 326-30). As geology and evolutionary theory have historialisé the Earth and life on Earth by bringing to light their incessant changes over millions of years, the big bang theory marks the complete historialization of the universe revealing the processes and the dramatic changes that have resulted in its present state over the 13.7 billion years of its existence. To date, the assumption of the big bang was checked for by numerous observations, and will undergo tests renewed at the CERN Large Hadron Collider. This will allow back in time on this side of the year 380 000: indeed, during its first 380,000 years the universe remains opaque (hindering the free electrons are moving light) and therefore inaccessible to telescopes.

The fifth chapter of our glorious sun, internal structure, its multiple effects on our ecosphere and terrestrial phenomena such as the rainbow sky and the blue color of the sky, inevitable subjects and whose scientific explanation should be known to everyone. Without the energy of the Sun, there would be no life on the surface of our planet. `I say to the surface of our planet 'because oceans contain living beings (extremophiles) at depths completely devoid of sunlight and whose metabolism is thus caters to an energy source other than light. The developments Thuan devoted to topical dependence of the phenomenon of life with regard to light, the greenhouse effect (there are two, one good, one bad), the anthropogenic global warming and the dangers it poses to existing forms of life should be part of the minimum scientific knowledge of every enlightened soul.

The sixth chapter examines the techno master of light: incandescent artificial light and neon, lasers, fiber optics, and many other fascinating topics, all presented with the gift of clarity to which the author has now accustomed us.

The seventh and final chapter instructs us in the physiology of vision (in the ratio of the eye to the brain), and concludes with a consideration of a series of theological and aesthetic concepts of light.

I would especially recommend this book to those who are concerned with philosophy, because it seems that philosophers today should be aware of the sciences and what they teach us about the world of ours and universe in which it is situated. It is dedicated this book to the philosopher, it is first of all the totalizing vision of the universe that it offers. Second, not only historical narrative, reminding us repeatedly that some discoveries and some scientific theories are made simultaneously (or almost) by different individuals, while others are rebuilt after being lost or neglected; but also systematic considerations, showing us that independent research ways and independent reasoning of each other towards the same results, give us a real sense of the objective nature of scientific, in particular, and the search for truth , in general.

Third, the book introduces us to the fact that the understanding of the world that gives modern science is acquired against our natural conscience, which is largely made up of unthought and unexamined notions (including the dogmas will be counted and religious beliefs). We can also express this state of affairs by saying that modern science is against-intuitive: to take two examples of the beginnings of modern physics: 1) the principle of inertia of Newton (we need the original formulation to Descartes) is counterfactual, which is to say we do not observe purely inertial motion in nature; and 2) that the same force because falling objects on Earth and retains the eight planets of the solar system in their orbits is a fact that Newton had shown as it is not obvious to ordinary consciousness. With regard to science, life unfolds in a mesocosm, that is to say, in a way or world world between the macrocosm and the microcosm. But as the unthought or the intuitions of our everyday life, conveyed by language and culture, are a measure of the mesocosm and that it remains opaque to macro- and microscopic phenomena, scientific understanding of nature s' achieved at the cost of educational effort, an Alternative and corrigendum process that leads out certainties and conceptual schemes that prevail within the mesocosm. In the book, our mésocosmique condition is shown by such passages as the following:

"So just as stars and galaxies give us a much misleading for the distribution of mass in the universe, the stars that make us delight the night give us a totally false impression of the various populations of stars in the Milky Way. We focus on only the light from the brightest objects may fool us. If we do not take into account the fact that the darkness also swarm of stars little bit massive and bright, we are likely to miss the reality. "

I note that Thuan does not use the term mesocosm, but expressions such as 'facts of life' (225) 'daily life' (226 and 850-51 (opposition between the physicist and daily life) ), 'everyday' (234 and 271), etc. It also uses the word 'gross' to describe both the mesocosm the macrocosm:

"... One wonders why the chance that reigns supreme in the atoms of the universe is not as ubiquitous in the macroscopic world, since things in life are merely aggregates of atoms. Why objects around us have they not also a wave nature that would allow them to spread throughout space and be everywhere at once? Why do not we see the Earth suddenly disappear of its orbit around the sun to reappear on the side of Jupiter? "(Pp. 225-26)

Modern science thus serves the very general concept of the contrast between reality and appearance. Unlike some philosophies where this distinction is between two ontologically heterogeneous areas, science appearance belongs to the physical world no less than reality: it is a natural effect of a natural cause. We see this opposition at work at the very beginning of modern science in the contrast established by the heliocentric theory of Copernicus between the apparent motion of the sun in the sky and the actual rotation of the Earth around the Sun and of itself. It is also present in the Newtonian theory of light which teaches that white light is simple in appearance.

Finally, the book shows that the scientific and technical activity continues growing as a team, and that in fact, given the complexity of the phenomena studied and of the equipment required by the investigative real ( for example, include particle colliders or telescopes carried by satellites), the search can be carried out in a team. One could argue that this only makes a synchronic state of affairs until the twentieth century has mainly prevailed diachronically in scientific research and is summarized by saying that "the brain is an organ that works network" (François Flahault "Twilight of Prometheus" (Arabian Nights, 2005), p 255;. see 215-16), and not in the solitary individual, separate from others, who would think of itself alone. The brain is a social being. Before teamwork, where the brain network consists of individuals in the flesh working together, the network consisted primarily treated, essays and articles (the publication of scientific journals began in the 17th century). To a large extent, so the act of thinking is an act that unfolds on inter-fund, a fund of knowledge and problems that has a character quite public.

Those interested in philosophical thought Thuan also read with interest the interview rich Thuan led by Patrice Van Eersel and published in "Is the world created by himself?" (Albin Michel, 2008), p. 17-71.

The book would have benefited from a reading correction. Aside from a few typos and syntax errors, we find there a number of Anglicisms.

Read, reader, read, and take your time.