DrHungarian science historian Karoli Simonyi says in his wonderful book “The Cultural History of Physics” that knowledge of light at the beginning of the seventeenth century was essentially the same as that summarized by Ptolemy and then supplemented and developed by Ibn al-Haytham.” The fact that this would suddenly change soon afterwards is mainly due to to the discovery of the telescope, but also to the development of increasingly accurate clocks.Serge Harroche details this story in his book.The author is a professor at the Collège de France and the École Normale Supérieure (ENS) in Paris and, as an experimental physicist, himself contributed to the understanding of the nature of light That’s why he got 2012 Nobel Prize for Physics excellent. Of course, he is primarily concerned with light as a physical phenomenon, but for Harroch it is also important as a metaphor often used, as in French discourse in the Siècle des Lumières of the Enlightenment. Harroch’s mission is to provide enlightenment.
Before the author delves into the history of the light, he provides an insight into his career. He is now being asked more and more about how he participated in the search for light in the laboratory and in such a successful manner. We learn that he was very fond of astronomy from a young age and was fascinated by mathematical structures, such as the curious number pi, which appears in fields as diverse as engineering and statistics. But as is so often the case, it is chance that decides the extra lifeline.
The infamous Schrödinger’s cat
As a physics student at ENS in the 1960s, he was fortunate to attend lectures by excellent teachers and researchers who introduced him to the pillars of quantum physics. It is worth mentioning above all to Claude Cohen-Tanduji, who in 1997 was awarded the Nobel prize You should receive. Harrush received his Ph.D. from it in 1971.
In fact, it was the laser, available since about 1960, that drove the research at the ENS Working Group. In the 1950s, two ENS scientists, Alfred Kastler and Jan Brussel, developed optical pumping, which is important for the function of lasers, i.e. raising electrons to higher energy levels in an atom. For this Kastler was awarded the Nobel Prize in 1966, and Brossel received nothing; The history of the Nobel Prizes is always the history of those who have been ignored. Unlike today, there was a great deal of freedom in the labs at the time, as Haroche sadly notes later. Working group chairs can focus primarily on research and support rather than on third-party funding.
After this autobiographical introduction, the author turns to the history of light in four easy-to-read chapters. Of course one will encounter Galileo, Newton, Christian Huygens, Thomas Young, Augustin Fresnel, Michael Faraday and others. Newton conceived of light as consisting of small particles, while Huygens postulated the wave nature of light. Not surprisingly, Newton’s authority ensured the dominance of particle theory, which would only change with Jung’s experiments on interference at the beginning of the nineteenth century.
Appeal for Freedom of Basic Research
Highlights of this story Albert Einstein Work on the quantum light hypothesis and the theory of special relativity. However, the light quanta of 1905 are not later on the so-called photons. Since it was supposed to teach quantum theory developed in the 1920s, the latter does not behave like classical particles that are independent of each other, but, according to Einstein, “sit together relatively frequently”. According to the modern view of quantum theory, light (like matter) has both particle and wave properties, and it depends on the conditions under which the aspect prevails. The author devotes a detailed account of the “anomalies” of quantum theory, including the infamous Schrödinger’s cat, which is in a strange intermediate state between the living and the dead.
Light from the early days of the universe can be observed in the cosmic background radiation discovered in 1965. The fact that there is anything other than light in the universe is due to the asymmetry between particles and antiparticles, ensuring that there are enough particles for our existence. Otherwise, as Hans Blumenberg once said, “A position is overwhelming from the point of view of absolute enlightenment: so much light, but no world that can ever shine.”
However, Harush only touches on cosmology. His focus is on laboratory physics and in particular the results of his working group, which are presented in detail and carefully in the remaining chapters. Without a solid knowledge of physics, you won’t be able to enjoy this part all the time, but even then, the author’s passion for his subject can be felt in every line. Haroche and his group succeeded in creating and controlling “Schrodinger’s cats” using single photons. These individual photons can be studied using atoms and, in particular, it has made it possible to highlight the transition from quantum properties to classical ones, but also to improve the accuracy of clocks. This is research that has been recognized by the Nobel Prize Committee. At the end of His History of Light, Harush made an impassioned appeal to freedom of fundamental inquiry and the ideas of the Enlightenment.
Serge Harush: “Light.” story. Translated from the French by Ursula Heald. Klett-Cotta Verlag, Stuttgart 2022. 464 pages, patient, hardback, €35.
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