Roland Lehoucq



Born in 1965, Roland Lehoucq is an astrophysicist with the Astrophysics Service of the Atomic Energy Commission in Saclay in the Essonne department in the Ile-de-France region.  He is also a professor of physics at France’s prestigious engineering college, Ecole Polytéchnique. He is one of France’s specialists in cosmic topology, a discipline whose goal it is to develop a method capable of determining the overall shape of the universe.

Passionate about the dissemination of scientific knowledge, he collaborated for three years on the monthly magazine Pour la Science (French version of Scientific American), has done a science column for seven years for the science fiction journal Bilfrost, and annually sponsors several elementary school classes in order to familiarize children with astronomy and scientific discovery. He has written for several magazines and is the author of more than 80 articles popularizing science. He has also published ten books, including: The Physics of Star Wars (published by Le Pommier, 2005); Where Do Superman’s Powers Come From? The Ordinary Physics of a Super Hero (published by EDP Sciences, September 2003); and Does the Universe Have a Shape? (published by Flammarion, September 2002).




1. Does the Universe Have a Shape?

While it may be possible to determine the shape of a galaxy or a cluster of galaxies, that of the universe is difficult to assess. Geometric concepts are generally intuitive as long as it’s a question of a plane or a sphere, because we can mentally immerse ourselves in a space of three dimensions in order to present them as «seen from the outside.»  But we have a great deal of trouble imagining the infinite variety of three-dimensional domains which could describe our universe. This way of conceiving of the universe leads us to consider the simplest representations, imagining it, for example, as a three-dimensional space having the same properties as a two-dimensional plane. However, we have no more reason to believe that our universe is constructed as thus than the ancients had in believing that the Earth was flat. It seems to us that a flat Earth can only be unlimited or be limited by an edge; it’s the same with our space. But we dislike the idea of an edge, because we will still say, “what’s beyond the edge?” Space is, therefore, generally regarded as being unlimited. During the course of this talk, I will show that it is not contradictory for a three-dimensional space to be both defined by limits and exist without edges, and that the infinite aspect of our universe could be just an illusion imposed by its particular shape. I’ll show that it is possible today to test this hypothesis experimentally by looking for traces of  it in the most recent cosmological observations.


2. Doing Physics with Star Wars

The cinematographic saga Star Wars enjoyed considerable success. It depicted futuristic technologies which clearly went well beyond our own. Certain scenes, however, seem like déjà-vu. Is it possible to take into account both science and fiction, dreams and reality? By using the tools of physics to decipher certain scenes in the film, Roland Lehoucq investigates topics such as: What could the nature be of the Force used by the Jedi? How would you build a laser sword? How do interstellar space ships travel? This, of course, does not intend to destroy the part played by dream that’s inherent to every work of fiction, but, rather, as something to support a discussion of physics that may also be fun. This questioning transforms the viewer of the film into an actor who is then on par with what the astrophysicist does in searching the universe for answers, with nothing more at his disposal than the light of the stars seen through his instruments. At the end of the investigation his world will be transformed. May the Force be with you!


3. Science Fiction and Energy

Works of science fiction often portray super high-tech gadgets, space ships, gigantic orbital stations, and planetary mega-projects. For the most part these contraptions and constructions come from someone’s unbridled imagination. On the other hand, others stand up to the most vigorous analysis based on what our times know about science: without being within the realm of the possible any time soon, still, they could conceivably work. If we suppose that the universe of science fiction obeys the same laws as our own, what is it we lack to match the exploits presented to us in those works? And what would be required to bring them about? Beyond the technological difficulties that are part of the process of constructing a serviceable mechanical device, whether it’s a toaster, a car, a laser sword or an interstellar space ship, the difference between us and these engineers of the future is first and foremost a question of the ability to produce and utilize massive quantities of energy.


4. Genealogy of Matter

Why do the stars shine? What is the fire that makes them shine? What message does their light send us? When Hernan Cortès asked the Aztecs where the iron came from that they used in making their daggers, they motioned to the sky. They were right about that: It is, in fact, inside stars where iron is made, as well as most of the other atoms with which things are made. In this talk we’ll plunge into the crucible of interstellar alchemy. How do we explain the variety and distribution of the atoms? When and how were they formed? The all-time biggest secret is no longer how gold is made but how matter emerged, all of it, from the debris of exploding stars. I will show that their nuclei, found on Earth, are all, for all intents and purposes, the consequence of stellar nucleosynthesis, which allows us to say with absolute certainty that we all come from star dust.


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