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The energy gamma rays

All amateur astronomers are accustomed to seeing images of the same object in different energy bands from radio observations, optical, infrared, ultraviolet, X-ray It is not so common, however, hear about most of the energy of the electromagnetic spectrum: gamma rays.

This light has an energy about 10 billion times greater than the light to which the human eye is sensitive. Unfortunately it is not possible to directly observe this radiation as the Earth's atmosphere is not transparent at these energies. The problem can be circumvented in part through the use of space telescopes , but what about an important part of gamma rays, high energy ones, this is not possible for purely logistical reasons: these photons are so rare that the dimensions of the telescope are prohibitive for an experiment to be sent into orbit.

Another way to observe these photons uses the same atmosphere of the Earth as a large particle detector. The gamma rays that pass through the atmosphere interact with the atoms thereof and lose energy, producing a cascade of particles. The particles in the cascade have a speed faster than the speed of light in the atmosphere (but still less than the speed of light in vacuum!) And produce the so-called Cherenkov radiation: this is a cone of light that, when it reaches the ground, it can illuminate an area of \u200b\u200babout 100 meters range!

This light is then gathered by telescopes and analyzed. Among the latest experiments in this field include HESS (High Energy Stereoscopic System), located in Namibia, MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov Telescope), located in La Palma, Canary Islands, and VERITAS (Very Energetic Radiation Imaging Telescope Array System), Arizona, United States. These experiments take advantage of the stereoscopic technique, or use multiple telescopes spread over an extensive area, to cover the cone of light produced by the waterfall: this allows us to determine more certainty the direction from which the photons and their energy.


Each telescope is not fundamentally different from a traditional optical telescope. The main difference is the size of the mirror: the two telescopes MAGIC experiment, for example, have a diameter of about 17 meters each, while that of the telescope to be built during the next phase of the experiment HESS is even over 20 meters ! Of course it is not monolithic mirrors, which consist of a single block, but made up of many small pieces.

Many and various are the astronomical objects that can be studied with this technique: an example is jets of particles emitted by the nuclei of so-called active galaxies, which hide within them a supermassive black hole that devours the surrounding matter, or nebulae of energetic particles ejected from the stars when, at the end of their lives, explode in the form of supernovae.

GIOVANNA PEDALETTI

picture, the four telescopes currently comprising the HESS experiment in the Plateau of Khomas, Namibia. The experiment is fully operational since 2004, will be enhanced in the coming years with more telescopes to achieve even better performance. (Credits: HESS Collaboration)

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Theatre tells the science

Life of Galileo: Bertolt Brecht staged the conflict of men search

It is not easy to talk about science to the general public. Even more difficult is to talk about the dynamics of socio-political issues related to science. If we try to do it in an artistic way (eg through the cinema or theater), we encounter an epic challenge. No coincidence that there are few films and / or plays that deal with scientific issues.

A milestone in this field is certainly the work "The Life of Galileo" by Bertolt Brecht German. In a lean and very effective, says Brecht of a Galileo who, inflamed by his own discoveries in astronomy, is focused on spreading the new way of conceiving the universe. This new world view is considered heretical by the Church that pushes Galileo to renounce all his discoveries, "recant."

The Brecht's Galileo is a very complex and at times heroic. For example, heroic and difficult to interpret and 'his recantation. Accusation of his disciples that he had bowed to the power of the Church, Galileo says, "better than empty hands tied." Do not recant would lead to the death sentence of Galileo (as had happened to Giordano Bruno) and perhaps the entire astronomical research of which he was an irreplaceable member suffered a breakdown. Galileo to recant, and then deciding to live secretly pursuing his studies on the motion of celestial bodies, and finally manages to deliver it to Andrea, his trusted disciple, which is managed in the Netherlands, the nest of the independent thinkers of the time.

Andrea is a perfect character to try to understand the complexity of some decisions related to science. Andrea, who grew up under the influence of Galileo, developed a love for the analytical method of genuine science. Later, young and full of enthusiasm for new astronomical theories, decided to leave Italy: "I go, I am a scientist," he says. The same Andrew, the news of Galileo dell'abiura, depressed states, "Unhappy the country that has no heroes." Only later in the text, Galileo will answer: "No. Unhappy the country that needs heroes. "

should not be too much effort to see that this story is 400 years old history now. In Italy today there are many of Galileo, less gifted but equally dedicated, many more are leaving Italy's Andrea to places where scientific research is given greater value. If it is true that no longer exists, the court of the Inquisition, the fact remains that those who decide to reduce (or should I say eliminate) the funds for research performs an act of censorship "post-modern." The forms are different but the problems now facing the world of science in Italy are all too similar to the Galilean vicedo.

MARCELLO HUNTED

"Life of Galileo" by Bertolt Brecht is currently on tour in Italy, in a co-production Teatro Stabile del Friuli-Venezia Giulia and Theatre of The Incamminati, directed Antonio Calenda. The dates of the tour you can find here .

In the picture of Thomas Le Pera, Branciaroli Franco plays the role of Galileo.