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The radiating heart of matter


From November 2000 to January 2001, the exhibition entitled 'Radioactivity, a facet of nature', proved a remarkable success in popularising science. Presented simultaneously in Paris, Wiesbaden and Milan, as part of Week 2000, the event was made possible thanks to the efforts of a consortium of European physics institutions.(1)



Artist's impression of the interaction between an alpha particle and an atom.

'One may wonder whether it is in man's interest to know nature's secrets, if he is ready to benefit from them or if this knowledge will harm him.... I am among those who believe that humanity will draw more benefit than harm from these discoveries.' (2)

Paris, November 2000, on the first floor of the Palais de la Découverte, displayed to visitors as they leave the exhibition, this quotation by Pierre Curie sums up what may well be on the visitor's mind at the end of a fascinating tour of the progress made by 20th-century science in penetrating matter's most intimate secrets.

Unfortunately, Professor Curie's prediction of the potential dangers proved correct, and nuclear weapons no doubt represent the embodiment of knowledge used for evil purposes. But this exhibition also shows to what extent the researcher's ultimate optimism was well-founded. Man's understanding of radioactivity - this 'signal' sent by the ballet of tiny elementary particles, charged with mass, electricity and energy, and gravitating to the heart of certain mutating unstable atoms - has permitted a triple scientific revolution. This was expressed in the three sections of the exhibition - entitled , and - with reference to the three principal types of radioactive radiation.


A portrait of Dr Chicotot, a pioneer of treatment for cancer, in 1908.

- The universe
To understand the nature of matter is also to enhance one's understanding of the universe. Increased understanding of the radiation created by the action of the disintegration and transmutation of atoms results from a twofold investigation: into the infinitely small and into the infinitely large.

On the one hand, physicists have made constant progress in identifying elementary particles and the fundamental forces by which they interact. On the other, in the vast expanses of the universe, astrophysicists have been tracing the mutations of matter since the original Big Bang.


Today's treatment. Beams of protons and carbon ions, produced by accelerators, permit the effective treatment of eye cancer and deep tumours. Such technologies originated in the nuclear sciences which continue to make a major contribution to progress in medicine.

- Nature
Since life first appeared on earth it has evolved not just in an ocean of radiation coming from the cosmos, but also in the natural radioactivity of a planet which, like any other, was born as a result of the laws and randomness of this cosmos. Volcanic eruptions, geysers and earthquakes are all reminders that, in bowels of the earth (just 4.5 billion years old) is also a 'nuclear machine' in which the transmutations of matter release vast quantities of energy.

At the same time, intense radioactivity can be a threat to life, its power of penetration being such that it attacks the very heart of the cells of which we are composed. And the reason our planet has succeeded in being hospitable to life is also because it is an oasis in the universe where the ambient radiation level allows it to be sustained. Meanwhile, all around us, the rocks of the earth's crust (from which we extract the fuel for nuclear power plants) retain the memory of this transmuting activity. The most notorious phenomenon, linked to the nature of the local geology, is radon, a gas emitted by the breakdown of uranium 238, which can be found in the cellars of houses.

As a result of the knowledge acquired, science has become highly sophisticated in the field of radioprotection, allowing us to determine reliable limits for natural and artificial radiation, which, in guaranteeing the effectiveness of the defence mechanisms of living cells when faced with radioactive attack, do not pose a danger to health.


Crouching Aphrodite - The Louvre Museum Radiation with gamma rays is able to eliminate fungi, larvae, insects and bacteria, and to protect works of art against deterioration.

- In practice
Progress in fundamental physics over recent decades has permitted the creation of irreplaceable scientific tools which can be used for a vast range of activities. We have become so used to their presence that we are usually unaware of their origins or of the principles by which they operate. In dentists' surgeries and museums, supermarkets and airports, technologies drawing on our knowledge of radioactivity are all around us. Medical imaging, the identification of gene sequences, the piloting of biological markers aimed at destroying cancerous tumours, the analysis of the atmosphere's chemical composition, smoke detection, food conservation, the inspection of the wear on materials, the luminosity of information panels, the dating of works of art, the detection of anti-personnel mines... The list is seemingly endless.

And that is without including the key question of the role of nuclear physics in energy production. Nuclear fuel currently meets 35% of European needs, principally in France, the United Kingdom and Belgium. In the nuclear industry, radiation had in theory been effectively and safely harnessed - until the Chernobyl disaster proved otherwise. What is more, the crucial problem of nuclear waste remains unsolved. But then again, in the light of the threat of global warming, does nuclear energy - which emits no greenhouse gases - deserve to be ranked among the discarded technologies?

Interview: the physicists' point of view

Professor of nuclear and sub-nuclear physics at Milan University, Ettore Fiorini is one of Europe's foremost researchers on particle physics. Among other things, he coordinates a European research network on cryogenic detectors with the aim of measuring the mass of neutrinos.

The mention of radioactivity more often frightens rather than fascinates people...

Ettore Fiorini : It is true that the term radioactivity immediately arouses feelings of concern and threat. This reaction is because the word is associated in people's minds with the terrible devastation caused by the atom bomb dropped on Japan and, more recently, the Chernobyl disaster - the only major nuclear accident we have seen. As a physicist, I share the same sense of dread at such a mortally dangerous use of scientific knowledge, whether for military purposes or due to the evident and irresponsible mistakes in terms of the security measures which caused the Chernobyl disaster.

But the fact that we discovered radioactivity means that it does exist and has always existed in nature. This discovery has been the source of formidable progress in our knowledge of particle physics and all the very beneficial applications which have derived from it. The general public must be reconciled with this essential scientific knowledge by making the effort to explain to them in detail what this knowledge consists of and the many extremely useful applications it enables - provided all the safety measures are applied to ensure that the radiation, limited to very low doses, is free of danger. It is up to the physicists to do this explaining.

What are the principal - or the most unexpected - fields in which you believe the control of radioactivity is able to bring essential benefits?
The list of the remarkably positive applications of nuclear physics would be too long to give. But let me just remind you of the impact of nuclear medicine and radiotherapy on the treatment of cancer, and the powerful nuclear magnetic resonance tool for many kinds of medical diagnostics. Environmental sciences is another key application of the study of radioactivity: the detection of radon, for example, and the applications that have followed, or the identification of very low levels of contamination by analysing neutron activation. The applications of radioactivity and the associated detection techniques are also very important in the new discipline of archeometry.

Harnessing the energy produced by nuclear fusion is often cited as a potential source of genuinely clean energy which could become available at some distant point in the future. In what way would this be radically different from the present nuclear power industry in terms of radioactivity?
The possibility of supplying vast quantities of energy by harnessing nuclear fusion is an option which for some years now has not appeared to be entirely beyond our reach, but it is difficult to predict when it could become a reality. However, as you are dealing with an energy based on the control of nuclear reactions, it is premature to say that it would be completely free of risk. What is clear is that the fusion reaction cannot get out of control and can, in the event of a problem, be stopped immediately. As to waste products, if any - produced by neutron activation for example - they are certainly going to be less dangerous and complex to manage than fission products.

(1) The Institut National de physique nucléaire et de physique des particules (FR), the Istituto nazionale di fissica nucleare (IT), the Gesellschaft für Schwerionenforschung (DE) and the University of Vienna (AT), under the aegis of the NuPECC (Nuclear Physics European Collaboration Committee) and the Société européenne de Physique.
(2) Speech given by Pierre Curie at the award-giving ceremony for the Nobel Prize for Physics in 1903, presented to Pierre and Marie Curie for the discovery of radium.


Alessandro Pascolini
Istituto nazionale di fissica nucleare,

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