The Nobel for gravitational waves and the role of Italy
The Nobel committee has recognized the key role of the VIRGO detector in Tuscany and the partnership with LIGO in the US.
* By Stefano Lami, Embassy of Italy in the United States
The 2017 Nobel Prize in Physics has been awarded to Rainer Weiss, Kip Thorne, and Barry Barish “for decisive contributions to the LIGO detector and the observation of gravitational waves”.
Italy is taking pride in this recognition, as the three American scientists are part of the LIGO-VIRGO partnership project — which includes many Italian researchers — mentioned by the Nobel committee.
LIGO-VIRGO has also been a key partnership in the first detection of gravitational waves produced by colliding neutron stars, the smallest and densest stars. The detection was announced by the National Science Foundation and LIGO-VIRGO scientists on October 16, 2017, only a couple of weeks after the Nobel announcement.
It represents a global effort where about 70 ground and space-based telescopes, alerted by the detection of a gravitational wave signal, pointed their instruments precisely at the same region of the sky. It was the first time that a cosmic event has been viewed in both gravitational waves and light.
Gravitational waves are ripples in space, vibrations sent outwards at the speed of light, caused by some of the most violent and energetic processes in the Universe such as neutron stars or black holes orbiting each other and eventually colliding, and the collapse of stellar cores (supernovae).
Gravitational waves were first predicted by Albert Einstein in his general Theory of Relativity about one hundred years ago. However, by the time these waves reach Earth, they are millions of times smaller and less disruptive than their violent origin — thus more difficult to detect.
It took many years in order to design and realize sensitive detectors for such inconceivably small measurements.
This is where Italy and the VIRGO project, mentioned together with LIGO in the Nobel announcement, play and important role.
The discovery of gravitational waves is the result of a scientific collaboration that sees the United States and Italy in the front row in the study of gravitational astronomy. An effort demonstrated by the broad participation of the Italian scientific community in this mission, with about 100 physicists involved in the VIRGO experiment, who co-authored the scientific article about the first observation of gravitational waves.
The Nobel Prize comes just a few days after the announcement of the first joint observation of a gravitational wave signal by the three detectors:
- The two National Science Foundation (NSF)-funded Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors in the US, respectively in Livingston, Louisiana, and Hanford, Washington State;
- And the VIRGO interferometer near Pisa, Italy, funded by the Italian Istituto Nazionale di Fisica Nucleare (IFNF) and the French Centre Nationnal de la Recherche Scientifique (CNRS).
The announcement was made during the G7 ministerial meeting on science hosted in the city of Turin and chaired by Italy.
During the press conference, NSF Director France Córdova commended Italy for the vital role that it played in VIRGO’s development and success.”
The Italian longtime tradition in the search for gravitational waves saw a turning point in the Eighties thanks to the foresight of Italian physicist Adalberto Giazotto.
Together with France’s Alain Brillet, Giazotto proposed the creation of a French-Italian VIRGO interferometer to be built in Cascina in Tuscany. The project was finally approved in 1993.
As major collaborative efforts, often international in scope, are becoming a common means to reduce costs, share risk, and augment scientific expertise, a global network of Gravitational Wave Detectors will expand over the next three decades the study of gravitational waves.
Among the first questions that must be answered about each gravitational wave observed is where it originates. A global network of detectors can answer this question by comparing the signals at widely separated detectors. This will enable gravitational wave sources to be studied using the tools of multi-messenger astronomy, such as optical telescopes, radio telescopes, or X-ray detectors.
In addition to the two LIGO detectors in the US and VIRGO in Italy, others are joining the club: the Kamioka Gravitational Wave Detector (KAGRA), an underground cryogenic detector in Japan, is almost complete; and LIGO-India will join the international network in the next few years. This network exemplifies how international collaborations are now moving from the regional to the international level, characterized by joint data-taking and a large-scale exchange of researchers.