Studying the history of the universe goingback in time, almost to the big bang, thanks to the detection on Earth of gravitational waves produced by cosmological events, such as the merger of black holes or neutron stars, which occurred a long time ago at unimaginable distances. This is what the Einstein Telescope will allow, the future large international research infrastructure that will be built in Sardinia at the Sos Enattos site in Lula, in the province of Nuoro. The project was presented today in Rome.

Einstein Telescope rather than observing the universe, will listen to it. Gravitational waves are, in fact, like the echo of the astrophysical events that produced them. Predicted over a century ago by Albert Einstein - for this reason Einstein Telescope was dedicated to the great scientist - as one of the consequences of his theory of general relativity, they were observed for the first time on September 14, 2015 by the LIGO and Virgo Scientific Collaborations thanks to the LIGO interferometers. They are tiny oscillations, vibrations, of space-time, that is, of the four-dimensional structure - the three spatial dimensions plus the temporal dimension - that constitutes our universe.

The Einstein Telescope will be ten times more sensitive than current interferometers, allowing us to observe virtually all mergers of black holes and neutron stars in our universe, as well as new astrophysical phenomena never seen before, such as supernova explosions.

To perform measurements of such precision Einstein Telescope needs the most advanced technologies and the network of laboratories funded in the PNRR with the ETIC project (IR0000004) at the INFN, the ASI, the INAF and 11 Italian universities has exactly this purpose. The INFN section of Perugia and the University of Perugia have a leadership role in the Einstein Telescope project and in the ETIC project. Michele Punturo, INFN Research Manager is the spokesperson of the international scientific collaboration of Einstein Telescope and principal investigator of ETIC. Monique Bossi, INFN Technologist Manager, is the Infrastructure Manager of the entire ETIC project and Helios Vocca, INFN Professor and Associate Researcher, is the head of the international laboratory CAOS, belonging to the ETIC network, under construction at the University of Perugia. The CAOS project collaborates with the ETIC operational unit of the INFN of Perugia, coordinated by Patrizia Cenci, INFN Research Manager and Director of the INFN Section of Perugia. "The international collaboration Einstein Telescope is growing rapidly, having exceeded in less than a year from its birth the 1430 members, ie scientists from 23 countries and 211 institutions and universities" - says Michele Punturo - "The coordinated effort of this great collaboration is to define in the coming years the technical design of ET and contribute to the selection of the site or sites where to build the observatory. The candidacy of Italy carried out by the President of the Council of Ministers and by a team so representative of the government puts Italy in a strong position in the international game for the selection of the ET website". "The candidacy to host ET in Sardinia finds solid foundations in the two components developed within the ETIC project - says Monique Bossi -. On the one hand the pre-feasibility study on the site in the Sos Enattos area and on the other the strengthening of the network of laboratories that contribute to the scientific and technological development necessary for ET: two ambitious objectives built around a complex structure of over 140 activities carried out by 27 operating units distributed throughout Italy that for the next 30 months can count on a funding of almost € 50M". "The INFN section of Perugia has a dual role in ETIC - says Patrizia Cenci - provide the management of the entire ETIC project with highly qualified personnel, and recruit young technologists for the implementation of scientific equipment in the CAOS infrastructure".

CAOS is an international infrastructure mainly aimed at the development of ET technologies in the field of seismic filtering and low noise controls, with possible great repercussions also in transversal fields, first of all that of seismology and early warning of earthquakes. "The laboratory, a world-class center of excellence, will be able to house a 10-meter arm interferometer with the 1:1 scale suspensions of third-generation gravitational wave detectors, such as ET, which are essential to reduce fluctuations that limit sensitivities," says Helios Vocca. In fact, no other laboratory in the world has these characteristics and this will allow the Italian collaboration and the University of Perugia to maintain this important technology in our country with evident repercussions for our entire territory". According to the Rector Maurizio Oliviero: "It is a source of great pride to host in Perugia, in the engineering center of our University, the international laboratory CAOS. This infrastructure will have enormous repercussions for the entire academic community in terms of employment, technology and economics, offering itself as a reference point worldwide. We can only thank the scientific collaboration of INFN and the Department of Physics and Geology, for this fundamental contribution to one of the most fascinating projects funded by the PNRR that aims to expand our knowledge of the universe". The University of Perugia coordinates a network of laboratories with long experience in this field for the study and implementation of CAOS. This network includes university groups, Italian INFN and INAF (Pisa, Camerino, GSSI-L'Aquila, Rome "La Sapienza", Bologna), EGO (the European Gravitational Observatory), and foreign groups (such as the Japanese NAOJ and ICRR).