RT Journal Article T1 The Science of the Einstein Telescope A1 Abac, Adrian A1 Abramo, Raul A1 Albanesi, Simone A1 Llanes Estrada, Felipe José A1 Lope Oter, Eva A1 Navarro Moreno, Pablo A1 Rubiera García, Diego A1 Rubio Peña, Javier A1 Blázquez Salcedo, José Luis A1 Zmija, Andreas AB Einstein Telescope (ET) is the European project for a gravitational-wave (GW) observatory of third-generation. In this paper we present a comprehensive discussion of its science objectives, providing state-of-the-art predictions for the capabilities of ET in both geometries currently under consideration, a single-site triangular configuration or two L-shaped detectors. We discuss the impact that ET will have on domains as broad and diverse as fundamental physics, cosmology, early Universe, astrophysics of compact objects, physics of matter in extreme conditions, and dynamics of stellar collapse. We discuss how the study of extreme astrophysical events will be enhanced by multi-messenger observations. We highlight the ET synergies with ground-based and space-borne GW observatories, including multi-band investigations of the same sources, improved parameter estimation, and complementary information on astrophysical or cosmological mechanisms obtained combining observations from different frequency bands. We present advancements in waveform modeling dedicated to third-generation observatories, along with open tools developed within the ET Collaboration for assessing the scientific potentials of different detector configurations. We finally discuss the data analysis challenges posed by third-generation observatories, which will enable access to large populations of sources and provide unprecedented precision. PB IOP Publishing YR 2026 FD 2026 LK https://hdl.handle.net/20.500.14352/137020 UL https://hdl.handle.net/20.500.14352/137020 LA eng NO Abac A, Abramo R, Albanesi S, Albertini A, Agapito A, Agathos M, Albertus C, Andersson N, Andrade T, Andreoni I, Angeloni F, Antonelli M, Antoniadis J, Antonini F, Sedda M A, Celeste Artale M, Ascenzi S, Auclair P, Bachetti M, Badger C, Banerjee B, Barba-González D, Barta D, Bartolo N, Bauswein A, Begnoni A, Beirnaert F, Bejger M, Belgacem E, Bellomo N, Bernard L, Bernardini M G, Bernuzzi S, Berry C P L, Berti E, Bertone G, Bettoni D, Bezares M, Bhagwat S, Bisero S, Bizouard M A, Blanco-Pillado J J, Blasi S, Bonino A, Borghese A, Borghi N, Borhanian S, Bortolas E, Botticella M T, Branchesi M, Breschi M, Brito R, Brocato E, Broekgaarden F S, Bulik T, Buonanno A, Burgio F, Burrows A, Calcagni G, Canevarolo S, Cappellaro E, Capurri G, Carbone C, Casadio R, Cayuso R, Cerdá-Durán P, Char P, Chaty S, Chiarusi T, Chruslinska M, Cireddu F, Cole P, Colombo A, Colpi M, Compère G, Contaldi C, Corman M, Crescimbeni F, Cristallo S, Cuoco E, Cusin G, Canton T D, Dálya G, D’Avanzo P, Davari N, De Luca V, De Renzis V, Della Valle M, Del Pozzo W, De Santi F, De Santis A L, Dietrich T, Dimastrogiovanni E, Domenech G, Doneva D, Drago M, Dupletsa U, Duval H, et al 2026 The Science of the Einstein Telescope J. Cosmol. Astropart. Phys. 2026 081 NO Artículo firmado por 489 autores.©2026TheAuthor(s).RYC2020-028870-IPROMETEO/2021/083CIPROM/2022/69IT-1628-22RYC2021-033786-I2019-T1/TIC-13177MSCA-101065736MSCA-101105915MSCA-2022-PF-01-01CA16104CA16214MSCA-RISE-2017MSCA-2021-SE-01RED2022-134411-T NO European Comission NO Ministerio de Ciencia e Innovación (España) NO Agencia Estatal de Investigación (España) NO Generalitat Valenciana NO Gobierno Vasco NO Consejo Superior de Investigaciones Científicas (España) NO Universidad Autónoma de Madrid NO Comunidad de Madrid NO Generalitat de Catalunya DS Docta Complutense RD 8 jun 2026