Gravity plays a central role in understanding the universe. It affects everything from planets and stars to galaxies, shaping the cosmos as we know it. Studying gravitational waves (ripples in spacetime caused by massive events like black hole mergers) can help us learn about the formation and evolution of black holes and to understand gravity better. It can also lead to groundbreaking discoveries with wide-ranging implications for astrophysics, cosmology, and our understanding of the laws governing the natural world.
The COST Action Gravitational waves, black holes and fundamental physics (GWniverse) fostered a network of experts in Europe, positioning them to become global leaders in the upcoming era of high-precision gravitational-wave physics. Vitor Cardoso from Instituto Superior Técnico de Lisboa, and the Chair of the Action, tells us how this GWniverse helped us unlock the mysteries of the universe by studying gravity, black holes, and gravitational waves.
Why look up?
According to Vitor, “learning and understanding are among the most honourable human endeavours. It’s very exciting to discover that there are countless holes in the universe where time appears to stop at their edges. It’s truly amazing! When we look up at the night sky, we can’t help but wonder what else is out there, and what goes on inside a black hole. Our understanding of the cosmos is based on fundamental interactions that govern the behaviour of matter. Once we understand this, we can piece together everything we know, from planets and stars to complex living organisms“.
“Unfortunately,” Vitor continues, “our knowledge is incomplete. Einstein’s theory cannot be the final description of gravity. Black holes still hold the deepest secrets of gravity. What are the laws that govern the interior of black holes? Is this knowledge useful for understanding what dark matter or dark energy is? The advent of gravitational wave astronomy finally gives us a way to learn about the gravitational interaction in its most extreme regime. These are incredible times!”
Watch the GWniverse short video:
GWniverse embracing challenges
Managing a team of 500 scientists from all over Europe, overseeing around 60 Management Committee members, and navigating the intricacies of acronyms and reimbursement procedures were just some of the challenges faced by the Action Chair. Establishing a fair and scientifically sound process for awarding Short-Term Scientific Missions (STSMs), while prioritising geographical and gender diversity, added another layer of complexity for GWniverse’s leaders. However, the unity of purpose among the 500 scientists made these challenges not only manageable, but also rewarding for Vitor.
“One personal moment stands out”, shares Vitor, “during the first Action meeting in Brussels, I was elected Chair, which at first felt overwhelming. As panic set in, a colleague reassured me by saying, “Vitor, it’s very simple. You tell us what to do, and we do it. We’re a community, and together we will overcome these challenges, and come out stronger.” And indeed, we have.” Vitor concludes.
Discoveries and outcomes of GWniverse
The Action led to a number of unexpected discoveries and outcomes, including the creation of specific tools to test the black hole paradigm in depth, and to explore how black holes can shed light on dark matter. Key achievements of GWniverse included the creation of the Roadmap, a pivotal document that united the gravitational-wave astronomy community and marked a groundbreaking assessment of the field. The Roadmap’s global influence and high citation rate highlighted its importance. Similarly, the BH Perturbation toolkit evolved into a mature collaborative effort, benefiting hundreds of users and welcoming new members. These findings had a significant impact, with LIGO now incorporating dedicated searches based on the studied physics, and next-generation detectors actively building their own research pipelines.
Numerous Action members are shaping the future of gravitational-wave science and black hole observations. They are now leading the scientific case for the largest European Space Agency mission (LISA), and heavily involved in two observatories, the Event Horizon Telescope and the Einstein Telescope.
Hundreds of young researchers of GWniverse benefited from Short-Term Scientific Missions (STSMs) across Europe. Furthermore, numerous PhD students from the project secured postdoctoral and faculty positions, collectively contributing to a flourishing gravitational research community.
“The future lies in the hands of all the early career researchers we trained. I still get messages from colleagues or students telling me how the action meetings or STSMs changed their career for the better. So, hurrah for COST!”Vitor Cardoso, Chair of the Action GWniverse
GWniverse members received prestigious prizes and awards from the European Research Council Grants, highlighting the timeliness and robustness of the research. Samaya Nissanke and Clare Burrage received the New Horizons Prize. A publication by PhD student David Benisty and Prof. Eduardo Guendelman, has been awarded a prize by the Gravity Research Foundation.
Other accolades included membership in the Lisbon Academy of Sciences, DNRF Chair in Denmark, and Distinguished Professorship in Lisbon for some members.
Prof. Jackson Levi Said’s election as Chair of a new COST Action CosmoVerse further exemplified the influence of the Action project.
The GWniverse long-term legacy
For Vitor, “Although knowledge is as important as anything else, it’s worth noting that knowledge often leads to practical applications. Some of these applications are already in use, while others will bear fruit in the future“.
A free-access repository for modified theories of gravity, with input from all the community and network will be one of the most tangible deliverables and a long-term legacy of GWniverse and of utility for the community-at-large. It will contain a database of all studied modified theories of gravity and corresponding observational bounds.
“Science is also knowledge passed from generation to generation, and occasionally experiments are started which only see the light of day one or two generations later. It’s a generous, grand endeavour, it’s humanity at its best”, concludes Vitor.