Physics Colloquium
Gravitational-wave (GW) observations with the Virgo and LIGO detectors have revolutionized astronomy and physics. With more than 200 detections today, we can start to study in greater detail the properties of black holes and their distribution in our Universe. The observation of the merger of two neutron stars in 2017 has led to the greatest astronomical campaign in human history with numerous publications dedicated to its study. Despite these outstanding achievements, the field is only in its infancy, and new revolutionary instruments are underway like the space-based LISA mission or the proposed Einstein Telescope. Even then, GW detectors will only observe a small portion of all possibly detectable GW sources in our Universe, and researchers have started to develop new detector concepts to further extend the scientific reach of GW detectors. Among these concepts is the Lunar Gravitational-wave Antenna (LGWA). The Moon itself acts like an antenna to GWs by starting to ring like a bell when a GW passes. A transducer needs to be built to read out the vibrations of the Moon. These transducers are being developed by an international team. The LGWA mission creates a tight connection between astrophysical observations and the geophysical properties and internal structure of the Moon, which determine the environmental noise and how the Moon responds to GWs. The Moon provides close to ideal conditions for LGWA, and it might well be the only place in our solar system where a detector like LGWA can ever be realized. The LGWA pathfinder mission Soundcheck was recently selected by ESA into the Reserve Pool of Science Activities for the Moon to study a possible LGWA deployment site.