by Brian Koberlein
July 25, 2021
https://www.universetoday.com/151959/a- ... ore-151959
(Universe Today) Gravitational-wave astronomy is set to revolutionize our understanding of the cosmos. In only a few years it has significantly enhanced our understanding of black holes, but it is still a scientific field in its youth. That means there are still serious limitations to what can be observed.
Currently, all gravitational observatories are based on Earth. This makes the detectors easier to build and maintain, but it also means the observatories are plagued by background noise. Observatories such as LIGO and Virgo work by measuring the distance shift between mirrors as a gravitational wave passes through the observatory. This shift is extremely small. For mirrors placed 4 kilometers apart, the shift is a mere fraction of the width of a proton. The vibrations of a truck driving down a nearby road will shift the mirrors much more than that. So LIGO and Virgo use statistics and models of black hole mergers to distinguish a true signal from a false one.
Because of terrestrial background noise, current observatories focus on the high-frequency gravitational waves (10 – 1000 Hz) generated by black hole mergers. There has been discussion of building a space-based gravitational-wave observatory, such as LISA, which would observe low-frequency gravitational waves, such as those generated by early cosmic inflation. But many gravitational waves are in the intermediate range. To detect these, a recent study proposes building a gravitational-wave observatory on the Moon.
The Moon has long been a coveted location for astronomers. Optical telescopes on the Moon wouldn’t suffer from atmospheric blurring, and unlike space-based telescopes such as Hubble and Webb, they wouldn’t be limited by the size of your launch rocket. Most of the ideas proposed have been very hypothetical, but as we look towards a human return to the Moon in the next decade they are becoming less so. Already NASA is studying the construction of a radio telescope on the far lunar surface. Building a lunar gravitational-wave observatory would be significantly more challenging, but not impossible.