This year the LIGO experiments have found evidence of Gravitational waves. In their experiments two black holes merge and give rise to huge ripples in spacetime. Now after the discovery, every scientific seminar I attended on the subject says that this opened up a new era of Gravitational wave astronomy. My question: Astronomy is usually referred to the observational study of universe, galaxies and stars. Given the gravitational waves we detect are anyway very feeble, I was wondering how is it possible to infer anything related to the structures of universe from these waves?
The statement that a "new era of Gravitational wave astronomy" has begun is certainly true, since we now can directly detect gravitational waves. This opens up more input on astrophysical events.
One buzzword would be "multi-messenger astronomy": at first we only had optical instruments then later other EM telescopes came along: X-ray, IR, UV,... After that we got neutrino detectors and now we even got detectors to directly detect gravitational waves.
The hope for the future is to investigate astronomical events; black hole or hopefully neutron star mergers, supernovae and more using input from all messengers: gravitational wave signal, neutrino signal and multiple EM signals. This gives a very extensive experimental picture of an event which can be compared to theory. The additional gravitational wave signal may give insight in areas, times and physics of events which where not experimentally accessible before.
Especially neutron star mergers or supernovea multi messenger signals could give massive insight on those events which are still in very active reasearch.
I mean it is true that those signals and their amplitudes are very small. Gravitational waves (meaning their propagation) might not effect our universe very much but the insight they give on the events where they originate from can be huge even if their ampiltude is small. And on those locations where they are emitted they actually have a massive impact: binary pulsars can radiate away massive amounts of rotational energy via gravitational waves, this is how they where first implicitly detected.