Additional detectors improve our ability to detect somewhat (assuming they're of similar sensitivity -- otherwise they can actually hurt our overall network sensitivity!). But the _real_ advantage is in source localization to guide multi-messenger (optical/gamma/neutrino) followup, which is where many of the most important discoveries will come from. It's like triangulation.

Given that an observatory costs on the order of ~$1B to build and operate for a few decades, we probably won't see more than five current (second generation) instruments (2x LIGO + Virgo + KAGRA + LIGO India).

There are also two proposed but not yet funded 3rd-generation ground-based instruments ("Cosmic Explorer" and the "Einstein Telescope"), one planned space-based instrument ("LISA"), and early efforts at proposing a future moon-based detector (the Gravitational-Wave Lunar Observatory for Cosmology, the Lunar Gravitational-Wave Antenna, and the Lunar Seismic and Gravitational Antenna).

To get to tens or hundreds of detectors, someone will have to invent a fundamentally different technology that can be produced at dramatically lower cost. Maybe next century...

I can donate my raspberry Pi if you need it ;)

Seriously, impressive cutting edge technology!

With three detectors, it becomes possible to measure the polarization of gravitational waves. https://ligo.org/science/Publication-O1StochNonGR/index.php

Some quantum-gravity theories predict additional polarization modes that general relativity doesn't, so such measurements may start ruling particular theories in or out.

You might be interested in this talk on the future of GW detectors and the resulting science prospects: https://www.youtube.com/watch?v=iet6pS4gxCk (esp. from ~25:40 to the end).

Thanks, that was very intersting!

The current ones are Louisiana, Washington state, and Italy.

So having another as far away as Japan should improve triangulation substantially.

The next stage should be putting them in space. Vibration on earth is a huge problem. Space has a much more stable environment. Also the distance between the laser detectors can be far, greatly enhancing the magnifying power.

In terms of the science, land-based and space-based GW detectors are complementary, as they detect GW waves at very different frequencies. One doesn't replace the other.

There are also serious (if obviously longshot) efforts by colleagues of mine to propose moon-based GW detectors: https://indico.ego-gw.it/event/263/

Isn’t to detect different frequencies it’s a matter of varying the distance between the detectors? Space based detectors can be placed arbitrary close or far, moved at will. Ground based is fixed. Also I remember isolation from Earth’s vibration was a huge if not the biggest engineering challenge. There’s no such problem in space.

Check out LISA.

https://lisa.nasa.gov/

note: I worked on the OG LIGO at Hanford in grad school.

When we have five or more detectors, will we be able to ‘see’ features of the earth’s interior using the discrepancies in the data?