Searches for Extraterrestrial Intelligence (SETI) have mostly adopted one of two strategies: surveying the whole sky (or large parts of it) looking for sources that stand out from the natural noise of the cosmos in some way, or targeted searches, where a list of stars chosen for properties believed conducive to or prerequisites for the origin of life and its development into a technological civilisation (for example, large, hot stars whose lifetimes are much less than life on Earth took to develop complex life are unlikely to have planets where life evolved spontaneously).
In this talk, Vishall Gajjar, now working with the Breakthrough Listen project, makes the case for “bulk searching” by, for example, aiming one’s telescope toward the centre of the Milky Way galaxy. While the actual centre of the galaxy is believed to be inhospitable to life (but who knows?—there’s a lot of energy to be had there and it may be where all the cool civilisations hang out once they figure out how to get there), looking in that direction picks up all of the millions of stars along the path from the Sun’s location to the galaxy’s central bulge, sampling a wide variety of galactic radii and star life histories without a priori assumptions about which are most promising to host advanced civilisations.
The galactic centre itself is a landmark which will be obvious to any civilisation in the galaxy that indulges in astronomy and might be just the place to put a beacon, powered by energy extracted from the central black hole, to invite others to join the Galactic Club (or, perhaps, inform grabby aliens in other galaxies, “This one’s taken—keep on looking).