[ApS]

Opened an astrophysics page, and found this revelation:

Luckily, it’s possible to learn something from the host of weaker signals that collectively form an unresolved background (Fig. 1).

Think of listening to frogs croaking in a swamp: We can pick up clear songs from the nearest frogs, but we can also hear an indistinct hum from the thousands of frogs that are farther away. The volume of this background hum provides a measure of the frog population. Similarly, the amplitude of the unresolved background in LIGO and Virgo’s detectors can tell us about distant black hole mergers that occurred when the Universe was much younger.

Source: https://physics.aps.org/articles/v11/36