Yes, it is possible to use gravity to detect galaxies that are beyond the limits of what we can observe through electromagnetic radiation. This approach is known as gravitational lensing.
Gravitational lensing occurs when the gravitational field of a massive object, such as a galaxy or a galaxy cluster, bends the path of light from a more distant object behind it. This bending of light can create magnification, distortion, and multiple images of the background object.
In the case of galaxies beyond our observational limits, their light might be too faint or absorbed by intervening matter. However, their gravitational influence can still be detected. When a foreground galaxy or cluster acts as a gravitational lens, it can distort and magnify the light from the background galaxy, making it observable indirectly.
By studying the gravitational lensing effects, astronomers can infer the presence and properties of these otherwise invisible galaxies. The precise measurements of the lensing phenomena allow scientists to reconstruct the mass distribution of the foreground lens and model the characteristics of the background galaxies.
Gravitational lensing provides a powerful tool for studying the large-scale structure of the universe and understanding the distribution of dark matter, as well as detecting and studying galaxies that would otherwise be beyond our observational reach.