In February 2016 researchers confirmed the existence of gravitational waves. Now they have proven, at least mathematically, that the lunar tide is a type of low frequency gravitational wave.
The study of gravitational waves are important because 1. they help bridge the gap between general relativity and quantum mechanics, the further study of which may lead to a Unified Field Theory of Quantum Gravity and 2. If you can learn to control them you may be able to come up with a measurement device or new form of communication that can traverse space through areas electromagnetism (light) cannot.
When objects in outer space move toward each other they often begin to converge, losing angular momentum. As they continue careening in to one other’s gravity well they emit gravitational waves in the direction they were moving prior to convergence. Similar to objects in a water vortex- they send ripples through out space and time, squeezing and stretching it at magnitudes smaller then a proton.
Furthermore, when the two objects eventually collide they can produce an even larger wave. However technically speaking, any source of gravity can produce a gravitational wave.
Now physicists Riturparno Goswani and George Ellis have proven, at least mathematically how the tidal force, stemming from the moon proximity to Earth, is a type of gravitational wave on it’s own, nonetheless at a different magnitude.
It is relatively well-known that a body of water facing the moon will exhibit a stronger rythmic tide, which has long been attributed to the force of gravity albeit with no in depth explanation until now.