There is a goal of the Ultra-High Frequency Gravitational Wave Research Initiative: "Gravitational waves at frequencies above 10 kHz inevitably arise from something outside the physics of the Standard Model, such as exotic astrophysical objects or cosmological events in the early Universe." A very interesting goal, but with vagueideas about the causes of the appearance and properties of gravitational waves. Yes, there is a fact and experiments in detecting gravitational waves, in this case, astrophysical objects. But what is a gravitational wave in this case? There is an understanding that this is a periodic superimposition of "gaps" in space, in the direction of the source of such gravitational waves, that is, the rotation of two connected massive astrophysical objects, neutron stars, "black holes". It is even possible to build mathematical models of the rotation ofmassive spheres with a certain frequency, within the framework of certain equations. But mathematics answers the question HOW? And physics answers the question WHY? In the framework of Einstein's General Theory of Relativity, we are talking about the curvature of space-time near a source of energy-momentum, massive spheres in this case.And here many questions arise.