Comments by "H. de Jong" (@h.dejong2531) on "The Moon Revealed: It's a Hollow Spaceship, so who built it and why?" video.

On Earth, seismic shocks are damped quickly by Earth's mantle and by the abundant water in the crust. The Moon has neither, so seismic chocks reverberate longer. We know the moon is not hollow because we have weighed it: from its orbit, we can calculate the moon's mass. The mass we found can only be achieved by a solid body.
2
@janethayes5941 No, nobody serious thinks the moon is hollow. On Earth, seismic shocks are damped quickly by Earth's mantle and by the abundant water in the crust. The Moon has neither, so seismic chocks reverberate longer. We know the moon is not hollow because we have weighed it: from its orbit, we can calculate the moon's mass. The mass we found can only be achieved by a solid body.
1
@dom_ferris_ As evidence for the moon landings, we have 382 kg of moon rock, hours of live TV, hours of film, thousands of photos, stacks of measurements and scientific results, eyewitness accounts, and photos of the landing sites made by later lunar orbiters. Detailed analysis of the physics and engineering required shows that it is possible to land on the moon with 1960s technology. No moon landing denier has ever produced convincing evidence of his claims. Every single argument they make turns out to be based on a basic lack of understanding of physics, misinterpretation of words, pareidoilia or flat-out lies.
1