There have been theories that this Earth was hollow. The author does not subscribed to this, however, the author has been interested in the data presented by Jim Marrs in his book Alien Agenda, Harper and Collins 1998. It gives support as to why the moon might be hollow.
Per Marrs, the moon is not a natural satellite of Earth and the arrival of the moon could be what ended the last ice age only 11,700 years ago. From the compelling evidence in Marr’s book it appears the moon may have arrived here about then. The moon is made from a very different composition than Earth. It seems to be older than Earth. Marr’s book is worth buying and reading cover to cover.
The moon is an anomaly. We also do not get to see the reverse side of the moon naturally.
There are also reports of UFO sightings from the moon, even by the astronauts themselves. Then there are UFO reports from people observing the moon through telescopes; too many to take up here.
HG Well used the hollow Earth concept, but he was not the first.
William R Bradshaw’s novel The Goddess of Atvatabar had a hollow Earth as central to the story. In this story was Interior World.