Someone who seems to be French / Canadian? read my hollow earth article a few years ago, where I suggested that someone get down a mile into a mine and take gravity measurements. It seems that has been done! But I don’t read French. Check out these photos of the mine, gravity graphs, etc. The experimenter seems to be saying that his data says the Earth is hollow.
“If the geologists, for their part, opted for the ferrous liquid, my experiment, in Timmins’s mine in the North East of Ontario in the Canadian Shield, show clearly that it would be rather about gas (space or air)…”