Hollow earth makes more sense to me than flat Earth. Do I think it's completely hollow? No but there are many caves and caverns and tunnels everywhere. Many of them are to big to map out. Like @fulltimegeek said check out Phil Schneider on you tube. He was a geologist for the government and committed "suicide" in the early 90s by strangulation with a catheter tube. He claims to have battled aliens and his hand is half melted off .