You’ve almost certainly heard about the flat earth theory — the evidence-denying belief that the world isn’t (mostly) round but, in fact, flat. But have you ever heard of the hollow earth theory? This is the idea that the earth is either entirely hollow or contains a large interior space that is capable of hosting life and, in some iterations of the theory, is home to species longthought extinct by us ignorant surface-dwellers and perhaps some species that we have never encountered at all. While many mythologies speak of a world inside our world, the ‘modern’ version of this theory can be traced to astronomer Edmond Halley (of Halley’s Comet fame) who first suggested this possibility. One early believer was American businessman John Symmes who built on the theory by suggesting that this inner world could be reached through giant holes in the earth’s polar regions, and even proposed sending expeditions to find these access points.
Others went even further by declaring that this Hollow Earth world was dominated by intelligent reptilian (and possibly alien) races and giants who are (in some iterations of the tale) the secret masters of humanity, pulling our strings from the unseen depths. While this may sound far-fetched I, for one, would be relieved to learn that someone is running this absolute mess on the surface. Unfortunately, this rather lovely theory has been conclusively debunked, and the only mentions you’ll now find of the Hollow Earth are relegated to pseudoscience and science fiction. But the earth still holds many mysteries, as Chinese spelunkers discovered earlier this year when they came across a 630-metre-deep sinkhole in south China. At the base of the pit, the explorers found a massive and “well-preserved primitive forest” with ‘prehistoric’ looking trees that grew to heights of over 30m.
Essentially, they found a unique and isolated ecosystem that had survived and thrived untouched by human hands for millennia, and researchers are interested in seeing if it is home to animal and insect species that cannot be found anywhere else on earth. Given that the sinkhole is also home to several cave entrances, a more thorough exploration may result in even more discoveries similar to the ones made in other lightless cave systems which were once considered to be too sulphureous to be home to any kind of life. But when such caves, such as the Frassasi Caves in Italy or those in Tabasco, Mexico, were explored, they were found to host a variety of creatures uniquely adapted to life in this hidden world. This is possible thanks to extremophiles, organisms known affectionately as ‘snottites’ or ‘snotticles’ because the massive colonies they form on the walls and roofs of these cave structures look exactly like … snot.
Apart from looking pretty, these snottites feed on sulphur and in turn provide sustenance for a variety of spiders, midges, gastropods and even large colonies of blind fish that feed on the snottites. Then there’s the cave of crystals in the Mexican Naica Mines, where the lowest temperature is about 47 degrees Celsius and the humidity reaches close to 100 per cent. Impossible to explore without protective gear, the cave, as the name suggests, is home to giant crystals (google it and be amazed!) which, in turn, contain pockets of fluid that are home to dormant microbes that may be 50,000 years old. The deeper you go, the crazier it gets: while we have yet to find any reptilian aliens, scientists have speculated that the pressure in the depths of the earth is so immense (roughly 200,000 times what we experience on the surface) that it creates minerals and substances that cannot exist on the surface of the earth, and which would melt if they were brought to the surface. That’s not as far-fetched as it may seem as deep-sea fish found some 7.5 kilometres below the ocean’s surface in the depths of the Atacama Trench are so perfectly adapted to the high-pressure depths that when they are brought to the surface by nosy researchers, they simply … melt.
Are there minerals with similar properties? Until recently, scientists had only informed speculation and lab experiments to go by; in one such experiment scientists simulated the conditions that exist in the earth’s mantle and synthesised a mineral they dubbed ‘davemaoite’. But then, just last year, mineralogist Oliver Tschauner and his colleagues were going through samples of volcanoejected diamonds (essentially diamonds ejected from the earth’s mantle via volcanos) and found that deep within the diamond was an actual, naturally occurring sample of this very mineral — formed about 645 km under the Earth’s crust — and kept from melting thanks to being encased in the diamond. Today, we are transfixed by images of distant galaxies coming to us via the James Webb telescope but tomorrow, perhaps we will have the capability to further explore the hidden worlds within our own.