It’s little wonder early civilizations were fixated on astronomy. Each night, after their skies faded to black, only the moon and stars offered protection from the imagined dangers lurking in the shadows.

The ancients also had a superstitious eye towards the ground underfoot, since it proved as mysterious to them as the heavens. Naturally, metaphysical concepts associated with subterranean spaces like Hades, Sheol and Hell developed within many societies. Like their celestial counterparts, the terrestrial beings of lore were usually bestowed with superhuman characteristics, whether they were ascended ancestors, gods or devils.

Here are a few examples:

· Buddhism: A race of advanced beings inhabit vast underground cities. They occasionally visit humans to aide in our development as a species.

· Hindu: A civilization of serpent people, the Nagas, dwell in the subterranean cities of Patala and Bhogavati. The Nagas abduct, torture and eat human beings.

· In Irish myth, a tunnel in northern Ireland leads to a realm inhabited by a non-human race that introduced Druids.

· In North America, the Iroquois believe their ancestors had originated from inside the earth.

· In South America, Brazilian Indians say their ancestors emerged from an underground world and many still remain.

I was surprised to learn the basic tenets of these ancient beliefs, dating back many thousands of years, had survived into the 20th century as the Hollow Earth Theory. The Hollow Earth Theory has several variations, but they all profess within our planet exists a central sun, oceans, continents and advanced civilizations.

Edmund Halley (Halley’s Comet) proposed this hollow Earth model in 1692. He derived this complex idea while trying to explain the fluctuations in the Earth’s magnetic field.

This is the most popular hollow Earth model. As depicted here, the inner world is accessible through polar holes measuring hundreds of miles across. Also, our planet’s interior has its own ocean, continents and sun.

The latest version of the hollow Earth theory was developed after technology and exploration proved giant holes in the polar regions did not exist. So, it’s the same model as Polar Holes mentioned above, but without the polar holes.

To me, it seems unlikely that millions of enlightened subterranean lizard men are basking under a sun hidden within our planet. I’ve read the evidence and I’m just not feeling it. On the other hand, just because I can’t plot Hell on my iPhone doesn’t entice me to live like it doesn’t exist.