There is no idea so stupid that you can’t get a collection of the gullible to believe it. Just Google “hollow Earth” and see what you get – 223,000 hits is what you get.

In times when we knew far less, some well known names speculated about the earth being hollow. They included both Edmund Halley (he of the famous comet) and Leonard Euler (one of the greatest mathematicians of his era). By the 20th century, the idea was less fashionable and credible. Nevertheless, in WW2, Hitler sent an expedition to Rugen, a Baltic island, where a Dr Heinz Fischer tried to use a telescope (pointed skyward) to photograph the British fleet on Scapa Flow, across the hollow interior of a concave earth. Yes, I know it sounds unlikely, but records indicate that it happened. The British fleet, completely unaware of this dastardly plan, only managed to evade detection by sheer luck. As luck would have it, the earth is not hollow.

The hollow earth nuts can be classified into two camps; those who believe that the earth is hollow and we live on the inside (see Cyrus Teed’s theory – you simply cannot trust any of those rigged NASA photos of the globe – it’s all a conspiracy) and those who believe that we live on the outside of a globe but there are cities of aliens and such buried under ground and hidden from us.

The second theory has a greater number of adherents. It’s easy to see why. With a well-imagined underground civilization you can explain anything unusual that happens to us surface folk, from the sudden appearances of Elvis to the rapid vanishing of UFOs. Admittedly wormholes are also good for explaining such things, but the hollow earth has the added attraction that you can draw imaginative maps of the underworld.

So where are the gateways to the underworld? Conveniently located in the regions of the North and South Pole, of course. Now don’t get all skeptical on me and insist that the North Pole is just one big floating iceberg. So what? The gateway is not on land. It’s at sea. If you sail north east of Franz Josef Land (around Latitude 84.4 N Longitude 141 E) you will sail straight in. That apparently is what Olaf Jansen did, and when you read his account of the 12 foot men and mammoths he met with, your skepticism melts away like ice in a freezer.

If you prefer the South Pole gateway, then my advice is to follow in the path of Admiral Richard E. Byrd, who flew 2300 miles beyond the South Pole and entered a “new unknown territory not shown on any map”. It’s a bit of a bummer, I know. If it’s not shown on any map, then finding it is going to be problematic.

But hey, don’t worry. Why not take one of the hollow earth expeditions that are advertised on the web. I’d provide links, but I don’t need to. Just Google “hollow earth” and “expedition” (23,000 hits!). “We are now signing up Expedition Members For Our First Voyage to Inner Earth via the North Polar Opening!” one site proudly proclaims.

And if you’re going to sign up for this then - hey listen, I’ve got this really cool invisible fish to sell you. Just send me your credit card details etc. etc.