Chances are that you have never had reason to contemplate quantum mechanics, alternative rock music, your own neighborhood and hidden treasure in the same context. Unless, perhaps, you live close to a physics facility on a tropical island populated by music geeks, or have participated in the sport of geocaching.

The theory of parallel worlds, first proposed in the 1950s by American physicist Hugh Everett III (dad of Mark “E” Everett, front man of the alternative rock band Eels), contends that multiple realities exist simultaneously. Ever since then, the greatest minds in quantum mechanics have tackled the theory with complex equations. They should take a hike. Literally.

There is a whole other world waiting to be discovered here and now, and all you need to find it is a GPS device (most smartphones include one) and free registration to a website, www.geocaching.com. In an instant, you are admitted to a global community, and your perception of your environment is permanently altered.

Geocaching effectively began on May 2, 2000, when the U.S. government lifted restrictions on the public use of GPS technology. Suddenly it became possible for someone to hide a container — a cache — and for others to find it using GPS coordinates.

From modest beginnings near Portland, Ore., the sport rapidly went global. With more than a million caches now concealed all over the world, there are almost certainly some within a mile or two of where you are now.

Geocachers belong to an informal fellowship. Outsiders are referred to as “muggles,” and it is important not to raise their suspicions when you’re out hunting for a cache. Geocaching, you soon learn, is a world of secrets and of hidden treasure.

I was oblivious to this parallel reality until my brother and nephew admitted me to the fellowship a few months ago. Our first cache involved deciphering a clue. We were initially directed to the local churchyard, where we were prompted by the instructions on the website to convert a headstone inscription into a sequence of numbers. These were the cache coordinates.

We eventually found the cache about a mile away, concealed in the roots of a tree that I had walked past countless times. Inside the container there was a logbook and pencil for us to record our details and some miscellaneous pieces of “treasure” which could be exchanged for something of equal value. My nephew decided to keep a small plastic dinosaur in exchange for a key ring. We then carefully replaced the cache and discreetly returned to the path without being noticed by a couple of dog-walking muggles.

The extent of this other reality is revealed on the geocaching website. Cache locations comprehensively speckle a map of the world. Not even Antarctica is untouched.

At its most basic, geocaching is an ideal outdoor pastime for the entire family. But it is also an activity that lends itself to an ascending scale of physical and mental challenges. There are caches concealed in some of the world’s most difficult mountain ranges. For me, geocaching might just shed some light on Hugh Everett’s mind-boggling theory.

Having begun to look at my surroundings through the knowing eyes of someone aware of the extensive network of hidden caches, when I observe unsuspecting muggles I gain some small understanding of how two realities can occupy the same space at the same time.

There really is a parallel world, and it doesn’t require expertise in quantum mechanics or endless reams of equations to prove it. All you need is a smartphone, access to the website and a sense of adventure.