As much as I enjoy kicking back on a hot summer day with a big mint julep and worrying myself sick about things I have no control over, I had never given much thought to an invasion by alien beings – until I saw “Signs.”

Now, however, I am obsessed with the idea, to the point where I refuse to leave the house without Secret Service protection.

For those who’ve yet to catch M. Night Shyamalan’s latest spookfest, I won’t spoil the ending by telling you that it features hundreds of scrolling credits and a disclaimer stating that no extraterrestrials were harmed in the making of the film.

What I will tell you is that it centers on the mysterious, centuries-old phenomenon of crop circles.

These are images formed overnight on our planet’s landscape, often in the shape of pendants worn by the Rev. Al Sharpton, only smaller.

They’re formed by strategically flattening the stalks in corn, barley and other grain fields, coincidentally located within stumbling distance of breweries and distilleries.

Crop circles, some up to 800 feet in diameter, have also shown up in snow, sand and grass, the latter after an eerie incident at the Pebble Beach Country Club involving several runaway golf carts.

The earliest known depiction of a crop circle is found in an English woodcut from 1678, whose caption reads, “Headless Barley in Wiltshire Topsoil.”

Since then, appearances have been documented on all seven continents, though Britain still holds the record for number of circles formed in the precise likeness of Benny Hill.

Their significance has long perplexed amateurs in the field, known as “croppies,” as well as professionals, known as “cerealogists” (a term I’d love to take credit for inventing, but, disturbingly enough, is real).

Over the centuries, one of the most widely embraced theories has been that crop circles are cryptic messages from God, such as (a) “The end is near,” or (b) “We’re only halfway there, so brace for another 5,000 years of intense pain and suffering.”

More recently, it is believed, they are navigational tools for alien life forms infinitely more advanced than our own, beings who spend an average of $32 trillion per mission to Earth, and thus don’t want to make a wrong turn somewhere and wind up on Pluto.

Their impact on human civilization, meanwhile, is anything but cryptic.

Visitors to the sites of well-known crop circles have experienced dizziness, nausea and blackouts upon being charged $64.50 for a souvenir glow-in-the-dark corncob.

But it is dogs – their senses extraordinarily fine-tuned through millennia of sniffing each other’s private regions – that react most severely.

In the days preceding the appearance of a crop circle, they will bark incessantly for hours before cowering dramatically behind a barn, as if to say, “Have I got the chops to play myself in the movie, or what?”

Which brings us to my original point (and thank goodness, too, because the julep kicked in a while back, so I hadn’t the faintest idea where I was were going).

My fear is that, despite the origin of the countless crop circles that have appeared to date, aliens will see “Signs” and feel compelled to live up to their reputation as repulsive creatures out to destroy the civilization we know and love, thanks to 24 hours a day of History Channel programming.

It may be only a matter of time before the invasion begins.

Unless, of course, we can convince them to see “Lilo and Stitch” instead.