If you don’t believe in them, that’s OK. We believe in them ... whatever they are. There may be several explanations for them, including a few natural ones that nobody has thought about.

Some of it may be residual energy. The living human body produces an aura of energy that can be recorded with what’s called Kirlian photography. A photo of your hand, taken with this process, shows that aura. So will that of a freshly-plucked leaf from a tree.

My old friend Frank Calemine’s arm would have showed up on such a photo, and he lost it when he was hit by a train at the age of 10.

He was torn up pretty badly, and the story is that the doctors told his mother he wouldn’t survive the night.

“Sew him up so he’ll look good in his coffin,” she said, and that’s what they did.

Frank woke up the next morning and was hungry. Then, he woke up hungry every morning for the next 80 years. (Now he leaves pennies for me, but that’s a story for another time.)

“The worst thing about this arm,” he told me, “is that when it itches, I can’t scratch it.”

The laws of physics say that energy can neither be created nor destroyed. Where does our energy go when we pass on to the next world? Do we take all of it with us, or do we leave part of it behind?

Considering all the human misery that was experienced at places like Gettysburg, where an estimated 6,200 men were killed and another 33,000 were wounded, it’s understandable that plenty of energy might still be around.

Some of what we encounter may be the spirits of those who died so suddenly that they don’t know they’re dead — or they know they’re dead and are afraid to go on to what awaits them ... or they don’t know how to go on. I suspect some have gone ahead, but return now and then for reasons known only to them.

Or not. All of this is mortal speculation.

Some may be angels. Many faiths believe in the life eternal, and who is to say what form it takes? I don’t know, nor does anyone else. Only the Lord knows, and He’s not saying.

Others may be demons. I believe in them just like I believe in angels and therefore avoid demonic or any place where I think demonic might be. An unmistakable, indescribably uncomfortable feeling tells me to scram.

Some of it shows a sense of purpose ... or harmless mischief.

We sat in our Gettysburg motel suite for an hour or more, watching one variety of these manifestations on a computer monitor.

Our motel suite is haunted. We see them, we hear them talking (they asked Gary to shut the door between the rooms one night, then thanked him after he’d done so), and we smell them brewing coffee. I woke up one morning to find that my bedspread had been turned upside-down while I was asleep.

Our friend Reggie, who has a paranormal research team, set up strategically placed day-and-night vision cameras in both of our rooms and hooked them to a four-screen monitor so we could watch in realtime.

(I wondered how I was going to take a shower and get dressed without winding up on display, then hung my hat over the camera that was aimed into our bathroom.)

We like to watch Ghost Adventures with Zak, Nick, Aaron and Billy the tech guy, and we appreciate the way they go about it.

If something strange happens, they look for a perfectly natural explanation, and frequently they find one.

Some of their footage shows what are believed to be spirit orbs flying around, usually one at a time. Sometimes, there is no explanation. Many times, Zack and company debunk the orb as being dust or an insect.

There must be millions of photos that show what people think are ghost orbs. Most are only a trick played by the camera lens. The rest are some kind of energy. What kind? You tell me.

One giant orb that Gary and Reggie saw on the monitor flew right over my head while I was sitting on my bed, and I missed it.

While Zak and company are lucky to catch one undebunkable orb, we lost track of how many we saw. At times, it almost looked like it was snowing. Reggie said, “This is rare.”

They zoomed around by themselves, or in groups of two, three or even more, dashing and weaving — sometimes in formation — as if in one of those chaotic aerial melees that World War I fighter pilots called a “furball.”

They reminded me of a 101 Dalmations-sized litter of frolicking puppies.

Some were at least as a foot in diameter and went right for what are called “trigger objects” ... bait, if you will. In this case, the trigger objects were a cigar that Gary left on the table and our coffee pot. (Civil War soldiers craved tobacco and coffee.)

We could see none of this with the naked eye.

We’re waiting for a report on what else Reggie found on his digital audio and video recorders. I’m particularly interested to know what caused the flash of light I saw at 3 a.m. in the passageway that separates our rooms.

We also paid a couple of nocturnal visits to cemeteries — with quiet respect and prayers that those who rested there were at peace with the Lord and their loved ones. Unlike Zack and them, we do no taunting.

Harry and Cathy, our friends from Pennsylvania, joined us along with the Buffalo Gals (one of whom described how she once dashed across a field in a Civil War-period gown that had no bloomers of any kind beneath it; her friends call her “Running Bare.”)

Cathy has heard about our ghost adventures and wanted desperately to have one of her own. She got her wish in an old churchyard.

“I saw it! I saw it!” she called out in a voice that was (you should pardon the expression) loud enough to wake the dead.

“There was a shadow behind that headstone,” she said, “and it kept moving around and peeking out at me, over top of it and then from one side or the other like it was playing hide-and-seek!”

Ya know, it could be that they’re as curious about us as we are about them. We go ghost-hunting; maybe they go mortal-hunting.

Whoever they are.