Are Doppelgangers Real? There's a 1 in a Trillion Chance

The word "doppelganger" comes from German and means "double-goer" or "double walker," a person who looks exactly like you. Unlike identical twins who share the same genes, a doppelganger has no relation to you but would have the same facial features as you.

In pop culture, doppelgangers are often evil entities that might signal bad luck. According to Vulture, TV and film have used these twin strangers to show the dichotomy between good and bad: "On 'The Leftovers' and 'Twin Peaks,' the trope serves another of its traditional functions: to highlight the symbiotic relationship between good and evil."

Fortunately for those of us who scare easily, the math says that the chances of you having your own doppelganger who shares your same facial appearance is just about impossible. So you don't have to worry about a case of mistaken identity.

"If we are talking about measurements of the face, there is a 1 in a trillion chance that two or more people will match one another on eight measurements of the face," emails Dr. Teghan Lucas, forensic anthropologist at The University of New South Wales and Flinders University, both in Australia.

She published a study on the subject of doppelgangers in 2015 where she compared people for eight facial and eight body measurements to see how alike they really were. Some of the fastidiously precise facial and head measurements she refers to include ear length, head circumference and the distance between the centers of the right and left pupils.

Hopefully, such an explanation gives you peace of mind, but if it doesn't, just know that when Lucas looked at the rest of the human body, she found that the odds of having a twin stranger were even bleaker.

"If we look at measurements of the body, the chance is even lower at 1 in a quintillion, based on eight measurements," she says. "This is because these measurements are larger and thus have a larger range which means there is less chance for people to match each other."

So the more measurements you consider, the less likely it is that anyone's going to 100 percent stack up against another person in true doppelganger fashion. "Two people may look very similar to the naked eye, but when you start measuring they will not match each other," Lucas says.

Despite these odds, many of us have had the experience of being approached by a stranger and asked if we were someone we weren't, or the identical twin to someone we don't know. So it's tempting to believe in the potential for doppelgangers.

"A lot of the people we see as doppelgangers are people we don't know very well," explains Dr. Michael Sheehan, a neurobiologist at Cornell University.

"You're a lot more likely to see a doppelganger of an acquaintance than your mom. You know your mom really well. If someone looks similar you can appreciate it," he says, adding that you'd nonetheless be likelier to quickly spot the differences if you know a real person intimately, as opposed to someone you don't know as well.

"There's only so much variation out there," he says. "Some people will happen to look similar."

Just because doppelgangers aren't really a thing doesn't mean that researchers will stop their investigation into body characteristics any time soon.

In fact, the subtle differences in human features are becoming more important in criminal investigations, as found by Lucas and co-researchers in the International Journal of Legal Medicine study.

"We looked at whether the face really was the best for identification and we found that it wasn't; measurements of the body are more unique than those of the face," Lucas explains. "This is extremely useful as many criminals who are caught on CCTV systems (such as those robbing a bank) cover their face, so we needed to find out if we can use the body in the same way as the face is used and we can!"

Even if you do run across someone who looks eerily similar, it's likely time, hairstyle and other factors will distort any doppelganger potential.

"Growing up one of my younger brothers was like the spitting image of me when I was 3," Cornell's Sheehan says. But time has done a number on that. "We look similar-ish now, but not the same."