Gravity Hills

There is a gravity hill, called “Spook Hill” just outside of Burkittsville, Maryland. If the name sounds familiar, you might remember it from the 1999 cult-classic, The Blair Witch Project. Unfortunately for Blair Witch enthusiasts, most of the movie was filmed about 25 miles away and the recognizable landmarks in the movie are not located in town or the area nearby.

Local legend holds that the spirits of disembodied Confederate soldiers haunt the area. It is these spirits—thinking they are pushing artillery uphill into position—that will push your car up the hill. For this to take place: bring your car to a complete stop at the bottom of the hill; put the vehicle in neutral; your car will then begin to move uphill and gain speed the further up the hill you go. I have personally reached speeds of 7–10 miles per hour.

As a side note, be very careful if you are in the area and attempt this. For a two-lane country road, there is more traffic than you might expect.

Of course, skeptics cannot accept a car moving uphill powered by disembodied Confederate soldiers. The riddle has been solved; Massimo Polidoro, writing for the Skeptical Inquirer, wrote:

The answer to this mystery is found using a simple tool. When the inclination of several such roads has been measured using spirit levels, the actual slope of the surface has consistently been found to be opposite to the apparent one. To answer the objection that gravitational anomalies would influence the level as well, my good friend and longtime colleague Luigi Garlaschelli, from the University of Pavia in Italy, also took measurements on an Italian spook hill in Montagnaga from a distance (i.e., away from the stretch of road in question) using a professional surveyor’s instrument called a theodolite.

The parallelism between a plumb line hanging within the critical area and another outside of it was first checked by Garlaschelli, then height quotes were taken on graduated yardsticks. The real slope was calculated at about 1 percent of the apparent slope in the opposite direction.

The simpler explanation for spook hills, then, is that they are visual illusions in a natural environment.1

Polidoro went on to describe in detail how researchers have been able to successfully recreate the gravity hills using a tabletop model. He wrote:

“The visual (and psychological) effects obtained in our experiments were in all respects analogous to those experienced on site,” the researchers concluded. “The more than twenty natural cases of antigravity hills reported to date are all variations on a single theme. Our study shows that the phenomenon can be recreated artificially, with no intervention whatsoever of magnetic, antigravitational, or otherwise mysterious forces. The spooky effects experienced at these sites are the outcome of a visual illusion due to the inclination of a surface being judged relative to an estimated eye level that is mistakenly regarded as normal to the direction of gravity. Using miniature or even life-size reproductions of our tabletop models, it should now be easy to re-create the fascination of this challenge to gravity in amusement parks and, for twice the benefit, science museums anywhere.2

Well, that really sucks.

Oh well, maybe Spook Hill is explainable, but I still prefer the local legend—I like thinking of ghostly soldiers pushing my vehicle rather than it being the product of an optical illusion. So, if you’ll pardon me, I’m going to stick with the legend—it’s a lot more fun.


Notes

1.) https://www.csicop.org/si/show/spook_hills_in_the_lab

2.) Ibid.