What is a gravity hill?

Seen in the video above, gravity hills (also known as magnetic hills) are a phenomenon that occurs when a false horizon creates the illusion of moving against gravity.

If you drive over a gravity hill, you might feel like you're headed uphill, but if you let off of the gas pedal, you'll keep accelerating. Obviously, that makes for a fairly confusing experience; vehicles might seem to defy gravity, and on rainy days, water seems to rush back up the hill.

There are hundreds of gravity hills throughout the world. Prominent examples in the United States include Spook Hill (Fort Gaines, Florida), the Oregon Vortex (Gold Hill, Oregon), Mystery Hill (Boone, North Carolina), and our favorite, Booger Mountain (Cumming, Georgia).

As these colorful names imply, some people believe that gravity hills occur due to strange magnetic imbalances or supernatural influences. In reality, though, the phenomenon is fairly easy to explain: When traveling on the hill, you're actually on a slight downward slope, but the surrounding landscape gives the impression that you're traveling uphill. You can't see the horizon, so your brain infers that it's behind the "peak" of the hill.

The effect becomes more pronounced when other landscaping oddities come into play. For instance, if the trees surrounding the hill grow at a slight angle, they may appear to be perfectly straight, and drivers will have an even tougher time determining the slope of the land.

Essentially, humans need a clear view of the horizon in order to determine whether they're moving up or down. When the horizon is obstructed, we have trouble judging the slope of a surface. The effect even works if you know that you're being tricked--you'll still feel like you're defying gravity.