Amazing Places

Gravity Hills Seem to Defy the Laws of Physics

Imagine standing at the top of a hill and tossing a ball down the slope, only to watch it mysteriously roll right back to you. That's the essence of a gravity hill: a slope that seems to defy the laws of physics. Spoiler alert: The laws of physics still apply here, but the reasons why they don't seem to are fascinating.

A gravity hill where slow speed cars are drawn against gravity is famously known as "Magnetic Hill."

Illusions on a Very Large Scale

Though some might say these hills are caused by a quirk in Earth's gravity (it's in the name, after all), and others might point to a magnetic field fluctuation, the explanation is a whole lot simpler: It only looks like things are rolling uphill. It all comes down to the scenery.

A 2003 study in Psychological Science concluded that the illusion of a gravity hill was usually caused by one of two things. The first is the horizon: If you can see the spot on the horizon where the road vanishes, your brain interprets that road as being level, even if it has a steep slope. Likewise, if the horizon appears high, you interpret the road as being downhill and vice versa, regardless of the actual slope.

The second cause was "contextual slope"; that is, you judge the slope of one hill by the slopes of those around it. According to the study, "when preceded, or followed, or flanked by a steep downhill slope, a slightly-downhill stretch is perceived as uphill." In a Science Channel video, UK psychologist Rob Macintosh says something slightly different but similar is at play on a gravity hill in Aryshire, Scotland. "We're standing within a tilted landmass," he says. "The whole landscape tilts this way, and the road tilts in the same direction, but by a smaller amount, so the relative slope appears to go the [opposite] way."

Confusion Hill amusement park in Mendocino County, California.
Magnet Hill, a gravity hill located near Leh in Ladakh, India.

See For Yourself

There are dozens of these hills throughout the world. There are more than 20 in the United States alone, including Confusion Hill in Northern California and Spook Hill in New York. Canada has Magnetic Hill, Brazil has Rua do Amendoim, and Ireland has The Magic Hill, among others. They're common enough that the one closest to you probably isn't more than a few hours' drive. So what are you waiting for? For the look on your friends' and family's faces, the trip is definitely worth it.

The Road Where Cars Roll Uphill

Key Facts In This Video

  1. In Ayrshire, Scotland, there is a hill that seems to make cars roll uphill. 00:05

  2. A hill in Ayrshire, Scotland is an optical illusion where, based on its surroundings, the top of the hill looks like it's the bottom. 01:33

  3. See a demonstration of how a car can seemingly roll "up" a hill: 02:45

Written by Ashley Hamer March 19, 2017

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