Why do cars roll up hill? Meaning of gravity hill explained

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Gravity Hills are an optical illusion that makes you feel like your car is magically rolling uphill when it’s actually going down

Have you ever hit a hill where your car will roll up?

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They make the driver feel like your car is magically rolling uphill when it’s actually going downhill.

One of the most common locations for this phenomenon is Electric Brae in Ayrshire on the A719 between Drumshrang and Knoweside.

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Turn off your car engine and your car mysteriously seems to roll uphill.

The small stretch of road has become a tourist attraction, with hundreds of visitors making the journey each year to try the Gravity Hill for themselves.

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Why is this happening? Here’s everything you need to know about it.

Why do cars roll uphill on the Electric Brae?

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Known locally as Croy Brae, this short 800m road appears to run uphill, but due to an optical illusion created by the surrounding landscape, all is not as it seems.

The sign warns of the strange goings on at Electric Brae. Image: Raymond Okonski [http://www.geograph.org.uk/profile/9875] (CC)

In the popular tourist spot, people travel to explore the gravity hill themselves.

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The curbside parking lane is the ideal place.

All you have to do is put your car in neutral going downhill and like magic the vehicle will roll backwards up the hill instead of rolling forward.

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Locals have developed their own theories and explanations for the Strait, from a buried string of powerful magnets, minerals in the rich coastal soil, false gravity and suspicions that the Brae is haunted by witches.

However, there’s a simple explanation: the hill is a gravitational hill, an optical illusion that makes drivers think they’re going uphill when they’re actually going downhill.

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Influenced by the horizon line, the peak of the rise is actually at the bottom of the hill.

The optical illusion that the road is uphill is influenced by the slope of the landmass.

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What is a gravitational hill?

The hill at Electric Brae and similar ones are called gravitational hills.

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Gravity hills are where a descent looks like a climb due to the surrounding landscape.

This creates the optical illusion that a coasting car is rolling uphill when it’s actually rolling downhill.

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How does a gravity hill work?

Gravity hills are an optical illusion.

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Although the slope is often thought of as being uphill, it is actually downhill.

The most important influence on a gravity hill is an obscured horizon, without being able to see a horizon clearly it can become difficult to judge the slope of a surface.

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Objects that you would expect to be straight like trees can be beveled, adding more confusing effects.

A 2003 study examined how the inability to see the horizon can affect a person’s perspective of gravitational hills.

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Researchers from the Universities of Padua and Pavia discovered that without an unobstructed horizon in sight, our brains can be fooled by ordinary landmarks like trees and signs.

Despite the scientific justification, many gravitational hills often come with supernatural claims that magnetic forces or even spirits are behind the phenomenon.

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Where are other gravity hills in the UK?

There are seven gravity hills in Britain.

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Here’s a full list of all the confirmed hills in the UK that cars will roll up.

  • Birmingham: Harborne Walkway Harborne
  • Buckinghamshire: Dancers End Lane Aston Clinton
  • Essex: Hangman’s Hill High Beech Epping Forest
  • West Sussex: Rogate on the A272
  • County Down: Morne Mountains off the B27
  • Ayrshire: Electric Brae on the A719
  • Powys: Llangattock (Crickhowell) Brecon Beacons

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