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Gravity hill

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Water appearing to run uphill at Magnetic Hill in New Brunswick
Magnetic Hill in Moncton, Canada

A gravity hill, also known as a magnetic hill, mystery hill, mystery spot, gravity road, or anti-gravity hill, is a place where the layout of the surrounding land produces an optical illusion, making a slight downhill slope appear to be an uphill slope. Thus, a car left out of gear will appear to be rolling uphill against gravity.[1]

The slope of gravity hills is an optical illusion,[2] although sites are often accompanied by claims that magnetic or supernatural forces are at work. The most important factor contributing to the illusion is a completely or mostly obstructed horizon. Without a horizon, it becomes difficult for a person to judge the slope of a surface, as a reliable reference point is missing. Objects which one would normally assume to be more or less perpendicular to the ground, such as trees, may be leaning, offsetting the visual reference.[3]

A 2003 study looked into how the absence of a horizon can skew the perspective on gravity hills, by recreating a number of antigravity places in the lab to see how volunteers would react. As a conclusion, researchers from Universities of Padova and Pavia in Italy found that without a true horizon in sight, the human brain could be tricked by common landmarks such as trees and signs.[4]

The illusion is similar to the Ames room, in which objects can also appear to roll against gravity.

The opposite phenomenon—an uphill road that appears flat—is known in bicycle racing as a "false flat".[5]

See also[edit]


  1. ^ "Can Things Roll Uphill?". Math.ucr.edu. Retrieved 8 April 2022.
  2. ^ Bressan, Paola; Garlaschelli, Luigi; Barracano, Monica (2003). "Antigravity Hills are Visual Illusions". Psychological Science. 14 (5): 441–449. doi:10.1111/1467-9280.02451. PMID 12930474. S2CID 10405595. Free full text
  3. ^ "The Mysterious Gravity Hill:Physicists Show "Antigravity" Mystery Spots Are Optical Illusions". ScienceDaily.com. Science Daily. Archived from the original on 2008-02-17.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
  4. ^ "These Gravity-Defying Hills Are One of The Strangest Natural Phenomena We've Seen". ScienceAlert.com. 6 March 2017. Retrieved 8 April 2022.
  5. ^ Schweikher, Erich; Diamond, Paul, eds. (2007), Cycling's Greatest Misadventures, Casagrande Press LLC, p. 114, ISBN 978-0-9769516-2-9, retrieved July 20, 2013

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