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Water appearing to run uphill at Magnetic Hill in New Brunswick

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] There are hundreds of recognised gravity hills around the world.

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 to judge the slope of a surface as a reliable reference is missing. Objects which one would normally assume to be more or less perpendicular to the ground, such as trees, may actually be leaning, offsetting the visual reference.[3]

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

A similar phenomenon—an uphill road that appears flat—is known in bicycle racing as a "false flat".[4]

See alsoEdit


  1. ^ University of California Riverside article on phenomenon
  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. Free full text
  3. ^ "The Mysterious Gravity Hill:Physicists Show "Antigravity" Mystery Spots Are Optical Illusions". Science Daily. Archived from the original on 2008-02-17.CS1 maint: BOT: original-url status unknown (link)
  4. ^ 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