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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
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
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
. Hundreds of gravity hills are recognized worldwide.
The slope of gravity hills is an optical illusion, 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 is missing. Objects which one would normally assume to be more or less perpendicular
In elementary geometry, two geometric objects are perpendicular if they intersect at a right angle (90 degrees or π/2 radians). The condition of perpendicularity may be represented graphically using the ''perpendicular symbol'', ⟂. It ca ...
to the ground, such as trees, may be leaning, offsetting the visual reference.
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
Pavia (, , , ; la, Ticinum; Medieval Latin: ) is a town and comune of south-western Lombardy in northern Italy, south of Milan on the lower Ticino river near its confluence with the Po. It has a population of c. 73,086. The city was the cap ...
in Italy found that without a true horizon in sight, the human brain could be tricked by common landmarks such as trees and signs.
The illusion is similar to the Ames room
An Ames room is a distorted room that creates an optical illusion. Likely influenced by the writings of Hermann Helmholtz, it was invented by American scientist Adelbert Ames Jr. in 1946, and constructed in the following year.
Usage and effect ...
, 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".
See also
*List of gravity hills
This is a list of gravity hills and magnetic hills around the world.
A gravity hill is a place where a slight downhill slope appears to be an uphill slope due to the layout of the surrounding land, creating the optical illusion that water flows up ...
* The Crooked House
The Crooked House is a pub and restaurant in South Staffordshire, England.
Its name and distinctive appearance are the result of 19th-century mining subsidence. One side of the building is now approximately lower than the other.
It stands ...
– a building with an internal gravity hill optical illusion.
References
External links
* {{Optical illusions