Nature all around us has many surprises and mysteries stored in it.  Some of these are being observed and tried to be explained by human and many more are still to be explored and answered.  Gravity hill or magnetic hill or mystery hill is called by many names and exists at many places all over the earth is also one of such mysteries of nature which people experience and try to put to various explanations. Gravity hill is a place where an uphill slope on the road acts as a downhill slope and bodies/vehicles moving there seems to be moving on their own without the use of engine power and appear to be working against gravity. As per internet information resources, places with such a phenomena have been reported in almost thirty five countries.  In India, magnetic hill located near Leh at Ladhak has been a place of attraction to people and country like UK has four such places where as USA is reported to have as many as twenty seven such places.

Explaining the phenomena

Gravity hills seem to defy the laws of physics. If an object, for example, a ball, is placed on a slope, it should naturally be pulled downwards by gravity. On gravity hills, the opposite appears to occur, i.e. the object moving upwards instead. Numerous explanations have been suggested to account for the existence of these hills. Sometimes, these are reflected in the names of such hills. The name ‘gravity hill’, for instance, suggests that the gravitational pull of such hills is uneven, i.e. the force at its bottom is weaker than that higher up, therefore causing objects to move up its slope. It is true that gravity is not uniform everywhere on earth. For instance, areas closer to the earth’s equator experience a slightly weaker gravitational pull than those situated farther away from it. Nevertheless, it has also been pointed out that there are no known areas where it has been scientifically proven that gravity does not act the way it is supposed to act. Thus, the explanation gravity hills are the result of a difference of gravitational pull between the top and the bottom of the slope is perhaps not quite feasible after all.

Gravity hills are a type of slope where things seem to move against gravity on their own accord. For instance, if water is poured onto the surface of the hill, it would seem to move upwards, instead of in the opposite direction, as one might expect it to. A 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. The layout of the area and surrounding slopes create the appearance of a hill. The hill road is actually a downhill road. Objects and cars on the hill road may appear to roll uphill in defiance of gravity when they are, in fact, rolling downhill. Another explanation, which is also perhaps the most plausible, attributes the existence of gravity hills to optical illusion. According to this explanation, the lay of the land and the surrounding landscape create an optical illusion, thus making us think that the downward slope of a hill is in fact one that goes upwards. Gravity hills continue to be a source of wonder, as the effects of the optical illusion can be quite convincing, even when one is aware of how they are formed.

These bizarre natural phenomena are just an elaborate optical illusion - an illusion so good, it'd be impossible to believe it without the proper equipment. The actual scientific explanation is required for every such slope we you encounter on earth where things seems to be working against gravity. With the help of some surveying equipment or GPS markers which actually can measure the difference between the 'top' of the slope and the 'bottom', we will realize that everything is actually in reverse.  The embankment is sloped in a way that gives the effect that we are going uphill where as we are, indeed, going downhill, even though our brain gives us the impression that we're going uphill. Researchers built tabletop models of several gravity hills around the world, and got volunteers to peer at them through a hole that gave them the perspective of actually being there. They then messed around with the horizon in the model to see how that would affect the volunteers' perspective on which way the slope ran. They found that without a true horizon in sight, landmarks such as trees and signs actually played tricks on the volunteers' brains. It is found that perceived slope depends on the height of the visible horizon; that surface slant tends to be underestimated relative to the horizontal plane; and that when preceded, followed, or flanked by a steep downhill slope - a slightly downhill stretch is perceived as uphill.  The visual (and psychological) effects obtained in experiments were in all respects analogous to those experienced on site. According to psychologists, it's all about the horizon - either it's obscured in areas with gravity hills, so we don't have a proper point of reference, or the horizon is there, but it obscures how the hill slopes in relation to the rest of the landscape.