Gravity is the fundamental force that attracts any two masses toward one another, and it is what keeps our feet on the ground. While often discussed as a uniform constant, the Earth is not a perfect sphere, meaning the pull of gravity is not identical at every point on its surface. This natural phenomenon is a consequence of the Earth’s shape, its rotation, and the uneven distribution of mass within its crust and mantle.
The Location with the Lowest Gravity
The location on Earth with the smallest measured gravitational acceleration is the summit of Mount Nevado Huascarán in Peru. This peak, which is the highest in Peru, sits at 6,768 meters above sea level and exhibits a gravitational acceleration of approximately 9.7639 meters per second squared (m/s²). When compared to the location with the maximum gravitational pull, the difference is approximately 1 percent.
General Factors That Reduce Gravity
Two primary and predictable factors account for much of the global variation in surface gravity. One of the most significant influences is a location’s latitude, which relates directly to the planet’s rotation. The Earth is not a perfect sphere; its spin causes it to bulge outward at the equator, creating an oblate spheroid shape. This equatorial bulge means that locations near the equator are physically farther from the planet’s center of mass than the poles.
The rotational speed is highest at the equator, generating a centrifugal force that acts against gravity. This outward-pulling force is maximized along the equatorial line, effectively counteracting the planet’s inward gravitational pull. The combination of greater distance from the center and the effect of the centrifugal force causes gravity to be weakest near the equator, which is a major reason for the low reading in Peru.
The second major factor affecting the gravitational pull is altitude, which is governed by the inverse square law of gravitation. This law states that the gravitational force between two objects decreases in proportion to the square of the distance between their centers. Therefore, any location at a high elevation, such as a mountain peak, will naturally experience a weaker pull simply because it is farther away from the planet’s center of mass than a location at sea level.
Mount Nevado Huascarán’s immense height of 6,768 meters contributes substantially to its low gravity reading by increasing the distance from the center. This effect is noticeable even over small changes in elevation; for example, an increase in altitude of 9,000 meters can decrease an object’s weight by about 0.29 percent. When combined with the effects of being near the equator, the high altitude ensures a low baseline gravitational force. However, these two factors alone do not fully explain why Huascarán is the absolute minimum, which brings in the role of deep Earth geology.
Deep Earth Density and Geoid Anomalies
The final, and most complex, influence on local gravity is the variation in the density of the material beneath the surface. To understand these variations, scientists use the concept of the geoid, which is a theoretical surface representing the shape the oceans would take under the influence of gravity and rotation alone, without external forces like tides. Because mass is unevenly distributed within the Earth, the geoid is not smooth; it rises over areas of high subterranean mass and dips over areas of low subterranean mass. These localized dips in the geoid are caused by a phenomenon called a mass deficit, where the underlying crust or mantle material is less dense than the average.
These geological features are referred to as gravity anomalies because they represent deviations from the expected gravitational pull based on the predictable factors of latitude and altitude. The mountain’s extremely low gravity reading is the product of all three factors working in concert: the predictable effects of high altitude and equatorial rotation, amplified by the unique local effect of low-density material deep beneath the Andes mountains. This particular geological structure beneath the surface pushes the location’s gravitational pull lower than any other point on the globe.
Contrast: Where Gravity is Strongest
In direct contrast to the minimum found in Peru, the location with the strongest gravitational force is generally considered to be the surface of the Arctic Ocean, specifically near the North Pole. This maximum acceleration is measured at approximately 9.8337 m/s² and occurs because the factors that minimize gravity at the equator are reversed at the poles. The Earth’s flattening at the poles means that the surface is closer to the planet’s center of mass compared to the equator.
Additionally, the centrifugal force from the Earth’s rotation is virtually nonexistent at the poles, as the rotational motion is minimal. The combination of being closer to the planet’s core and the lack of an opposing centrifugal force makes the Arctic region the point of maximum gravitational pull on Earth’s surface.