Gravity is weaker in certain places on Earth due to variations in the density and composition of rocks beneath the Earth's surface, as well as the irregular shape of the planet which creates local differences in gravitational attraction.
Our planet is not a perfect sphere: it is more like a slightly squashed ball at the poles. This phenomenon, called flattening, comes from the rapid rotation of the Earth, which creates a stronger centrifugal force at the equator than at the poles. As a result, matter is concentrated more at the equator, and the distance to the center of the Earth is a little greater there. Since gravity decreases as you move away from the center, it is therefore slightly weaker near the equator than in polar regions. That’s why you would weigh a tiny bit less at the equator than at the North or South Pole.
Beneath our feet, the Earth is not uniform: the rock, minerals, or density of the subsoil vary greatly depending on the location. Some regions, rich in very dense rocks like metallic ores, attract objects more due to a slightly stronger gravity. Conversely, areas composed mainly of less dense rocks, such as sediments, exhibit weaker gravity. These differences, though small, do exist: not enough to float, obviously, but measurable with precise instruments. It is particularly thanks to these small variations that scientists detect underground reserves or study the Earth's crust.
The Earth's rotation creates a centrifugal force that pushes us slightly outward, much like when a ride spins quickly and you're slightly pulled outward from the seat. This force is strongest at the equator because that is where the rotational speed is maximum. At this point, it acts against earth's gravity, which slightly decreases our weight. Towards the poles, it's different; the centrifugal force is almost zero because we rotate more slowly. As a result, we weigh a little less at the equator than at the poles. It's not huge, but it's enough to be measured and taken into account by scientists.
Gravity decreases as you move away from the center of the Earth. The Earth is not a perfect sphere; its radius varies depending on the location. Near the equator, for example, you are farther from the Earth's center, which means that the gravitational force is slightly weaker there than at the poles, where the surface is closer to the center. This small difference is enough for a person's weight to vary slightly depending on where they are on the planet. The closer you get to the center, the stronger the gravity you experience.
The point on the Earth's surface where gravity is the weakest is located on Mount Huascarán in Peru, due to its high altitude and the lower density of the rocks in the area.
The gravity on Earth is measured precisely using instruments called gravimeters, which are capable of detecting extremely subtle variations in the gravitational field due to the composition and structure of the terrain.
The reduced gravity at the equator, due to the Earth's rotation, makes rocket launches easier. This is why space launch sites, such as the one in Kourou in French Guiana, are located near the equator.
Gravity is so sensitive that it can even vary slightly depending on significant rainfall or seasonal changes in groundwater distribution.
Yes, satellites in orbit experience these variations in the gravitational field. That is why they must be accurately taken into account when planning their trajectories and altitude to ensure optimal functioning.
Yes, the density and nature of rocks and minerals in the local subsurface influence the gravitational field. For example, areas rich in denser materials like iron ore will locally increase the gravitational force, while conversely, an area with less dense rocks will slightly decrease the local gravity.
The summit of Mount Chimborazo in Ecuador is often cited as the place where gravity is the weakest due to its maximum distance from the Earth's center, caused by the flattening of the Earth at the equator and its high altitude.
In most cases, these differences are extremely small (on the order of fractions of a percent) and therefore impossible for a person to perceive directly. High-precision instruments are required to detect these tiny variations.
Due to the centrifugal force caused by the Earth's rotation and its slight polar flattening, the effective gravity at the equator is slightly weaker than at the poles, resulting in a slight but measurable decrease in a person's weight.
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