Gravity is not a selective force reserved only for planets and stars. The universal law of physics dictates that any object possessing mass exerts a gravitational pull on every other object in the universe. This means that humans, as masses, are surrounded by their own gravitational field, which extends outward indefinitely. This personal gravity is never noticed in daily life because its strength is incredibly small, a consequence of the relatively tiny amount of mass contained within a human body.
The Fundamental Physics of Gravity
The presence of gravity is determined by the most basic property of matter: mass. This principle is codified in Sir Isaac Newton’s Law of Universal Gravitation, which describes the force of attraction between any two objects. This universal attraction acts between every particle, causing phenomena like an apple falling to the ground or the Moon orbiting the Earth.
The strength of this gravitational force depends on two primary factors: the amount of mass involved and the distance separating the objects. The force is directly proportional to the product of the two masses, meaning that if either mass increases, the gravitational attraction between them grows stronger. Conversely, the force weakens very quickly as the distance between the objects increases, following a relationship known as the inverse square law.
The inverse square relationship means that if the distance between two masses is doubled, the gravitational force between them drops to one-fourth of its original strength. The gravity of a human body is a physical reality because the force is a property of mass itself. However, due to the extremely small value of the gravitational constant, gravity is the weakest of the four known forces in the universe.
Quantifying the Gravitational Pull of a Human
Applying the principles of universal gravitation to a human body reveals the resulting force is extremely small. The gravitational interaction between two average-sized people, such as two individuals weighing 70 kilograms each and standing one meter apart, is approximately \(3.27 \times 10^{-7}\) Newtons.
To put this number into perspective, this gravitational force is roughly equivalent to the weight of about 44 particles of common household dust. For comparison, the weight of a single dust particle on Earth is approximately \(7.38 \times 10^{-9}\) Newtons. This illustrates why two people standing close to each other do not feel any perceptible pull toward one another.
Theoretically, the gravitational pull of a human body can be measured with sensitive instruments. Even if a person were floating alone in the vacuum of space, their gravitational field would be too weak to noticeably attract a nearby pebble within a human lifespan. The force is real, but it is easily overpowered by even the slightest push or any other force acting on the body.
Why Earth’s Gravity Overwhelms Human Gravity
Human gravity is never experienced due to the vast difference in mass between a person and the planet they stand on. The Earth has a mass of approximately \(6 \times 10^{24}\) kilograms. An average human, in contrast, weighs around 70 to 80 kilograms, creating a massive disparity.
This imbalance means that the gravitational force exerted by the Earth is much greater than the gravitational pull of any single person or object nearby. For an 80-kilogram person, the Earth’s gravitational pull is approximately 784 Newtons. This force is felt as weight, and it is billions of times stronger than the mutual attraction between two people.
All objects on the planet, including every human body, are constantly being pulled toward the Earth’s center of mass. This force completely masks the gravitational attraction between two people. The small gravitational tug you exert on the person standing next to you is insignificant compared to the downward pull exerted by the planet.