Calculate Gravity and Mass

The force of gravity is one of the four fundamental forces of physics. Although it is the weakest of these four, it only acts attractively and never repulsively. Gravity causes masses to attract each other, and the attraction is stronger the larger the masses and the smaller the distance between them. The other three fundamental forces are the strong and weak nuclear forces, which operate on the scale of atoms, and the electromagnetic force. The latter involves positive and negative electric charges that neutralize each other and are often balanced. Therefore, despite its weakness, gravity often prevails in nature. This requires at least a large mass, which, in the case that is usually relevant to us, is the planet Earth. A person is pulled towards the center of gravity of this planet and held back by the solid ground, allowing us to move around on Earth. Smaller masses also attract each other, of course. For example, with very precise measuring instruments, it can be determined that two freely movable steel spheres attract each other, even if this is not perceptible to the naked eye.

In general relativity, gravity is not understood as a force in the classical sense. Instead, it describes the curvature of spacetime caused by mass and energy. Large masses, such as planets or stars, alter the geometric structure of space and time in their vicinity, causing other bodies to move along the resulting trajectories. An object therefore does not fall to Earth because a force attracts it, but because it follows a path that is as straight as possible in curved spacetime. The solid ground of the Earth prevents this movement and exerts a counterforce, which we perceive as weight.

Physics commonly uses SI units. Here is a calculator to convert units.