GRAVITY

PRERNA FOR IAS

GRAVITY

1. What is Gravity?

Gravity is a fundamental force of attraction that exists between all objects having mass. According to Newton, every object in the universe attracts every other object, and the strength of this attraction depends on their masses and the distance between them. Larger masses produce stronger gravitational forces, while greater distances weaken the attraction. Einstein later explained gravity as the curvature of spacetime caused by massive objects. In this view, planets move around the Sun because they follow curved paths in warped spacetime. Gravity is responsible for keeping planets in orbit, causing objects to fall toward Earth, and shaping the structure of the universe.

2. Newton’s Universal Law of Gravitation

Newton’s Universal Law of Gravitation states that every particle in the universe attracts every other particle with a force proportional to the product of their masses and inversely proportional to the square of the distance between them. The mathematical expression is F = G(M₁M₂)/r², where F is the gravitational force, G is the universal gravitational constant, M₁ and M₂ are the masses, and r is the distance between their centers. The force acts along the line joining the two masses and is always attractive. This law successfully explains planetary motion, satellite orbits, and many gravitational phenomena.

3. The Gravitational Constant (G): Value and Units

The universal gravitational constant, denoted by G, is a fundamental constant used in Newton’s Law of Gravitation. Its value is approximately 6.674 × 10⁻¹¹ N·m²/kg². It represents the strength of gravitational attraction between two masses. The value of G is extremely small, showing that gravity is the weakest of the four fundamental forces. Despite its weakness, gravity dominates at astronomical scales because it acts over very large distances and is always attractive. The SI unit of G is Newton meter squared per kilogram squared. It is the same everywhere in the universe and does not vary with location.

4. Cavendish Experiment (Torsion Balance)