What is Gravity Explained by Tariq Pathan
Introduction
Gravity is one of the four fundamental forces of nature, governing the motion of planets, stars, and galaxies. From the fall of an apple to the orbits of satellites, gravity shapes the universe at every scale. In this article, Tariq Pathan breaks down the concept in simple terms for learners and exam aspirants.
Definition of Gravity
Gravity is the attractive force between two masses. Every object with mass exerts a gravitational pull on every other mass. The strength of this force depends on the masses involved and the distance between them.
Newton’s Law of Gravitation
In 1687, Sir Isaac Newton formulated the universal law of gravitation:
F = G·(m₁·m₂) / r²
- F = gravitational force between two objects
- G = gravitational constant (6.674×10⁻¹¹ N·m²/kg²)
- m₁, m₂ = masses of the two objects
- r = distance between the centers of the masses
This inverse-square law explains why gravity weakens with distance but never completely vanishes.
Einstein’s Theory of General Relativity
In 1915, Albert Einstein expanded our understanding by describing gravity not as a force but as the curvature of spacetime caused by mass and energy. Massive objects like Earth warp the fabric of spacetime, causing other objects to follow curved paths—what we perceive as gravitational attraction.
Key equation (simplified):
Gμν + Λgμν = (8πG/c⁴) Tμν
Effects and Manifestations
- Weight: The force of gravity acting on an object’s mass (W = m·g).
- Free Fall: Objects accelerate toward Earth at ~9.81 m/s² (ignoring air resistance).
- Orbits: Planets and moons remain in orbit due to the balance between gravity and inertia.
- Tides: Gravitational pull of the Moon and Sun causes ocean tides.
Practical Applications
- Engineering: Designing stable structures requires accounting for gravitational loads.
- Astronomy: Calculating orbital trajectories for satellites and space missions.
- Geophysics: Measuring Earth’s density and detecting underground structures.
- Everyday Life: Using scales to measure mass via weight under gravity.
Key Experiments & Evidence
- Cavendish Experiment (1798): Measured G by observing tiny gravitational attraction between lead spheres.
- Eddington’s 1919 Eclipse: Confirmed spacetime curvature by observing star positions near the Sun during an eclipse.
- Modern Tests: Precision measurements with lunar laser ranging and atomic interferometry.
Conclusion
Gravity is the invisible glue that binds the cosmos, from apples falling on Earth to galaxies colliding across the universe. Understanding its principles is essential for physics, engineering, and space exploration. With both classical and modern perspectives, this force continues to inspire scientific discovery.
