October 6, 2025

What Is The Gravitational Constant G

Q: What is the difference between G and g?

'G' (Universal Gravitational Constant) is a fundamental physical constant that determines the strength of gravity and is constant throughout the universe. 'g' (acceleration due to gravity) is the acceleration an object experiences due to gravity at a specific location, which varies depending on mass and distance from a celestial body (e.g., 'g' on Earth is different from 'g' on the Moon).

Q: How was the value of G first measured?

The value of G was first accurately measured by Henry Cavendish in 1798 using a highly sensitive torsion balance experiment. His method involved measuring the tiny gravitational force between lead spheres, laying the groundwork for subsequent, more precise measurements.

Q: Is G truly constant throughout the universe and over time?

Based on current scientific understanding and extensive experimental evidence, G is considered a universal constant, meaning its value is the same across all space and time. However, physicists continue to conduct experiments with increasing precision to test this fundamental assumption.

Q: Why is the value of G so small?

The small numerical value of G reflects that gravity is an extremely weak force when compared to the other fundamental forces (electromagnetic, strong nuclear, and weak nuclear forces). This weakness explains why gravitational effects are only significantly noticeable when objects possess very large masses, like planets or stars.

Discover the Universal Gravitational Constant (G), a fundamental physical constant in Newton's Law of Universal Gravitation, essential for understanding gravitational force.

Have More Questions →

Definition of the Gravitational Constant (G)

The Universal Gravitational Constant, denoted as 'G', is a fundamental physical constant used in Isaac Newton's Law of Universal Gravitation. It quantifies the strength of the gravitational force between any two objects. Its value is infinitesimally small, indicating that gravity is the weakest of the four fundamental forces of nature.

Role in Newton's Law of Universal Gravitation

Newton's Law states that the gravitational force (F) between two masses (m1 and m2) is directly proportional to the product of their masses and inversely proportional to the square of the distance (r) between their centers. The mathematical expression is F = G * (m1 * m2) / r^2. Here, G serves as the proportionality constant that translates the relationship into an exact equality.

Numerical Value and Units of G

The internationally accepted approximate value of the Universal Gravitational Constant (G) is 6.674 × 10^-11 N⋅m²/kg² (Newton meters squared per kilogram squared). This extremely precise, experimentally determined value is critical for accurate calculations in fields such as astrophysics, orbital mechanics, and understanding the large-scale structure of the universe.

Importance and Applications

G is indispensable for calculating the gravitational attraction between any two objects, ranging from planets and stars to everyday items. It enables scientists to determine the mass of celestial bodies, predict their orbital paths, and model various cosmic phenomena. Unlike 'g' (the acceleration due to gravity), which varies with location, G is a universal constant, maintaining the same value everywhere in the cosmos.

Frequently Asked Questions

What is the difference between G and g?

How was the value of G first measured?

Is G truly constant throughout the universe and over time?

Why is the value of G so small?