Astronomy Study Guide

The weight of an object is the force of gravity acting on its mass. This force depends on both the object's mass and the gravitational field strength (g) at its location. The gravitational field strength is not constant throughout the universe; it varies depending on the mass and radius of the celestial body exerting the gravitational pull. For example, the Moon has a significantly smaller mass and a different radius compared to Earth. This results in a much weaker gravitational field strength on the Moon's surface (approximately 1.6 N/kg) compared to Earth's surface (approximately 9.8 N/kg). Consequently, an object with the same mass will weigh considerably less on the Moon than on Earth, even though its mass remains unchanged. The difference in 'g' is fundamentally due to the varying gravitational potential caused by differing masses and sizes of the celestial bodies.