How much does the Earth weigh?

Strictly speaking, scientists measure Earth’s mass rather than its weight, because weight depends on gravity pulling on an object. The first accurate measurement came from Henry Cavendish in 1798, who used a delicate torsion balance to measure the tiny gravitational pull between lead spheres. From this he calculated that Earth is about 5.4 times denser than water, very close to the modern value. With an average density of about 5.51 grams per cubic centimetre, Earth is the densest planet in the solar system. The Moon, by comparison, has only about 1.2 percent of Earth’s mass.