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For billions of years, the Earth has orbited the Sun while the Moon has orbited the Earth. When the Sun, Moon, and Earth line up, the Moon can cast a shadow on our planet—what we call a solar eclipse. Conversely, when the Earth sits between the Sun and Moon, we see a lunar eclipse. Although these events are visually striking, they do not create a noticeable change in the gravitational forces acting on Earth.
Every mass in the universe attracts every other mass—a principle first formalized by Isaac Newton. His law of universal gravitation quantifies this attraction:
F = G·(m₁·m₂)/r²
where F is the force, G is the gravitational constant (6.674×10⁻¹¹ m³ kg⁻¹ s⁻²), m₁ and m₂ are the masses, and r is the distance between their centers.
• Average Earth–Sun distance: 1.5 × 10¹¹ m
• Sun’s mass: 1.99 × 10³⁰ kg
• Earth’s mass: 6.0 × 10²⁴ kg
Applying Newton’s formula gives a Sun–Earth attraction of 3.52 × 10²² N (≈ 7.9 × 10²¹ lbf).
• Average Earth–Moon distance: 3.8 × 10⁸ m
• Moon’s mass: 7.35 × 10²² kg
The resulting Moon–Earth force is 2.03 × 10²⁰ N (≈ 4.5 × 10¹⁹ lbf), roughly 0.5 % of the Sun’s pull.
When the Sun and Moon align on the same side of Earth (solar eclipse), their pulls combine, giving a total of 3.54 × 10²² N toward the Sun. During a lunar eclipse, the Moon pulls in the opposite direction, producing a net force of 3.50 × 10²² N toward the Sun.
For comparison, the annual variation in Sun–Earth attraction—from perihelion (closest) to aphelion (farthest)—spans 3.43 × 10²² N to 3.67 × 10²² N, a difference over ten times larger than the eclipse‑induced change.
The Sun exerts about 0.0603 % of the Earth’s pull on a person, while the Moon contributes only 0.0003 %. A 68‑kg (150‑lb) individual would weigh roughly 0.6 g (0.02 oz) less at noon during a solar eclipse—or any new moon—than at noon on a full moon.
In short, eclipses are dramatic astronomical events but the associated shift in gravitational forces is minuscule and has no perceptible impact on daily life.
