What causes tides on Earth?

What causes tides on Earth?

• A. The Moon's gravity alone pulls on Earth's oceans.
• B. Only the Sun's gravity pulls on oceans.
• C. Tides are caused by Earth's rotation.
• D. The Moon's and Sun's gravitational forces pull on Earth's oceans.

Answer: (D)

Tides on Earth come from gravity acting on the oceans from two bodies: the Moon and the Sun. The Moon’s gravity pulls on the near side of Earth a bit more strongly than on the far side, creating a bulge of ocean on the side closest to the Moon and another on the opposite side. As Earth rotates, coastlines move into and out of these bulges, producing the regular rise and fall of sea level we call tides. The Sun also exerts a strong gravitational pull on Earth’s oceans, and even though it’s far away, its enormous mass means its pull is significant enough to affect tides. When the Sun and Moon line up, their gravitational forces reinforce each other, making higher high tides and lower low tides (spring tides). When they are at right angles, their forces partly cancel, leading to lower high tides and higher low tides (neap tides). Since tides result from the combined pulls of both the Moon and the Sun, not just one body or Earth’s rotation alone, the correct understanding is that tides are caused by the Moon’s and Sun’s gravitational forces acting on Earth’s oceans.

Tides on Earth come from gravity acting on the oceans from two bodies: the Moon and the Sun. The Moon’s gravity pulls on the near side of Earth a bit more strongly than on the far side, creating a bulge of ocean on the side closest to the Moon and another on the opposite side. As Earth rotates, coastlines move into and out of these bulges, producing the regular rise and fall of sea level we call tides. The Sun also exerts a strong gravitational pull on Earth’s oceans, and even though it’s far away, its enormous mass means its pull is significant enough to affect tides. When the Sun and Moon line up, their gravitational forces reinforce each other, making higher high tides and lower low tides (spring tides). When they are at right angles, their forces partly cancel, leading to lower high tides and higher low tides (neap tides). Since tides result from the combined pulls of both the Moon and the Sun, not just one body or Earth’s rotation alone, the correct understanding is that tides are caused by the Moon’s and Sun’s gravitational forces acting on Earth’s oceans.