What causes tides?

What causes tides?

• A. Solar wind
• B. Earth's rotation
• C. Differential gravity of Moon and Sun on oceans
• D. Atmospheric pressure changes

Answer: (C)

Tides come from tidal forces created by gravity acting on the oceans. The Moon’s gravity pulls more strongly on the side of Earth that is closer to it and more weakly on the far side, which stretches the oceans and creates a bulge toward the Moon and another bulge on the opposite side. As Earth rotates, different coastlines pass through these bulges, causing the regular rise and fall of sea level we experience as tides. The Sun also exerts gravity that contributes to tides, though its effect is smaller because it is so far away; when the Sun, Moon, and Earth align, their gravitational effects add up and tides are higher, while when they’re at right angles, tides are lower. The other options don’t explain the main cause: solar wind affects space weather, not ocean tides; atmospheric pressure changes can cause weather-related sea level variations but not the regular, global tide pattern; and Earth’s rotation influences the timing of tides but not the gravitational mechanism that creates them.

Tides come from tidal forces created by gravity acting on the oceans. The Moon’s gravity pulls more strongly on the side of Earth that is closer to it and more weakly on the far side, which stretches the oceans and creates a bulge toward the Moon and another bulge on the opposite side. As Earth rotates, different coastlines pass through these bulges, causing the regular rise and fall of sea level we experience as tides. The Sun also exerts gravity that contributes to tides, though its effect is smaller because it is so far away; when the Sun, Moon, and Earth align, their gravitational effects add up and tides are higher, while when they’re at right angles, tides are lower. The other options don’t explain the main cause: solar wind affects space weather, not ocean tides; atmospheric pressure changes can cause weather-related sea level variations but not the regular, global tide pattern; and Earth’s rotation influences the timing of tides but not the gravitational mechanism that creates them.