TIDES — Cause of the periodic rise and fall of sea level Question: The periodic rise and fall of sea level (tides) on Earth is primarily related to which factor?

Introduction / Context:
Tides are long-period waves that travel through the oceans in response to gravitational forces. Understanding their cause is fundamental for navigation, coastal engineering, and environmental planning.

Given Data / Assumptions:

• Two principal tide-generating bodies: the Moon and the Sun.
• Relative positions (syzygy vs quadrature) modulate tidal range.
• Electromagnetic or radiative effects are negligible in directly driving tides.

Concept / Approach:
Tidal forces arise from the gradient (difference) in gravitational attraction across Earth’s diameter. The Moon, being closer, exerts the dominant effect, while the Sun contributes a secondary component. Alignment (new and full moon) produces spring tides; right-angle positions (first and third quarter) produce neap tides.

Step-by-Step Solution:
Identify relevant force: gravitational attraction and its differential across Earth.Recognize lunar dominance due to proximity; add solar contribution.Conclude that tides reflect the changing geometry of these bodies relative to Earth.

Verification / Alternative check:
Observed fortnightly cycles of spring and neap tides correspond to Moon–Sun–Earth geometry, confirming the gravitational explanation.

Why Other Options Are Wrong:
Infrared/Ultraviolet rays alter temperature or chemistry but do not generate periodic global sea-level oscillations.None of the above — incorrect because the gravitational mechanism is well established.Electromagnetic induction is unrelated to ocean-basin-scale tidal patterns.

Common Pitfalls:
Confusing wind-driven storm surges with astronomical tides. Wind and pressure cause weather-related sea-level changes, not the regular tidal cycle.

Final Answer:
The position of the Moon relative to Earth and the gravitational pull exerted mainly by the Moon and partly by the Sun