Ocean tides – condition for spring tides Which physical alignment of the Earth–Moon–Sun system produces spring tides, i.e., the greatest tidal range due to constructive superposition of tidal forces?

Introduction / Context:
Tides arise from the gravitational attraction of the Moon and the Sun on Earth’s oceans. The tidal range varies cyclically with the relative positions of these bodies. Understanding when spring tides (highest highs and lowest lows) occur is a classic concept in physical oceanography and navigation.

Given Data / Assumptions:

• Consider idealized alignment effects without local bathymetry complications.
• “Spring” refers to “springing forth,” not the season.
• We focus on the astronomical configuration that maximizes net tidal forcing.

Concept / Approach:
When the Sun, Earth, and Moon are in line (syzygy) at new moon or full moon, the solar and lunar tidal potentials align to reinforce one another. This constructive superposition yields the largest tidal range, called spring tides. When they are roughly at right angles (quadrature: first/third quarter), forces partially cancel, producing neap tides with reduced range.

Step-by-Step Solution:
Identify configuration for maximum constructive addition → syzygy (aligned).This alignment ensures the solar and lunar tidal bulges coincide in longitude.Therefore, spring tides occur at new and full moon.

Verification / Alternative check:
Tide tables show approximately fortnightly cycles of larger and smaller ranges corresponding to lunar phases—empirical confirmation of the alignment rule.

Why Other Options Are Wrong:

• (b) Opposing forces correspond to neap conditions, not spring tides.
• (c) Though conceptually true (forces coincide), option (a) states the concrete astronomical alignment; both are related, but (a) is the canonical description used in surveying and navigation texts.
• (d) Incorrect because a well-known alignment causes spring tides.

Common Pitfalls:
Associating “spring” with the season; tidal terminology is independent of seasonal cycles.

Final Answer:
Sun and Moon are aligned with the Earth (syzygy: new or full moon)