Introduction / Context:
Seasons are governed by Earth’s axial tilt and its orbit around the Sun. In calendar and celestial terms, the Northern Hemisphere’s spring begins at the vernal equinox, one of two times each year when day and night are nearly equal worldwide.
Given Data / Assumptions:
- The question concerns the specific solar declination at spring onset.
- Vernal equinox occurs around March 20–21.
- Overhead Sun position refers to solar declination matching surface latitude at local noon.
Concept / Approach:
At each equinox, the Sun’s declination is 0°, meaning it is directly overhead at the geographic equator. Solstices differ: at the June solstice the Sun is overhead at the Tropic of Cancer (approximately 23.5° N), marking the start of Northern summer; at the December solstice it is overhead at the Tropic of Capricorn (approximately 23.5° S), marking Northern winter. Therefore, the start of spring corresponds to the Sun being directly overhead the equator.
Step-by-Step Solution:
Recall equinox condition: solar declination = 0°.Match overhead position: equator at local noon.Identify seasonal label: vernal equinox → Northern spring.Select the option that states the Sun is directly overhead the equator.
Verification / Alternative check:
Analemma/equation of time charts and astronomy references show declination crossing 0° at equinoxes, confirming the overhead equator condition.
Why Other Options Are Wrong:
Tropic of Cancer: June solstice → start of Northern summer, not spring.“Sun returns to equator”: Vague phrasing; while true conceptually, the precise and accepted statement is overhead at equator.“Sun is at the Tropic of Cancer”: Repeats solstice condition, not equinox.
Common Pitfalls:
Confusing equinox with equal temperature; it actually refers to equal day and night lengths due to Earth’s geometry, not weather conditions.
Final Answer:
the sun is directly overhead the equator
Discussion & Comments