EARTH GEOMETRY — Hemisphere separator Which great-circle plane divides Earth into the Northern and Southern Hemispheres?

Introduction / Context:
Basic Earth geometry defines hemispheres by fundamental reference planes. Knowing which plane separates north from south is essential in geography, navigation, and astronomy.

Given Data / Assumptions:

• We are asked about the division between Northern and Southern Hemispheres.
• Only one great circle fulfills this definition.
• Lines like tropics and meridians serve other reference purposes.

Concept / Approach:
The equatorial plane is perpendicular to Earth’s axis of rotation and intersects the globe at latitude 0°. This great circle is the boundary between hemispheres. Other circles (Tropics at ±23.5°) mark solar declination limits, not hemisphere division.

Step-by-Step Solution:
Identify required boundary → 0° latitude great circle.Name of plane → equatorial plane.Select the matching option.

Verification / Alternative check:
World maps and globes label the equator as the standard divider of hemispheres.

Why Other Options Are Wrong:
International Date Line — divides time zones/day change, not hemispheres.Tropics — mark solar limits, not hemisphere boundaries.Prime Meridian — divides Eastern and Western Hemispheres, not north–south.

Common Pitfalls:
Mixing up time/date boundaries with geometric hemisphere boundaries.

Final Answer:
The plane of the equator