The Axis of the Earth
Explanation
The Earth rotates on an imaginary line known as its axis. The orientation of this axis relative to the plane in which the Earth revolves around the Sun (the orbital plane or the plane of the ecliptic) is a fundamental geographic concept that determines seasons and the variation in the length of day and night.Detailed Analysis:
- The orbital plane is the flat plane defined by the Earth's orbit around the Sun.
- The axis of the Earth is the imaginary line passing through the North and South Poles.
- The axis is not perpendicular to the orbital plane; it is tilted.
- The angle of inclination of the Earth's axis from the vertical (the line perpendicular to the orbital plane) is 23½°.
- Consequently, the angle that the axis makes with the orbital plane itself is 66½° (calculated as 90° - 23½°).
Key Takeaway: It is crucial to distinguish between the two angles of the Earth's tilt: 23½° from the vertical (perpendicular) and 66½° from the horizontal (orbital plane).