The Circle of Illumination
- The Circle of Illumination represents an imaginary line that demarcates the Earth into two distinct hemispheres.
- On one side, which faces the Sun, there is illumination and thus daytime, while on the opposite side, in shadow, there is darkness or nighttime.
- The Circle of Illumination precisely separates these two halves.
- The Circle of Illumination is in constant motion due to the Earth's rotation.
- Consequently, this dynamic boundary is responsible for the continuous transition between day and night.
- As the Earth revolves, the Circle of Illumination traverses its surface.
- When this boundary passes over a particular geographic location, it designates daytime for that region, and as it moves away, it designates nighttime.
Days for the Earth to complete one orbit around the sun
- It takes approximately 365.25 days for the Earth to complete one orbit around the sun
- Six hours saved every year are added to make one day (24 hours) over a span of four years.
- This surplus day is added to the month of February.
- Thus every fourth year there is a leap year with 366 days.
Earth's orbit around the Sun
- Earth's orbit around the Sun is not perfectly circular; it is elliptical.
- An elliptical orbit means that the path Earth follows as it revolves around the Sun is slightly elongated and resembles an ellipse, or an oval shape, rather than a perfect circle.\
- This elliptical shape causes Earth's distance from the Sun to vary slightly throughout the year.
- At certain times in its orbit, Earth is closer to the Sun, which is known as perihelion, while at other times, it is farther from the Sun, known as aphelion.
- This variation in distance does have some impact on our climate and seasons, but the tilt of Earth's axis remains the primary driver of seasonal changes.
