OCCURRENCE

• Earth reaches aphelion every July.
• In 2024, Earth reached aphelion on a Friday.

DEFINITION AND CAUSE

• Aphelion: The point in Earth’s orbit where it is farthest from the Sun.
• Earth’s orbit is elliptical, not circular.
• This elliptical orbit is a result of gravitational influences from other planets.

Distance from the Sun

• At aphelion: Earth is approximately 152.1 million km from the Sun.
• At perihelion (closest point to the Sun in January): Earth is about 147.1 million km from the Sun.

Influence of Gravity

Elliptical Orbits

• All planets in the solar system have elliptical orbits.
• Eccentricity measures how much an orbit deviates from a perfect circle.
  • Higher eccentricity means a more elliptical orbit.
  • Examples:
    • Mars: Eccentricity of 0.094.
    • Pluto: Eccentricity of 0.244.
    • Earth: Eccentricity of 0.017.

Gravitational Effects

• Jupiter, being the most massive planet, has the most significant gravitational influence on other planets’ orbits.
• The planets’ gravitational pulls create a “chaotic tug of war,” affecting their orbits.

SEASONAL EFFECTS

Sunlight and Temperature

• We receive 7% less sunlight at aphelion compared to perihelion.
• This results in slightly milder summers and winters in the Northern Hemisphere.
• Earth’s axial tilt is the primary factor for seasonal changes, not the varying distance from the Sun.

Hypothetical Scenarios

• No Aphelion (Perfect Circular Orbit):
  • Seasons’ lengths would be exactly the same.
  • Minimal changes in overall climate and seasonal patterns.
• Increased Eccentricity:
  • More extreme seasons in the Southern Hemisphere.
  • Potential catastrophic impacts on climate:
    • Unbearably hot summers.
    • Intolerably cold winters.
    • Possible crop failures and freezes.