News Excerpt:
Earth orbits the sun in an ellipse, rather than a circle. On Friday, it reached its farthest point from the sun, known as aphelion.
- Earth reaches its aphelion every July.
Earth’s elliptical orbit
- The existence of an aphelion is due to Earth’s elliptical orbit rather than a perfect circular one.
- All planets in our solar system, and likely those around other stars, follow elongated circular orbits rather than perfect ones.
Causes of elliptical orbit
- The cause of these elliptical orbits is gravity.
- All the planets tend to jostle each other around, pulling their orbits away from perfect circles.
- This interaction is described as a chaotic tug of war between the small gravitational influences that planets exert on each other.
- Jupiter, being the most massive planet in our solar system, has the most significant influence.
Orbital eccentricity
- Orbital eccentricity measures how much an orbit deviates from a perfect circle.
- A higher eccentricity indicates a more elliptical orbit. For example, Mars has an eccentricity of 0.094, and Pluto's is 0.244, whereas Earth’s eccentricity is only 0.017.
How Far is Earth from the Sun at Aphelion?
- At aphelion, Earth is about 152.1 million km from the Sun.
- Six months later, in early January, Earth reaches perihelion, the point at which it is closest to the Sun, with a distance of approximately 147.1 million km.
Impact of Aphelion on Earth’s Temperatures
- It is a common misconception that Earth’s varying distance from the Sun causes the seasons.
- Although Earth receives 7% less sunlight at aphelion compared to perihelion, leading to slightly milder summers and winters in the Northern Hemisphere, this effect is offset by Earth’s axial tilt.
If There Were No Aphelion?
- If Earth’s orbit were a perfect circle, the lengths of the seasons would be exactly the same.
- Currently, spring and summer are slightly longer than fall and winter in the Northern Hemisphere.
- However, if Earth’s orbit became more eccentric, the consequences could be severe.
- The Southern Hemisphere would experience extreme seasonal variations, with unbearably hot summers and intolerably cold winters, potentially leading to crop failures and freezes.
