Here's why:
* Kepler's Laws: Johannes Kepler's laws of planetary motion state that planets move faster when they are closer to the Sun and slower when they are farther away.
* Conservation of Angular Momentum: As the Earth moves closer to the Sun, it needs to speed up to conserve its angular momentum. Angular momentum is a measure of an object's tendency to rotate, and it's always conserved in a closed system.
Here's how it works:
1. Perihelion: Earth reaches its closest point to the Sun (called perihelion) around early January. At this point, it travels at its fastest speed.
2. Aphelion: Earth reaches its farthest point from the Sun (called aphelion) around early July. At this point, it travels at its slowest speed.
The difference in speed is significant:
* Earth's speed at perihelion is about 30.3 km/s (18.8 mi/s).
* Earth's speed at aphelion is about 29.3 km/s (18.2 mi/s).
This means Earth travels about 1 km/s (0.6 mi/s) faster when it's closest to the Sun compared to when it's farthest away.
