Here's why:

* Earth's Orbital Speed: Earth orbits the Sun at an average speed of approximately 29.78 kilometers per second (18.5 miles per second). This speed varies slightly depending on its position in its elliptical orbit.

* Other Planets: While other planets have different orbital speeds, Earth's speed is closest to 30 km/s. For example, Mars has an average orbital speed of about 24 km/s, and Jupiter orbits at about 13 km/s.