Cadet Competition Written Practice Exam

Why does the distance between the Moon and the Earth change slightly?

1. The Moon is moving faster

2. The Moon has an elliptical orbit

3. The Earth's orbit fluctuates

4. The gravitational pull changes

The correct answer is: The Moon has an elliptical orbit

The distance between the Moon and the Earth changes slightly due to the Moon's elliptical orbit around our planet. Unlike a perfect circle, an elliptical orbit results in varying distances between the two celestial bodies as the Moon travels along its orbital path. At its closest point, known as perigee, the Moon is significantly closer to the Earth, and at its farthest point, called apogee, the distance is greater. This variation affects not only the distance but also the gravitational interaction between the two bodies, leading to changes in the observed size of the Moon and affecting tidal patterns on Earth. While other factors, such as fluctuating gravitational influences or changes in the Earth's orbit, can play roles in the complete understanding of celestial mechanics, the fundamental reason for the changing distance specifically pertains to the Moon's elliptical orbit.