Army Space Cadre Basic Course Practice Exam - Prep Guide and Practice Questions

The assertion that the orbit size relates to the semi-major axis length is accurate according to Kepler's laws of planetary motion. Kepler’s First Law states that planets move in elliptical orbits with the Sun at one focus. The semi-major axis is a critical parameter of the ellipse, essentially defining the size of the orbit. In terms of orbital mechanics, the semi-major axis directly influences the orbital period of a celestial body, with larger semi-major axes leading to longer periods of orbit according to Kepler's Third Law. This law links the square of the orbital period of a planet to the cube of the semi-major axis of its orbit, reinforcing the connection between orbit size and this parameter.

By understanding this relationship, one can predictions about a celestial body’s movement and the effects of gravitational influences within a solar system.