Which property describes the Mean Sun's movement?

The Mean Sun is a theoretical concept used primarily in the context of timekeeping and the measurement of solar time. It is defined as an average representation of the sun's movement in the sky, which simplifies and corrects the irregularities caused by the Earth's elliptical orbit and axial tilt.

The correct description indicates that the Mean Sun moves along the celestial equator, which is pivotal for understanding celestial navigation and the equatorial coordinate system. The right ascension of the Mean Sun increases at a uniform rate due to its definition; this uniform movement allows for a consistent measure of time, as the Mean Sun is used to define standard time systems.

In contrast, the actual sun's apparent motion is more complex due to the elliptical shape of Earth’s orbit and its axial tilt, which leads to variations in its speed over the course of a year. However, the Mean Sun simplifies this by providing a uniform rate of increase in right ascension, which is essential for timekeeping.

Understanding this concept is fundamental for geodetic engineers, who often rely on precise timing and positioning influenced by celestial movements.