What defines the position of Earth at perihelion?

The position of Earth at perihelion is defined as the point in its elliptical orbit where it is closest to the Sun. This phenomenon occurs annually and is significant in understanding Earth's distance from the Sun and its orbital mechanics. The temperature and solar radiation received by Earth can vary slightly due to this proximity, although the difference in distance does not lead to dramatic seasonal changes, as seasons are more directly influenced by Earth's axial tilt.

In contrast, other options relate to different concepts; the farthest point from the Sun is known as aphelion, equal daylight and darkness refers to the equinoxes, and greatest tilt relates to the axial tilt, which influences the variation in seasons, not distance from the Sun. Understanding these definitions helps in comprehensively grasping Earth's spatial relationship with the Sun throughout its orbit.