No one really knows, however, there have been some astrologers and thinkers, such as Issac Newton, and Johannes Kepler, who have written of another force they've seen working within mathematics, through the angles of the celestial bodies relative to the Earth that correlate to events that seem to repeat with the passage of time itself in mathematical planetary configurations.
Time itself cannot exist without the movement of the planets, according to Plato, and we know that all things are in motion, as is the weather, which, according to ancient astrologers is regulated by the motions of the Sun, Moon, and planets.
For human beings, metaphysically, the astrologer C.C. Zain surmised that all human beings have astral forms, bodies of light, which are formed by celestial forces that constitute the stellar cells of the astral body. In effect, we as human beings, are made of star stuff, and we thus are affected by celestial bodies relative to points in time (of our personal nativities from birth.)
Observations of planetary significance, made by the movements, or transits, of the planets relative to sensitive placements of an individual correlate to personal events in the person's life.
The ancient astrologers believed that the Moon ruled the human brain which fluctuates its water levels according to the phases of the Moon, with the highest level occurring during the Full Moon week.
We know that the human body consists of 71-percent water, the same percentage of the Earth's water content, and we also know that the motions and phases of the Moon, for instance, do affect the atmospheric tides of the Earth, with observations over time of effects on human beings.