Is the fourth dimension 'time'? This picture attempts to convey the
idea of time, not in the sense of calendars or clocks (those are seven
dimensional models of time) but in the sense of the field or stage upon
which all three dimensional interactions are played out. The universe is
cycles on top of cycles, planets and stars orbiting through eternity, accumulations
of matter plummeting through space in a repetitive dance of energy.
The fourth archetype, the Emperor rounds out the set of Jehovah's inorganic universe. Four is the force-field of Gravity or Time (same thing when you think about it), the fourth field of physics which sets the limitation the other three; it is Entropy. Gravity brings order to the universe with the invention of up and down, past and present, inertia and momentum. Color-wise, green stabilizes the emotional lightness of yellow (three) and reminds us of it's corresponding element earth.
Four is possibly the most important number in a mystical sense since it can evoke the four seasons, the four directions, the four elements, and so on. The hebrew word for God is spelled with four Hebrew letters, yod, hay, vov, hay (Je Ho V aH) symbolizing this powerful truth and symmetry in the cosmos.