Surya (the Sun) illumines all beings in the ten regions with His rays. Surya is the very Self of Prajapathi, so all beings born in the regions so illumined become the very “self” of Prajapathi. The word “vital air (prana)” therefore refers to Aditya (the Sun) Itself, for the Sun gives the vital essence (prana). Since all beings are able to live by consumption of food, etc., the Sun is also known as the Cosmic Universal Personality (Vaiswanara). The whole universe is of His nature, so He is also known as Cosmic Form (Viswa-rupa).
The year is an indicator of time, according to the position of the sun. Time is but a series of days and nights, and these phases are caused by the sun. The rotation of the moon causes phases in fullness. The twin forces, the sun and moon, are products of Prajapathi, so time, which is marked out by the tropics, seasons, months, etc., is also of the same essence. Prajapathi also has northern and southern cycles.
The contemplation and worship of Prajapathi in this universal aspect is referred to as “spiritual wisdom (jnana)” itself. Those who are endowed with this spiritual wisdom and who have mastery over the senses as well as faith in the Vedas can easily convince themselves that they are the very Atma. Pursuing the northern path (uttara-marga), they reach the spiritual stage known as the world of the Sun (Surya-loka). That world is the refuge of all living beings. Only those who worshipfully engage themselves in their daily duties, without any desire for the fruits thereof, can enter that world of the Sun.
The seasons like spring are the feet of the Sun, the symbol of time; the twelve months are His personal traits; He is the Cause of the worlds —these truths are expressed in the fourth and sixth mantras of Prasna Upanishad. The rains are also caused by the Sun, so He is the master of another world too, the third, the heavenly world (dyu-loka).