Sunrise to sunset is the route the Sun takes in his giant golden chariot harnessed to seven horses. Here, Surya's chariot is driven by Aruna, the Morning Star or Dawn.
yac-caksur esa savita sakala-grahanam
raja samasta-sura-murtir asesa-tejah
yasyajnaya bhramati sambhrta-kala-cakro
govindam adi-purusam tam aham bhajami
The sun who is the king of all the planets, full of infinite effulgence, the image of the good soul, is as the eye of this world. I adore the primeval Lord Govinda in pursuance of whose order the sun performs his journey mounting the wheel of time.
Certain professors of the Vedic religion worship the sun as Brahman. The sun is one of the hierarchy of the five gods. Some people target in heat the source of this world and therefore designate the sun, the only location of heat, as the root cause of this world. Notwithstanding all that may be said to the contrary, the sun is after all only the presiding deity of a sphere of the sum total of all mundane heat and is hence a god exercising delegated authority. The sun performs his specific function of service certainly by the command of Govinda.
The sun is not stationary; it is also moving like the other planets. The sun's movements determine the duration of night and day. When the sun travels north of the equator, it moves slowly during the day and very quickly at night, thus increasing the duration of the daytime and decreasing the duration of night. Similarly, when the sun travels south of the equator, the exact opposite is true -- the duration of the day decreases, and the duration of night increases. When the sun enters Karkata-rasi (Cancer) and then travels to Simha-rasi (Leo) and so on through Dhanuh-rasi (Sagittarius), its course is called Daksinayana, the southern way, and when the sun enters Makara-rasi (Capricorn) and thereafter travels through Kumbharasi (Aquarius) and so on through Mithuna-rasi (Gemini), its course is called Uttarayana, the northern way. When the sun is in Mesa-rasi (Aries) and Tula-rasi (Libra), the duration of day and night are equal.
On Manasottara Mountain are the abodes of four demigods. East of Sumeru Mountain is Devadhani, where King Indra lives, and south of Sumeru is Samyamani, the abode of Yamaraja, the superintendent of death. Similarly, west of Sumeru is Nimlocani, the abode of Varuna, the demigod who controls the water, and north of Sumeru is Vibhavari, where the demigod of the moon lives. Sunrise, noon, sunset and midnight occur in all these places because of the movements of the sun. Diametrically opposite the place where the sunrise takes places and the sun is seen by human eyes, the sun will be setting and passing away from human vision. Similarly, the people residing diametrically opposite the point where it is midday will be experiencing midnight. The sun rises and sets with all the other planets, headed by the moon and other luminaries.
The entire kala-cakra, or wheel of time, is established on the wheel of the sun-god's chariot. This wheel is known as Samvatsara. The seven horses pulling the chariot of the sun are known as Gayatri, Brhati, Usnik, Jagati, Tristup, Anustup and Pankti. They are harnessed by a demigod known as Arunadeva to a yoke 900,000 yojanas wide. Thus the chariot carries Adityadeva, the sun-god. Always staying in front of the sun-god and offering their prayers are sixty thousand sages known as Valikhilyas. There are fourteen Gandharvas, Apsaras and other demigods, who are divided into seven parties and who perform ritualistic activities every month to worship the Supersoul through the sun-god according to different names. Thus the sun-god travels through the universe for a distance of 95,100,000 yojanas (760,800,000 miles) at a speed of 16,004 miles at every moment.
The sun-god, who controls the affairs of the entire universe, especially in regard to heat, light, seasonal changes and so on, is considered an expansion of Narayana. He represents the three Vedas -- Rg, Yajur and Sama -- and therefore he is known as Trayimaya, the form of Lord Narayana.
Sometimes the sun-god is also called Surya Narayana. The sun-god has expanded himself in twelve divisions, and thus he controls the six seasonal changes and causes winter, summer, rain and so on. Yogis and karmis following the varnasrama institution, who practice hatha or astanga-yoga or who perform agnihotra sacrifices, worship Surya Narayana for their own benefit. The demigod Surya is
always in touch with the Supreme Personality of Godhead, Narayana.
Residing in outer space, which is in the middle of the universe, between Bhuloka and Bhuvarloka, the sun rotates through the time circle of the zodiac, represented by twelve rasis, or signs, and assumes different names according to the sign he is in. For the moon, every month is divided into two fortnights. Similarly, according to solar calculations, a month is equal to the time the sun
spends in one constellation; two months constitute one season, and there are twelve months in a year. The entire area of the sky is divided into two halves, each representing an ayana, the course traversed by the sun within a period of six months. The sun travels sometimes slowly, sometimes swiftly and sometimes at a moderate speed. In this way it travels within the three worlds, consisting of the heavenly planets, the earthly planets and outer space. These orbits are referred to by great learned scholars by the names Samvatsara, Parivatsara, Idavatsara, Anuvatsara and Vatsara.
The sun-god, who is Narayana, or Visnu, the soul of all the worlds, is situated in outer space between the upper and lower portions of the universe. Passing through twelve months on the wheel of time, the sun comes in touch with twelve different signs of the zodiac and assumes twelve different names according to those signs. The aggregate of those twelve months is called a samvatsara, or an entire year. According to lunar calculations, two fortnights -- one of the waxing moon and the other of the waning -- form one month. That same period is one day and night for the planet Pitrloka. According to stellar calculations, a month equals two and one quarter constellations. When the sun travels for two months, a season passes, and therefore the seasonal changes are considered parts of the body of the year.