This chapter informs us of the movements of the sun. 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 Karkaṭa-rāśi (Cancer) and then travels to Siṁha-rāśi (Leo) and so on through Dhanuḥ-rāśi (Sagittarius), its course is called Dakṣiṇāyana, the southern way, and when the sun enters Makara-rāśi (Capricorn) and thereafter travels through Kumbharāśi (Aquarius) and so on through Mithuna-rāśi (Gemini), its course is called Uttarāyaṇa, the northern way. When the sun is in Meṣa-rāśi (Aries) and Tulā-rāśi (Libra), the duration of day and night are equal.