Day will be longer than night.
Explanation
The variation in the length of day and night across the Earth's surface is primarily determined by the Earth's revolution around the Sun and the inclination of its rotational axis ($23.5^\circ$) relative to the plane of the ecliptic.
Detailed Analysis:
- Astronomical Position: On December 22nd, the Earth is in the position known as the Winter Solstice for the Northern Hemisphere and the Summer Solstice for the Southern Hemisphere.
- Solar Incidence: During this time, the South Pole is tilted towards the Sun, and the Sun's vertical rays fall directly on the Tropic of Capricorn ($23.5^\circ$ S).
- Day Length in Southern Hemisphere: Because the Southern Hemisphere is tilted towards the Sun, the circle of illumination covers a larger portion of this hemisphere. Consequently, locations in the Southern Hemisphere remain exposed to sunlight for a longer duration than they are in darkness.
- Comparison: Therefore, the length of the day is longer than the length of the night. The duration of daylight increases as one moves from the Equator towards the South Pole.
- Eliminating There will be no night.: The phenomenon of "no night" (24-hour daylight) is observed only in the region south of the Antarctic Circle ($66.5^\circ$ S). Since the question implies a general observer in the Southern Hemisphere, not specifically within the polar circle, Day will be longer than night. is the scientifically accurate generalization.
Key Takeaway:
On December 22nd (Summer Solstice in the Southern Hemisphere), the Southern Hemisphere receives maximum insolation with days being longer than nights, while the Northern Hemisphere experiences its shortest days.