Sunset

The Mekong is a river in Southeast Asia. It is the world's 12th-longest river and the 7th-longest in Asia. Its estimated length is 4,350 km (2,703 mi), and it drains an area of 795,000 km² (307,000 sq mi), discharging 475 km³ (114 cu mi) of water annually

From the Tibetan Plateau this river runs through China's Yunnan province, Burma, Laos, Thailand, Cambodia and Vietnam. In 1995, Laos, Thailand, Cambodia and Vietnam established the Mekong River Commission to assist in the management and coordinated use of the Mekong's resources. In 1996 China and Burma became "dialogue partners" of the MRC and the six countries now work together within a cooperative framework.

The extreme seasonal variations in flow and the presence of rapids and waterfalls in this river have made navigation difficult. The river is a major trading route linking China’s southwestern province of Yunnan to Laos, Burma and Thailand to the south, an important trade route between western China and Southeast Asia.

Sunset or sundown is the daily disappearance of the Sun below the horizon in the west as a result of Earth's rotation.

The time of sunset is defined in astronomy as the moment when the trailing edge of the Sun's disk disappears below the horizon in the west. The ray path of light from the setting Sun is highly distorted near the horizon because of atmospheric refraction, making the sunset appear to occur when the Sun’s disk is already about one diameter below the horizon. Sunset is distinct from dusk, which is the moment at which darkness falls, which occurs when the Sun is approximately eighteen degrees below the horizon. The period between sunset and dusk is called twilight.

Locations north of the Arctic Circle and south of the Antarctic Circle experience no sunset or sunrise at least one day of the year, when the polar day or the polar night persist continuously for 24 hours.

Sunset creates unique atmospheric conditions such as the often intense orange and red colors of the Sun and the surrounding sky.