The Sumerians are thought to have formed the first human civilization in world history. They lived in southern Mesopotamia, between the Tigris and Euphrates Rivers in the Middle East. Cradle of Civilization. Many historians think that cities and towns were first formed in Sumer around 5000 BC.
At noon, on March 21 and September 23rd are the vernal and autumnal equinoxes. The sun is directly overhead at the equator at these times. On June 22nd is the summer solstice, in the Northern Hemisphere. The sun is at the 23.5 degrees Northern latitude.
During astronomical twilight the center of the sun is between 12 and 18 degrees below the horizon. Between the end of astronomical twilight in the evening and the beginning of astronomical twilight in the morning, the sky is dark enough for all astronomical observations.9:23 7:23 PM. During civil twilight the geometric center of the sun is between 0 and 6 degrees below the horizon. Objects are clearly distinguished without artificial light. During nautical twilight the center of the sun is between 6 and 12 degrees below the horizon.