Chlorofluorocarbons or CFCs are a chemical compound containing carbon, chlorine, and fluorine. Throughout the 20th century, CFCs were mass produced for their popularity in refrigeration and spray cans. In the 1970s, evidence began to show the harmful effects of CFCs on Earth.
Originally created as Great Sand Dunes National Monument on March 17, 1932, Great Sand Dunes National Park and Preserve was established by an act of the United States Congress on September 13, 2004.
Khufu, the pharaoh meant to be buried in the Great Pyramid, took power in 2470 B.C., according to Nur El-Din and colleagues. The researchers therefore compared the modern calendar, the ancient Egyptian calendar, and the cycle of the star to find the exact day Sothis would have appeared that year. The team believes the ancient Egyptians observed the star from July 17 to 19, and the inundation period began 35 days laterâon August 23.