A staff member of Lawrence Hall of Science introduces knowledge on solar eclipse at the Lawrence Hall of Science near San Francisco, the United States, on Aug. 21, 2017. A once-in-a-century total solar eclipse is spanning the continental United States on Monday, creating a 70-mile-wide (112 kilometers) path of totality stretching from Oregon in the Pacific Northwest to South Carolina on the Southeast Coast. (Xinhua/Ma Dan)
