The umbral and penumbral shadow cones travel across the surface of the Earth during the August 21, 2017 total solar eclipse.
A solar eclipse occurs when the Moon's shadow falls on the Earth. The shadow comprises two concentric cones called the umbra and the penumbra. Within the smaller, central umbra, the Sun is completely blocked by the Moon, and anyone inside the umbra sees a total eclipse. Within the larger penumbra, the Sun is only partially blocked.
In this animation, the umbra and penumbra cones are viewed through a telescopic lens on a virtual camera located far behind the Moon. Long focal lengths like the one used here appear to compress the distance between near and far objects. Despite appearances, the geometry of the scene is correct. The Earth is roughly 112 lunar diameters beyond the Moon, and the angle at the apex of the umbral cone is only about half a degree.
From this point of view directly behind the Moon, the edges of the shadow cones look circular. The edge of the penumbra is outlined in yellow. It passes over all of North and Central America and the Amazon basin, as well as Greenland and the North Pole. Everyone there will see at least a partial eclipse. The path of the umbra (the small black dot) crosses the United States from Oregon to South Carolina.