Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Horizon specified by linear perspective. On the left, the actual horizon is visible through the window. On the right, the horizon is hidden by the wall, but its location is revealed by the vanishing point of the room’s perspective. (Adapted from Sedgwick, 2010.)
