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.
This animation demonstrates how the front and back illusions are generated. The signal is presented from the location marked by the filled star but appears to emanate from the location marked by the open star. Click image to view animation.
