This is a re-creation of a color plate from Interaction of Color, by Josef Albers. The two X's are are exactly the same — it's the different backgrounds that make them look like very different colors.
Source: Josef Albers Interaction of Color
The cruise ship Carnival Magic floats behind a catamaran off Cozumel, Mexico on Oct. 17. The ship skipped a planned stop there Friday, the cruise line says, after Mexican authorities delayed granting permission to dock.
Avian influenza, or bird flu, causes an infectious and contagious respiratory disease. In the lab, several scientists have made the H5N1 strain more contagious, a controversial line of research.