“Lycurgus Cup: A Roman glass goblet made with ancient color-changing nanotechnology”

Key points

• Lycurgus Cup is a fourth-century Roman-era glass goblet with color-changing properties.
• The cup changes from jade green to ruby red depending on light direction.
• Experts doubt where it was found or whether color change was intentional by the glassblower.
• Bronze frame likely added in the 19th century; original cup may be Italian-made.
• Nanoparticles of gold and silver cause the dichroic effect observed in the glass.