From the page: "When asked by the Pope to demonstrate his artistic skill, 14th century Italian painter Giotto di Bondone supposedly drew a perfect circle freehand and said: "That's more than enough." Now, an international group of engineers and craftsmen has gone him one better and built a pair of nearly perfect spheres that are thought to be the roundest objects in the world.
The unusual balls, discussed last week at the SPIE Astronomical Telescopes and Instrumentation conference in France, were created as an answer to the "kilogram problem".
The kilogram is the only remaining standard of measurement tied to a single physical object: a 120-year-old lump of platinum and iridium that sits in a vault outside of Paris, France. But the mass of this chunk of metal is slowly changing relative to the 40-odd copies kept by other countries, and no one knows why or by how much."