• We must have been feeling a little giddy when we said the GPS-free car navigation system developed in Chicago (13 July, p 23) used motion sensors. It doesn’t.
• Oops. In our story on musicians jamming while up to 3000 kilometres apart (13 July, p 21) we may have inadvertently broken the speed of light. Rather than the overall delay in the connection, it is the encoding and decoding of sound that takes just 5 milliseconds.
