• We said that Russia is claiming 1.2 square kilometres of oil and gas-rich Arctic sea floor around the North Pole (7 July, p 4). That should have been 1.2 million square kilometres.
• We said the Pierre Auger cosmic ray observatory in Argentina was 3000 kilometres square (7 July, p 8). It actually covers 3000 square kilometres.
• Apologies to Veronica Beccabunga who was misnamed by Feedback (7 July).
