• Hear this! Hearing aids need to locate where sounds are coming from to work well (29 July, p 12).
• If, hypothetically, Michael Phelps kept up his world record speed for freestyle swimming 200 metres – four lengths of an Olympic pool – for two months, he would complete over 200,000 lengths (29 July, p 8).
• For every kilogram of organic waste that anaerobic bacteria consume, they emit methane with a climate change impact equivalent to 2 kilograms of carbon dioxide (22 July, p 39).
