Geshuang Chen’s photo shows an optical corona (13 July, p 25).
To gauge the ideal bowl size for spent pistachio shells, they were modelled as hollow half-spheres with 73 per cent of the packing density of the whole nuts in shells (13 July, p 9).
Boston Dynamics’s robots are banned from having weapons such as flamethrowers fitted to them. One used for agricultural research was equipped with a weed-suppressing propane blowtorch (27 July, p 13).
