Letter: For the record – 11 January 2020

From Andrew Forrest, Epping, Essex, UK

• Brass is an alloy of copper and zinc, and bronze of copper and tin (14 December 2019, p 10).

• A white dwarf star is made of atoms, and doesn’t collapse further because that would require their electrons to occupy the same energy levels, contrary to the rules of quantum physics (14 December 2019, p 15).

• Cavitation consists of low-pressure bubbles forming in a fluid and then imploding (14 December 2019, p 16).

• The flakes shedding from Jupiter’s Great Red Spot have an area of 100,000 km² (30 November 2019, p 11).