Dispute over accord with Mauritius intensifies ahead of talks between UK prime minister and US president next week ...

Shortly after François Arago discovered the optical activity of quartz in 1811, Jean-Baptiste Biot observed a similar rotation of linearly polarized light in organic liquids and gases.

Observed at 00:00, Tuesday 18 February BBC Weather in association with MeteoGroup, external All times are Central European Standard Time (Europe/Paris, GMT+1) unless otherwise stated.