72 reactions · 22 comments | Get the whole picture. Start your 14-day free trial to the Guardian Digital Pack. Enjoy your daily newspaper, optimised for tablet. | The Guardian | Facebook

43K views · 188 reactions | For Professor Marcus du Sautoy, the ‘enigma of prime numbers’ is at the heart of the greatest unsolved problem in mathematics. Riemann’s formula calculates how many primes there are – an infinite number that is crucial to the security of online banking | The Guardian | Facebook

Direct action group Extinction Rebellion paralysed central London to protest against what they see as the government's inaction on climate change. They blocked five bridges over the Thames, and police made 82 arrests. This is how it happened, and why it’s going to happen again. | The Guardian