From a great and vanished African civilisation to NASA’s quest to find funnier, kinder astronauts and the mathematical formula that could save democracy—our double issue has plenty to read over Christmas. Clues to 18 special articles are on the cover https://t.co/HFiIRBPF56 pic.twitter.com/V9mRUL3Ije

— The Economist (@TheEconomist) December 17, 2021