SpaceEverything we know about the universe – and a few things we don'tHow big is the universe? What shape is it? How fast is it expanding? And when will it end? We answer these questions and more in our essential guide to the current state of cosmological knowledgeFeatures
PhysicsBall lightning is so strange it might just come from another dimension Mysterious floating orbs of light have puzzled scientists for centuries, inspiring no end of creative explanations. A new idea suggests they aren't entirely of this world Features