Debate and switch? Biden’s stumble

America’s president had one primary task at last night’s debate: to close down speculation about his mental faculties. It went so poorly his whole campaign is now in doubt. Tentative results from a newish instrument give tantalising hints that the leading theory on the universe’s makeup might need reworking entirely (10:20). And bullfighting moves from literal arenas to the political arena (18:40).

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