For decades, experts have debated how to tell when machines cross into true intelligence. On Wednesday in Berlin, OpenAI CEO Sam Altman and British physicist David Deutsch agreed on a new benchmark: If an AI could crack quantum gravity — and explain why — that might be enough to call it human-level smart. Altman stopped at Axel Springer's headquarters on Wednesday to meet with tech leaders and collect an award. That night, in a fireside chat, publisher Mathias Döpfner asked about Altman's favorite book — D ...