Sam Altman sits behind his desk with his knees pulled up to his chest, eating dried apricots. He’s 29, but even the most laissez-faire bartender would card him. His hand is forever grabbing his hair while he thinks, making it stick up in Einsteinian tufts. He says his main interest is indeed physics, though when he got to Stanford University he majored in computer science because “I already knew a lot about physics.” His T-shirt reads “make something people want,” the slogan of Y Combinator, the accelerator he runs. In exchange for 7 percent equity, it hands out $120,000 and three months of Wi-Fi, coffee, parking, and free advice to brand-new startups.