Science has changed the world. It has created new products and ease of service. What the future will bring is, of course, always uncertain. “It’s not every day you have robots running through your house,” Barack Obama quipped last week at the White House science fair, a showcase for student exhibitors that also gave the US president a chance to reiterate a favourite theme. Science and technology, he said, “is what’s going to make a difference in this country, over the long haul”.