When our memories are detailed, the moment seems to last longer. Here’s what Neuroscientist David Eagleman said in a profile in the New Yorker: “This explains why we think that time speeds up when we grow older,” Eagleman said-why childhood summers seem to go on forever, while old age slips by while we’re dozing. The more familiar the world becomes, the less information your brain writes down, and the more quickly time seems to pass.