If you had traveled from the future to the present, you might be likely to mention some things that you'd learned there (for example: buy this lottery ticket). Using this logic, physicists searched for prescient mentions of future events on the present-day internet, scouring Twitter, Facebook, Google, Google+ and Bing. They used these services to see if anybody had mentioned Pope Francis or the comet ISON before these terms existed, looking at the time span from the early 2000s to mid-2013, the idea being that both terms represented major events travelers-from-the-future might talk about somewhere online. But they came up empty.