This is News Plus Special English. I'm Marc Cavigli in Beijing.
Time travelers, if they really exist, seem to be keeping their adventures to themselves.
Researchers with perhaps a bit too much time on their hands conducted an extensive Internet and social media search for evidence of time travelers going back in history and then bragging about it online.
And they came up empty. No real life Dr. Who or Marty Mc Fly from "Back to the Future" tweeting secrets a bit early.
An astrophysicist and his students at Michigan Technological University in Houghton, the United States, searched for mentions of Pope Francis and Comet ISON before they popped into reality. Francis was elected pope last March and ISON was first detected in September 2012.
The idea: If someone mentions a Pope Francis in a 2011 tweet, Facebook post or blog item, then they must have come back from the future with special knowledge.
But no one posted anything prescient.
This and other disappointing results are presented at the American Astronomical Society conference in Washington.
Astrophysicist Robert Nemiroff says if someone went back in time and said something to hint about the future, it would prove the concept of time travel.
Nemiroff says he didn't believe much in traveling backward in time before, and believes less in it now. He jokes unless he himself goes back in time and publishes lots of papers.
