Immediately, the two would-be time hunters ran into issues.

The first: Google+ doesn’t always order search results by time, confusing the research, they found. “It was therefore too difficult, in practice, to find older and potentially prescient informational mentions,” they lament. They abandoned the network.

Facebook search proved perhaps more frustrating. The service allows statuses to be backdated: A user could have made a post in the summer of 2013 about Pope Francis, then dated it to April 2008. As such, a user would look exactly like a time traveler. Furthermore—and perhaps even worse—Facebook frequently failed to return results for statuses posted too far in the past.

Attention, Facebook and Google+: Your social network’s crappy search is preventing humanity from finding time travelers from the future.

Even working through these issues, Nemiroff and Wilson failed to find a single particularly prescient post on Facebook or Google+.

On Twitter, though, they did find one tweet, posted before March 2013, referencing “Pope Francis.” Once they consulted the blog post it advertised, though, they the tweet “deemed overtly speculative and not prescient.”

Apparently, if time travelers are on a social network, they aren’t using it to spoil the news.

The physicists made other attempts to discover future time travelers. One of the study’s authors, Robert Nemiroff, helps run NASA’s long-running online feature, the Astronomy Picture of the Day. He looked at logs of search requests performed on the site to see if anyone had searched for Comet ISON before it was discovered. He found, unfortunately, no prescient searches.

So he and Wilson made one last effort. In August of 2013, for instance, they searched Twitter for two hashtags. They also checked their inbox for emails containing the hashtags. In September 2013, they asked any time travelers to go back in time and send them emails or post tweets containing the hashtags. They had neither found nor received, a month before, any tweets or emails containing the hashtags.

The study, alas, turned up no time travelers. But that doesn’t quite mean anything. The authors admit that the study might have failed for many reasons: Time travelers might not have the ability to physically adjust the past; they might not have posted about the events the authors were looking for; they might have posted about the events but not turned up in a search. Time travelers might have also read the study or this news story about it, and been sure to making avoid any careless mistakes.

I so enjoyed the study that I called up Brian Greene to talk about it. Greene is a theoretical physicist at Columbia University, a PBS host, and the author, most recently, of The Hidden Reality . He had another idea about why time travelers didn’t presciently post.

“Maybe social media doesn’t persist in the far future, so time travelers don’t know how to tweet,” he said.