Lonely physicists have searched for time travelers before, and they'll probably do it—and fail—again.
In the spring of 2005, an MIT graduate student hosted a convention for chrononauts, but sadly nobody from the future attended. Stephen Hawking once threw a summer soiree for them, and sent invitations after the fact. Again, not much of a party.
In a separate 1992 paper, Hawking concluded in nearly unreadable jargon that time travel into the past is pretty much impossible: "These results strongly support the chronology protection conjecture: The laws of physics do notallow the appearance of closed timelike curves."
These previous findings did not discourage Michigan Technological University astrophysicist Robert Nemiroff and one of his graduate students from recently conducting what the authors term the "most sensitive and comprehensive search" for time travelers in history. Not surprisingly, the team discovered absolutely no evidence that people from the future are traversing the space-time continuum, especially to post hashtags on Twitter or to email nerdy physics researchers.
The study, presented Monday at the meeting of the American Astronomical Society in Washington, D.C., focused on locating time travelers by seeking "prescient information," or "content that should not have been known at the time it was posted," on the Internet.
In one experiment, the researchers selected two terms with little chance of being used on Twitter before they came into the "public lexicon:" "Comet ISON" (a unique astronomic label that only emerged in September 2012) and "Pope Francis" (a name selected in March 2013). Then, they searched exhaustively for them in a window of time between 2006 and when they first emerged. Not surprisingly: "No clearly prescient content involving "Comet ISON," "#cometison," "Pope Francis," or "#popefrancis" was found from any Twitter tweet -- ever. "
In another test, they looked for prescient queries of "Ison" in NASA's Astronomy Picture of the Day Web page, which is co-edited by Nemiroff. The team uncovered a few instances in which someone had looked for the term, but, unfortunately, none were time travelers. "Upon further investigation, each of these instances was related to extraneous information or misspellings, leaving no queries as possibly prescient," the authors wrote.
The first two methodologies allowed the researchers to search for "passive" time travelers, but they also wanted to determine whether they could bait someone in the future into "actively" communicating with them. They explain:
A post was created in 2013 September on a publicly available online bulletin board requesting that one of two hashtags be tweeted or emailed before a certain date. Specifically, time travelers were requested to respond with a communication including either the hashtagged term "#ICanChangeThePast2" or "#ICannotChangeThePast2" on or before 2013 August.
A message incorporating the hashtagged term "#ICannotChangeThePast2" would indicate that time travel to the past is possible but that the time traveler believes that they do not have the ability to alter the authors' past. A universe where the past cannot be changed is termed as having a "fixed history", where history can be regarded as a single timeline. Such universes may uphold the Novikov Self-Consistency Conjecture . For example, in a fixed history universe, nothing the time traveler could do would change the existence of the Wars of the Roses, so content involving that event could always be found by the authors on the Internet.
Conversely, a message incorporating the hashtagged term "#ICanChangeThePast2" would indicate that time travel to the past is possible and that the time traveler can demonstrate the ability to alter the authors' past. Theoretical universes where the past can be changed are termed as having a "plastic history", where history cannot be regarded as a single timeline.
No emails came into the Nemiroff's Yahoo! account, and no tweets were issued. All of this may indicate that time travelers from the future are:
- Not interested in astronomy
- Not Catholic
- Not on Twitter
- Not wasting their time reading random online bulletins from 2013
Or, maybe, it suggests the obvious: time travelers from the future probably don't exist at all. The authors themselves call attention to that fact at the beginning of their paper, writing that the theory is "controversial, at best, and impossible according to conventional views of the laws of physics."
But the physicists conclude that their results "are by no means proof" that time travelers cannot communicate with the present-day. They write:
There are many reasons for this. First, it may be physically impossible for time travelers to leave any lasting remnants of their stay in the past, including even non-corporeal informational remnants on the Internet. Next, it may be physically impossible for us to find such information as that would violate some yet-unknown law of physics, possibly similar to the Chronology Protection Conjecture . Furthermore, time travelers may not want to be found, and may be good at covering their tracks. Additionally, time travelers just may not have left the specific event tags that we were searching for. Finally, our searches were not comprehensive, so that even if time travelers left the exact event tags searched for here, we might have missed them due to human error, oversight, incompleteness of Internet catalogs and searches, or inaccurate content time tags.
Perhaps. One thing the study proves definitively is that these guys have a lot of time on their hands.