Searching the Internet for evidence of time travelers

This is interesting, but these methods don't strike me as really viable. The Twitter outreach was specifically targeted at the cooperation of Twitter-using time travelers, and while Pope Francis might or might not be historically significant enough to warrant prescient mentioning, I'm sure comet ISON is not. The assumption is also (and maybe it has to be) that time travelers would blurp out important prescient information - however, I don't think that holds true if they were either well disciplined or engaged in historical research - which would mean they know little more (if anything) about our immediate future than we do.

I'm obviously not advocating time travelers are present (I would think with the certain prospect of leaving your time line in order to create another one, the proposition of time travel seems akin to a one-way change in universes that doesn't sound very inviting), but it's definitely fun to speculate about. Realistically, one would also have to take into account the fact that, by mere virtue of being present, a time traveler will change the course of history in the long run.

A more thorough effort could center on large-scale automated data mining for prescient terms on the internet. Of course, there would be many false positives, but as a side effect we could learn more about the epidemiology of ideas even if we don't discover time travelers. It seems to me that a disciplined time traveler would not purposefully drop historically significant hints - however, if they are from a future and culture close enough to our own, they might still reveal themselves inadvertently through idiosyncratic phrases and reference to concepts that are from the future. Hand-picked phrases are not enough to discover this, it would have to be large-scale AI-supported text mining.

What if there is no internet in the future?

you are assuming time travelers change history, but it's different if you subscribe to the idea that you can't change past because in fact you did not change the past.

Then you can detect people saying stuff about the future, or possibly attempting to kill hitler while failing miserably.

> Let's also assume that somebody had a reason to travel into the past, say to kill Hitler. Our timeline would record that an Austrian artist was murdered in the 1920s.

This would prevent World War 2 and the associated advances in technology, possibly including those leading to the time travel being possible in the first place.