The Problem with Time Travel

I recently saw, and was amused by, this Abstruse Goose comic:

http://abstrusegoose.com/526

History buffs are often asked (in the process of making an acquaintance) what time period they'd like to inhabit, or at least to visit for a little while. I find that I tend to give answers as if I were white, male, and Christian (my main area of interest is pre-modern and early modern Europe). After all, the Scientific Revolution, or Republican Rome, or the Italian Renaissance are fascinating times to have been alive if you weren't being downtrodden, persecuted, or discriminated against. (I imagine that, being both female and Asian, I would have twice as much difficulty as either of the above characters. I wonder if the probability of death by persecution would increase logarithmically with each undesirable trait?) If I were to actually consider the logistics of visiting a particular time and place, I'd be largely limited to China and, well... there really isn't a good historical era in which to be female.

What Would You Do with a Time Machine?

I've been asked the above question quite a few times (I think it happens to history majors fairly frequently), and my answer tends to vary depending on the classes I happen(ed) to be taking, the books in my bag, the day of the week, &c. By now, I do have a list of responses that I cycle through and explain in depth at parties (which, for me, are of the variety that includes social dancing, board games, home cooking, or karaoke).

This is an answer I've given before, because I think it's one of the great tragedies of the classical world:

I imagine the "Dark Ages" would have turned out quite differently had the libraries of Egypt, Rome, and all the other great ancient cities not burned. So much knowledge -- especially in the sciences -- was lost, setting human progress in the West back several centuries. If I had a time machine... I would definitely go back to save the second volume of Aristotle's Poetics, and Aristarchus's text on astronomy, and Ovid's Medea, and Euripides's lost plays...

In short, I would be both the best and worst Doctor's Companion ever.

Discover: How Would Time Travel Actually Work (or, something for all the Whovians)?

A good, cogent article on the physics of time travel:
http://discovermagazine.com/2010/mar/02-the-real-rules-for-time-travelers/

I first encountered this explanation of time travel in Harry Potter and the Prizoner of Azkaban, where Harry and Hermione use a Time-Turner to save Sirus and Buckbeak. (I trust that I didn't spoil the book for anyone -- and if I did, you're way behind the times!) The detail of the Time Turner chapter that I found most memorable was the thud of the executioner's axe: Harry and Hermione heard it fall in real time and assumed that Buckbeak had been beheaded; however, when they went back in time to rescue the hippogryff, they realized that the sound they'd thought was Buckbeak's decapitation was actually the executioner swinging the axe into a hunk of wood in frustration upon discovering that Buckbeak had escaped. Harry and Hermione, therefore, did not change the timeline using the Time Turner; rather, events incorporated all nonlinear parts and intersections of the timeline.

The concept of free will, as the above article notes, becomes problematic if this framework of time is true. Nature, it would seem, is more like a Greek tragedy than we Americans would like to believe. We are uncomfortable with the idea of external limits on our free will, and time is too nebulous to most of us to think its laws as insurmountable as, say, those of Newtonian physics. If we were told that our free will is limited by gravity (no matter how much we might wish to levitate through the air, we cannot), we do not find it unjust. Told that Oedipus had no choice but to kill his father and marry his mother, despite all of his attempts to escape his fate, we find his situation grossly unfair. The above description of time travel suggests that our universe operates more like Oedipus's than we'd imagined.

I believe in free will. I do. But I'd love to try time travelling -- it sounds fascinating.