It’s likely that we can’t do time travel. But we don’t know for sure. The arrow of time comes from the increase of entropy, meaning that the universe started out organized and gets messier as time goes on. Every way in which the past is different from the future can ultimately be traced to entropy. The fact that I remember the past and not the future can be traced to the fact that the past has lower entropy. I think I can make choices that affect the future, but that I can’t make choices that affect the past is also because of entropy. I can choose to have Italian food tonight, but I cannot choose to have not had it last night. But if I travel into the past, all that gets mixed up. My own personal future becomes part of the universe’s past. We’re not going to make logical sense of that. So the smart money would bet that it’s just not possible.
– Physicist Sean Carroll, in a New York Times interview.
This is a pretty tremendous — if too brief — interview. Carroll puts a whole lot of crazy, big-picture science stuff into layman’s terms and nails precisely why I never paid much attention in my high-school science classes but now read Discover and the Science Times whenever I can.
As for the time travel thing, it strikes me that he’s probably right, and that’s depressing. I fantasize about time travel a lot, and I read and watch enough science fiction that sometimes I feel like it’s inevitable that we’ll eventually figure out a way to manipulate time. But when you really, really think about the implications of it, as Carroll suggests, it just doesn’t seem possible.
For what it’s worth, I wonder if time-travel narratives are more popular, relatively, in somewhat recent Western culture than in others. This Wikipedia page mentions incidences of time travel in ancient Hindu mythology and a Japanese folk tale from the 8th century A.D., but naturally it would take a lot more research to determine exactly when, why, and how often people started speculating about moving forward or backwards in time.
It feels like something that should be universal, but I guess I have only lived in a world where speculating about time travel is a regular happenstance. To me it seems at least partly driven by the Butterfly Effect; probably half of my time-travel fantasies involve going back in time to convince myself against some decision I made — even if it’s not something I particularly regret — just to see how it would impact my life now.
The other half involve tasting dinosaur meat, observing a dystopian future, harassing historical figures, and all the standard time-travel fare.
Tedquarters 
But if you could time travel would you go back and be a fan of a different team than the Mets?
BTW I would become an As fan mostly because that dude yelled at A-Rod about walking on his mound.
That and if you’re going to suck at least suck intelligently?
I would time travel back to 2006 and after attending Game 6 of the NLCS which I did do, I would attend Game 7 instead of travelling back to Boston to minimize the days I took off at work, which proved worthless when my boss told me “why didn’t you go to game7, I would have”. That way, I would find a way to tell Aaron Heilman not to hang a pitch to Yadier Molina, and hopefully the rest would take care of itself, with me in attendance watching this glory.
/wakes from dream, vomiting.
Ted,
do watch the science channel at all? Recently they’ve had some interesting shows about the concept of time and time travel.
Not enough, I guess. I should probably check that out.
The two I watched recently were called “what time is it” and the other was and episode of a series called Sci-Trek. That particular episode was about time travel. Its all real scientific, quantum mechanics, theory of relativity, einsteisn concept of space-time etc.
I dont realy understand half of it, but its interesting none the less.
Most excellent post, Ted.
Dinosaur meat.
I wish I could photoshop Ted’s face on Fred Flintstone’s body, sitting in the foot powered car, with a huge rack of dinosaur ribs causing the car to tip over.