Wednesday, November 7, 2012

Lunch Chat (11/8): Time Travel

With Einstein's relativistic physics, we get a sort of fusing of space and time. One of the interesting consequences of this fusing is the fact that no moment is objectively present — it depends on our frame of reference — and past, present, and future are all equally real. All of time exists.



Kurt Gödel (1906–1978)
This raises a fascinating possibility: could we actually travel to other times? As it happens, it was the famous mathematical logician, Kurt Gödel, who demonstrated how to solve the field equations of General Relativity in such a way as to introduce "closed timelike curves". Many other solutions have been offered since. Some of these solutions describe universes that are very unlike ours in structure (despite being physically possible — so far as Relativity is concerned anyway).

Without getting into any details, let's suppose that physics has indeed signed off on the possibility of time travel. What does that mean for philosophy? What consequences does it have on our conceptions of time? Of free will? Of causation? Of information? Think of the time travel stories that involve people intervening in the past. What if the way I intervene is to prevent time travel from ever being discovered — can I succeed? If I succeed, I fail! On the flip side of this coin, suppose a mysterious time traveler appears out of nowhere and provides me with instructions for building a time machine. I spend my life gathering parts and working out the delicate engineering necessary. After 30 years of exhausting work, I realize that I was the time traveler who gave myself the plans. I dutifully travel back 30 years and hand over the plans. Where did the information about how to build a time machine come from?!

In this lunch chat we'll puzzle over these paradoxes, talk about time travel stories/movies good and bad, and (as usual) enjoy some pizza and friendly conversation. Thursday at noon in the Philosophy Lounge (Coleman 62).