Topics Time

Question Say we could speed up matter and go further into time. I went and I saw my future self, no interaction, and I noticed that I had a finger missing or some dramatic change in my body since my present self. Could I dedicate my life to keeping my finger safe, or will it happen anyway?

Accepted:
November 25, 2005

Comments

On one picture of time travel, you could dedicate your life to that task, but you will fail. If it's true now that you will lose a finger next year, then you will lose a finger next year and zipping into the future isn't going to change that. Just as, if it's true now that you did lose a finger last year, then you just did lose that finger last year, and no backwards time travel will reverse that loss. (See also Question 528 and further references there.)

I agree with Professor George's answer, but I would like to add one thing. Suppose you are a professor of English. You take a time-machine trip into the future and learn from a reliable source that you died in dramatic fashion: in the midst of teaching a Shakespeare class. You tend to get very excited while teaching Shakespeare, and you died from cardiac arrest while giving a spirited lecture. However, you do not learn anything about the date of your death. Then you travel back to 2005 and continue your life. When your department chair asks you what you would like to teach next year, it would be perfectly rational for you to say, "Anything but Shakespeare." By not teaching Shakespeare, you cannot change the future from what it will be. (Apparently, despite your determination never to teach Shakespeare again, you end up doing so, somehow, and die in the midst of it.) But by not teaching your Shakespeare class next year, you can make it true that you lived a longer life. It is no different from your deciding today not to play in traffic. By doing so, you can make it the case that you live longer than you otherwise would.