From: Robin Hanson (rhanson@gmu.edu)
Date: Tue Oct 31 2000 - 06:40:13 MST
Curt Adams wrote:
> >There have been a bunch of physics articles about time machines over the
> >last few decades. They clearly show that time machines are not logically
> >impossible, though it is not yet clear whether or not they are physically
> >possible with standard physics. ...
>
>Yes, but the proposed time travel models do not allow the past to be
>*changed*. If a future event causally affects a past event, that past
>event was always altered. It's similar to a micro-time-travel
>model that Hawking used for predictions on black hole radiation.
>The current models agreed that changing the past creates paradox,
>and demonstrated that in certain limited worlds you could have time
>travel that didn't change the past.
Well yes of course you can't literally change the past, any more than you
can literally change the future. If you learn something about the way the
future will be, via a time machine or something else, then you are stuck
with that being the way the future will be no matter what you do.
And yet it does make sense to talk about choosing aspects of the future,
in situations where you don't know how the future will be and those
future events are casually connected to actions you will not take.
In exactly the same way in can make sense to talk about choosing aspects
of the past via a time machine.
You don't remember every dollar you spent on every day of your life.
So there is no paradox with your considering to use a time machine to
give your ten year ago self one more cookie, or one more sip of soda, etc.
Robin Hanson rhanson@gmu.edu http://hanson.gmu.edu
Asst. Prof. Economics, George Mason University
MSN 1D3, Carow Hall, Fairfax VA 22030-4444
703-993-2326 FAX: 703-993-2323
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