RE: BOOKS: Pournelle's *A Step Farther Out*

Billy Brown (
Wed, 17 Feb 1999 08:44:42 -0600

Michael S. Lorrey wrote:
> I am increasingly of the opinion that even though time travel is
> theoretically possible through wormholes, in practice I think that the
> amount of time it takes to make use of such travel will waste any time
> gained in traveling into the past, then back to your original locality
> in space. I doubt that it will ever be more than a laboratory
> curiosity..
> It does not matter whether you travel from the other side of the
> wormhole back through normal space, or wait until the wormhole can be
> spun down to travel back to the original local frame at an
> earlier time..
> The time gained will be lost this way causality can be
> conserved while allowing specific FTL loopholes like that.....

I believe current wormhole theory allows the following method of time travel:

  1. Create a wormhole in your lab, spanning some short distance. Call its two ends openings A and B. If you step into opening A ten minutes after the wormhole is opened, you emerge from opening B ten minutes after the wormholes was opened (i.e. at the same time).
  2. Put opening B on a spacecraft, and accelerate it to near the speed of light. Let it coast in that frame of reference for awhile, so that you build up an age difference between the two ends of the wormhole.
  3. Bring opening B back to your lab, and put it next to opening A again. Let's say that opening A is ten years old at this point, but opening B has only experienced 8 years of time passage due to relativistic effects. This means that if you step into A, you will not emerge from B for 2 years. Likewise, if you step into B you emerge from A two years in the past.

The obvious consequence is that a wormhole allows for time travel, but only through the span of time in which the wormhole exists. So if you create one, you are issuing an open-ended invitation for visitors from the future.

I'll be very interested to see if this actually works in practice.

Billy Brown, MCSE+I