Re: TimeTravel

Hal Finney (
Fri, 23 Oct 1998 10:41:32 -0700

Michael Lorrey, <>, writes:

> Actually, if Feynman's Transactional Interpretation of QED holds true,
> then travelling in to the past should be no more difficult than a device
> that converts the traveller's mass into antimatter in the future, then
> back to matter in the past. Of course, this necessitates that time
> travel will only be possible where/when a matter/antimatter converter
> is in existence. If your mass is instantly converted to antimatter, you
> should start travelling back in time, as anti matter is merely matter
> that is travelling backward in time, according to the transactional
> interpretation. Granted, building a device that not only turns normal
> matter into antimatter, but will maintain the biological structure of
> the human body is a technological acheivement in and of itself.

Not to mention it would violate conservation theorems...

But actually I don't think this would cause you to travel backwards in time. Although the individual particles might be thought of as travelling backwards in some theoretical sense, the larger system's arrow of time will be determined by entropy and not by the nature of its particles.

If you crowd antimatter particles into the left half of a sealed chamber, they will expand to fill the chamber just like regular matter does. The system changes to increase its entropy. The same thing happens in our bodies, as chemical and physical reactions occur. Two copies of the body, one made of antimatter and one of regular matter, should evolve in parallel (modulo some esoteric asymmetries between the two kinds of matter).