Some Time Travel Details

Today we visited Levens Hall, a building full of English history, for example the Duke of Wellington's glasses and gloves, but, most pertinently to Poul Anderson's works, armor worn during the Civil War.

Back to time travel:

Harry Harrison wrote a definitive historical circular causality novel, The Technicolor Time Machine, but was less successful with Rebel In Time. In the latter novel, our hero knows that the villain has traveled back to a particular time in order to help the Confederates win the American Civil War. Hero travels back to thwart villain. The method of time travel used ensures that he arrives at the same place. (They are transmitted back from a particular research establishment rather than traveling in a vehicle.) Hero arranges to arrive a few hours after villain and then has to find him. Why did he not arrive before him in order to apprehend him on arrival?

It may be replied that this would have deprived the novel of the drama of pursuit in a historical period but this is not the point. The method and circumstances of time travel could have been adjusted to allow for this, e.g., if it is not possible to be precise about arrival times, then the hero might have to arrive a considerable time beforehand and hide elsewhere while waiting. Then, circumstances could prevent him from returning to the arrival point in time to catch the villain arriving. The point is that both the author and the characters seem to confuse time travel with travel through space or on the Earth’s surface. In familiar travel, if we depart after someone else, then we arrive after him as well. It seems to be taken for granted that this should also apply to time travel. That none of the people experimenting with time travel realizes this amounts almost to a logical contradiction in the novel.

-copied from The Logic of Time Travel: Part II.

 

Poul Anderson, of course, gets it right:

 

from 1973, Saunders has briefly visited 1953 and 1993;

 

however, small automatic time projectors, sent to 2073, have not returned (remember the Time Traveler's model Time Machine and the Time Patrol message capsules);

 

in the large time projector, Saunders and Hull travel a hundred years ahead minus the number of days since the first automatic was sent because they do not want any futurian to have removed it;

 

the automatics are not there so they must have started to return but failed en route;

 

returning in ten-year hops, the two chrononauts, so to call them (Wells wrote "The Chronic Argonauts"), find two weathered projectors in 2013;

 

so the projectors got back further, then stopped and aged;

 

fighting back against increasing resistance and energy drainage, the chrononauts take two hours to reach 2008, then deduce that they would need infinite energy to reach 1973.

 

Notice that, in their initial attempt to retrieve the automatics, they aimed for the automatics' arrival time, not for a date a few days later.