A Trick With A Time Machine

Poul Anderson, "The Nest" IN Anderson, Past Times (New York, 1984), pp. 71-111.

I basically understand what Trebuen and his companions do with their time machine, the Rover, but nevertheless have some questions about it.

There are four people in the Rover:

Trebuen, the Cro-Magnon;
Don Miguel, the Spaniard;
Olga, the Martian colonist;
Inini, the Babylonian.

The first three agree on what they will do. Inini, recently rescued from slavery by Trebuen and Don Miguel, cannot yet understand time travel.

Having taken the Rover a thousand years into their future, they then return to within a second of their departure time and:

"We stepped out of the machine." (p. 109)

Does "We..." mean three or four?

As they leave the chamber, the Rover appears again beside itself and three figures get out. This time the number is stated. The Rover appears yet again several times and soon there is a crowd of people who have stepped out of it. This crowd, numbering at least three hundred, and armed, exits the chamber and the castle and joins the battle which Trebuen etc had left where liberated slaves are attacking their Norman oppressors.

The three hundred or so stick together firing at the Normans but they do this for only twenty minutes. At the end of twenty minutes, they would return to the chamber where they would re-enter the Rover, take it back into the future:

"...and return within one second and some feet of our last departure point." (p. 109)

Why go back into the future? Why not simply travel back to within one second and some feet of their last departure point? Or do they take time to rest in the future? (Anderson probably does mean this but I have only just reasoned it out while writing about it.) But doesn't he mean that they return within one second of their last arrival point? All three hundred are there simultaneously, not in threes (or fours) successively.

After twenty minutes of sustained fire from the three hundred, the enemy breaks and runs:

"...and the four of us were all there - victors." (p. 110)

So here we are told that all four were involved.

Trebuen comments:

"I hate to think about seventy-five of myself acting as targets at the same time..." (ibid.)

Seventy-five multiplied by four gives us three hundred. This confirms that all four were involved in the time traveling - except that, on at least one occasion, only three left the Rover.

If there were seventy-five coexisting Trebuens, then let us call them Trebuen-1 to Trebuen-75. If, e.g., Trebuen-20 were shot and killed, then Trebuens-21 to -75 would not exist. Therefore, the fact that there were seventy-five Trebuens at the beginning of the twenty minutes is sufficient proof that none of the Trebuens were going to be killed during the twenty minutes.

Trebuen refers to:

"...twenty minutes - or twenty-four hours, depending on how you look at it." (p. 109)

He means twenty minutes of objective time and twenty-four (?) hours of subjective time. If he experienced the same objective twenty minutes seventy-five times, then his subjective duration was twenty-five hours. But, even if it were only twenty-four, they would certainly need some rest periods in the future. However, time travel allows both these possibilities:

a time traveler co-existing with himself for, e.g., twenty minutes;
a time traveler sleeping for eight or more hours between living through a twenty minute period and again living through that same twenty minute period.