People From The Past

Warning: this lap top is at the end of its life and there will be a delay before getting another, especially since I will be away all next week.

Poul Anderson's Time Patrol series is two long volumes on time travel whereas his History of Technic Civilization is seven long volumes on interstellar civilization: two lengths, long and longer, and two basic sf themes.

People From The Past In The Time Patrol

(i) Babylonians at the Time Patrol Academy have to be given a battle of the gods routine.
(ii) A Roman from Caesar's time never learns that machines cannot be treated like horses.
(iii) Pummairam of Tyre discerns that his temporary employer Everard will battle wizards in a strange realm. Pum is recruited to the Patrol.
(iv) Jack Hall, a cowboy recruited in 1875, works in his own period and time travels only to holiday in the Pleistocene.

There will be more. We only ever scratch the surface of the Time Patrol. The phrase "causality vortex," used a few times but never really explained, is applied to the random space-time-energy change in medieval Europe counteracted by the Patrol in Part Six of The Shield Of Time.