"Why," Padme asked, as the TARDIS began coming in for a landing, "doesn't going back and forth through time make you meet people in the wrong order?"
"Blinovitch limitation," said the Doctor immediately, precisely because he knew he'd never defined the term to her.
"Which means?" How did all these girls learn that facial expression? He'd had such hopes for this one.
"I could show you the math," he offered, just so she knew he knew she knew he was being difficult.
"Thank you, no." Well-bred at least, this one, unlike some.
"Being recognized by someone I never met is something that almost never happens," the Doctor came clean. "There was a chap called Vader. And another called Ancelyn," he added quickly, though not quickly enough to sound as if he was avoiding a subject. "But time-travel is like climbing something, say a tree trunk on Juvinghiviss III, that's a spiral or corkscrew shape. It's easy to drop from this loop to the one below, or perhaps to reach up and pull yourself onto the one above, but it's much more difficult to just crawl back and forth along the loop you're on. Few people have lifespans that encompass more than a fraction of one loop."
"What about institutions?" Padme asked, as the Doctor swung the TARDIS door lever and led her toward the exit. "Are you known to my civilization in other times, as you are in mine?"
Twice in a minute he'd had to dodge that bullet! But he wasn't going to saddle Padme with this time paradox when there was no need - bad enough he'd let on as much as he'd done to Yoda and Mace Windu. "I'm not all that well known in the Republic," he said, a half-truth. "In fact I purposely try to remain unnoticed by, to use your word, institutions. Not so much to keep from running into people who already know me, but to keep down the chances of an institution that has come to know me in one era discovering me too soon."
Even as he spoke, he and Padme closed the TARDIS door behind them, and noted that they'd materialized in the cramped corridor of a spaceship. Simultaneous with their departure from the TARDIS, a group of uniformed people entered the corridor from a room partway down the hall.
"Who the hell are you?" demanded the man in the lead, a fortyish fellow with an open face.
"Why, I'm the Doctor," said the Doctor, putting his hand out and having it reflexively shaken. "And you are?"
"I'm Captain Jonathan Archer of the starship Enterprise."