The TARDIS was dying.
The Doctor closed his eyes as it finally hit him. He didn't have a replacement power source, and with Gallifrey in ruins, there was nothing he could do. His days of wandering were over. He set his destination time and place to a place he knew he would have to call home for the rest of his life: Earth. He could hardly believe it was actually happening. Perhaps on Earth he could find some shred of power he could use to do something…anything was better than settling down, hopeless.
"Come on, old girl, you can do it. Just a little more. Then you can rest."
The TARDIS grunted in reply, and there was a whump of landing. No more could the Doctor do to save the last piece of his home he had left. It was over. He pushed a few buttons, to put his beloved machine in stasis while he looked for hope. A tear fell onto the console. The Doctor looked up to compose himself before he stepped out the door and into 57th century Earth.
He had landed about 36 centuries short. A few people were staring at the run-down police box and the disheveled, sad man who emerged. All the people started to trickle away, some snapping pictures with their cell phones (Typical twenty-first century humans, thought the Doctor) and others just walking away from the box that had appeared from thin air.
The Doctor got a job as Physics professor at the nearest college. He had a flat near the TARDIS, just so he could keep an eye on his old traveling companion. He had to grow used to not going in the TARDIS to do the daily routine. And now he realized the sort of life his companions had had to adapt to once they stopped traveling with him.
He had to be careful about his health-what in the world would happen if he had an accident and had to go to the hospital? "Oh, this is odd-this man has two hearts!" No, thank you, he'd had that already, and it had been the catalyst of his seventh regeneration cycle. The last Time Lord in the universe, doomed to die a quiet death on Earth. Not at all pleasant prospect for a galactic wanderer. The mundane routine of wake up, wander the city, come home, eat chips, go to bed, repeat process made him feel even more lonely. Thankfully the summer holidays were nearly over so he could start teaching.
"Now, does anyone actually know anything about physics?"
One student, a young girl about eighteen years old, raised her hand. A little young for university.
"Yes, ah, what was your name again?"
"Deora. I do actually know quite a bit about physics."
"Care to elaborate?"
"We all live in one universe. There are many other universes parallel to ours, separated by a thin layer of Nothing in between. Our current universe was formed when two other universes collided for a brief instant. This event was known as the Big Bang, or so it is termed in this universe. The recent events with the Cybermen were caused when a ship guarded by a people known as the Daleks crossed through the layer of Nothing and the Cybermen followed from their alternate universe. But that's history, not physics. There are four universal forces: gravity, electromagnetism, and the strong and weak nuclear forces. Of these, gravity is the weakest. The strong and weak forces hold the fabric of the universe, atoms, together. Is that enough, professor Smith?"
The Doctor had to admit he was rather flabbergasted. He was reminded of a girl named Susan, his granddaughter, who he had traveled with in his first regeneration.
"That was-that was quite enough for now, miss-what was your last name, Deora?"
"I'd just rather you called me Deora. Professor. Sir."
"Alrighty then, Deora. Now tomorrow we are going to start working experiments involving the weakest of the forces, gravity. Don't need your books, only your brains."
Deora stayed a bit after class. "Professor," she timidly asked, blue-gray eyes looking straight into his brown ones.
"Hmmyes? Don't you have another class?"
"Sir," she said with a shy smile, "It's the last class of the day."
"Oh…right. Uh, I'm afraid I'm not open for tutoring, that would be Professor Hallinson."
"I don't need tutoring, sir. I was just wondering-"
"Don't touch that!" He yanked the TARDIS key out of her hands.
"Sorry. I was wondering if you might permit me more higher-level thinking type activities. Experiments in four dimensions or something like that."
"What makes you think I can supply that?"
"It's sort of hard to explain."
Boom.
"What was that?"
"It sounded like it was coming from the teacher's lounge. To answer your question, it was an explosion. Sir."
"Shall we investigate?" Some sparkle was returning to his eyes at this.
Deora smiled.