"I think it's going to rain." Bill commented, raising a potato chip to her mouth as she watched the starry night sky, along with a few scattered clouds.
She looked at the timelord beside her, who was more occupied with straightening the telescope he was fiddling with. He looked at the sky, finding some specific point, and then went back to adjusting the object. Finally, he pulled away and motioned for the girl to look through the lens.
"An introduction to our next class next wednesday," The Doctor stated.
Bill handed over to him a newspaper that was rolling the potatoes and he stared at the food for a few seconds, don't understanding why she had given it to him. Then he shrugged and picked up one of the biggest potatoes and brought it to his mouth.
The Doctor watched Bill bend down and look through the telescope lens at the point he had selected. The girl smiled, even though she didn't even notice the expression she was wearing. And he liked to observe the look on her face in those moments, of discovery, of the new, of the intriguing... It was like a pleasure to teach that young woman.
The Doctor wished that more students at the university he lectured would have the same desire she had.
"Proxima Centauri, from the Alpha Centauri star system." He cut off the train of thought, explaining where he'd focused the telescope, as he picked up another big potato chip. "They are the closest stars in the Solar System."
"And that one besides is Southern Cross," Bill said, taking her eyes from the sky and back to the Doctor. "Hey! My potatoes!"
The timelord took another of the potatoes to his mouth, followed by an 'sorry' gesture.
"Exactly." Absently, he picked up another potato and pointed it at the sky. Bill didn't even notice, having turned her gaze back to the sky. "Right at the edge of the constellation, we have Alpha Cruc…"
"How do stars come to life?" The young woman interrupted his explanation, but he did not care, seeing genuine curiosity in her eyes.
It wasn't just the smile, but the eyes, which seemed to glow like the stars they gazed at from the college observatory. It was really lovely to see that sparkle in her eyes, dazzled by things that were so common to him, so many times he had seen them. It was in that fraction of an instant that the Doctor was really sure: he had made the right choice. Not just by choosing Bill to be his 'pupil'. He had made the right choice in deciding to invite her to travel with him.
The universe was vast, infinite, yet after so many thousands of years traveling through it, most things became… He didn't want to use the word 'ordinary', however, he couldn't think of any other at the moment. But that was really what he felt: that wonder was starting to go away. But it was because of it that he had them. They look admired at the space, that thing that he almost called "his backyard".
And Bill was like that. The eyes that glowed with a glow similar to those that made the stars burn. And that smile, that she didn't even realize it was forming, but that showed so much of what was going through her mind in those moments.
And speaking of starlight…
"See those clouds?" The Doctor pointed to the sky that was beginning to cloud over. Bill was right, it would probably rain during the night. However, for now, they could enjoy the spatial view.
Bill nodded, having taken her gaze from the top of their heads and back to the timelord beside her.
"In space there are also clouds, full of gases and dust. And it is within them that the star is born". He smiled, remembering how many times he had witnessed the birth of one of these heavenly bodies. Then he turned his eyes upward. This gesture was imitated by Bill. "Gravity then starts pulling more gases into the cloud, causing the atoms to collide with each other and to heat up more and more, until boom!" He demonstrated with his hands, even though he was still holding the newspaper with the potatoes, more empty, in one of them. Bill laughed at the onomatopoeia employed by the Doctor. "It is through this explosion that a star is born, which will shine for a few million or billions of years, until it dies."
Bill turned to face him, ignoring that more than half of her potatoes were gone, after all, she was more amused by the explanation she was getting.
"And what happens when they die?" she inquired, really interested in the topic that herself had raised.
Briefly, she noticed the Doctor turn his eyes to the sky, with a feeling that looked like… Was that nostalgia in his eyes? She couldn't say, however, she believed it was.
He had traveled for so long through time and space, until finally stopping for decades — from what she had heard, the Doctor had been lecturing at that university for at least fifty years —. No wonder he found himself nostalgic looking up at the sky. Maybe even homesick.
Bill smiled wistfully at the look in his eyes. Sometimes he looked so sad…
"The gases never stop fusing. After a while, they start to form other elements and the star's core becomes so dense that it releases the energy, creating a supernova."
Bill opened her mouth in 'oh!', finally understanding how a supernova is formed. The Doctor smiled for a few seconds at the girl's expression. Encouraged by this, he decided to continue.
"After that, the supernova can either turn into a neutron star or, depending on the size of the star, turn into a black hole."
When the explanation was over, he picked up one of the potatoes again. Bill ceased asking questions for a while, returning her attention to the sky. She gets really marveled at how the Doctor could explain such complex things in such a simple way.
"And do you miss it?" She voiced the question that was on her mind, receiving a confused look from the timelord. "Do you miss there, seeing the stars, the supernovas…" In response, the Doctor was silent and Bill regretted asking that question. "It's just…you seem to miss something when you look over there." She pointed to the sky with her head. The girl had switched her attention from the stars above them to the timelord beside her. Both the skies and the Doctor were really intriguing.
He seemed to feel so much at the same time, with just this questioning, that she couldn't even guess all the feelings passing through those blue eyes.
When the Doctor seemed ready to formulate an answer, after pondering what to say for more than a full minute, Bill interrupted him:
"Why don't you take me there?"
He frowned, surprised by the young woman's sudden proposal.
"And on the way back you can buy me some potatoes. I'm still hungry." She pointed a finger at the newspaper the Doctor was still holding, containing only a half dozen potatoes, as he had devoured the rest during his explanation of the stars.
"How about seeing Alpha Centauri?" he suggested, referring to the constellation that had started the whole conversation.
The timelord really hadn't expected that 'practical class' about something he was going to start teaching Bill to turn out to be such a sudden invitation. And who would have thought she was the one to propose that to him? He would always be surprised by humans, no matter how much time he spent between them.
"Somewhere, something amazing is waiting to be discovered," Bill said suddenly, taking one of the last potatoes to her mouth. The Doctor frowned at her sentence.
"Carl Sagan." In a matter of seconds he had recognized the phrase she quoted. "He was a brilliant man. And he agreed with me about the similarity between physics and poetry."
The two started to go down the stairs towards the observatory exit, with the Doctor in front, leading the way to his office, where the Tardis was standing.
"I read one of his books on your desk," Bill confessed, finishing the last of the fries.
"Have you been messing with my desk?" he returned, not looking very happy with the girl's statement.
Bill just laughed, tossing the newspaper into a trash can as they reached the corridors of the Exact Sciences building.
And so she let the Doctor lead the way and then show her, at least a little, that immensity of the universe. All the time she kept the same glow in her eyes, almost the same intensity as the stars they watched so closely. And the Doctor smiled too. A smile full of nostalgia for being in the place he missed so much. But at the same time, it was also a happy smile. Glad to see that amazed smile on Bill's face.