Spike shuffled up the steps to Twilight's balcony, bearing a platter of cookies and a friendly smile. He found her nestled on a cushion and peering through her telescope at the night sky.

"Hey, Twilight!" he said excitedly. "I brought you some cookies."

"Thanks, Spike," she said without looking up. "You can just set them down over there." She gave a vague wave of her hoof.

Spike slumped a bit. Still, he was intent on spending some time with her, and he had learned a few tricks in all of his time as her assistant.

"Why're you studying space, anyway?" he asked, trying to sound casual. "I don't see what the big deal is."

She tore away from the telescope and straightened up in shock.

Works every time.

"'The big deal'?" she asked, incredulous. "Astronomy is one of the natural sciences--one with a history almost as fascinating as the science itself."

"Really?" Spike plopped down and stuffed a cookie into his mouth. "Do tell."

"Well, if we're talking about the history of astronomy, I'd have to start with Ptoleneigh." She shifted on her cushion to fully face him. "Like many ponies and astronomers in his time, he held that our planet was the center of our system, and that the sun and moon orbited around it."

Spike swallowed another mouthful of cookies. "Well, yeah—isn't that obvious?"

"It might sound obvious to us, Spike," Twilight agreed, "but throughout history, there were other astronomers with different theories. For example, Coponicus had a model of the system—one that was even supported by famed griffon astronomer Galla Leo—where the [i]sun[/i] was in the center."

"The sun?" Spike's eyes narrowed as he attempted to visualize it. "So, our planet and the moon are supposed to go around the sun...?"

"Well, no," Twilight said. "In that model, we go around the sun while the moon goes around us."

Spike started tracing circles in the air with his claws, trying to adjust his mental-image. "Wha...?" It was starting to make him dizzy.

"And day-and-night cycles were not because of the movements of the sun and moon, but because of the planet turning on its axis of rotation," Twilight finished.

Spike suddenly froze.

"...Axes of what?"

"Basically, they thought the planet is constantly spinning as it goes around the sun."

"Uh, Twilight?" he said with a chuckle. She had to be joking. "I think we'd notice if the planet was spinning. We're [i]standing[/i] on it." After all, it doesn't take a pony very long to realize if they're standing on a merry-go-round.

Twilight let out a giggle. "I know it sounds silly, Spike, but astronomers really believed this stuff. Of course we know the truth now. It's as the philosophers say: the simplest solution is often correct." Twilight nodded. "But you see, that's precisely [i]why[/i] we continue to study space or... anything, really. Our understanding is constantly changing and growing, and..." She turned to look at her telescope, smiling softly. "And I'd like to be a part of that."

Spike nodded slowly.

"Well, I hope that answers the question, Spike." She levitated a cookie over and took a bite.

"Yeah, it does." Spike got up and dusted himself off. "Thanks for explaining it to me." He smiled bashfully, grateful for the time they spent together.

"No problem," Twilight said, returning her attention to her telescope. "Just let me know if you have any other questions. I'll be happy to answer them."

"You got it." Spike took a step to leave but stopped. "Well, actually, there is something else I've been wondering for a while..."

Twilight turned away from the telescope and smiled to him. "Yes, Spike?"

Once again, Spike's eyes were narrowed in thought.

"...Where do babies come from?"