AN: So, here's some Valentine's Day fluff. I'm not that a fan of Valentine's Day to be honest, that's why this isn't all cheesy and pinkish. Hope you like it though, I think this suits our two boys much better. Enjoy your day with your beloved ones and have a nice weekend!
I would love to read some opinions about this in the reviews. ;)
~ Pockethobbit (who changed her name from TheNameIsAllieHolmes to Pockethobbit, if you haven't noticed already. Sorry for annoying you with this fact.)

The thing with the solar system

Sherlock was laying lazily on the sofa and John sat in his chair, reading a novel, when Mrs. Hudson knocked at the door. "Are you decent, boys?", she called joyfully. John made an affirmative grunt. Get one time walked in on stripping your flatmate in the kitchen and you'll never hear the end of it, he thought, sighing heavily as their landlady entered the flat. She came in with a tea tray and let her gaze wander over the scenery playing out in front of her.
"Oh boys", she tsked, walking over to the kitchen and putting the tray onto the table. "You two should do something", she said, pointing her index finger accusingly into their direction.
John frowned up at her, giving her a confused look. "Doing what?", he asked, glancing over at Sherlock who hadn't moved.
"I don't know, something more romantic than lazing around in the flat the whole day", she said, giving John a hopeful smile. He still didn't get it. Yeah, sure, they weren't the most romantic couple in the world, but even if they were, why should Mrs. Hudson randomly scold them for not being romantic enough?
Comprehension started to form on the woman's face and she looked at him in horror. "You can't tell me you've forgotten! I did expect Sherlock to forget, but you John?"
Panic started to rise in the doctor. Was today Mrs. Hudson's birthday? Had he forgotten? Oh god, he had, didn't he? He glanced to the calendar which hung at the wall beside the bookshelf, looking what date it was. 14th of February.
He frowned again. Mrs. Hudson's birthday was in March, he was sure of that.
"Mrs. Hudson, what should I have forgo-", he trailed of, noticing the little heart on the calendar, right next to the date. "Oh", he said, looking back to her now beaming face, and then said once again: "oh".
At this words, Sherlock opened his eyes to look at John's astonished face. Mrs. Hudson was standing in the middle of their flat, beaming and nearly vibrating with joy and John stared at her looking a bit lost. He had missed something. He hated missing anything. Swiftly he stood up from the sofa, looking down at John and demanded: "What is it?"
John just let his gaze wander from Mrs. Hudson to Sherlock, not saying a word. The detective just rolled his eyes, looking sternly back. "John", he said impatiently.
"Uhm… Sherlock, today is… Valentine's Day", he said, looking up at him hesitantly. Sherlock made a dismissive gesture with his hand. "And?", he asked. He didn't see the point John was getting at.
"Oh Sherlock", Mrs. Hudson scolded from behind him. "You surely want to spend your first Valentine's Day as an official couple somehow special."
"What do you mean official couple?", John asked, frowning at her in the same time as Sherlock said: "We already do." Both the landlady and the doctor turned to him, sending him confused looks.
"Do we?", John asked, trying to find a moment in the current they which had been special in any way.
Sherlock turned around, flopping back down on the sofa and steepling his fingers in front of his face. "Of course we do. Every moment I spend with John is special", he explained in his isn't that obvious, you idiots – voice. A small smile tugged at John's lips as he felt himself blush from that rare compliment. Mrs. Hudson made an indefinable noise and looked proudly down at Sherlock.
"Anyway, I just wanted to tell you that I'll be with my sister for the weekend, so you have an empty house", she said, winking at John and went out of the flat. John blushed further.
After a moment of silence, he cleared his throat. "So… uhm, do you wanna do something?", he asked Sherlock cautiously. The detective looked up at him, frowning. "Why?"
"Because it's Valentine's Day, and Mrs. Hudson is right, it's our first as a couple. Though I didn't understand what she meant with official."
"She has the impression we've been together since you moved in and just didn't tell anybody", he explained in a bored tone of voice. But inwardly he was thinking hard. Did John expect him to do anything because of a dull tradition which had been invented by brainless idiots? Did John expect him to be romantic? He had no idea how to do such things. What if John expected him to? No he wouldn't. Or did he?
He looked at John inquiringly. "Do you… want to do something?", he asked, not sure what he should do if John said yes.
"No", he answered, then quickly adding: "I mean, nothing like going out for dinner or baking or whatever. Unless you want to?"
Sherlock shook his head. They looked at each other for a moment, both not knowing what to do next.
Then John sighed, slumping down onto the sofa next to Sherlock who immediately put his head on his lap. The doctor reached for the remote and switched the TV on. They sat there comfortably, John running his fingers through Sherlock's hair and Sherlock correcting nearly every word of Casa Blanca.
When the film ended, the news got on. They watched for a moment, before Sherlock stated "dull", and turned his head, so that he could look up at John's face. Hand still in the detective's hairs, John shushed him and watched the weather news. "In the afternoon today will come some rain over London but in the evening the clouds will vanish again. For tonight the sky will be clear and it'll be relatively warm, thanks to the south-foehn."
Sherlock watched John's face suddenly doing something amazing. His eyes lit up and crinkled into a grin while his lips pulled down into a frown. He knew that expression. John always looked like this, when he had an idea or a thought which he didn't want Sherlock to notice. As if.
"What is it?", Sherlock asked, looking up at him and trying to deduce.
John glanced down and asked innocently: "What is what?"
The detective just rolled his eyes. "You clearly just had an interesting thought, certainly triggered by the weather forecast."
John started to smirk. "Have I?", he asked, before pushing Sherlock's head from his lap and getting up. He went to the door and put his coat on while looking for his keys. Quickly Sherlock got up from the sofa, striding over to him and grabbing his wrist. He turned him around and asked: "Where are you going?"
John grinned at him. "Having a little chat with Copernicus." Then he shook Sherlock's hand off, winked at him and left the flat.

Sherlock stood in the middle of the flat, baffled by the sudden turn of events. What had gotten into John? And who was that Copernicus? He knew John didn't know somebody with that name in person, he had never mentioned him. But why was he saying this then? He started pacing through the flat, his fingers clasped together under his chin in his usual thinking pose. He had to gather all the evidence. First thing: Something which was in the weather forecast had triggered an idea in John. So, something about the weather. And he didn't want Sherlock to know, so it was a surprise for him. It had to be. John was old-fashioned, he wouldn't do something on Valentine's Day for anybody else but him. Next point: Copernicus.
Quickly he strode over to John's laptop, opening it and deducing the password (SherlockDontYouDareToUseMyLaptop). He opened google and searched for Copernicus.
Nicolaus Copernicus was a Polish Renaissance mathematician and astronomer who formulated a model of the universe that placed the Sun rather than the Earth at its center. The publication of this model in his book De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres) just before his death in 1543 is considered a major event in the history of science, triggering the Copernican Revolution and making an important contribution to the Scientific Revolution.
He frowned. This clearly had to do with John's obsession for the solar system. But why the hell wanted John to do something with stars today? Wasn't the point of all that dull romanticism stuff that you did something the other one liked? And John knew that the solar system was utterly boring. So, what was up with him?
Determined to solve the puzzle, Sherlock sat down on the sofa and went into his mind palace.

Hours later, he got ripped out of his thoughts when his mobile went off. "John", he called. He didn't get an answer. "John, hand me my phone", he called after a moment, irritated by the lack of movement in the flat. Than he remembered. John had gone out. That was why he was thinking the whole time. Grunting he got up and fetched his mobile. It was a text from John.
Put on your coat and come outside.
Sherlock frowned down at the missing information but fetched his coat and scarf. When he opened the door to the stairs there was a little sticky note on the staircase with an arrow on it, pointing up the stairs to John's former bedroom. He seldom used it anymore since they were together, but still had most of his stuff in it. He went upstairs, asking himself why the hell he needed the coat to go into a room.
"What is this about?", he asked by entering. But John wasn't there. The only thing other than usual was the small sticky note laying on the bed. On it was only one sentence.
Where am I?
Slowly Sherlock swirled around. Nothing had been moved, there was no object or dust lacking. The room looked like it always did, so John wasn't here. He took in the bed again. Around the note was a bid of dust. That was odd. Where did it come from? He glanced up at the ceiling. A smile tugged at Sherlock's lips as he discovered the loop which was detached to a little scuttle. He reached up, pulling at it and while the port opened, a ladder slipped down.
The detective immediately ascended it.
When he got to the end of the latter, he found himself on the roof of 221. A flambeau was attached to the balustrade around the terrace and enlightened a wonderful sight which made him stop dead on the last step.
John was sitting on a few blankets and pillows, a glass of wine in his hand and something which suspiciously looked like a case file next to him. He grinned at him, his hair a bit ruffled from the light wind which blew through the air and his eyes sparkling. Sherlock couldn't breathe.
After a few seconds, John's grin got smug. "Are you planning to get up here soon?"
Embarrassed, Sherlock shook himself out of his torpor, climbing up the remaining steps and joining him on the blankets. John smiled at him and gave him a glass of wine. He held his out for a toast. "To us", he said. The flames of the flambeau were dancing in his eyes and his smile was soft and warm. He couldn't not smile back. "To us", Sherlock confirmed, before being pecked lightly on the lips.
He took a sip of his wine, glancing down at the file. Yep, it was definitely a case file.
"Little Valentines gift", John chuckled, noticing his gaze and gave it to him. "It's an old one, Greg gave it to me."
Sherlock frowned. "Greg?", he asked confused. The doctor just rolled his eyes, not bothering with an answer. Sherlock flicked it open, skimming the contents.

One hour later they were laying on the blankets, the wine neglected, the case solved. Sherlock was using John's arm as a pillow as they lay cuddled against each other and looked up at the sky. The stars were unusually bright this night, glittering down at them. "You see these three stars there, right next to each other? That's Orion's belt. And these three above and these two beneath it also belong to it", John explained him, pointing up at the sky with his free hand. Sherlock didn't really listen to what John was telling him. He was contently lying there, listening to the sound of John's voice and marveling in the warmth he radiated. Maybe the solar system wasn't that bad at all.