#physics!

the term "sound barrier" has absolutely nothing to do with how loud something is.

a powerful singer does not break the sound barrier. a loud crowd does not break the sound barrier. if you hear an opera soprano belt out an aria and you say she broke the sound barrier you sound like a fucking idiot. that is not what it means.

"but it's just a joke why should i car--"

no. sit down. THAT IS NOT WHAT IT MEANS.

"sound barrier" refers to the increase in aerodynamic drag that occurs as a moving object approaches the speed of sound.

it's called a "barrier" because when the first aircraft starting reaching high enough speeds, they would shake so much pilots were afraid they would get torn apart. it was perceived as a real physical limit, but that perception was false. there is no actual barrier. there is only engineering; it was the drag on the aircraft making them feel like they were shaking apart. turns out if planes are built well enough and go fast enough, they can break the sound barrier just fine without falling apart. the first time this happened was in 1947, in a plane flown by US Air Force pilot Chuck Yaeger.

this means that "breaking the sound barrier" applies to things that are moving very fast, not to things that are very loud.

please read that sentence again to make sure it sinks in. fast, not loud. read it again because tiktok has been lying to you and you need to unlearn what you have learned.

(that also means it applies only where there is a speed of sound, which is not everywhere in the universe. but let's not complicate things by thinking about a pure vacuums or the extreme low density of space.)

the speed of sound varies depending on the density of what it's moving through, but at sea level on Earth it's about 770 miles per hour. once an object is going faster than the speed of sound, it is supersonic--and, again, that refers to speed, not volume. bullets break the sound barrier even if they are muffled at firing. a bullwhip can be snapped fast enough that the very end breaks the sound barrier, even if the noise they make is a sharp crack and not unusually loud.

but people standing still and shouting or singing do not, because nothing that is standing still can break the sound barrier. so unless you are sharing a cool vid of a soprano getting yeeted out of an operatic cannon at >770 mph, she has not broken the sound barrier. and if that is what you are sharing, she breaks the sound barrier whether or not she's singing her aria.

there can be a very loud noise associated with objects moving so fast they have broken the sound barrier. that noise is called a sonic boom, and it happens because the object is generating shock waves as it travels. it's not a single boom; it only sounds like that because when you hear it you are listening at a single point. it is in fact a continuous, traveling shock wave that happens as long as the object is moving faster than the speed of sound. it's just that you only hear it when the shock wave passes directly over you, so it sounds like a finite noise. it's also not necessarily a boom. it can be a crack or a snap or a clap or whatever. it's just called a sonic boom because the ones generated by supersonic aircraft are big fucking booms.

in conclusion please stop saying loud noises break the sound barrier.

🚫 wrong kind of hyperbole: "wow that man shouted loud enough to break the sound barrier!"

of "Every Flavor of You"

⬅️ Prev | Index | Next ➡️

Derek would never know what happened during the first half of physics the following Monday. At least he would never know what happened in the front of the classroom. As far as he was concerned the entire universe was just where his hand met Stiles’ on their lab table. 

It started small. The side of Stiles’ hand was against Derek’s. Just a single point of contact: Stiles’ knuckle against his. It was easy enough to believe that Stiles’ hand was there accidentally. That he didn’t even realize he was touching Derek.

Then Stiles’ pinky twitched. A small jerk, and then a soft swipe, and then Stiles was slowly, steadily, stroking his pinky against Derek’s.

Derek had to remind himself to breathe.

Stiles made Derek feel like a battery: inert, until hooked up to him, then a constant stream of energy flowing from first contact. 

Derek couldn’t say how much time had passed, but eventually Stiles’ pinky moved from stroking the side of Derek’s pinky to stroking the top of it a few times before it slid into the space between Derek’s pinky and ring finger, and then curled around it, wrapping his pinky around Derek’s. Derek curled his finger around Stiles’, hoping Stiles could keep him steady as the world spun around him.

Right as Derek was figuring out how to ride the wave of contact between them and still exist in the rest of his body, everyone in the room started shifting around in their stools.

Derek moved to grab his backpack before he noticed that no one was leaving, just turning to face their lab partners.

“Uh,” Derek started, meeting the wide smile on Stiles’ face, “what are we doing?”

“We’re talking to our lab partners to set up the next time we work on our project to make sure we’re ready to submit our mid-semester project proposals.”

“Oh. Right.”

“I was thinking: dinner. This week? Well, actually, my dad was thinking dinner.” Then Stiles started impersonating someone talking in a stodgy voice, “‘When do I get to meet this boyfriend of yours, Stiles?’”

Warmth spread over every inch of Derek’s skin. “I’m your boyfriend?”

“Um,” Stiles said, blushing, “I mean. I’d like you to be.”

“I’d like me to be too.”

“Yeah. Good. Um, boyfriends then.”

“Boyfriends.”

The bell rang. 

Stiles stared at Derek for a moment before he swooped in and kissed him, and before Derek could even react, Stiles was already out the door.

---

At break Derek saw he had a text from Stiles.

Stiles: hey

Derek: Hey

Stiles: :)

Stiles: :X)

Stiles: you never said if youd come over for dinner

Derek: When and where?

Stiles: my house

Stiles: wednesday

Stiles: you could come with me after practice?

Derek: Okay :X)

Stiles: is it too much if I ask you to eat lunch with me and Scott too?

Derek: No

---

Derek had to adapt fast or else he was going to fail physics. Unfortunately it was an arms race between Derek and Stiles. Or at this point a legs race? 

When Derek got to the point where he could manage multi-tasking feeling Stiles’ hand against his and jotting down the page numbers he would have to read in the textbook later, Stiles escalated by winding their ankles together.

There was a part of Derek that felt like failing physics couldn’t be that bad when weighed against getting to bask in Stiles’ affections, but being Stiles’ lab partner in addition to being his boyfriend meant that part of Stiles’ grade depended on Derek’s contributions to their term project, and he couldn’t stand the thought of being dead weight to Stiles.

“See you after school,” Stiles said as he broke the contact between them.

Derek looked around and realized that half the class was already out the door. 

As Derek stood up to leave, he saw a bemused Mr. Everett looking at him.

“Chapter four, Mr. Hale,” he said, pointing to the page numbers written on the corner of the board.

---

“Do you want to ride with me in my car? I can drive you back to the parking lot later.” Stiles asked when he came over to Derek’s spot in the bleachers at the end of practice.

“Sure,” Derek said. 

The whole time Stiles was showering and changing, Derek was left wondering if Stiles was worried he would try to escape if he brought his car too, or if Stiles just wanted more time with him alone afterward.

Stiles’ dad wasn’t home yet when they got there. 

“Do you want the house tour?” Stiles said as he closed the front door.

“We already did that last time,” Derek said.

Stiles bit his lip. “What I really meant was, my dad won’t be home for an hour and it’s only going to take me forty-five minutes to cook dinner. I was wondering if you would come make out with me on my bed until I need to start cooking.”

“How long would it take you if I helped?”

Stiles’ smile was wide and wild. “Maybe half an hour.” Stiles reached for Derek’s hand and practically dragged him up the stairs.

---

They might have lost track of time, a little bit, and were still working together in the kitchen when Stiles’ dad got home from work.

“You must be Talia’s boy,” Stiles’ dad said, offering his hand.

Derek wiped his hands on the apron Stiles’ lent him and shook the offered hand. “Yes sir. Derek. It’s nice to meet you, Sheriff Stilinski.”

Stiles’ dad smiled. “You can call me John, Derek.”

“Yes sir. You know my mom?”

John nodded. “She used to run a support group for grieving spouses.”

“Oh.” Derek didn’t really know what to say. “She never said anything.”

John laughed. “Your mom’s a professional. She wouldn’t have said anything unless I did first.”

“Now that you’ve made it thoroughly awkward,” Stiles said to his dad, “why don’t you clear off the table? Dinner’s almost ready.”

When they made their way to the table, Derek was surprised to find how quickly Stiles’ dad had cleared spots for the three of them among all of his papers and files. Though, having seen Stiles’ desk, maybe he should’ve considered it a special Stilinski skill.

Stiles served them all, and the three of them ate without talking, the only sounds coming from their knives and forks against their plates. 

“So, I hear you and Stiles are working together on a physics project?” John finally said.

“Yes sir,” Derek said.

“Please,” John smiled warmly, “you can call me John.”

“Yes s— John,” Derek caught himself. He glanced over and saw Stiles smiling down into his plate.

“What kind of project is it?” John asked, not letting on whether or not he caught Derek’s slip.

“We’re supposed to do a report about something related to entropy,” Derek said. “Stiles found something called Maxwell’s Demon, so that’s what our topic is.”

“Sounds like something Stiles would be interested in,” John said. “So what’s this demon?”

“We don’t really know yet,” Stiles said. John cocked an eyebrow and Stiles pushed on “we’ve met up a few times but we…haven’t gotten to that part yet.”

John looked at Stiles for a long moment. Derek could feel his face heating, so he looked intently down at the contents on his plate. John teased, “Well when you boys work on the project tonight, don’t forget to leave the door open. Maybe then you’ll figure out what the topic is.”

---

“Our topic is actually pretty cool,” Stiles said up in his room after the two of them had been reading scraps of things about entropy and Maxwell’s demon online for a while.

“So what is it?”

“You know what entropy is, right?”

Derek had not been doing great in physics lately. He had been distracted. He knew the word entropy, and could recite a few facts about, but he still didn’t understand what it actually meant.

Stiles smiled. “You remember that second experiment we did? With the beakers and the wire where I was trying to flirt with you and you shot me down?”

“What? No. That didn’t happen.” Derek couldn’t imagine shooting Stiles down.

“I grabbed the wire and said I felt sparks and you said you didn’t.”

“You were flirting with me?”

“Derek, I’ve been flirting with you all year.” His smile was mischievous. “Not the point. That experiment. The point was the two beakers. You remember them?”

“Yeah. Ice water and hot water.” 

“There was a temperature difference, and the difference was what made it possible to extract energy from it. It’s not just hot. It’s hot and cold together.”

“But I thought heat is energy.”

“Yeah. True. But without the difference you can’t extract the energy. If you had a normal gas engine but everything else around it was also hot, the engine wouldn’t work. That’s what entropy is about.”

“What is entropy about?”

“So, that difference, when there’s hot and cold separated out, that’s order. The hot molecules are in one beaker. The cold molecules are in another beaker. Order means low entropy. No difference: high entropy. In the experiment we used that order, that difference, to extract energy. The spark.”

“Is that why there’s a spark between us? Opposites attract?”

“Maybe,” Stiles said, and he leaned forward to steal a kiss from Derek.

Derek’s brain still reset every time Stiles kissed him. He had to run back through what Stiles had been saying to keep up and not make his boyfriend fail physics. “So entropy is the opposite of order? It’s…chaos?”

“Yeah. Kind of. If we mixed the two beakers together, that’s high entropy. All the hot molecules and all the cold molecules are jumbled together, and so you can’t extract any energy from it.”

“Okay?”

“So here’s the thing. You know how we’ve been learning the laws of thermodynamics?”

“Yeah?” Despite Stiles’ best efforts to keep Derek distracted in class, Derek had been doing his best outside of class. Even if he was just spinning his wheels. The laws of thermodynamics were in a highlighted box in his textbook, so Derek had memorized them in his attempts to learn what he was missing in class, even if it was about as good as memorizing lyrics to a song in a language he didn’t speak.

“So the first law–”

“Energy can’t be created or destroyed.”

“Yeah! And the second?”

“The entropy of an isolated system can only increase with time.”

“So you get it!”

“No,” Derek shook head. “I just know the words.”

Stiles furrowed his brow. “Okay. Together they mean that even though energy stays the same, no matter what you do the order goes away, entropy increases, so you can extract less energy over time. Everything mixes together.”

“Okay?” Derek said, still not sure if he got it. “So why is there a demon there too?”

“So the demon is a thought experiment. It’s like ‘what if we could undo the second law? What if we could unmix the hot and cold water?’”

“That’s stupid.”

“What? No, it's awesome!”

“Definitely stupid. Here are some laws. Now what if…not? Just because?”

“Not just because,” Stiles insisted. “It has a whole thing behind it.”

“What’s the point of the laws then? I thought physics was supposed to have unbreakable laws.”

“Dude, I don’t know. I just read about this now. But the guy who it’s named for, Maxwell, he was like a serious physicist. He was the one who figured out the equations for electricity or something, so it’s not just random ideas.”

This is how sci-fi felt to Derek. Stupid and hard to follow while pretending that it worked. Because reasons. Derek huffed. Stiles liked sci-fi. Liked his stupid Stardoor. And he liked Derek, even if that didn’t seem to make sense either.

“Okay,” Derek said. “How does he unmix the water?”

“Okay!” Stiles sounded genuinely excited, and even though the whole thing felt dumb, his excitement made Derek feel warm. “So imagine the water is all mixed together in a container with two chambers. And there’s a little door between the two parts. Okay?”

“Okay…”

“The water molecules are all bouncing against each other,” Stiles waved his fists in the air like bouncing molecules. “Sometimes they hit each other and one is going a little faster, and another is going a little slower.” His two fists came together, and one bounced off fast, while the other bounced off slow. “And there’s the demon, right? And he’s controlling the door. Every time a fast molecule is headed toward the door from one side, the demon opens the door letting just that molecule through. And from the other side if a slow one is going to go through the door, the demon opens it for that one too. So the slower colder ones end up on one side and the faster hotter ones on the other. So the demon unmixes the water with his little door.”

“And that means the entropy goes…?”

“Down. It’s more ordered now.”

“And the second law says it only goes up.”

“Yup.”

“That sounds like a problem for the law then.”

“It is.”

“And that can’t happen. So how did the physicists fix this?”

“They haven’t yet.”

“What do you mean they haven’t?”

“I mean they haven’t agreed on what fixes the problem.”

⬅️ Prev | Index | Next ➡️

@erraaxh @danielrp78 @icysnowydragon @smuttylover12 @slut-for-fictional-men

And in this fic I have the opportunity to derive special relativity. I also, as an individual possessing degree in physics, not only have to knowledge to do that but can do it with mathematical rigor and heaps of physics jargon.