read from up down


save him. 

Brother’s Best Friend (M)

Jaehyun x Reader (feat. Johnny)

Word Count: 3.6k

Genre: Smut, Slight angst

A/N: My first published smut ayy.. I was stuck on this for a while but last night lordt I just went on one and finished it at like 4am lmao… Ty to my FLOwer (@nctreacting) for helping me out with this 💕

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Ancient history can be oddly amusing at times

Once, in high school, I read an excerpt from an account by a Roman soldier of an unsuccessful attempt to take over part of Ireland or pre-Roman-influence Britain. He was talking about how he had been fighting a Celt man and had nearly beaten him.

Except he hadn’t counted on one thing.

The Celt was married.

Apparently, over the hill in high dudgeon came a giant of a woman with her whole body painted red. She stormed over to the Celt and the Roman like “Hey, who do you think you are, picking on my smol husband? Back off!”

And from what I remember reading, she knocked the Roman down, picked up her husband under one arm, and marched off.
Presumably, the Roman wasn’t too much the worse for wear, as he had to have survived long enough to write his “Celt women are terrifying” report.

Sense8 Season 2 Poster Analysis:

First, I’m going to do a technical summary about the new season 2 poster, listing important details for you to understand, “the psychological analysis”.

Clarification: I am a qualified graphics designer.

The poster has a lot of details that are very important, and there are themes that are present throughout the design: For instance: There is a variation between gradients and lights - The objective: complexity vs minimalist.

Sense8’s Poster has a degraded background which is blue-white-grey and it also has warm and cold lighting. This lighting stands out in specific points, creating luminance & contrast.

Rule of Thirds: The poster is divided exactly in this way:

Here we can see six imaginary lines. These lines show us important details at the crossing points. Our brain sees the poster from left to right and from top to bottom.

First point (left up): Will’s face.

Second point (right down): Capheus’s body.

Third point (left up): Kala’s body.

Fourth point (right down): Building - This point doesn’t seem to matter

Instead, the lines make us to read the poster this way:

Vertical left line: Sun - Will - Titles

Vertical right line: Kalagang - Cities

Horizontal up line: Will (again) - Lito

Horizontal down line: Riley

Also, like I said, we read the poster from left-up to right-down. Like this:

It redirects our mind with the different directions of the character’s faces.

Sun looks towards the opposite side of our view: from right to left. Some asiatic countries read this way.

Wolfgang + Kala: Their direction is the opposite as Sun’s, and they are the only ones who are shown together in the same shot. This could be telling us that they will be going down the same road, like a journey together.

Will + Lito: Both of them are looking towards the front. This could be telling us that they are going to advance a lot when it comes to their individual plots & story lines.

Capheus: He is looking in the same direction as Sun, towards the left. Sincerely, I don’t like this because it looks as though he turns his back on Riley and Nomi. Capheus faces the opposite side, but not like Sun. You can tell that she is looking towards the front, but he is looking down, and he looks worried. I DON’T LIKE THIS.

But if I don’t like Capheus’ position, I hate Nomi’s. It is horrible. First, she doesn’t even fall on an important line. She is looking far right and it seems she is a bit isolated from the rest.

Psychological Sensory (Three blocks):

Orange: Serious and decisive looks towards a certain point represent a goal.

Purple: Lost and serious looks, with an open mouth - something to say perhaps?

Green: You can calm down. Relax - happiness.

Lastly, love in the Cluster:

Pink: They are distant. I don’t know if that’s a good sign or not (they always try to fool us or throw us off). I have the sensation that this is for a particular reason though. Maybe Riley and Will will be separated in a physical way this season. Also, I would like to put an emphasis on Will. He appears bigger, while Riley has more of her body in the poster. All of this equilibrates the couple.

Blue: Togetherness. The opposite to Blueski, who is an important part of the poster. Both are in different places and this separates them. But Kala+Wolfgang are together. Are they trying to telling us that Kalagang is going to be physically together this season? I want to believe that this is true, and my instincts tell me I am right - I’m crazy, sorry.

Other objects in the poster:

The buildings from each country tell us that they are united as a cluster, and that they are all connected through the same line.

“Sobreviviendo. Juntos” or “Survive. Together” is the definition of the season - The trailer says the same kind of message.

In big letters we have “SENSE8”, although it is in the corner of the poster, which grabs less attention - for me, this is an error - It would have been preferable in the upper corner. Until now I haven’t read the date - May 5th - because it is so small. This is a problem.

Lighting: This caught my attention. The poster has a warm stroke across it. Kalagang and Lito+Nomi are highlighted. This light is a way to create unity and bring attention to certain points.


It’s a very different poster if we compare it to the poster from season 1 - The 8 unrecognizable faces - But in this case, they show us the 8 sensates with a different attitude, unity… For me, the characters that are less prominent in the poster are Nomi and Capheus. Lito is in the center and he look like a boss - I like it - But the main point of the poster is Will, he is graphically tagged. Although our hearts say “Oh Kalagang, OMG!”, our brain says: “Why do you look so serious Will?”. There are a lot of conflicting moods coming from all 8 of them. Sun is a big point too - Look at her size - And all of this is in the trailer as well; Will and Sun are the point of attention while Kalagang is shown very little and the others are just there somehow.

For me the poster is beautiful, it’s beautifully composed - there are always some mistakes, especially through the eyes of another (it’s all perspective) - I think that they don’t tell us so much, but at the same time they tell us many things - just like the trailer. They gave us a basic idea of season without leaving us with much more than the obvious.

Thank u @ww-n-double-d for making my English better, you are gold!

I hope you enjoy the analysis and I hope to hear your opinions about it!

They call him the Guess Monster. With his flawless aim and terrifying ability to read and predict his targets, he was a born assassin. Other than that, not much else is known about him. To hire this mysterious man is tricky, somehow he always knows who needs him and who he needs to kill. It goes with the alias most people conclude. He is an enigma wrapped in a mystery and sealed in a conspiracy. Not much is known about him although rumour on the streets says that he’s part of the notorious assassins organisation; ‘Shiratorizawa’. To attempt to dig any deeper is a fools quest - those who have tried to unravel the mystery have simply ceased to be…

I told myself not to but after reading @gue55-monster‘s headcanon submissions, this one in particular stuck out to me and I couldn’t help myself. I have so much other stuff to do which is why this is a massive scribble but I can never resist an opportunity to draw my son being a murderer. 

AND just on the off chance there ends up being a Shiratorizawa Assassins!AU, I would be totally on board with that. *hint hint*

Stronger- Theo imagine- part 2

Originally posted by bysamoylova

Request: artfuck said:

Can you do a part two to stronger? Please it’s so good

A/N: I wasn’t intending on doing a part two so I’m sorry if it’s not very good xx enjoy!

Words: 1676

part one is here

“How am I going to do that?” you questioned. You had no clue where to begin even if you’d adapted to this new world remarkably fast.

“That’s what we’re going to figure out.” Theo mused. “First things first, you’re going to have to learn how the hide the wings.” He walked over so he was opposite you.  

“I don’t know how” you blushed. He smiled at you, his fingers reaching out to touch the feathers. Subconsciously you tensed your back, the wings fluttering in response to the contact. With admiration, Theo turned his attention back to your rosy cheeks.

Keep reading


Notes- While at a bookstore, you bump into Evan Peters. He ends up asking you out and coming to your apartment. Fluffy with a make-out scene. If you guys want a continuation please let me know.

Words~ 1,129

Originally posted by ahs-monster

You stepped into the aisle to examine another row of bookshelves. You already had a bag started with books you were going to buy. Every few months you treated yourself with brand new books to read. You bent down to pick a book up from the bottom shelf, knocking into someone as you stood back up. “I’m sorry,” you said without looking back at who it was.

 “You’re good,” he said as he started looking at books next to you. After reading the summary on the back of the book you were holding, you finally looked at the man standing next to you. You gasped slightly as you saw Evan Peters carefully looking over books. Out of all the people you could have bumped into happened to be one of your crushes. You’re just like everyone else and never really thought you’d ever come into contact with any celebrity that you found attractive.

 “ What kind of books do you normally read,” Evan’s voice snapped you out of your thoughts.

“Fantasy, sometimes mystery.”

“ Whenever I’m near here I always try to stop at this bookstore.”

“ I come here once every couple of months.”

“So,” Evan trailed off,” What’s your name?”

“Y/N, and you’re Evan Peters aren’t you?”

“Yeah, most people freak out a little when they figure that out,” Evan gave you a little smile as he finished his sentence. “ Could you help me pick out a couple of books? I need some of them to get me in the mood for my next role.”

“ I would love to,” you felt your cheeks getting hot as you spoke. You spent about forty-five minutes helping Evan pick out books before you both went to the counter to check out. The cashier rang up your books as you went to pull out your wallet. The cashier said the price allowed and Evan said, “ I got it for you.”

“You don’t have to do that.”

“You helped me pick out books, so I’m going to pay for yours.”  You walked out of the building together and went to walk in the direction of your home, but Evan stopped you. “Do you want to go out with me later? We can do whatever you want, I haven’t hung out with anyone lately and I like talking to you.”

 “ Sure.”

 Evan pulled out his phone and you told him the numbers. He sent you a text to make sure the number was right before telling you he could come get you from your house later. When you got home, you quickly put your books away and jumped into the shower. You put on your favorite clothes and texted Evan your address and apartment number. 

Thirty minutes later you heard a knock at your door and practically ran to answer it. “Hey, Y/N,” Evan said sticking his hands in his pocket. You grabbed your stuff and locked the door as you stepped out into the hallway. “I have an idea of where we should go,” you announced to Evan as you were in the elevator.

 “ Good, are you going to drive than?”

“ Yeah,” you said leading Evan to your car. The ride there wasn’t super long or at least it didn’t feel that way. You and Evan chatted about different things like TV shows and movies. He asked you about your job, your family and those kinds of things. You parked your car and started a short walk up a hill to get to where you wanted to take Evan. Lucky for you no one else was there. 

 The sun had almost finished setting and was framed by the river below. The hill you were standing on had a perfect view of the river and some of the city lights. You sat down, patting the ground next to you for Evan to sit down. “So, what’s it like,” you asked.

“What’s what like?”

“Being the Evan Peters and being famous.”

“It keeps things interesting. Sometimes not being home often can kind of suck.”

“Yeah, I bet.

”“ Being able to travel is nice, but having cameras following you around can be annoying sometimes.”

“Sometimes I wish I were famous for something simple, like writing,” you said,” but I’m glad I’m not because I don’t think I could deal with not having my own space.” 

“So you’re a writer,” Evan questioned.

“I’ve tried, and have never finished anything.”

“They’re probably some of the best untold stories ever.”

“ I doubt that,” You said sighing. You started drawing circles with your hand on the ground and accidentally brushed your hand against Evan’s. “Sorry.”

“It’s alright,” Evan answered back. You looked at Evan and moved your hand back to his and intertwined your fingers together. Evan moved closer to you and you leaned to rest your head on his shoulder. At noon you thought it was miraculous that you bumped into the man and now you were holding hands with him as you watched lights bounce off of the river’s surface. You felt Evan’s chest rise at he let out a yawn. “We don’t have to stay here if you need to get some rest,” you told him.

“I still want to hangout with you though,” Evan stated on the verge of being a whine.Evan laid his head on top of yours,” You know,” you said,” We could go hangout at my place, that way in case you fall asleep at least we’ll be there.”

 “Yeah, that’s cool.” 

You both climbed into your car making the journey back to your apartment building. You walked into your apartment leading Evan behind you. He had began to hold your hand again as soon as you got into the building. “It’s small, but super cozy,” you said as you walked into your living room. “I like it. It’s cute,” Evan said. You both paused for a moment. You looked into each others eyes and it was almost as if someone sounded an alarm. 

Evan’s hands gently grabbed your face as he pulled your lips to his and you wrapped your arms around his neck. He let out a soft moan as you pushed your tongue into his mouth. His hands moved to rub down your back and moved under your shirt. He rubbed your back with his thumbs as you lead him to your couch. You laid down with him on top of you. He had his arms on either side of you, keeping his weight off of you. You pulled at the collar of his shirt as he moved to kiss down your neck. Once he got to your collarbone, he moved to take off his shirt. “Sorry,” he said before lifting his shirt up.  

 “It’s fine, trust me,” You said as you pulled him back down to meet your lips.  

Thanks so much for reading. Please like/ reblog. If you want a continuation of this story please let me know. Requests, ships, preferences, head canons, and everything else are always welcome ❤❤❤ 

The Adventures of Percival the Red Panda

This is for an admired author that I follow, @funkzpiel. I know that others have answered your wish already, but the more the merrier right? It’s a bit late to the game too, but eh. I hope someone can enjoy it at least. But here a scene as to how Percival might have got there:


The night was dark. The snowy grounds created a clearer vision of the Central Park Menagerie than it would otherwise be with just the moon and stars.

There was a loud pop, disturbing the ambience of chittering animals. A man wearing a dark trench coat—or at least, what seemed to be one—had suddenly appeared holding a cage the size of a small suitcase, and he continued walking as if he had been taking a stroll through the park the entire time. The animal inside the cage was indistinguishable beyond its tiny black paws that gripped one of the bars tightly.

The man stopped at an enclosure with five sleeping deer inside and an antlered buck. A small raccoon could also be seen scurrying around inside the glorified cage, climbing onto one of the bare trees when noticing the intruder. He flicked his wrist out, and a sleek black wand shot into the man’s grip. Setting the small cage onto the snowy floor, the animal could now be clearly seen; it appeared to be similar to the raccoon, but reddish brown with a very thick ringed tail. The animal became even more distinct as the man used his wand to open the cage and float the auburn creature in front of him. It made growling noises as it tried to grip onto the man, most likely to slash his eyes out from the way it swiped at his face viciously. The man looked at the teddy bear sized creature indulgently.

“Poor little Percy,” the man crooned. There was a wicked gleam in his dark eyes, and the smile on his face seemed almost unnaturally wide. The man leaned closer to the animal hovering in mid-air in front of him to the point where the swiping claws just barely touched his face.

“Do you want to see your pretty little face scratched up that badly? I never took you for a masochist, dear Percy,” the man gazed into the desperate eyes of the animal as it growled loudly in frustration. The meager attempt to cause harm upon his person seemed to make the man incredibly amused, especially when considering the fluffy visage of the one attempting it. “Don’t worry, dearie. I won’t leave you here forever. You understand why I must do this.”

An answering bark disagreed with him, along with an intensified attempt to maul him. The man frowned. “Don’t be like that, Percival.” But it seemed like the contradiction ruined his playful mood. The man sighed and flicked his wand hand sharply. To the naked eye, it appeared as if Percival was blasted by an invisible force. The creature was thrown pass the barrier of the large cage as if it were intangible. Percival landed on a snow mound and sank within the small white dune. His snow covered head quickly popped up from the mound, and he struggled to escape from it.

The man watched his failed attempts, but quickly grew bored. “Since you seem to have your paws full, I shall now take my leave. Zum Gröβeren Nutzen, Percival Graves.”

The man turned sharply where he stood, and disappeared with a crack. Percival, after finally escaping from the heap, ran as he were a human on his two back paws and grappled at the bars of his new prison. The gaps were too small for him to even have hopes of squeezing between the bars. He threw his little arms out in frustration, but fell onto the snowy ground as he no longer had a support. The winking stars from above seemed to be mocking his predicament. All Percival could think was, “That goddamn bastard. He definitely won’t get away with this!”

My Brightest Star - 2

Sirius Black x Reader

After his initial stuttering and nervousness around Y/N, Sirius was back to being himself. Which didnot mean that Y/N was free to go. Sirius had his own way of doing things.

He would sit behind her in class. Or opposite her in the Great Hall. Or in the common room, he would occupy the couch from where he was always in her line of sight. He just HAD to be around her ALL the time.

Y/N was aware of all the attention she was getting from Sirius, but she barely ever reacted. She knew of his ways, and she was being cautious.

                            * * *

“Im quite sure Black’s staring at you Y/N” Alice said one morning at breakfast.

Y/N knew he was, and slowly she glanced his way, and their eyes met. Sirius smiled. Not a flirty one. But a genuine happy one.

Y/N smiled back, and was almost lost in it, when Lily shook her back to reality.

“Whats going on ?” She asked, sitting beside Y/N, eyebrows raised.

Y/N shrugged.

“Ready to go?” Lily asked.

Nodding, Y/N collected her things, and began walking out of the hall. Only something seemed to be pulling her back.

Frowning, Y/N turned back only to see Sirius watching her with a big toothy grin, and his friends doing the same, beside him. Sirius gave a little wave. Y/N just flashed him a tight-lipped smile and followed the girls quickly.

                            * * *

Sirius begged Lily to invite Y/N over to hangout with them.

“Please Lily ! Just try !! I’ll do anything for this !” Sirius whined. “Please !!”

“Come on Lils, just ask her” James said.

She didnt think Y/N would agree, but after repeatedly being persuaded by the boys, she agreed to try.

“Hey, Y/N” said Lily, as she stood in front of the mirror, adjusting her scarf.

“Mhmm” said Y/N, looking up from the book she was reading.

“We’re going down to the lake for a while” she said.“Wanna come ?”

“With your friends ?” asked Y/N raising her eyebrows. “Is that a good idea ?”

“Yep” said Lily. “Come on, Y/N ! Its always them and just me ! Please ?”

Y/N looked away for a moment, thinking.

“I…um…” The thought of having to actually interact with Sirius, maybe for the first time after the incident made her nervous.

“Please ?” Lily said again.

“Alright…” Y/N said closing her book, and standing up. “I dont trust that boy, though”

“Who ?” teased Lily.

“Sirius Black”

Lily was sure that she saw a hint of a smile on Y/N’s face.

                                * * *

The Marauders regularly invited Y/N to their hangouts after that. She went for most of them, where Sirius would be flirting with her mercilessly. And if ever she skipped, he would pout and sulk throughout the day.

Spending so much of time with them, Y/N found Sirius quite attractive , too, but she kept that thought to herself. Her heart would speed up seeing him, and there was such excitment bubbling inside her every time she spoke to him.

Lily knew her friend was quite fond of Sirius, but she never said anything. Things will have to fall in place on its own.

Bros help bros (joshler blowjob)

Tyler’s back arched off the sofa as he palmed himself, small gasps and whimpers making Josh look up from his magazine. “C-Can you..” Josh crossed the room without further instruction. Tyler stayed still whole Josh unzipped and pulled down his jeans, because what are bros for, right?

They had started ‘helping’ each other in the early days of touring because nothing really felt as good as someone’s hand. Josh sat beside Tyler and rested his magazine on his crossed his knees, his right hand working Tyler slowly. Josh knew how Tyler liked it, slow to start then a big finish.

Tyler made a high pitched whining sound and Josh looked up from what he was reading and smirked, his eyes flicking down to his hand. “Fuck!” Tyler cried as Josh swiped his thumb over the head of his dick. “No homo” Josh laughed, thinking it was the funniest thing ever. Tyler just whined in response, bucking his hips up into Josh’s hand. This was where Josh knew to speed to, give him more. “Fuck Josh..”

Josh hesitated at that because they never addressed each other while doing this. Josh felt something stir in his stomach. Of course, they got hard sometimes because who wouldn’t? The thought of jacking off always got Josh hard, let alone watching Tyler do it, let alone /doing/ it to Tyler. But this was a different kind of stir. Tyler huffed a breath, his cheeks tinted pink and Josh suddenly wanted to kiss him.

“Just fucking do it” Tyler snapped, reading Josh’s mind. So Josh did. He leaned down over Tyler and kissed his lips, letting his magazine fall to the floor. Tyler kissed Josh back with force, using his teeth on Josh’s lips and Josh quickly decided that it was the best kiss he’d ever received. John put a little more pressure on Tyler’s cock, tightening his fist and Tyler whined, his hands coming up to squeeze Josh’s shoulders. “Fuck Josh-” Tyler moaned again and Josh suddenly had a thought. Before he could change his mind, Josh was leaning down and pressing a kiss to the head of Tyler’s cock, licking him lightly. Tyler cried out, one hand gripping Josh’s hair so Josh carried on.

He had never done this before and wasn’t quite sure how it worked but he opened his mouth around Tyler and sucked on the tip. Tyler was babbling and cursing above him and Josh lowered himself slowly, already feeling too full. He gagged and pulled back a little, bringing his hand up to take care of what he couldn’t fit into his mouth. “Oh fuck” Tyler breathed as Josh sucked up his length before sliding back down. Tyler was a hair puller Josh soon found out, but Josh kind of liked it, it was like encouragement and Josh took more of Tyler into his mouth.

He found himself a rhythm and soon got used to the feeling. “You’re so good” Tyler moaned “fuck you’re so good”. Josh swirled his tongue around the tip and tasted salt. It wasn’t bad though and Josh done it again and once more before Tyler was coming. He shouted, what Josh could only guess was his name, a second before he came, spilling out of Josh’s mouth and running down his chin. Josh pulled off and watched Tyler. He had his eyes closed, his back arched and his mouth hanging open as he panted for breath.

Tyler looked down at Josh once he’d finished and groaned. “You have come all over your face dude” he mumbled and Josh laughed before wiping a hand over his face. “You’re just spreading it” Tyler smirked and Josh frowned “help me out?” He asked referring to the come on his face. Tyler seemed to get the wrong idea as he slipped off the chair and knelt in front of Josh, his fingers undoing his jeans.

Josh almost corrected Tyler but as he watched Tyler press a kiss to the font of his boxers, he decided against it. After all, bros help bros.

I was apparently accepted to the other institute I applied to for the exchange program (the one in the Arctic Circle.)

I know this because their website lets us access our application. Every single bit of it. Including the bit where I can see they approved my study plan and they changed the status to “accepted” three days later which was two days ago (yes, I can see this, down to the second.)

This was before I actually received any kind of official notification so I’m not even 100% sure I am not misunderstanding things, but well, spoiler alert much :’)

hey lads who dares me to spill out all my Important Feelings and overshare to my gf at 3am when she’s asleep and then immediately regret it and worry that she’ll hate me ????

anonymous asked:

FRAs reactions to finding out mc is super talented in all things musical? singing, playing an instrument, writing music etc

First imagines post!


- You guys are spending the day at the college library

- while cute little Yoosung is studying you check out a book on writing music (not for the first time)

- you sit down across from him and begin reading

- Yoosung glances up and thinks your reading another langauge

- “MC…?”

- you explain this is how music is made

- his eyes go wide and he begs you to teach him, you tell him to keep studying

- he does but he keeps giving you this woman puppy dog eyes

- you sigh

-when begin talking about notes and measures he’s so confused

-eventually he gives up


-There was an old guitar in the back of Jaehees closet

-you pulled it out while she was at work and brushed your hand over the strings

-you used to play when you were little

-You begin to play and forget the time

-you play for hours until Jaehee got home

-she heard you playing and was amazed

-she stood in the doorway until you stopped

-it had taken her a year to play one chord on the damned thing

-she stood there for an hour

-She clapped when you finished


-Zen likes to bring you on set with him some days

-one day he decides putting a microphone on you might be cool

-after you guys mess around for awhile you go to hangout back stage

-too pass the time you begin to sing

-it’s one of those cheesy songs on the radio

-your finishing the chorus when zen bursts in

-“MC your hot!”


-He tells you your mic is on (hot)

-you look down and sure enough

-your so embarrassed!

-you hold your breath as he turns it off

-Zen thinks your cutest when your all pink

-uh oh zens gonna be late for rehearsal


-Jumin does not like being away from you

-so naturally your spending the day at C&R

-like all fancy places there’s a grand piano in the lobby

-it’s dusty

-you remember when you used to play in ninth grade

-maybe you remember?

-you take a seat and begin to play

-eventually your full out Beethoven style

-You forget your in a populated lobby

-eventually a crowd gathers around

-you notice but it would be awkward to stop playing

-when Jumin comes looking for you he’s pleasantly surprised

-he has no clue how a piano even worked

-Sheltered bby

-he has got that little half smile on his face you know the one

-he’s gonna buy a piano for his house now

-whoops he already bought it


-It all started when Seven found his new favorite song and started playing it over and over and over

-eventually it was engrained your mind

-he was dead meat

-the next morning he heard you singing it in the shower

-He literally bust down the door

-what was that in his hands.

-was that.. an accordion,

-oh my god it is

-ohmygod he’s playing the song on accordion While your in the shower

-smh seven

-you love him too much not to keep singing

-eventually your voice turns into a bad screechy southern accent

-what are you two even doing anymore

Matchups will be closed for a few days ~ Sorry >_<

BTW the apps we will be using are Kik, Whatsapp, and Discord (and in that order for the chats)… I really didn’t want to make you guys have THREE apps for this, but a lot of you agreed to this arrangement… if there are any problems, please let me know… and please take care of yourselves

anonymous asked:

This makes me sound stupid but what does a feynman diagram mean?

You don’t sound stupid! They can be pretty confusing at first, and I’m sure you’re not they only one that doesn’t fully understand them (myself included) so let’s learn how to draw Feynman diagrams!

You do not need to know any fancy-schmancy math or physics to do this!

I know a lot of people are intimidated by physics: don’t be! Today there will be no equations, just non-threatening squiggly lines. Even school children can learn how to draw Feynman diagrams. Particle physics: fun for the whole family.

For now, think of this as a game. You’ll need a piece of paper and a pen/pencil. The rules are as follows (read these carefully):

1. You can draw two kinds of lines, a straight line with an arrow or a wiggly line:

You can draw these pointing in any direction.

2. You may only connect these lines if you have two lines with arrows meeting a single wiggly line.

Note that the orientation of the arrows is important! You must have exactly one arrow going into the vertex and exactly one arrow coming out.

3. Your diagram should only contain connected pieces. That is every line must connect to at least one vertex. There shouldn’t be any disconnected part of the diagram.

In the image above, the diagram on the left is allowed while the one on the right is not since the top and bottom parts don’t connect.

4. What’s really important are the endpoints of each line, so we can get rid of excess curves. You should treat each line as a shoelace and pull each line taut to make them nice and neat. They should be as straight as possible. (But the wiggly line stays wiggly!)

That’s it! Those are the rules of the game. Any diagram you can draw that passes these rules is a valid Feynman diagram. We will call this game QED. Take some time now to draw a few diagrams. Beware of a few common pitfalls of diagrams that do not work (can you see why?):

After a while, you might notice a few patterns emerging. For example, you could count the number of external lines (one free end) versus the number of internal lines (both ends attached to a vertex).

  • How are the number of external lines related to the number of internal lines and vertices?
  • If I tell you the number of external lines with arrows point inward, can you tell me the number of external lines with arrows pointing outward? Does a similar relation hole for the number of external wiggly lines?
  • If you keep following the arrowed lines, is it possible to end on some internal vertex?
  • Did you consider diagrams that contain closed loops? If not, do your answers to the above two questions change?

I won’t answer these questions for you, at least not in this post. Take some time to really play with these diagrams. There’s a lot of intuition you can develop with this “QED” game. After a while, you’ll have a pleasantly silly-looking piece of paper and you’ll be ready to move on to the next discussion:

What does it all mean?

Now we get to some physics. Each line in rule (1) is called a particle. (Aha!) The vertex in rule (2) is called an interaction. The rules above are an outline for a theory of particles and their interactions. We called it QED, which is short for quantum electrodynamics. The lines with arrows are matter particles (“fermions”). The wiggly line is a force particle (“boson”) which, in this case, mediates electromagnetic interactions: it is the photon.

The diagrams tell a story about how a set of particles interact. We read the diagrams from left to right, so if you have up-and-down lines you should shift them a little so they slant in either direction. This left-to-right reading is important since it determines our interpretation of the diagrams. Matter particles with arrows pointing from left to right are electrons. Matter particles with arrows pointing in the other direction are positrons (antimatter!). In fact, you can think about the arrow as pointing in the direction of the flow of electric charge. As a summary, we our particle content is:

(e+ is a positron, e- is an electron, and the gamma is a photon… think of a gamma ray.)

From this we can make a few important remarks:

  • The interaction with a photon shown above secretly includes information about the conservation of electric charge: for every arrow coming in, there must be an arrow coming out.
  • But wait: we can also rotate the interaction so that it tells a different story. Here are a few examples of the different ways one can interpret the single interaction (reading from left to right):

These are to be interpreted as: (1) an electron emits a photon and keeps going, (2) a positron absorbs a photon and keeps going, (3) an electron and positron annihilate into a photon, (4) a photon spontaneously “pair produces” an electron and positron.

On the left side of a diagram we have “incoming particles,” these are the particles that are about to crash into each other to do something interesting. For example, at the LHC these ‘incoming particles’ are the quarks and gluons that live inside the accelerated protons. On the right side of a diagram we have “outgoing particles,” these are the things which are detected after an interesting interaction.

For the theory above, we can imagine an electron/positron collider like the the old LEP and SLAC facilities. In these experiments an electron and positron collide and the resulting outgoing particles are detected. In our simple QED theory, what kinds of “experimental signatures” (outgoing particle configurations) could they measure? (e.g. is it possible to have a signature of a single electron with two positrons? Are there constraints on how many photons come out?)

So we see that the external lines correspond to incoming or outgoing particles. What about the internal lines? These represent virtual particles that are never directly observed. They are created quantum mechanically and disappear quantum mechanically, serving only the purpose of allowing a given set of interactions to occur to allow the incoming particles to turn into the outgoing particles. We’ll have a lot to say about these guys in future posts. Here’s an example where we have a virtual photon mediating the interaction between an electron and a positron.

In the first diagram the electron and positron annihilate into a photon which then produces another electron-positron pair. In the second diagram an electron tosses a photon to a nearby positron (without ever touching the positron). This all meshes with the idea that force particles are just weird quantum objects which mediate forces. However, our theory treats force and matter particles on equal footing. We could draw diagrams where there are photons in the external state and electrons are virtual:

This is a process where light (the photon) and an electron bounce off each other and is called Compton scattering. Note, by the way, that I didn’t bother to slant the vertical virtual particle in the second diagram. This is because it doesn’t matter whether we interpret it as a virtual electron or a virtual positron: we can either say (1) that the electron emits a photon and then scatters off of the incoming photon, or (2) we can say that the incoming photon pair produced with the resulting positron annihilating with the electron to form an outgoing photon:

Anyway, this is the basic idea of Feynman diagrams. They allow us to write down what interactions are possible. However, you will eventually discover that there is a much more mathematical interpretation of these diagrams that produces the mathematical expressions that predict the probability of these interactions to occur, and so there is actually some rather complicated mathematics “under the hood.” But just like a work of art, it’s perfectly acceptable to appreciate these diagrams at face value as diagrams of particle interactions.  Let me close with a quick “frequently asked questions”:

  1. What is the significance of the x and y axes?
    These are really spacetime diagrams that outline the “trajectory” of particles. By reading these diagrams from left to right, we interpret the x axis as time. You can think of each vertical slice as a moment in time. The y axis is roughly the space direction.
  2. So are you telling me that the particles travel in straight lines?
    No, but it’s easy to mistakenly believe this if you take the diagrams too seriously. The path that particles take through actual space is determined not only by the interactions (which are captured by Feynman diagrams), but the kinematics (which is not). For example, one would still have to impose things like momentum and energy conservation. The point of the Feynman diagram is to understand the interactions along a particle’s path, not the actual trajectory of the particle in space.
  3. Does this mean that positrons are just electrons moving backwards in time?
    In the early days of quantum electrodynamics this seemed to be an idea that people liked to say once in a while because it sounds neat. Diagrammatically (and in some sense mathematically) one can take this interpretation, but it doesn’t really buy you anything. Among other more technical reasons, this viewpoint is rather counterproductive because the mathematical framework of quantum field theory is built upon the idea of causality.
  4. What does it mean that a set of incoming particles and outgoing particles can have multiple diagrams?
    In the examples above of two-to-two scattering I showed two different diagrams that take the in-state and produce the required out-state. In fact, there are an infinite set of such diagrams. (Can you draw a few more?) Quantum mechanically, one has to sum over all the different ways to get from the in state to the out state. This should sound familiar: it’s just the usual sum over paths in the double slit experiment that we discussed before. We’ll have plenty more to say about this, but the idea is that one has to add the mathematical expressions associated with each diagram just like we had to sum numbers associated with each path in the double slit experiment.
  5. What is the significance of rules 3 and 4?
    Rule 3 says that we’re only going to care about one particular chain of interactions. We don’t care about additional particles which don’t interact or additional independent chains of interactions. Rule 4 just makes the diagrams easier to read. Occasionally we’ll have to draw curvy lines or even lines that “slide under” other lines.
  6. Where do the rules come from?
    The rules that we gave above (called Feynman rules) are essentially the definition of a theory of particle physics. More completely, the rules should also include a few numbers associated with the parameters of the theory (e.g. the masses of the particles, how strongly they couple), but we won’t worry about these. Graduate students in particle physics spent much of their first year learning how to carefully extract the diagrammatic rules from mathematical expressions (and then how to use the diagrams to do more math), but the physical content of the theory is most intuitively understood by looking at the diagrams directly and ignoring the math. If you’re really curious, the expression from which one obtains the rules looks something like this (from TD Gutierrez), though that’s a deliberately “scary-looking” formulation.

You’ll develop more intuition about these diagrams and eventually get to some LHC physics, but hopefully this will get the ball rolling for you.