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"The Planetarium Collision" is the fifth episode of the twelfth season of the American sitcom The Big Bang Theory. The episode aired on Thursday, October 18, 2018.


When Amy doesn't have time to work on super-asymmetry, Sheldon goes to great lengths to ensure she's available to work with him even it if means accidentally sabotaging her career in the process. Also, Koothrappali doesn't want Wolowitz to join him in hosting a show at the planetarium.[1]

Extended Plot[]

Raj is finishing up his lecture on the moons of Jupiter at the Griffith Planetarium as Sheldon and Amy pass notes back and forth. Penny finds out that the Coopers were working on Sheldon's Super-Asymmetry String Theory project. Howard goes up to Raj to congratulate him on the show even though he slept through it. He gets to meet the director of the planetarium who learns that Howard is an astronaut and then invites him to join Raj doing one of the shows. Raj goes not like that idea.

Amy has a student volunteer whom she is checking his sensory reactions while his head is isolated in a box. Sheldon comes in and asks if she is busy to talk string theory. Amy says that she is really excited about their paper, but she is in the middle of her experiment. He just gives her one clue, “Lambda calculus” and then touches her nose saying, “boop.”


Amy's sensory experiment.

In the Wolowitz bedroom, Bernadette's trying to start something with Howard who is distracted that Raj is mad at him. Howard thinks that it would be fun, but Bernadette feels that he wouldn't want some sexy-assed astronaut sharing the stage with him. How sexy? Thor (Marvel Comics)|Thor sexy and then Bernadette gets what she wants.

Sheldon is explaining his string theory to Penny!?! Leonard comes in and immediately decides to leave. Penny calls him back and is proud that Sheldon came to discuss science with her. Leonard reminds Sheldon that he's not supposed to bore other people's wives. Sheldon then complains about how little time Amy has been able to work with him on super-asymmetry. He finds her work with the brain so boring. Penny then leaves so that Sheldon can talk science with Leonard and she can get away.


Howard goes to talk to Raj in his office, to discuss about them working together. Howard feels that that would be like doing karaoke with a rock star. Raj doesn't have to feel intimated. Raj replies that he is also very accomplished in his field. And even though he has fears, one is not sharing the spotlight with an astronaut.

Sheldon goes to see President Siebert, who may be a physicist, but Sheldon doesn't think he knows anything. He has a Doctorate from Indiana University which causes Sheldon to go very slowly. He explains that Amy was helping him and is distracted by her own work. And she was helping him conceptualize the differences between symmetry and a-symmetry. After throwing in a comment about their sex life, President Siebert says that he doesn't enjoy their little conversations.

Amy enters her lab and finds her colleague Dr. Park going through her research. He explains to the unaware Amy that he was taking over her project while she was on a sabbatical doing other work. Sheldon runs in with the exciting news that they will be working together full-time. Amy is not happy. He learned that Amy was very difficult to replace. Amy is incensed since she has been years on her projects and that Sheldon has no right to request her removal.

In Apartment 4A, Raj comes in with Chinese food to talk about Howard. Raj folded to let Howard join him and he is afraid that Howard will make it all about himself. Penny tells him to cancel, but Raj doesn't want to look insecure. Leonard tells him that he is insecure and that he walked up three flights of stairs for nothing. Penny insists that it is four flights since they are on the fourth floor and leaves to check it out.


Amy is mad at Sheldon.

Sheldon and Amy both go into to see President Siebert. Amy says that he had no right to reassign her project which Sheldon agrees with. Didn't Sheldon ask him to do it? Amy tells her husband that it is his fault. The President tells Amy that it's not that easy to move her back to her project due to manpower considerations. Sheldon tries to interrupt that and ends with giving Amy a “boop” on the nose.

Back at the planetarium, Penny and Bernadette are waiting for show. She asks Bernie when he last saw Howard in his astronaut uniform. A week ago during Date Night sex where she is a sexy Russian cosmonaut who is an expert on physics and sex. Penny doesn't want to hear any more about Howard's sex life. Raj starts the show and introduces astronaut Howard Wolowitz. Instead of topping each other, they spend the time overly complimenting each other and finally embracing declaring their love for each other. Now Bernadette looks worried while Leonard is moved to tears.


Sheldon's Jedi mentor-Professor Proton.

Sheldon and Amy are asleep in Apartment 4B, as Sheldon dreams about another encounter with his Jedi mentor, the spirit of Professor Proton. They are in a deli on the Star Wars planet of Dagobah. Professor Proton does not recommend the Rueben. Sheldon wants advice after having upset Amy and he wants to make it better. Sheldon knows the advice is coming from his own self-conscious; however, it sounds better from someone older and who is glowing. Professor Proton: Rule number 1: Never go to bed angry. Rule number 2: If you don't recognize the shoes under the bed, they are not your shoes. Sheldon thinks that they are her shoes, so the Jedi master tells him not just go with rule number one.

Sheldon wakes up and then gets Amy to wake up too. Sheldon doesn't want them to go to bed angry; while Amy wants him to go back to sleep. She turns over and he goes, “Amy, Amy, Amy!” She doesn't want to talk now! “Fine,” says Sheldon. He just wants her to know that he wasn't doing anything malicious. Amy defines it as selfish, like not letting her sleep. Finally Amy joins him and admits that she enjoys working with him, but she finds it scary and that "she" doesn't want to get lost in the “we” of their relationship. When Sheldon had her taken off her own project, she felt that her fear was coming true. Sheldon doesn't want her to feel lost. They make up and turn over to go back to sleep, but not before he checks under the bed for strange shoes. Sheldon feels that when you favorite ghost tells you to do something, you must do it.



  • Title Reference: The title refers to the conflict between Raj and Howard when he is asked appear in Raj's planetarium show.
  • Taping date: September 25, 2018
  • This episode was watched by 12.22 million people with a rating of 2.1 (adults 18–49).
  • Total viewers including DVR users 16.78 million.
  • This episode aired in Canada on October 18, 2018.


  • Caroline Preece at Den of Geek! - Of all the various relationships present on The Big Bang Theory twelve years in, there's one that's been there from the beginning and never really faltered. Howard and Raj have had their differences, but their friendship has managed to endure right up until the end...Their disagreement in The Planetarium Collision is a familiar one, but its resolution shows how far the two of them have come...Over in Shamy land, the couple have had their first proper marital spat. It doesn't feel nearly as contrived as the one in the season premiere... but he genuinely doesn't know Amy will be upset. Most satisfying is her reaction, as she tells her husband that she doesn't want to sacrifice her individuality for the relationship. [1]


  • Professor Proton Makes his last appearance in a deli on the planet Dagobah which he had asked for the last time he and Sheldon met.
  • President Siebert reveals Sheldon is taking the paradigms of supersymmetry, but removing the limitations of obeying the Poincaré algebra, in his super-asymmetry theory. With Amy serving as his conceptual sounding board, Sheldon considers utilizing lambda calculus in his theory.
  • Siebert has a doctorate in physics from Indiana University Bloomington.
  • Bernadette role plays as a Russian cosmonaut-physicist in the bedroom. Recall she would have gone into physics (or ice dancing) if she did not become a microbiologist as per "The Gorilla Experiment".
  • In "The Staircase Implementation", Penny acknowledges that her apartment is up three flights of stairs; however, in this episode, she believes that it's four and that the lobby and first floor are different floors until Leonard corrected her.
  • Sheldon and Amy released their Super-Asymmetry paper in January, three months after this episode, "The Paintball Scattering. A few weeks off from Amy's research would not have had a major impact on her career, especially since that work lead her to winning the Nobel Prize.
  • As of the time the episode takes place, 232 people have been to the International Space Station.


Colin: I smell baby powder.
Amy: That's just my husband!

Leonard: What were you guys giggling about?
Penny: They were passing notes to each other.
Leonard: Oh-ho, love notes?
Penny: If you love math.
Sheldon: And we do.
Amy: It's for our super-asymmetry theory.
Sheldon: Yeah, Amy and I have been having so much fun collaborating together.
Penny: Well, you know what they say, you never collaborate as much as your first year of marriage.

Amy: Look, I'm really excited about our paper, too, but I've got a lot of my own work to catch up on, so let's talk later.
Sheldon: Okay, I'll just say one more thing: lambda calculus. And if that wets your whistle, you know where to find me. Boop.

Sheldon: The fundamental problem with elementary quantum mechanical formalism is that the Fourier transform extends to minus infinity in time.
Penny: Hey, don't dumb this down for me.

Amy: You got me removed from my own project?
Sheldon: Yeah, and it wasn't easy. Apparently, you're very difficult to replace. Hey, just between you and me, they consider Dr. Park quite the step down.
Dr. Park: I was trying to pick my moment to leave. This seems like it.
Sheldon: Wow. Banker's hours. No wonder you're not on the tenure track.

Raj: I came here for your support.
Leonard: Well, then, you just walked up three flights of stairs for nothing.
Penny: Wait, don't you mean four flights?
Leonard: No, it's actually three.
Penny: But we're on the fourth floor. I mean, you have the lobby, first floor, second, third, fourth.
Leonard: The lobby's the first floor, so lobby, second, third, fourth.
Penny: That does not seem right.

Amy: You had no right to reassign my project.
Sheldon: Yeah, no right at all.
President Siebert: Dr. Fowler, I don't understand. Dr. Cooper assured me this is what you wanted.
Sheldon: Oh-oh! Can you believe this guy? Oh, sure, so a couple of men get together behind closed doors to decide the fate of a woman's career. I thought we'd moved past this.

Penny: So when was the last time you saw Howard in his astronaut uniform?
Bernadette: About a week ago.
Penny: Really? What was the occasion?
Bernadette: Date night. We do a little role-playing.
Penny: What role do you play?
Bernadette: (Russian accent) I am Katarina Nazdorovya, lonely Russian cosmonaut who is expert at physics and making love.
Penny: Okay, that just made the next hour really weird.

Howard: Thank you, Raj, that was a really nice introduction.
Raj: Well, it's from my heart. So, Howard, you are in an elite group. Only 232 people have ever been on the International Space Station. How does that make you feel?
Howard: Honestly, lucky. Most astronauts have to train their whole lives. I was just in the right place at the right time.
Raj: Oh, please, luck had nothing to do with it. You people need to know how impressive this man is. He was up there because he's the only one qualified to install a piece of equipment that he designed.
Howard: Thanks, but if you want to talk impressive, this guy right here discovered a planetary object outside the Kuiper belt.
Raj: He worked on the Mars rover.
Howard: He helped launch the New Horizons space probe.
Raj: He went to space on a Russian rocket.
Howard: And I was scared the whole time.
Raj: And I was scared for you, but also proud.
Howard: Wow. I don't think you've ever said that to me before.
Raj: I should have, and I'm gonna say it again. I'm proud of you. You're my best friend, and I love you.
Howard: Aw, Raj, I love you, too.
Bernadette: What is happening?
Raj: Bring it in, spaceman, you've been cleared for landing.

Professor Proton: Hello, Sheldon.
Sheldon: Hello, Arthur. Now, I'm confused, usually when you appear to me in my dreams, we're on the planet Dagobah.
Professor Proton: This is Dagobah.
Sheldon: I didn't know that Dagobah had delicatessens.
Professor Proton: Not good ones. Whatever you do, don't order the Reuben.

Amy: Okay, listen to me. I love working with you, but you have to understand how scary this is for me.
Sheldon: Why?
Amy: Because I don't want to get lost in this relationship. And when you pulled me off my project, it seemed like my biggest fear was coming true, the-the things that are mine are getting subsumed into the things that are ours.
Sheldon: I wouldn't want that to happen, either. Thank you for explaining, and for using the word "subsume," that's one you don't hear enough.