The Lunar Excitation

"The Lunar Excitation" is the twenty-third episode and the final episode of the third season of the   The Big Bang Theory. This episode first aired on May 24, 2010.

Summary
The gang meets Penny's dim-witted new guy Zack while performing a experiment on the apartment building roof. Raj and Howard sign up Sheldon for online dating and find him a match,   Amy Farrah Fowler.

Extended Plot
The guys are up on the apartment roof performing a lunar ranging experiment. While Raj is using the telescope after he's done watching The Good Wife on someone's TV, Leonard thinks Penny would like to be up here to see what they are doing. Sheldon does admit that retro-reflector left by on the moon that they are using could qualify as a shiny object. Leonard goes to Penny’s apartment and finds her with Zack, her date, wonders how you can bounce stuff on the moon if there's no gravity up there. Zack wants to see it anyway. Zack designs the menus for the Cheesecake Factory. Upstairs, Leonard tries to explain what's going on Zack is afraid that when the laser hits the moon, the laser will blow it up. Sheldon tells everyone that Zack is a man for Penny. They fire the laser and get a return 2.5 seconds later and the guys are excited. Zack is not impressed. Leonard, “Don't you see what we've done? It's the only definitive proof that a species put objects on the moon. A species that only 60 years before had just invented the airplane.” Zack doesn’t know what species Leonard is talking about. Now Sheldon thinks that Penny can do better. Penny and Zack depart with Penny having been embarrassed by Zack.

Back in Apartment 4A, Howard suggests getting Leonard an online dating profile. He’s had eight dates in the last month, twelve if you count the ones that just show up and leave. Sheldon asks for help with a heavy nitrogen tank down from the roof and Leonard ends up getting it himself. Raj suggests that they create an online dating profile for Sheldon like when Frankenstein's monster was lonely and they found him a wife.

Early in the morning Leonard answers a banging on their door and it’s a drunken Penny. She claims that Leonard had ruined her because she would have never have known that Zack was so stupid. He has destroyed her ability to tolerate idiots. Therefore, the two of them are going to have sex which Leonard is fine with. Sheldon wakes up and is advised to break out the noise canceling headphones because this was going to get loud. Sheldon is disturbed that he is going to have to put up with the two of them again.

In the morning, Penny tries to sneak out, but disturbs Sheldon. He comments on her use of the phrase 'yee-haw' used during their carnal activities  which thrills Penny as she leaves. Leonard wonders why Penny left without saying good-bye. Sheldon replies that Penny went back to her apartment to shower and vomit.

Leonard and Penny run into each other as she heads off to work. Leonard wants to go dinner and a movie, and Penny tells him last night was a mistake since she was angry and drunk. She wants him to forget it, but the whole rodeo thing is kind of implanted on his brain. Leonard accuses her of using him for sex and then learns that Mrs. Gunderson in 3A also heard them last night. (Yee-haw!)

Later, Raj has the proof that aliens walk among us since the dating site matched Sheldon with a woman. An actual woman with breasts and everything. They reply to her with an email.

What Leonard thinks he has learned is that it’s okay for people to return to former lovers and have casual sex with them. He goes to see Leslie Winkle who talks awkwardly with him including asking him whether “Blondie” had dumped him. Since it's OK to have recreational sex with people they've known before, he asks her. She says she'll think about it...and slams the door in his face.

Now Sheldon's perfect match wants to meet him. Howard and Raj decide to resort to the truth. They got Sheldon a date with his perfect match for the next day. Of course, Sheldon thinks the algorithms used to determine the compatibility of potential mates is pure hokum, but that is literally the answer they gave when the questionnaire asked what they thought of online dating sites. Even Spock had a date once every seven years. Sheldon correct them that he was experiencing pon farr, burning lust. Raj also hid the dirty sock that freaked Sheldon out on the roof somewhere in the apartment and refuses to take it out unless Sheldon meets Amy Farrah Fowler. Sheldon curses him, but agrees to do it.

Leonard comes back to the apartment drunk and goes to Penny's. He tells her that he was a perfectly happy geeky, lonely little guy, and you ruined it for me! He wants to have sex and it's not going to mean a thing. Penny tells him that he’s out of your mind and throws him out. Leonard feels that he experiencing a double-standard.

At the coffee shop, Sheldon tells them that their experiment is going to fail. (Neener-neener.) Amy Farrah Fowler shows up because she agreed to date once a year just to keep her mother off her back. She shares Sheldon's aversion to soiled hosiery and they connect over agreements they had made with their mothers. And all forms of physical contact up to and including coitus are off the table. Sheldon offers to buy her a beverage as they step up to the counter. Amy turns away and has a very satisfied expression on her face. Howard wonders, “Good Lord, what have we done?”

Critics

 * "As we end season three I thought the writers addressed the Penny-Leonard relationship in a nice way. For both the relationship has changed their perspective on their future partners. The point was made in a somewhat subtle way that they both now have higher standards thanks to the other...It's a familiar refrain but the writers still don't handle Penny and Leonard's situation with the skill they need to...A passable end to a really decent season from The Big Bang Theory . "Really decent" might sound like damning with faint praise but the show has got better this season. The writing went to new places and did on occasion flesh out its characters." - The TV Critic's Review
 * IMDb user reviews

Quotes

 * (Howard. Sheldon and Raj are at the café waiting to meet Amy Farrah Fowler.)
 * Amy Farrah Fowler: Excuse me, I'm Amy Farrah Fowler, you're Sheldon Cooper.
 * Sheldon: Hello, Amy Farrah Fowler. I'm sorry to inform you that you have been taken in by unsupportable mathematics designed to prey on the gullible and the lonely. Additionally, I am being blackmailed with a hidden dirty sock.
 * Amy: If that was slang, I'm unfamiliar with it. If it was literal, I share your aversion to soiled hosiery. In any case, I am here because my mother and I have agreed that I will date at least once a year.
 * Sheldon: Interesting. My mother and I have the same agreement about church.
 * Amy: I don't object to the concept of a deity, but I am baffled by the notion of one who takes attendance.
 * Sheldon: Well then, you might want to avoid East Texas.
 * Amy: Noted. Now before this goes any further, you should know, that all forms of physical contact, up to, and including coitus, are off the table.
 * Sheldon: May I buy you a beverage?
 * Amy: Tepid water, please.
 * (Both go to the counter, while Raj and Howard just stare.)
 * Howard: Good God, what have we done?

(Sheldon notices Penny taking Leonard to his bedroom)
 * Sheldon: What's going on?
 * Penny: Get your noise-cancelling headphones, 'cause it's gonna get loud.
 * Sheldon: Oh, not this again!


 * Sheldon: That's not afternoon. That's prevening.


 * Penny: Damn you, you rat bastard! In the olden days, I never would have known he was that stupid!


 * Zack: Is that the laser? It's bitchin'.
 * Sheldon: Yes. In 1917, when Albert Einstein established the theoretic foundation for the laser in his paper "Zur Quantentheorie der Strahlung", his fondest hope was that the resultant device be bitchin'.
 * Zack: Well, mission accomplished.


 * Leonard: (Explaining the significance of the experiment to Zack) Think about what this represents. The fact that we can do this is the only way of definitively proving that there are man-made objects on the moon, put there by a member of a species that only 60 years before had just invented the airplane.
 * Zack: (Astonishingly) What species is that?


 * Zack: One question. How can you be sure it won't blow up?
 * Leonard: The laser?
 * Zack: The moon.


 * Leonard: Okay, we’ve got power to the laser.
 * Sheldon: I should’ve brought an umbrella.
 * Leonard: What for? It’s not going to rain.
 * Sheldon: I know that, but with skin as fair as mine, moon burn is a real possibility.
 * Howard: That’s a bazinga, right?
 * Sheldon: One of my best, don’t you think?

Trivia

 * The gang's lunar laser ranging experiment utilizes a, as is referenced on the whiteboard near Sheldon and Leonard's apartment door. crystal lasers typically emit light with a wavelength of 1064 nm, in the . However, the high-intensity pulses may be efficiently  to generate green laser light at 532 nm. Both of these wavelengths are written on the lower half of the whiteboard, along with the chemical formula Y3Al5O12 for the yttrium aluminum garnet crystal structure and the atomic transition 4F3/2 → 4I11/2 in the neodymium ion, after being "pumped" into excitation. The upper half of the whiteboard calculates the round-trip travel time of a light pulse bouncing off lunar retro-reflectors as 2.56 seconds, based on the ratio of the semi-major axis of the lunar orbit to the speed of light.
 * Raj loves, in which Christine Baranski, who plays Leonard's mother, is enlisted in the main cast.
 * Sheldon refers to Albert Einstein establishing the theoretic foundation for the laser in his paper Zur Quantentheorie der Strahlung (On the Quantum Theory of Radiation) in 1917.
 * Sheldon mentions that he only drinks in months with an "r" in them. Thus, his quirk doesn't allow him to drink hot chocolate in the consecutive months of May, June, July, and August, which spans the summer season in the . It makes perfect sense; in, it would be much too hot in the summer months to drink hot chocolate.
 * Raj states that Sheldon's answer for the question "How do you feel about online dating services?" would be "hokum", which was exactly the same word that Sheldon himself used to described on-line dating algorthms in "The Barbarian Sublimation" (S2E03).
 * last appearance of a main character (Leslie) and the first appearance of another main character (Amy).
 * This is Amy Farrah Fowler's first appearance in this series; interestingly, her full name is revealed even before her first appearance.
 * Sara Gilbert's final appearance as Leslie Winkle. Interestingly enough, Leonard's final line in her scene- "She's not coming back," refers to both Leslie not taking him back and not returning to the series.