Control
by Jeff
Image text: Which, at one point, led to a study showing that LSD produces no more hallucinations than a placebo.
This comic is a reference to the common practice in a research study in which one group is given the drug or treatment and the other is given a placebo which is a pill filled with sugar water or something to that effect. The idea is that the placebo has no effect, but in a blind study, the patient would not know if they took the placebo or the real drug. In this case, the person referenced in this comic has a hobby of replacing the placebo with LSD or Lysergic acid diethylamide, also known as acid. LSD is frequently used for its psychological effects or "trips" like the one referenced in the comic in which the person believes they have spiders crawling all over their body. I would imagine envisioning spiders crawling over ones body is not the desired effect.
The joke in the comic is that the researchers (The two people in the forefront, one of whom has a clipboard) are confused why the person who took the placebo is acting so strange when they are supposed to have just taken a sugar or water pill.
If it was a double-blind study, the researchers would not be confused because they would not know who was the control group and who was actually being given the drug.
Open Mic Night
by Jeff
Image text: Ever notice how the more successful observational comics become, the more their jokes focus on flying and hotels?
Alright, open mic night. Everyone's favorite night.
In the first frame Cutie/MC Aphasia is not a very good rapper because Aphasia is a disorder that effects the part of the brain that controls the ability of speech. So, as you can see in the comic, MC Aphasia has a very difficult time speaking let alone rapping.
In the second frame, Black Hat is reacting to a Yo Momma joke that someone in the audience possibly yelled his way and starts off a common "Yo Momma" joke - "When yo momma sits around the house, she really sits AROUND the house." But instead he goes in another direction to something that is a bit more off the beaten path.
In the third frame Cueball/MC Quine is a computer science joke. A Quine is a program that produces its source code as its output. In other words, what MC Quine puts into the rap is exactly what he gets out of it. Hence the repetition of the same line. In this case, the source code of the rap is "Yo, I'm MC Quine and I'm here to say,".
And completing the xkcd trifecta is the last comic, is a Lord of the Rings joke. I'll call him "Beret" and is riffing off a common observational comic routine in which the comic observes that men go to the bathroom alone and women go in groups.
The image text is a reference to how when comedians become more famous, they travel more to other cities to do their comedy. In the case of observational comics, the more they travel, the more they have time to observe both hotels and flying and nothing else.
Pore Strips
by Jeff
Image text: I'm sure they're a harmful tool of the cosmetics-industrial complex and all, but my goodness do those strips ever work to pull gunk out of your pores. I was shocked, disgusted, and vaguely fascinated by the result.
In this comic, Cueball uses the anti-acne deep cleaning strips that you are supposed to rub all over your face to get the dirt and sweat out of your pores. However, as the box in the comic explains, the pore strips are deep cleaning and in the case of the comic too deep. The pore strips used in the comic cleaned too deep and in the process of cleaning his face, Cueball pulled out his skull, which resides deep within his face. Whoops!
Green Flash
by Jeff
Image text: The exact cause of the phenomenon is unknown, but it's thought to be linked to atmospheric refraction and you getting a really cool car.
The green flash is an atmospheric optical phenomena in which a small green spot will appear above or around the sun as it sets below the horizon. The green flash occurs because of refraction of different colors of light. Green light is higher frequency than red and orange light and so green light stays visible after the red and orange lights are blocked by the Earth. Wikipedia has a great gallery of examples of the green flash. Personally, I have been looking for the green flash my whole life and have never seen it. The name is slightly a misnomer as it is not really a flash at all, but stays for a few minutes.
The Tesla roadster is a new car from the Tesla Motors. All of the Tesla Motors cars run entirely on electricity. Check out the car here, as it is a pretty sweet little sports car. No wonder the Black Hat Character wants to smash the other character over the head with the bottle he is holding to steal the car.
Dilution
by Berg
Image Text: Dear editors of Homeopathy Monthly: I have two small corrections for your July issue. One, it's spelled "echinacea," and two, homeopathic medicines are no better than placebos and your entire magazine is a sham.
Homeopathy is a form of alternative medicine which makes bold claims as to its efficacy without offering any sound science to back it. Although the angles from which one can viably attack homeopathy are as diverse as they are numerous, this particular panel is taking on serial dilution. In a serial dilution, a substance is dissolved in solution. The solution is then divided, and diluted. This dilution is then divided and diluted, and then the dilution of the dilution may be divided and diluted again, and again, and again.
While serial dilution does serve a function in many legitimate procedures, homeopathic remedies prepared using serial dilution are often diluted so much that none of the original substance remains in the final preparation. This point was proven dramatically by noted skeptic James Randi at TED 2007, when he ingested a purportedly lethal dosage of homeopathic sleeping pills on stage. Spoiler alert: James Randi is still alive.
So, back to the comic. The couple in question is preparing a serial dilution of semen and expecting its potency to either remain constant or perhaps increase, resulting in a pregnancy. However, we the ever-so-well-informed xkcd reader know full well that if James Randi isn't dead, then that lovely young woman isn't getting pregnant. If she can't get pregnant, then she can't pass on whatever part of her or her partner's genetic makeup it is that makes them susceptible to a belief in homeopathy. Since the couple's belief in homeopathy is negatively affecting their ability to have offspring, its lowering their fitness (Darwinian fitness, not gym membership fitness). A belief in homeopathy which is so strong that it prevents it's believers from having offspring is therefore an evolutionary dead end, and is not selected for.
This point is underscored by the image text, which is playfully realized in this comic as a letter to the editors of Homeopathy Monthly, a fictional homeopathy magazine which we can imagine is of some import the homeopathic community. The jab against homeopathy is set up with a classic use of the foot-in-the-door technique, opening up with a nitpicky correction about the spelling of "echinacea." Now that the editors of homeopathy are paying attention, the payload is delivered and their passion is called out for being what it is: a complete sham.
Study
by Jeff
Image text: Volunteers needed for a study on transmission of urushiol from digital contact with thin strips of fibrous cellulose pulp.
I'm always wary of these things, especially when they said they will require a 24-48 hour stay at "our facility". Yikes.
The key word in the image text is: Urishiol is the chemical produced by poision ivy.
From there you can probably figure it out, but essentially the image text is a soliciting volunteers for a study in which the volunteers use their fingers or toes to touch poison ivy leaves. Brilliant readers have notified me that fibrous cellulose pulp is not leaves, but in fact the strips of paper that are on the ad in the comic. Thanks for correcting me!
Sounds like fun!
Seismograph
by Jeff
Image text: The reverse only works if the subject has a nervous twitch.
This is another instance of the "pro tip" meme, which is designed to turn the reader into an expert from a novice in one easy step.
This comic is suggesting that if a lie-detector was placed on its side, that it would function as a seismograph to detect the size of earthquakes.
Snow Tracking
by Jeff
Image text: I suppose that's more accurately a hare dryer.
Moose and Squirrel is a reference to the Rocky and Bullwinkle series of cartoons.
Longcat is a internet meme from pictures of cats all stretched out that make them look very tall (or long).
Mouse riding Bicycle is a reference to Ralph S. Mouse, a series of novels by Beverly Cleary.
The image text is a pun on the Rabbit with a hair dryer frame.
Legolas is a reference to the character by the same name in the Lord of the Rings trilogy of books and movies.
Knight is a chess reference as the tracks move just like the knight piece in chess.
The two "Kid with" frames are a reference to Calvin and Hobbes.
Prius is a reference to current events in which the car Toyota Prius's pedals have malfunctioned causing accidents.
The final frame is the Higgs Boson which is an elementary particle they are attempting to find evidence of in the Large Hadron Collider.
Anyone know what the Bobcat on a Pogo Stick is a reference to? That's the only one I can't get.
Complexion
by Jeff
Image text: Why do all my attempts at science end with me being punched by Batman? (P.S. benzoyl peroxide soap works great.)
This comic is a reference to the Batman villain "Two-Face". Because the main character had pimples on one side of his face and not the other, he resembled the Batman villain. Two-Face is also fond of flipping a coin to decide what to do. The two different sides of his face and the flipping of the coin is what drew Batman into the comic.
FIRST Design
by Jeff
Image text: Pool on the roof must've sprung a leak.
This comic is about a robot competition between two sides. The protagonist's side comes up with a robot that has a match on an extending arm to set off the sprinkler system to disable the opposing robot. Then the protagonists added an umbrella to their robot so that their robot could complete the competition without getting wet.
The image text is the protagonist's flimsy excuse for the reason there is water everywhere.
UPDATE: As Zero Cool and Alexandra said in the comments, the Image text is a reference to the movie, Hackers.