Interdisciplinary
by Jeff
Image text: Replace the pendulums with history students and you'll qualify for a grant!
This is another theme in xkcd. The ripping of psychology, history and english majors is very common in various comics.
Seismic Waves
by Jeff
Image text: The USGS operates a really neat email/SMS earthquake notification service (earthquake.usgs.gov/ens/) that allows fine-grained control of notifications.
This is a very relevant cartoon strip because of the earthquake that rocked northern Mexico and Southern California on Sunday afternoon. And this is certainly true as everyone takes to Twitter and Facebook to announce that they have gotten an earthquake.
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.
Gravity Wells
by Jeff
Image text: This doesn't take into account the energy imparted by orbital motion (or gravity assists or the Oberth effect), all of which can make it easier to reach outer planets.
This is awesomely epic. Click the image to see the full image in detail.
Christmas Plans
by Jeff
Image text: Physicists who want to protect traditional Christmas realize that the only way to keep from changing Christmas is not to observe it.
This comic is a pun on the word "observe".
In regards to Christmas, the phrase is "I don't observe Christmas". In regards to physics, just like in the Schrodinger Cat problem, the physicists don't know where the cat is in the box (or whether it is alive or dead) until they observe it.
In the comic, the character at the computer does not know where Christmas is because he doesn't observe it in the physicist way.
Revolutionary
by Jeff
Image text: I mean, what's more likely -- that I have uncovered fundamental flaws in this field that no one in it has ever thought about, or that I need to read a little more? Hint: it's the one that involves less work.
This comic is a discussion between two characters, the main character and the Philosophy major who has a goatee. The image text is an additional comment by the character which the goatee.
The character with the goatee is suggesting that the people of science like the main character are holding firmly to their belief of the theory of special relativity.
This is a stereotypical representation of people such as Philosophy majors who thumb their noses at Phyics majors or other scientific ideas, which thinking that they always have the answers and have thought of a new idea that has never been thought of before. This is referenced in the image text.
Experiment
by Jeff
Image text: The other two are still lost on the infinite plane of uniform density.
Let's see if we can work through this one. The Black Hat character and a female accomplice knock out a Physics professor and put him in a frictionless vacuum. The professor wakes up and tries to talk but the vacuum prevents him from being able to say anything. In the first two frames of the bottom section, the professor tries to move, but falls down because the vacuum is frictionless as well.
EDIT: Please see the comments below for Rob and Paige's explanations of the comic who are much more attuned to physics jokes than I am. Thanks Rob and Paige!