The core is basically a set of classes that everyone must either take or place out of. Caltech doesn't take any AP credit because the classes are much more analytical and thorough than the AP examinations. The core is currently going through revisions, so it may be a little different when you come to Caltech. The current core consists of 5 terms of mathematics (calculus, linear algebra, multivariable calculus, differential equations, and probability & statistics); 5 terms of physics (classical mechanics, electromagnetism, waves, quantum mechanics, statistical physics); 2 terms of chemistry (taken first two terms of frosh year), 1 term of biology (taken third term of frosh year), 2 introductory lab courses (taken whenever), a menu course (generally taken third term frosh year), and of course humanities classes.
You might be thinking: wow...that's a lot of science classes! But I guess that's part of what's different between Caltech and different colleges. It also makes sure that people who actually enroll at Caltech are those who are truly passionate about math and science, and aren't coming here just for the name. Although I can't honestly say that I like all of the core subjects, I like having the core. It makes sure that you have a solid background in all subjects, and not just your major. As my roommate Sarai says, they're all classes that she'd probably take anyway, even if they weren't required.
Since I'm only on my 2nd term, I haven't taken that many core classes yet. If you could, I would suggest you try placing out of some classes since it frees up space in your schedule to take more classes you want to take. I passed out of calculus and linear algebra, so I took differential equations last term and I'm taking probability & statistics this term. The differential equations class was pretty basic, and rather similar to the class I took in high school. First term physics and chemistry was very similar to the material on the AP Physics C Mechanics and AP Chemistry exam, except more in depth and involves more problem solving.For the menu course, you can choose from astronomy, geology, information science and technology, environmental engineering, and energy science. I plan on taking the geology class, and there's a field trip to the Grand Canyon!
I'll write about the workload at Caltech and the classes I'm taking this term on another post later :)