A physics textbook is a great start, but it has one major drawback: it's linear, and can't adapt to the reader. Maybe I already understand half of the textbook, but I can't figure out this one section. I'm out of luck, because the textbook won't expand on the part I struggle with.

One major value of the teacher in the classroom is to be able to sense when students are getting lost, and have ways to slow down, re-explain concepts that they missed.

A basic AI sounds like it could soon do a great job of providing the content of a physics textbook, with the adaptability of a one on one teacher.