Teaching is not easy. One of the main reasons why it is not easy is that the existing descriptions of the teaching process are not very precise -- and thus, we cannot use the usual optimization techniques, techniques which require a precise model of the corresponding phenomenon. It is therefore desirable to come up with a precise description of the learning process. To come up with such a description, we notice that on the set of all possible states of learning, there is a natural order s ≤ s' meaning that we can bring the student from the state s to the state s'. This relation is similar to the causality relation of relativity theory, where a ≤ b means that we can move from point a to point b. In this paper, we use this analogy with relativity theory to come up with the basics of such an order-based description of learning. We hope that future studies of these basics will help to improve the teaching process.