After seeing the complex numbers, you might wonder whether there were algebras of even higher dimension that act like the real numbers. Such algebras do exist. Alexander Hamilton invented the first in 1843, and named it the quaternions.
The question is, in what way should these algebras behave like the real numbers? If an algebra is exactly like the real numbers in every way, then it is the real numbers.
There are many ways of generating such higher-dimensional algebras, depending on which algebraic properties of the real numbers you want to preserve. Two such ways are the doubling procedure and the Clifford algebras.
These pages are meant to be understandable to anyone with sufficient mathematical background to appreciate the issues. Most can be read by students who have completed a second-year high school algebra course.