Position

The spacetime position $$\mathbf r$$ of a body is given by

$$\mathbf r = ct\,\mathbf e_0 + x\,\mathbf e_1 + y\,\mathbf e_2 + z\,\mathbf e_3 + \mathbf e_4$$ .

The position $$\mathbf r$$ has units of length.