\magnification=\magstep2


$$
{\rm Fred\ measures\ } (x, y, z, t)   \quad  \Rightarrow \quad
       {\rm Jane\ measures\ } (x', y', z', t') 
$$

$$
x, y, z, t \quad {\rm \ and\ relative\ speed\ } \quad \phantom{-}v \quad {\rm \ along\ x\ axis\ }
$$

$$
x', y', z', t' \quad {\rm \ and\ relative\ speed\ } \quad -v \quad {\rm \ along\ x\ axis\ }
$$

$$
\eqalign{
x' &= x - vt  \cr
y' &= y   \cr
z' &= z  \cr
t' &= t   \cr
}
$$



\bye
