Null separation
= Null separation
{title2=$s^2=0$}
Distinct <spacetime events> have <null separation> when their displacement has zero <Minkowski interval>, equivalently $c|\Delta t|=|\Delta\mathbf x|$. They can be joined by a straight vacuum light ray. Their nonzero displacement is a <null vector>, so the zero squared interval does not mean that the <spacetime events> coincide. For example, $(t,x)=(3\,\mathrm s,3\,\mathrm{ls})$ is null separated from the origin.