  A comprehensive description in all dimensions is provided for the scaling
exponent $y$ of low-energy excitations in the Ising spin glass introduced by
Edwards and Anderson. A combination of extensive numerical as well as
theoretical results suggest that its lower critical dimension is {\it exactly}
$d_l=5/2$. Such a result would be an essential feature of any complete model of
low-temperature spin glass order and imposes a constraint that may help to
distinguish between theories.
