  We present numerical evidence that in strong Alfvenic turbulence, the
critical balance principle---equality of the nonlinear decorrelation and linear
propagation times---is scale invariant, in the sense that the probability
distribution of the ratio of these times is independent of scale. This result
only holds if the local alignment of the Elsasser fields is taken into account
in calculating the nonlinear time. At any given scale, the degree of alignment
is found to increase with fluctuation amplitude, supporting the idea that the
cause of alignment is mutual dynamical shearing of Elsasser fields. The
scale-invariance of critical balance (while all other quantities of interest
are strongly intermittent, i.e., have scale-dependent distributions) suggests
that it is the most robust of the scaling principles used to describe Alfvenic
turbulence. The quality afforded by situ fluctuation measurements in the solar
wind allows for direct verification of this fundamental principle.
