  We present a quantitative assessment of the Toner and Tu theory describing
the universal scaling of fluctuations in polar phases of dry active matter.
Using large scale simulations of the Vicsek model in two and three dimensions,
we find the overall phenomenology and generic algebraic scaling predicted by
Toner and Tu, but our data on density correlations reveal some qualitative
discrepancies. The values of the associated scaling exponents we estimate
differ significantly from those conjectured in 1995. In particular, we identify
a large crossover scale beyond which flocks are only weakly anisotropic. We
discuss the meaning and consequences of these results.
