  We present a comparison of radio observations of the archetypal powerful
radio galaxy Cygnus A and 2-D numerical hydrodynamical simulations. We
characterize some global trends in the observed radio properties and compare
them with the properties of a simulated radio source. The numerical results are
the following. Jets propagating in a constant density atmosphere will
decelerate with time. Thus, the estimated dynamical age of the source will be
greater than the actual age of the source. For a source similar to Cygnus A the
difference will be about a factor of 2. The second moment gives an accurate
representation of the "true" width of the simulated source. The Gaussian FWHM
tends to be about 40% larger than the true width and can be systematically in
error if the surface brightness exhibits multiple peaks. We suggest that the
ratio of the Gaussian FWHM to the second moment may be a diagnostic of the
emissivity profile in the lobes. The simulations can qualitatively reproduce
the overall observed morphology and the behavior of the cross-sections in
surface brightness, the decline in surface brightness with distance from the
hot spots, and the width of the lobes. This suggests that the 2-D simulations
give a reasonable representation of the properties of Cygnus A.
