Thomas Gold was the first to suggest in the 1950s the presence of <br />
interplanetary shock waves as part of the physical mechanism involved in the <br />
modulation of galactic cosmic rays. Rapid progress followed in theoretical <br />
understanding in the US (Eugene Parker) and in the USSR (Leonid Sedov) to <br />
name just a few workers in solar physics and astrophysics. I will review <br />
(based on a subjective interpretation of shocks that is independent of their <br />
genesis) basic self-similarity theory for the classical one-dimensional <br />
geometries and their support by the results from non-symmetrical numerical <br />
simulations. Spacecraft in situ and remote observational measurements will <br />
be noted in conjunction with some theoretical predictions. <br />
When \"real life\" situations exceed theoretical assumptions, numerical <br />
simulations can point the way to improved understanding of shocks\/ formation <br />
at the Sun and their propagation throughout the heliosphere. This procedure <br />
is not without controversy. For example, one may justifiably, ask, \"What <br />
initialization inputs should we use from the available observations?\" I <br />
will conclude by demonstrating how many of the above ideas have been <br />
incorporated into a real-time space weather scheme (the Hakamada-Akasofu-Fry <br />
solar wind model, HAFv.2) that has been used during Solar Cycle 23 in <br />
collaboration with the US Air Force Weather Agency and NOAA\/s Space <br />
Environment Center. <br />