Marcus wrote:
Contrails? They're left by water condensing out of engine exhaust, so unless Clark is breathing really fast I'm not sure why they should be there. Bullets, the tips of whips, etc. travel faster than sound and they don't leave them.
Not quite. They're produced by water condensation, true, but it's the pressure generated against the humid air that does it. A jet or turboprop motor will do it, but so will a wingtip moving at high speed. You can see WW2 fighter planes pulling contrails from their wingtips on sharp, high-speed turns in some of the old wing camera footage, and the jet fighters used over Korea would do the same thing. The smoke trails of rockets taking off are mostly made up of combustion by-products, but some of it is contrail residue, too.
You don't see the contrail left by a bullet because it's usually not moving enough air. But spotters working with snipers who fire .50 caliber rifles will say that there's a faint contrail behind the bullet on humid days. It's one of the ways they track the bullet's path.
But I still like the contrail behind Superman. Really cool effect, along with the sonic boom.
