In numerous photos and films of nuclear explosions, there appear to be vertical streamers along side the fire ball/mushroom cloud. What are they?
The smoke trails were not caused by the blast itself, but rather were created to provide points of reference for measuring the shock wave caused by the nuclear blast.
In the first few milliseconds after a nuclear detonation, the fireball and shock wave are indistinguishable, but soon after, the fireball cools a little and the shock wave continues on beyond it. The shock wave is a layer of high density air that expands out from the blast very rapidly. In nuclear testing, the scientists and engineers wanted to be able to track the progress of the shock wave well after it went beyond the fireball. So, they launched smoke rockets well behind the detonation site seconds before detonation. The dense layer of air acted as a sort of lens, refracting the image of the smoke rockets behind it, and allowing those working on the project to calculate the shock's velocity and its other properties as a function.
Justin Clifford, None, High School Student, Alpine, Utah
'Our job in physics is to see things simply, to understand a great many complicated phenomena, in terms of a few simple principles.'