♪ Baroque-n-Chords ♪ (telemann) wrote in scientificwhims,
♪ Baroque-n-Chords ♪

A question

In films of nuclear tests, you typically see these cloud formations that appear a split second after the bomb explodes. What's causing this? My initial hunch is something about a sudden increase in temperature in the air above and around the bomb. In some videos you see these long stringy ribbon like clouds from the air (it can't be debris because the mushroom cloud is not even completely formed). Thanks!
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It's a shock wave. It comes from the pressure wave that travels out from the blast.
I mean it's from the shock wave.


July 10 2011, 01:23:16 UTC 5 years ago Edited:  July 10 2011, 01:23:33 UTC

Aye, as the above poster said, it's a visible shockwave in the air. Also, for the stringy clouds, if you mean those vertical ones that are sometimes seen beside the cloud itself, and off to the side, those are trails from data gathering rockets that are launched just before or concurrent with the detonation itself.
ok, never knew that about the rockets!

This clip has those vertical things (this was a nuclear artillery shell), so are you still sure these were little rockets?
Don't just take my word for it: http://www.physlink.com/education/askexperts/ae503.cfm ^^
My guess is that it's the same effect you see when a fighter jet goes supersonic, but on a much larger scale. When the shock wave breaks the sound barrier.
I guess heat is moving at the same speed of light? Meaning you'd see these clouds before you heard the explosion?
yes, heat (infrared electromagnetic waves) travels at the speed of light, but the schock wave moves much slower, since in propagates through the air. It would be interesting to know the times and distances in the movie to calculate the speed of the shock wave.
Yeah, the shockwave would be the speed of sound, I'd think?
I don't know. Certainly there is a sonic wavefront that travels at the speed of sound, but I don't know if the shock wave would be so constrained. At some distance from the blast the winds are traveling at a few hundred mph, maybe that's the remnant of a hypersonic shock wave. Now you've got me all curious.
Superheated steam, forced outwards from the event of the blast.

Just my .02¢