Speed of Sound Distorted During Fireworks. (This time I have proof)?

Question

Last night I videotaped these fireworks:
http://weber.edu/WSUToday/062707pops2007.html

The edge of the campus of this university is 1.2 miles from my house. So that's the minimum possible distance to the school. They were launching fireworks straight up in the air. I video taped them from my back yard. The sound was ~2 seconds after the explosions.

Can sombody explain that?

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Jay: You're the man!
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One other factor. I found this:
http://www.princeton.edu/~dominic/2003%20-%20Johnson%20et%20al.%20-%20Puzzle%20of%20Human%20Cooperation.pdf

That might expain it.

Answer 1

There is another factor...

Most fireworks shells contain flash powder for a burst charge. The flash power 'detonates' (vs. 'deflagration' for gunpowder and other effects), which produces a pressure wave which does indeed travel faster than the speed of sound.

http://en.wikipedia.org/wiki/Detonation
"Detonation is a process of supersonic combustion in which a shock wave is propagated forward due to energy release in a reaction zone behind it. It is the more powerful of the two general classes of combustion, the other one being deflagration. In a detonation, the shock compresses the material thus increasing the temperature to the point of ignition. The ignited material burns behind the shock and releases energy that supports the shock propagation. This self-sustained detonation wave is different from a deflagration, which propagates at a subsonic speed (i.e., slower than the sound speed of the explosive material itself), and without a shock or any significant pressure change. Because detonations generate high pressures, they are usually much more destructive than deflagrations."

Answer 2

So you are claiming that the sound traveled faster than the speed of sound?

Since sound is really pressure differences in a medium, a lot of things can effect how fast sound travels. Temperature, elevation, humidity, etc.

However, I would think the main problem is that you probably have not accurately measured the time from the launching of the fireworks to the time sound arrives. First, you have to take into account of how accurate you were in measuring the two seconds. Unless you freeze framed the video frame by frame to determine when the explosion vs sound occured your timing may be off there. Secondly, the video camera probably records at arround a 60Hz rate. This presents the possibility you could be up to 1/30 of a second off on measurements from the video (also the video recorder could be off on synchronizing video and sound).

Answer 3

Assuming light's speed is virtually instantaneous (relative to sound's speed) what are you asking to be explained??

I have no doubt that explosions (which generate waves of sound) can distort the media (air) to the point that other sounds' speed can be impacted.

Your 2 seconds from sight to sound however would suggest that the fireworks speeded up the sound of the explosions from the fireworks. (It takes approximately 5 seconds for sound to travel 1 mile.)

The precision of your timing and the electromechanical lag of your videotaping camera have to be considered too. All of those factors may have a bearing on the significance of your observations.

Answer 4

You are also assuming the bang and the flash started at the same time. Doesn't it take time to explode the container before you see the flash. The noise from the ignition you hear may come quite a bit of time before you see the big flash. Reactions are not instantaneous, they have to grow. The speed of sound would change under extreme conditions, but those extreme conditions don't last for 1.2 miles, I suspect.

Answer 5

The speed of light (186,000 mps) is much faster then the speed of sound (~600 mph)