Nuclear Explosions are Loud

Yesterday Huxley and I were out on the porch checking out the incoming thunderheads. Then we heard thunder. Huxley immediately ran over to the door and pulled it shut.

“We don’t want thunder going in the house.”

Good idea. Who knows what it would do in there.

Anyway, everybody knows that when you see lightning, the thunder takes a while to get to your ears because lightning is percieved by us first from its light which travels at…the speed of light!…while lightning is percieved by us later from the sound it makes which travels at…the speed of sound! The latter is much much slower than the former.

So, when you see a video of an A-bomb or H-bomb explosion, either for real or as a dramatization, or for that matter, any kind of explosion, you should feel strange if the sound of the blast happens at the same exact time as the sight of the blast. We don’t, after all, see lightning and thunder coming at the same exact time when that is depicted on film or video. I think.

Now, this might make sense, depending on perspective. If the narrative mode is omniscient, I suppose one sees the blast and hears the blast because one is…well, omniscient. But an omniscient narrator may actually be hanging around with the characters who are experiencing the blast form a distant, so it still makes no sense.

Anyway, there is a YouTube video out there now that shows the unedited film of an atomic blast, and the sound is what it was at the time…a bunch of people chatting and then “KaBlam” and then “Holy Shit” and so on. It’s a long time between the blast (a bright flash of light) and the KaBlam. Here it is:

From the YouTube page:

Atomic bomb test ANNIE, March 17, 1953. This footage is interesting because the audio is more or less unedited. The timing between seeing the explosion and hearing the blast wave is off by a few seconds, which is how it would be in reality for an observer at that distance (because light travels much faster than sound). All together the audio is great here, so put on some headphones and experience it as if you were actually there.

“In an effort to calm public fears about weapons testing, Annie was an “open shot” — civilian reporters were permitted to view it from News Nob, 11 kilometers south of the shot-tower.

Hat Tip: Joe

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21 thoughts on “Nuclear Explosions are Loud

  1. I was thinking as I watched the flash…. I could set a stopwatch and time the pause between the flash and sound to figure out how far away they were from the bomb. Amazing!

  2. I recall during grad school going to the now closed mine at Eagle Mountain Ca. We were putting speakers down to get the time of the blast. After we had set everything up, they pulled us back a distance from the blast. Then they set of a few hundred thousand pounds of explosive. You saw the dust start rising, then felt the ground wave, and then heard the noise. I suspect that the same thing happens in a nuclear blast you feel the sound thru the ground before thru the air.
    It also is a great way to impress on one the difference in the velocity of sound in different media.

  3. Did you hear the slight noise that was electronically imposed on the soundtrack at the moment of detonation? I guess that’s what an EMP sounds like on a camera of that time.

    When I was a third grader and living in San Bernardino, California, I remember getting up extra early, well before dawn in about that year. My family and I watched as the San Benardino Mountains to our north suddenly were silhouetted with light from behind, coming all the ways from an open-air H-bomb at the Nevada Test Site.

  4. What is wonderful here, that sound goes after the lighting or that sound of nuclear explosion is loud?
    I still don’t understand it.

  5. Yeah, that thing drives me mad – just look at fireworks shows on tv/news/movies. It especially annoys me when people do it to an alleged nuclear blast. The Real Thing is far more impressive – on the reels you see a bright flash which overexposes the film for several seconds, then you see the blast cloud, and ~20s or so from the initial flash there’s an incredible boom and roar which screws up the sound (it’s too loud to record properly); a few seconds before the air blast you actually hear a (very loud) rumbling from the shock transmitted through the ground.

  6. Perhaps a little off topic, but nuclear explosions are not as loud as one may think. The one on the Michigan border along with extreme high radiation levels and hundreds of military personnel, vehicles, and a high number of armed blackhawk helicoptors did not even make the evening news. Civilians were not allowed in the area – a major suburban area with a high population! Not one damned news report on the evening news, unless they were told to shut up about it.

    Thank God for rebels and patriots like Alex Jones. To hell with the rest of the traitors and globalists.

  7. Well, that would be the stealth nuclear explosion they have. They use special implosion waves to silence them. Same idea as your basic noise dampening headphones.

  8. Long ago, Arthur C. Clarke wrote a short story about a noise-cancelling device. Where does the energy from both the sound and the inverse waves sent out by the device go? Clarke had an amusingly scary idea where it goes.

  9. No, the energy just built up in the machine until there was a tremendous explosion. The machine was essentially an analog device. It created silence in any room in which it was operated. Mics picked up sound, then a matching reversed wave was output through speakers, One of the scientists had been wondering where the energy went, and finally found out.

    It’s been about 50 years since I read the story, and I can’t recall its title or many details. I think it was part of Clarke’s “Tales from the White Hart” collection, though. Remembering the short story, I found it interesting when outside-noise-canceling headphones began to appear in recent years. I think they use the same basic technique.

    But none of those headsets have exploded, as far as I know. Otherwise, they’d be banned on planes as a potential terror weapon : )

    (By the way, that thermonuclear blast that my family and I distantly witnessed in the 50’s: We didn’t hear it.)

  10. Actually the sound will arrive quicker than what you’d calculate using the speed of sound. All explosive blast waves start out as supersonic shock waves -essentially the speed of sound goes up with temperature, and in a shock the pressure is high enough that the adiabatically heated high pressure portion is at considerably higher temperature than the ambient air.

  11. Found the following, at . . .

    “‘Doubtless some of you will already see what I am driving at, and will appreciate the basic principle of the Fenton silencer…

    It consisted of a microphone, a special amplifier and a pair of loud speakers. Any sound that happened to be about was picked up by the mike, amplified and inverted so it was exactly out of phase with the original noise. Then it was pumped out of the speakers, the original wave and the new one cancelled out, and the net result was silence.

    Of course, there was rather more to it than that. [But]… it’s a simple application of negative feedback.'”

    From “Silence, Please” in “Tales from the White Hart,” Published by Ballantine Books in 1957
    So, Omega Centauri, that makes sense. The air-borne sound we hear must come from the outer edge of the shock wave, where it’s slowed own to the speed of sound. Then there’s whatever noise is transmitted via the ground, where both shock and sound travel much faster than in the air. And, of course, the electromagnetic “sound” that the camera picked up, which traveled at light-speed,

    So one would experience first, light flash and electromagnetic pulse together, then earth shock, and lastly “normal” sound (the last a bit earlier than one would expect by calculating the speed of sound from ground zero due to the initial air shock wave)?

  12. I thought there was a heat blast thingie that went way faster than sound. Also, don’t different sorts of near light speed radiation have slightly different travel rates? I’d be curios to know the comparison between the distance from the blast site to the camera, and the distance between the blast sight and the upper reach of the mushroom cloud during its initial rapid formation.

  13. I thought there was a heat blast thingie that went way faster than sound.

    Yes, shock waves can move faster than sound. The temperature of the air behind the shock is significantly higher than in front of the shock, thus the heat blast (or pressure blast, if you prefer–that volume of hot air is also expanding) arrives before you hear the explosion.

    If it’s a ground explosion, then the sound will travel through the ground faster than in air. But if it’s an air burst, you probably won’t get the ground wave. You’re not directly displacing dirt, so the coupling is not efficient.

  14. At a distance of 11 km the sound should have arrived more than 33 seconds after the blast, if it worked the same way as with lightning. The early arrival of the sound at first made me think the distace quoted was wrong, but now you have explained it.
    — — — — — — —
    BTW I have read that EMPs are strongest with ground explosions and space explosions, but modest at altitudes in between (airbursts).
    I am not familiar with the cause of the difference.

  15. There are mechanisms by which people can hear “sounds” associated with distant events.

    The initial expansion of the fireball of a nuclear explosion is not as a shock wave, it is via thermal radiation. The initial products of the nuclear reactions are extremely hot, and radiate as a black-body. They are so hot, they radiate as a black body in x-rays. These x-rays have a very short path length in air, so they are absorbed quite quickly (few meters), which then heats the air that absorbs those x-rays so hot that it starts radiating x-rays too. This heating-radiation-heating is how the initial fireball expands until it cools down enough for the mean free path of the thermal radiation gets long enough that it isn’t all absorbed promptly.

    The initial plasma emits at all wavelengths, you can only see the ones that the atmosphere is transparent to. The others get absorbed and cause the heating, expansion and reemission. The cooling is due to loss of wavelengths the atmosphere is transparent to, and also the heating of ambient material that was cool to start with.

    What causes EMP is charge displacement due to the prompt radiation field, mostly due to Compton scattering. The high energy gammas ionize air molecules and the electrons get ejected with a high energy in a direction away from the gamma source. The ions are stationary, so this generates a charge separation between the electrons and the positive ions. This charge separation generates an electric field. When that field is large in extent, there can be significant far-field effects. This is most apparent in near Earth space where there is no atmosphere so the high energy x-rays can travel many miles before hitting anything, but then hit the atmosphere and generate the charge separation over a large area. In space something like 40% of the energy ends up as prompt x-rays, so there is a lot of energy that can be coupled into the EMP.

  16. The camera was 6.84 miles from the explosion based on the speed of sound (which varies with atmospheric pressure and humidity) using 1129 ft/sec. for the speed of sound and an arival time of 32 seconds for the sound of the blast.

  17. daedalus2u, thanks for that explanation. I figured it was something along those lines, but I could not remember the details.

  18. The sound on the video that occurs at the moment of the detonation is not from EMF.
    I have discussed this video and sound with quite a few film and fellow audio experts and the consensus is that what you hear at the initial detonation is the sound of the intense light leaking onto the optical sound track.
    Remember that a film camera of that era would record an optical track and not a magnetic track.

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