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Comment by aatish | Hacker News Reader

Hey, I'm the author of the post (on twitter @aatishb). Thanks for voting it up. Would love to hear your thoughts and constructive feedback. Cheers. (PS the references linked to at the bottom of the post are packed with fascinating information about Krakatoa, for anyone who wants to dig deeper.)

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I was also captivated by this vivid first person account of a Dutch pilot in the coastal town of Anjer who survived the ensuing Tsunami http://www.vansandick.com/familie/links/vulcaan2.php#h1

It's a great article - makes me wonder how long the shockwave of the impact that killed the dinosaurs must have been echoing across the globe, or the one that created the moon (well, that one was before earth had an atmosphere, but it probably was strong enough to make the entire planet vibrate for quite a while).

> impact that killed the dinosaurs

I once saw a talk about this at a scientific meeting, so the papers are out there. All I can remember from it is that they estimated the ejecta at "about the mass of the Sierra Nevada". This was quite a while ago so I'm sure they've got a better estimate by now.

This is one of my favorite things i've read on the internet in recent memory.

Yes! There's a lot of fluff on HN nowadays, but every once in a while we strike gold.

How does something like the Tzar bomb compare in terms of sound pressure? Would the immense volume of ejected material from the volcanic explosion move more air than a nuclear explosion? I'd guess lots of mass (air molecules) is just vaporized in a nuclear explosion, leaving much less mass to create pressure deltas.

That was my first thought, too. Fun facts [1]:

- its ignition was the most powerful artificial explosion in human history

- The seismic shock created by the detonation was measurable even on its third passage around the Earth

[1] http://en.wikipedia.org/wiki/Tsar_Bomba

Wikipedia says it was four times as powerful as Tzar Bomba, which would put it in the neighborhood of 200Mt. Technically Tzar Bomba was suppose to yield about 100Mt, but the scientists dialed it down a bit because they were worried about it.

Kind of crazy to think that humans made a bomb 1/4 as powerful as the Krakatoa eruption.

My understanding is that the yield was halved by the use of a lead tamper, rather than a uranium one. The tamper is a shield around the core that slows down the explosion in order to consume the reactants more fully. In production they commonly make the tamper out of waste uranium, which undergoes fission during the blast and contributes a significant amount of energy, but if you don't need the boost then lead works fine, or anything else heavy. The other thing about uranium is it greatly multiplies the radioactive fallout (fusion bombs are actually pretty clean when lead is used), which may have contributed to the decision not to use it.

The Tsar bomb was in the ballpark of a 50 megaton explosion, whereas estimates that I've seen for Krakatoa put it at up to 200 megatons. That said, there would be differences due to the fact that h-bombs are exploded at a height to maximize the damage from the blast wave, and that a significant fraction of Krakatoa's energy would have been spent on throwing earth around. It's always hard to compare different explosions because it's difficult to know what fraction of the energy output goes into acoustic energy, but I think it's reasonable to assume that Krakatoa was louder (at least in that the sound was heard further).

"The Tsar Bomba's fireball, about 8 kilometres (5.0 mi) in diameter, was prevented from touching the ground by the shock wave, but nearly reached the 10.5 kilometres (6.5 mi) altitude of the deploying Tu-95 bomber."

I'd love to hear the pilot's thoughts on this. From what I can guess, he couldn't have traveled very far away by the time the explosion occurred. At the very least, he must have felt tremendous turbulence.

I wonder if the scientists knew how close the explosion would be to the aircraft.

The bomb had a parachute to retard it's decent in order to give them time to get away.

One thing I'm surprised you didn't mention is infrasound[1], which is sound so low that it can potentially damage the human body. Some of the newer non-lethal weapons the US military use for crowd control include a directional infrasound "gun" that basically vibrates your inner organs fast enough to make everyone super nauseous.

[1] http://en.wikipedia.org/wiki/Infrasound

Infrasound is about a specific frequency range of sound which isn't audible but still carries energy (which is why it can be dangerous).

This article was about a wideband sound that was so loud that it defies comparison. Loudness is related to the amplitude, or "height" of the wave, not frequency.

Oh agreed, the article just goes into so much detail about sound. Seemed relevant (in my head).

Some of the newer non-lethal weapons the US military use for crowd control include a directional infrasound "gun" that basically vibrates your inner organs fast enough to make everyone super nauseous.

Do you have a cite for this? A "directional" outdoor infrasound weapon would be huge (10s of feet) and quick web search seems to indicate these types of weapon are at best "not mature" and at worst fiction.

http://www.globalsecurity.org/military/systems/munitions/acc...

That article describes a theoretical infrasound weapon, not something that is being used today:

But this [infrasound weapon] has seemed to be not a very practical weapon, since large banks of speakers were required to provide directionality, and power demands were deemed excessive.

The article goes on to describe LRAD which does exist and has been deployed, but is a high-frequency weapon, not an infrasound weapon (and can be defended against with a good pair of earplugs).

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