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Comment by johnohara | Hacker News Reader

Krakatoa erupted 8 years later.

Wikipedia: "The sound was claimed to be heard in 50 different locations around the world and the sound wave is recorded to have travelled the globe seven times."

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The pressure wave was recorded around the globe seven times, on barometers. I am actively monitoring my digital pressure sensors on my home weather station and have seen the pressure waves from the Tonga blast go by 4 times and counting (2 in each direction). Hoping to see a 5th pass tonight here in Seattle at around 10:55pm. I wrote a little python script to predict the future passes based on the first two very obvious ones. Very fun.

Fun indeed. And interesting. Well done.

Ninja edit: I blogged about it here if you want to see the script, predictions, and measurements: https://partofthething.com/thoughts/measuring-the-tonga-erup...

Thanks for the writeup! Glad to see you around.

Wouldn't pressure waves travelling in opposite directions interfere with each other?

Only if you're exactly on the opposite side of the world I think?

If you were exactly opposite the source in terms of distance traveled by the waves, yes?

If they were opposite waves (One negative wave, one positive wave, emitted from two points opposite on the globe) then yes. But if they are both positive, they just add in place where they meet and then travel away as they did before.

Correct, and I saw somewhere on twitter that someone near the antipode did see a huge pressure wave from constructive interference.

Looks like a 2mb initial fluctuation - any idea what Krakatoa was, that circled the world (at least) 7 times?

The barometers around the world recording the shock wave is one of the coolest things.

“Krakatoa: The Day the World Exploded: August 27, 1883” by Simon Winchester went into this point.

Also, this write up from 2016 at Nautilus after the Papua New Guinea Volcano eruption. https://nautil.us/issue/38/noise/the-sound-so-loud-that-it-c...

The pressure wave(s?) for this Tonga one were detected across the US [0].

[0] https://twitter.com/NWSPortland/status/1482639604540854275

Does anyone know what it would sound like? Would it be a crack like a sonic boom from a jet?

Less sharp the further away you are.

In Fiji it sounded like thunder rumbling. In Alaska it was nearly infrasound.

There is a video floating around of people close enough to the blast to hear a significant boom, here: https://www.youtube.com/watch?v=owlRuul5Tk4

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