6 ms·

The explosion is clearly audible 25 seconds in to this clip: http://www.youtube.com/watch?v=Np_mpGYSBSA http://www.youtube.com/watch?v=Np_mpGYSBSA

dredmorbius 14y ago
Explosion or sonic boom. Large object, moving fast, not very aerodynamically optimized.
harshreality 14y ago
Great video except for the Vertical Video Syndrome [1]. Is that glass breaking right after the shockwave? I wonder what kind of overpressure it generated. eta: ghshephard posted a link to a better video with the clear sound of glass breaking. https://news.ycombinator.com/item?id=5224858 https://news.ycombinator.com/item?id=5224858 [1] http://www.youtube.com/watch?v=Bt9zSfinwFA http://www.youtube.com/watch?v=Bt9zSfinwFA
- empraptor 14y ago
  Maybe the sound that we heard traveled faster than the acoustic waves that broke the glass due to having different frequencies.
  - lutusp 14y ago
    > Maybe the sound that we heard traveled faster than the acoustic waves that broke the glass due to having different frequencies. Unlikely. A powerful sonic boom could cause all that damage, and collapse an aging brick structure, and yet travel at or near the speed of sound.
InclinedPlane 14y ago
I'm almost certain that's a sonic boom. The upper atmosphere is several miles high and it would take the better part of a minute for the sound from a sonic boom to reach the ground from the stratosphere.
- InclinedPlane 14y ago
  I'm going to change my mind on this. The more I watch videos the more I'm convinced that the loud bangs are actually the sound of the meteor exploding in an air burst, although I think there are some sonic booms mixed in. Edit: OK, I'm going back to it being a sonic boom. The sounds are too sharp and too similar to other sonic booms. That's what I get for not trusting my gut the first time.
  - dredmorbius 14y ago
    I'm sticking with a sonic boom. Even the explosion of the meteorite is going to be a series of booms (one video from inside a building clearly includes numerous loud reports). Remember: each meteorite fragment will produce its own boom. And a meteorite explosion doesn't result from interior forces fracturing the body, but the body fracturing under aerodynamic stress. For a rocky bolide, what you've got is basically a flying rockpile, its internal bonding forces are relatively low, and the whole thing's going to have a pretty strong tendency to fly to pieces particularly in a hypersonic jetstream (a nickle-iron meteorite much less so, though Phil Plait links to the Sikhote-Alin meteorite Wikipedia page, which did just that: http://en.wikipedia.org/wiki/Sikhote-Alin_meteorite http://en.wikipedia.org/wiki/Sikhote-Alin_meteorite). So it's less an explosion (internally generated forces) and more a shattering (smashing into air) resulting in multiple fragments. Impressive all the same.
  - Udo 14y ago
    I think your original impression was correct. The first big bang is most likely a sonic boom that occurred shortly after entering the atmosphere. There are several smaller bangs and some crackling noise after that. Some of these I suspect are echoes, but party it would also be the sound of the thing passing through the air, and then possibly breaking up. I doubt the burst from the breakup was that loud (it looked more like a relatively gentle split), especially compared to the massive energy that the entry interface boom must have released. Damn that thing was fast! Tore through the whole atmosphere in just a few seconds...
    - InclinedPlane 14y ago

dredmorbius 14y ago

Explosion or sonic boom. Large object, moving fast, not very aerodynamically optimized.

harshreality 14y ago

Great video except for the Vertical Video Syndrome [1]. Is that glass breaking right after the shockwave? I wonder what kind of overpressure it generated. eta: ghshephard posted a link to a better video with the clear sound of glass breaking. https://news.ycombinator.com/item?id=5224858 https://news.ycombinator.com/item?id=5224858 [1] http://www.youtube.com/watch?v=Bt9zSfinwFA http://www.youtube.com/watch?v=Bt9zSfinwFA

empraptor 14y ago
Maybe the sound that we heard traveled faster than the acoustic waves that broke the glass due to having different frequencies.
- lutusp 14y ago
  > Maybe the sound that we heard traveled faster than the acoustic waves that broke the glass due to having different frequencies. Unlikely. A powerful sonic boom could cause all that damage, and collapse an aging brick structure, and yet travel at or near the speed of sound.

InclinedPlane 14y ago

I'm almost certain that's a sonic boom. The upper atmosphere is several miles high and it would take the better part of a minute for the sound from a sonic boom to reach the ground from the stratosphere.

InclinedPlane 14y ago
I'm going to change my mind on this. The more I watch videos the more I'm convinced that the loud bangs are actually the sound of the meteor exploding in an air burst, although I think there are some sonic booms mixed in. Edit: OK, I'm going back to it being a sonic boom. The sounds are too sharp and too similar to other sonic booms. That's what I get for not trusting my gut the first time.
- dredmorbius 14y ago
  I'm sticking with a sonic boom. Even the explosion of the meteorite is going to be a series of booms (one video from inside a building clearly includes numerous loud reports). Remember: each meteorite fragment will produce its own boom. And a meteorite explosion doesn't result from interior forces fracturing the body, but the body fracturing under aerodynamic stress. For a rocky bolide, what you've got is basically a flying rockpile, its internal bonding forces are relatively low, and the whole thing's going to have a pretty strong tendency to fly to pieces particularly in a hypersonic jetstream (a nickle-iron meteorite much less so, though Phil Plait links to the Sikhote-Alin meteorite Wikipedia page, which did just that: http://en.wikipedia.org/wiki/Sikhote-Alin_meteorite http://en.wikipedia.org/wiki/Sikhote-Alin_meteorite). So it's less an explosion (internally generated forces) and more a shattering (smashing into air) resulting in multiple fragments. Impressive all the same.
- Udo 14y ago
  I think your original impression was correct. The first big bang is most likely a sonic boom that occurred shortly after entering the atmosphere. There are several smaller bangs and some crackling noise after that. Some of these I suspect are echoes, but party it would also be the sound of the thing passing through the air, and then possibly breaking up. I doubt the burst from the breakup was that loud (it looked more like a relatively gentle split), especially compared to the massive energy that the entry interface boom must have released. Damn that thing was fast! Tore through the whole atmosphere in just a few seconds...
  - InclinedPlane 14y ago