4 ms·

I am seeing other analyses that put the size of the explosion at about one tenth of this size. The analysis in this Twitter thread correlates the observed degr

by kgm 6y ago

I am seeing other analyses that put the size of the explosion at about one tenth of this size. The analysis in this Twitter thread correlates the observed degree of damage with the distance from the explosion. It comes up with an estimated 240 tons TNT-equivalent, though naturally this comes with a considerable margin of error. https://twitter.com/GeorgeWHerbert/status/1290719719545159680 https://twitter.com/GeorgeWHerbert/status/129071971954515968... This Twitter thread is making the point that the explosiveness of ammonium nitrate can vary significantly depending on how it is stored. 2750 tons of AN at 20% efficiency gives 550 tons TNT. https://twitter.com/ArmsControlWonk/status/1290795532701425664 https://twitter.com/ArmsControlWonk/status/12907955327014256... This range is also apparently consistent with the explosion registering as a 3.5 seismic magnitude. https://twitter.com/ArmsControlWonk/status/1290734850769526784 https://twitter.com/ArmsControlWonk/status/12907348507695267... There are still a great many unknowns, and none of this should be mistaken for the real analysis which will come later, but these disparate sources of information all seem to agree with each other, to a first approximation.

WalterBright 6y ago
My fluid mechanics prof told the class that a scientist in the 1940's published the yield of the Hiroshima bomb. Since this was top secret, he got investigated. But he showed how the yield could be calculated from the film of the explosion - how fast the blast radius expanded. So I imagine the yield of the Beirut explosion could be calculated the same way from the video.
- selimthegrim 6y ago
  It was G.I. Taylor.
  - tigerlily 6y ago
    Using the Buckingham Pi theorem.
    - hanche 6y ago
      And data from smaller explosions of known magnitude, in order to determine the dimensionless constant that cannot be determined from Buckingham’s theorem alone.
- raverbashing 6y ago
  There's a story about Feynman estimating yield by dropping pieces of paper and seeing how far they'd travel in the shockwave
  - kleton 6y ago
    Feynman told that story about Fermi.
    - raverbashing 6y ago
      Ah you're right!
    - mhh__ 6y ago
      Imagine being so good that Feynman tells stories about you (rather than himself). Fermi also put Dyson down gently once "A successful theory must have either a strong physical intuition or a rigorous mathematical basis: you have neither"
      - lordgrenville 6y ago
        Fermi was an inveterate experimentalist, always trying to measure and test things. Hence the idea of the Fermi estimate. There's a good piece about him here: https://www.lrb.co.uk/the-paper/v40/n10/steven-shapin/think-like-a-neutron https://www.lrb.co.uk/the-paper/v40/n10/steven-shapin/think-... >Fermi saw the Trinity Test as an opportunity for one of his famous exercises of rational estimation, a Fermi problem. First, he offered to take wagers from other scientists on whether the bomb would ignite the atmosphere, destroying New Mexico or even the entire world. Then, the evening before, he carefully prepared an experiment to estimate the bomb’s explosive yield: > "About forty seconds after the explosion the air blast reached me, I tried to estimate its strength by dropping from about six feet small pieces of paper before, during and after the passage of the blast wave. Since, at the time, there was no wind, I could observe very distinctly and actually measure the displacement of the pieces of paper that were in the process of falling while the blast was passing. The shift was about 2.5 metres, which, at the time, I estimated to correspond to a blast that would be produced by ten thousand tons of TNT." > "He was so profoundly and totally absorbed in his bits of paper," his wife recorded, "that he was not aware of the tremendous noise." The answer later calculated by the instrumentation specialists was 18 kilotons, but Fermi’s answer was arrived at on the spot – and it was correct within an order of magnitude.
- rmm 6y ago
  Paper in question. http://sites.science.oregonstate.edu/~restrepo/MTH481/Classnotes/GITaylor/GITaylorAnalysis.pdf http://sites.science.oregonstate.edu/~restrepo/MTH481/Classn... From videos: R=450m t=1.5s rho=1.2kg/m3 E=9.84E12 kg.m2/s2 or 9.84E19 erg Equiv TNT = 2.5kTonnes -TNT Equiv AN = 5400 Tonnes So double what current media is saying. edit:formatting.
  - deleted 6y ago
    [deleted]
  - WalterBright 6y ago
    You da man! Thank you.
  - Denvercoder9 6y ago
    You have to be careful about your errors though with this method, because you get higher-order powers. If the radius estimation was wrong by only 10%, your final answer will be wrong by almost 50%.
ashtonkem 6y ago
2750 tons of AN perfectly mixed to make ANFO only gets you 2.2kt. So unless if the actual amount of AN was higher, or something else detonated with it, 2.2kt is probably our theoretical ceiling.
lm28469 6y ago
> I am seeing other analyses that put the size of the explosion at about one tenth of this size. Random twitter users are guesstimating from smartphones videos and have 0 knowledge of the actual location, so yeah, it's just guesstimates. I'm still wondering why people do that, it's kind of a weird flex and bring literally nothing of value to the table besides trying to sound like a smartass.
- caf 6y ago
  Some of those are involved in the OSINT community where they do this as their day job, because analysing random strange explosions can sometimes tell you things about military weapons development programs that aren't otherwise advertised.
DC-3 6y ago
Damage estimates in some cases may underrate the explosion because that grain elevator which remarkably remained largely upright seems to have acted like a huge sandbag, subtending an angle so large as to shield the heart of the city of Beirut from the worst ravages of the blast.
kortex 6y ago
I went on Nukemap and twiddled the yield until the radius of overpressure damage roughly matched the damage seen in the footage. I arrived at 0.25 +/- 0.1 kT before the 2750T figure came out. That's in line with TNT-equivalent efficiency of AN and incomplete reaction due to scattering. Tragically, this suggests a much higher death toll than currently reported. I am not sure if nukemap factors local population density; fortunately the epicenter was a sparsely populated pier. (down for me right now, I bet their site is slashdotted/DoS'd by people doing similar) https://nuclearsecrecy.com/nukemap/classic/ https://nuclearsecrecy.com/nukemap/classic/
mzs 6y ago
an expert's thread from this morning: https://twitter.com/johnismay/status/1290858204788924416 https://twitter.com/johnismay/status/1290858204788924416
- ximeng 6y ago
  https://mobile.twitter.com/johnismay/status/1291007795316297728 https://mobile.twitter.com/johnismay/status/1291007795316297... think this is what you meant
  - mzs 6y ago
    Yes, thanks for the correction!

by kgm 6y ago

WalterBright 6y ago

My fluid mechanics prof told the class that a scientist in the 1940's published the yield of the Hiroshima bomb. Since this was top secret, he got investigated. But he showed how the yield could be calculated from the film of the explosion - how fast the blast radius expanded. So I imagine the yield of the Beirut explosion could be calculated the same way from the video.

selimthegrim 6y ago
It was G.I. Taylor.
- tigerlily 6y ago
  Using the Buckingham Pi theorem.
  - hanche 6y ago
    And data from smaller explosions of known magnitude, in order to determine the dimensionless constant that cannot be determined from Buckingham’s theorem alone.
raverbashing 6y ago
There's a story about Feynman estimating yield by dropping pieces of paper and seeing how far they'd travel in the shockwave
- kleton 6y ago
  Feynman told that story about Fermi.
  - raverbashing 6y ago
    Ah you're right!
  - mhh__ 6y ago
    Imagine being so good that Feynman tells stories about you (rather than himself). Fermi also put Dyson down gently once "A successful theory must have either a strong physical intuition or a rigorous mathematical basis: you have neither"
    - lordgrenville 6y ago
      Fermi was an inveterate experimentalist, always trying to measure and test things. Hence the idea of the Fermi estimate. There's a good piece about him here: https://www.lrb.co.uk/the-paper/v40/n10/steven-shapin/think-like-a-neutron https://www.lrb.co.uk/the-paper/v40/n10/steven-shapin/think-... >Fermi saw the Trinity Test as an opportunity for one of his famous exercises of rational estimation, a Fermi problem. First, he offered to take wagers from other scientists on whether the bomb would ignite the atmosphere, destroying New Mexico or even the entire world. Then, the evening before, he carefully prepared an experiment to estimate the bomb’s explosive yield: > "About forty seconds after the explosion the air blast reached me, I tried to estimate its strength by dropping from about six feet small pieces of paper before, during and after the passage of the blast wave. Since, at the time, there was no wind, I could observe very distinctly and actually measure the displacement of the pieces of paper that were in the process of falling while the blast was passing. The shift was about 2.5 metres, which, at the time, I estimated to correspond to a blast that would be produced by ten thousand tons of TNT." > "He was so profoundly and totally absorbed in his bits of paper," his wife recorded, "that he was not aware of the tremendous noise." The answer later calculated by the instrumentation specialists was 18 kilotons, but Fermi’s answer was arrived at on the spot – and it was correct within an order of magnitude.
rmm 6y ago
Paper in question. http://sites.science.oregonstate.edu/~restrepo/MTH481/Classnotes/GITaylor/GITaylorAnalysis.pdf http://sites.science.oregonstate.edu/~restrepo/MTH481/Classn... From videos: R=450m t=1.5s rho=1.2kg/m3 E=9.84E12 kg.m2/s2 or 9.84E19 erg Equiv TNT = 2.5kTonnes -TNT Equiv AN = 5400 Tonnes So double what current media is saying. edit:formatting.
- deleted 6y ago
  [deleted]
- WalterBright 6y ago
  You da man! Thank you.
- Denvercoder9 6y ago
  You have to be careful about your errors though with this method, because you get higher-order powers. If the radius estimation was wrong by only 10%, your final answer will be wrong by almost 50%.

ashtonkem 6y ago

2750 tons of AN perfectly mixed to make ANFO only gets you 2.2kt. So unless if the actual amount of AN was higher, or something else detonated with it, 2.2kt is probably our theoretical ceiling.

lm28469 6y ago

> I am seeing other analyses that put the size of the explosion at about one tenth of this size. Random twitter users are guesstimating from smartphones videos and have 0 knowledge of the actual location, so yeah, it's just guesstimates. I'm still wondering why people do that, it's kind of a weird flex and bring literally nothing of value to the table besides trying to sound like a smartass.

caf 6y ago
Some of those are involved in the OSINT community where they do this as their day job, because analysing random strange explosions can sometimes tell you things about military weapons development programs that aren't otherwise advertised.

DC-3 6y ago

Damage estimates in some cases may underrate the explosion because that grain elevator which remarkably remained largely upright seems to have acted like a huge sandbag, subtending an angle so large as to shield the heart of the city of Beirut from the worst ravages of the blast.

kortex 6y ago

I went on Nukemap and twiddled the yield until the radius of overpressure damage roughly matched the damage seen in the footage. I arrived at 0.25 +/- 0.1 kT before the 2750T figure came out. That's in line with TNT-equivalent efficiency of AN and incomplete reaction due to scattering. Tragically, this suggests a much higher death toll than currently reported. I am not sure if nukemap factors local population density; fortunately the epicenter was a sparsely populated pier. (down for me right now, I bet their site is slashdotted/DoS'd by people doing similar) https://nuclearsecrecy.com/nukemap/classic/ https://nuclearsecrecy.com/nukemap/classic/

mzs 6y ago

an expert's thread from this morning: https://twitter.com/johnismay/status/1290858204788924416 https://twitter.com/johnismay/status/1290858204788924416

ximeng 6y ago
https://mobile.twitter.com/johnismay/status/1291007795316297728 https://mobile.twitter.com/johnismay/status/1291007795316297... think this is what you meant
- mzs 6y ago
  Yes, thanks for the correction!