Tianjin Explosion Seen by Himawari and Other Weather Satellites | Hacker News Reader

Tianjin Explosion Seen by Himawari and Other Weather Satellites

cimss.ssec.wisc.edu

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The videos people took of the explosions are really remarkable. Sorta-cool at first, then scary. http://www.liveleak.com/view?i=0e5_1439474009

this synced-up version is impressive as well. unfortunately, it seems to be confirmed that the upper right video was a live stream and the streamer did not survive the blast :(

https://www.youtube.com/watch?v=6v5RQ2cDfiU

This is where I see Periscope going. Imagine a web app with that type of view for a breaking news event. An algorithm picks the best or most diverse streams and shows them synced side by side.

The estimates being thrown around is that the larger explosion was equivalent to 21 tons of TNT. Does that seem low to anyone?

The explosion seems to be in the air so seismic shock - basis for 21 tons TNT - is lower than would be oversize. I think - based on the blast wave in the video at 7 seconds sound travel distance - it is several hundred tons TNT, 200-500.

Yep - it was many hundreds of tons. Based on comparing with other records, I'd wager both explosions together likely approached a kiloton of TNT. One of the larger (possibly?) non-military explosions ever.

Compared with this video for 100 tons of TNT [1], the explosion in Tianjin was a few times larger. And there were two explosions, with the second being significantly larger.

Also, compare with other explosions on this list [2]. The AZF explosion [3] was listed at 20-40 tons of TNT. The Tianjin explosion was far larger. ~20 tons of TNT worth of energy was converted into a seismic wave - the rest (the majority) of the energy was dispersed above ground.

[1] https://www.youtube.com/watch?v=PgLzgdbfeJE

[2] https://en.wikipedia.org/wiki/Largest_artificial_non-nuclear...

[3] https://www.youtube.com/watch?v=K_jodgDNG0o

yes. Similar situation to Tianjin - about 200 tons explosion at 7 seconds sound distance (0:35 explosion and 0:42 sound wave) The blast wave in Tianjin video seems to be somewhat stronger.

https://www.youtube.com/watch?v=32RCWk5ez34

It also should be noted that "21 tons" is an estimate by China Earthquake Networks Centre [1], so it can be deliberately understated.

[1] http://www.theguardian.com/world/2015/aug/12/china-explosion...

According to a wikipedia article, the force of the explosion can be estimated by the height of the mushroom cloud.

I think nuclear weapons have made us a bit jaded about quantities of TNT, with talk of kilotons and megatons. But a ton of TNT is still a LOT of explosive. A single stick of TNT blows stuff up good.

The number seems very low, but I believe that estimate has been misinterpreted by english sources.

The figure comes from a Chinese Earthquake monitoring organisation, and it seems to say that the energy of the earthquake was equivalent to 21 tons of TNT.

The bulk of the energy in the explosion would've dissipated through the air, and wouldn't be involved in the earthquake at all.

Is there any information on what caused it yet?

It appears that it was a chemical storage warehouse, which contained calcium carbide (among other hazardous chemicals). A fire broke out in the warehouse and firefighters were fighting the fire with water. When calcium carbide reacts with water it produces acetylene gas, which is highly explosive.

http://www.cnbc.com/2015/08/14/china-experts-focus-on-chemic...

Great link, I agree with the comment that if the carbide went off it could set off the ammonium nitrate. Basically a really really big car bomb at that point.

Wow, what a title: "Lei Jinde, the deputy propaganda department head of China's fire department"

I hope that's a translation error. Fire Fighters are the last people who should need a propaganda department.

The only difference between a "propaganda department" and a "PR department" is the word used in the title.

Some non-English speaking government officials are ignorant to the word's modern meaning.

https://en.wikipedia.org/wiki/Ministry_of_propaganda

> Some non-English speaking government officials are ignorant to the word's modern meaning.

Or, rather, in some parts of the world, the negative connotations (not actual a change in meaning) it developed in some places from popular association with the German use of the term hasn't caught on, so there is no perceived need to replace it with a new word with the same denotation that "propaganda" has had for centuries.

Nope. Go to a large Chinese police/tax building and you'll see a sign for the "Propaganda Department". Part of me respects them for being honest about it.

I think probably my (engineers in general?) distaste for "marketing" and "public relations" and "spin" is the propaganda (telling you what we want you to think) component that is often there. It sounds nicer if you say PR, and in the US we tend not to be quite so blatantly at odds with the facts, but PR and marketing are often trying to accomplish the same thing. At least the Chinese are honest about what they are doing.

It is so easy to forget how did the term Public Relations come into wide use.

> Due to negative implications surrounding the word propaganda because of its use by the Germans in World War I, he promoted the term "Public Relations".

https://en.wikipedia.org/wiki/Edward_Bernays#Life_and_influe...

For more I recommend the BBC documentary "The Century of the Self".

"Public Relations" was invented (and named) by Edward Bernays after "propaganda" got a bad name from the German's use of it during the First World War.

Otherwise, it's the same thing.

a list of suspected chemicals at the Tianjin warehouse:

https://www.washingtonpost.com/world/asia_pacific/firm-says-...

It also contained a bunch of oxidizers like potassium nitrate. In fact, I was a bit confused because I didn't pick up the calcium carbide -> acetylene generation, and just a huge amount of oxidizers wouldn't cause such an explosion without sufficient fuel.

Per the comment there is some speculation on carbide. Something I don't think anyone has done is try to get a spectrum reading off the fireball. Typically various chemicals burn at different wavelengths so perhaps a hint of what was burning might be discernible by analyzing the spectra of the resulting light. What I don't know is how accurately a cell phone camera can reproduce that spectra, or if there is a mapping function from camera to spectra.

I sincerely cannot wait for those quantum dot spectrometers to arrive inside our cell phones [1].

Edit: these things could've saved lives, specifically the firefighters.

[1]: http://newsoffice.mit.edu/2015/quantum-dot-spectrometer-smar...

Ok, that is really slick. I really really hope this gets incorporated into phones.

I want one!! I've always wanted a spectrometer!

>how accurately a cell phone camera can reproduce that spectra

Not accurately at all. In terms of spectrum analysis, they're essentially as useless as the human eye. You're trying to get information from a detailed continuous function that varies wildly all along visible wavelengths (and beyond), and all you get are three data points. In fact, I've already analyzed the spectrum and I can confirm: Yup, it's red.

I suppose you could try gathering the exact spectral response of each camera having filmed the same thing (something like this [1]) and combine the resulting data to attempt getting a more detailed spectrum, but it would be very difficult and likely to yield disappointingly vague results.

[1]: http://www.gamutvision.com/docs/images/Kodak_KAF-10500-CX_re...

The drone flyovers taken at night hours after the explosion show fires burning with multiple different spectra - white, blue, gold, orange and red fires all burning down below.

A total mess of chemicals.

video footage after explosion:

http://us.sinaimg.cn/001ZEXa6jx06UCsnbb15050401049TNs0k03.mp...

Some footage taken the next morning on a freeway near ground zero:

BBC analysis: https://www.youtube.com/watch?v=kcONSn5kc2s

view from freeway: https://youtube.com/watch?v=z1LIQ5XgvOw

Any news on long-term health risks from chemical exposure/half-lives/concentrations/wind direction etc? Last I heard the wind was blowing sea-wards after the blast, but there are a lot of people in Tianjin (and Beijing?) that could be effected if chemical contaminants stick around...

It was originally reported as between 2.2 and 2.4 Richter. By The Guardian. Should have showed up on the USGS real-time earthquake map. But didn't.

Searched 7 days, all magnitudes, still nothing.

I would not think that a shallow, surface induced quake like this would travel far.

The USGS cutoff outside the US is ~magnitude 4.5.

http://earthquake.usgs.gov/earthquakes/map/doc_whicheqs.php

Thanks for the link. Did not know this about the map.

I continue to be shocked that these explosions didn't kill thousands of people.

Don't be shocked yet. I think it is safe to say that they do not have a full tally, nor have authorities any desire to publish such numbers until they have a literal body count.

They occurred at night in an industrial area surrounded by warehouses and container storage lots, so there wouldn't have been many people around. A high percentage of the deaths are unfortunately from fire fighters who showed up to fight a fire that got out of control and led to these explosions.

Here's a map shot of roughly where the explosions occurred:

https://goo.gl/maps/NLgmJ

What is that other dot that shows up in the sea to the east/southeast?

Sometimes it feels like big events happen that lots of people here want to talk about, but need to find some kind of technology or "hacker" article to submit as a center for discussion. It's a bit weird and it feels like there should be some exceptions to the rules to allow these kind of events to be discussed as they are happening.

It may not provide the same type of discussion you are hoping for, but I find Reddit to be a pretty decent source for that kind of coverage.

Highlighting mine...

   Hacker News Guidelines

   What to Submit

   On-Topic: Anything that good hackers would find interesting. That 
   includes more than hacking and startups. If you had to reduce it to a 
   sentence, the answer might be: ***anything that gratifies one's 
   intellectual curiosity***.

   Off-Topic: Most stories about politics, or crime, or sports, unless 
   they're evidence of some interesting new phenomenon. Videos of 
   pratfalls or disasters, or cute animal pictures. ***If they'd cover it 
   on TV news, it's probably off-topic.***

It's a fine line, but I think it's a good line. For example, the news aspect isn't really appropriate for Hacker News, but the cause may be (in this case, it sounds like the chemistry is very much of intellectual interest [1]), as may be methods for identifying, recording, and sharing aspects of the explosion (e.g. "quantum dot spectrometers" [2], the OP, and the "synced-up version" of recordings[3]).

All links point to other parts of this discussion:

[1] https://news.ycombinator.com/item?id=10062226

[2] https://news.ycombinator.com/item?id=10062399

[3] https://news.ycombinator.com/item?id=10062300

Edited in attempt to improve readability.

Reply on news.ycombinator.com