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No-one knows how explosions work (yet)
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- Опубліковано 4 чер 2023
- The first few moments of an explosion can't be simulated yet. But there's a team at the University of Sheffield working on it. ■ A paper about their work, including data from a similar test: www.mdpi.com/1424-8220/23/2/964 ■ More from them: www.sheffield.ac.uk/civil/
Previously: why Hollywood explosions don't look like real explosions: • Why Hollywood explosio...
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An update from Sam, the scientist in the video! He says: "It's been great reading through your comments and seeing people excited and intrigued by our research. I thought it'd be useful to answer some of the common questions that keep cropping up:
1. Yes, high speed video/photography of explosions is nothing new. They did this all the way back in the 40s and it's famously how GI Taylor estimated the yield of the Trinity test. Our high speed video is not what gives us the new scientific insight, but it does help give us a steer as to what is going on, and it's a fantastic way to demonstrate what an alien world it is so close to an explosion (in time and space!)
2. Our pressure measurements from the MaCE rig do give us the new scientific insight. If you want to see an example of our recorded data then please feel free to read our recent paper (link in description), Figure 5. We're measuring pressures higher than the strength of normal steel that are applied and removed in 50 microseconds. For comparison, a blink lasts >100 milliseconds, so over two thousand times longer!
3. Scientists know a lot about nuclear explosions, that's true. There, the energy is released effectively instantaneously and effectively as a point-source. With high explosives, the reaction rates are comparatively slower. That means we have an ongoing chemical reaction that changes if/when the blast wave and fireball come into contact with structures. The exact loading applied to said structure is a function of the pressure-volume-energy state of the fireball, so there's an intricate dance between the two (pressure and reaction rates). This is where current models break down. Yes, even the sophisticated physics-based ones.
4. We're only just discovering the extent of our ignorance, because until now we simply haven't had the experimental data to compare to. We do know that these secondary reactions are significant, which makes explosions (from high explosives) so difficult to simulate, because we've measured explosions in normal air and in an almost pure nitrogen environment.
5. Yes, the mottled/bumpy surface of the fireball as it expands outwards is a genuine physical feature, and seen at larger scales too (see photos of the "Minor Scale" test). When we're performing tests that we intend to publish we form our explosives into a 3D-printed mould, but even then we still see these features.
6. We filmed at 250 thousand frames per second for this video, but our camera can go all the way to 10 million frames per second.
Thank you once again for showing an interest in our research. Cool, innit?"
For even more explosions and high speed video from Sam and the team, come find us at Sheffield Blast! 💥
Appreciate the follow up information, very exciting stuff!
Harold Edgerton, who developed the camera that photographed the Trinity test, is my scientific hero. He's a rare giant in both the arts and sciences and is one of the reasons I became an electronics engineer. He's a great example of how scientifc outreach using advanced technology can shine a light on the world and inspire the general public at the same time.
That definitely is very cool!
Thanks for the paper. I enjoy the feeling of the "I know some of these words, but I'm glad someone knows the worth of them"
It does make sense why it's difficult to observe what happens in an explosion up close
You should be able to do it efficiently atleast once.
@Bluestrawberry while computers and such are fast nowdays, they likely are not fast enough to send the data about the explosion that fast. the only chanche would be to send the raw output from the sensor trough a wire, but you would still propaply only get about half to quater of it at max, and it would cost a few tens of thousands do to the camera breaking.
couldn't they just send lasers through the expanding wave to measure the density changes? with that you could even make a 3d model of it...
@tesafrack the light from the lasers will be reflected and refracted therefore producing inaccurate data, at least thats what i think.
It's easy though, just stand closer....
The actual data from this test didn't make it into the video (it's just a LOT of numbers), but there's a paper in the description for those so inclined! And this week's pinned-comment plug: the Technical Difficulties are back! A new season of four adventures from me, Chris, Gary and Matt over at uaclips.com/user/techdif - one every Thursday.
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3 days ago, how?
weewoo tom
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Pre-upload
5:51 interesting to see the shockwave resonates the dust under the table. Wonder what impact this has on the signals within the data cables which run out from here and if a deflector would be beneficial
The dust is kicked up but I see no resonance. The shockwave through the air will hit the striped screen and bounce back. This could cause the appearance of a interference-pattern. I think the dust kicks up because the barrel restricts the flow of air underneath it. Also, the barrel's 4 wheels are pushed into the dirt, so they cause some disturbance too.
@DreadX10 what's the differnece?
As the wave passes through the cable linearly at any one point, as a radio wave would, you could likely use conventional noise removal techniques.
@( ͡° ͜ʖ ͡°) Quite literally everything.
You can always tell it's going to be a cool video when we see High Visibility Tom Scott appear.
It's hard not to see High Visibility Tom Scott appear.
@Pattoe He's hard to miss.
Then the high vis worked!
He needs a red hi-vis jacket
Should be a TS hiviz for sale as merch - missing a fortune
I’m imagining the researchers pausing for moment when Tom asked what the purpose of this was and they had to fight the urge to say “because explosions are cool”
"We're definitely not planning something malicious."
“Because we haven’t had a decent pay rise...”
@Mad Isn’t It most dangerous trade to displease the labor union: high explosives research scientists
"It's about sending a message."
@Borrego a Yudando Nah. The auto industry. Millions of deadly several-tons things with the power of several hundred horses that nobody bats an eye about whereever they are. THOSE are dangerous.
Tom is the only person that makes a saftey vest look like reasonable casual wear.
We're just so used to it now that it's like him adorning a red t-shirt.
I think a lot of this has to do with how the color of the reflective strips match the color of the hoodie.
@The Zouave my exact thoughts
...whereas colinfurze is the only person that makes a casual tie look like reasonable safety equipment :D
ever been in an English pub around lunch time?
Always amazes me that a scientist 100 years ago can think up theories that we can only test today.
Kinda same nowdays, there are a lot of theories that we have no way to prove but who knows, maybe 100 years later someone will prove or disprove them (string theory etc)
When you have people who dedicate their lives for their dreams, they excel. The entire lives of these scientists were composed of constant studying and creativity. Like Isaac Newton, he studied daily. And with his creativity, he began applying his knowledge to many other fields.
And if those scientists were still alive I'd like to believe they'd be very smug about it.
@Titan idk if string theory will ever be falsifiable, it's just so out there, and they always say that they'll get evidence in the next decade.
then again, we were able to disprove theories that explained dark energy as instead the universe existing on a 5d shape via closely measuring gravitational waves, so maybe we'll be able to someday.
@Colopty Who wouldn't be? It would be amazing to be that correct that far back.
The best of these videos are when the chaperone is as giddy and excited about the tech as Tom is.
There nothing better than a excited adult. May be because most are pretty boring and unexcitable.
@David Knowlesand perhaps also because we have been conditioned by society not to show excitement even if we feel it 🥲
@N P H absolutely and it's such a loss for every one of us. Let's all get giddy about things we love!
@N P H Not to show excitement? Ever been to a football match? Sometimes there's way too much excitement.
That's *Dr* Chaperone to you... ;-)
3:17 Tom: “What’s the use for this?”
Researchers: “Uh, because *it’s rad?”*
"We'd like to look at an explosion in slow motion"
The funding board: "say no more fam"
maybe they also **deg** it.
The researcher's last word on the subject is "cool, innit?"
When the researchers are excited by their work, that's when you get the most results.
That's science
@Peppery Peppers "Remember kids, the only difference between screwing around and science is writing it down." - Alex Jason/Adam Savage Edit: I got the quote slightly wrong. Fixed.
If you go to 5:06 and use the . button to go frame by frame, you can see that the ground lights up 1 frame before the explosion is visible. This is because the camera scans in "lines" of pixels top to bottom. When it was at the explosive material, it had not gone off yet, by the time it got to the ground, it had.
thank you for the dot button tip!
@richcolour You can also use the comma to go back a frame.
Equally interesting is the shape and location of the light. It almost looks masked off somehow.
Thanks for the tip on how waste even more time on you tube. Now I have watch all the slowmo guys videos again.
Wow, cool find! Thanks!
I love it when a sciency person says, "We don't know what we don't know", it's both so true, and so honest.
Or sometimes just "we don't know."
It actually kind of is a sign of a good sciency person that they WILL say that.
If you don't know what you don't know, does that involve research research?
Unknown unknows are an important concepr in theory of knowledge as it requires different approaches and heuristics.
@Beans Just ask Donald Rumsfeld. Unknown unknowns ruined his life.
Tom, this has been a game changer video. I cannot understate how much this has solidified what I want to do as a career. I’m currently working on a forensic science degree and have been thinking of doing something like explosives and/or fires. Yes, I do definitely want to do this. This blew my mind up with it! Thank you!!
you could say, mind blown?
An explosive epiphany!
Cool, good luck!
Oh hey, this is something I actually do active research and development on! We’ve actually gotten pretty good at making computer simulations of these kind of explosions using multi-phase physics models. The Kingery-Bulmash model that Tom mentioned is still used in places, but it’s ridiculously simple compared to real simulations.
I've always been curious: how do you wrangle the positive feedback from heating? Do you let it run wild but put a cap on transport rates, or what's the strategy?
That's so cool! Are any of those simulators publicly available?
And here I thought blowing things up industrially was fun. I really want to get into the research/engineering side of things, but that generally requires more education than I've got/am willing and able to acquire at this point.
@Colin Davies That's such a good question. If you're modeling the chemistry, then the heat production will be limited by how much reactant is available. So like you say, it's limited by transport, either how fast fresh reactant can get in by diffusion, or how fast the heat can spread by thermal conductivity. Or in the case of a detonation, it's limited by the how fast the shock wave can travel and how much energy can be released by the material.
In my case, we don't really model the detailed chemistry because it'd be so expensive. We have an equation of state for the energetic material, which controls the amount of energy and temperature that's released.
@Krazylegz42 got any recommended reading for equation of state models? I’ve done some reading on impact constituent models like Johnson cook, but I had trouble finding a primer of shock EOS
tom scott is THE cool guy that doesn't look at explosions
He is HIM
He blows things up and then walks away
He just listens
He strides forward in his dimond covered boots
He does, however, give a cheesy grin to camera!
Sam was my lecturer in the blast protection module of my civil engineering degree. Fascinating subject and a great teacher.
Sam popping off and getting the limelight he absolutely deserves
Nothing a scientist loves more than someone who obviously appreciates their work, you could see how chuffed he was at Tom's genuine amazement.
It’s amazing how many things there are that people had theories about how they worked 100+ years ago, and yet we’re either no closer to actually knowing or we’re JUST getting into it, like this
Just imagine life 100 years from now
We had this problem when designing our detonation rig at the University of Southampton. We needed a way to collect experimental data that wasn't just qualitative, and it was incredibly difficult to find a sensor that we could expose directly to the detonation on the inside of a detonation chamber that could read data fast enough, resist the 3,000 Kelvin instantaneous temperature, and sustain anywhere from vacuum to 60 atmospheres of pressure. Using strain gauges is a cool idea to look at detonation wave speeds, but I don't see how they can read static pressure and temperature with time
No-one knows how explosions work (yet), but Tom Scott will be there to tell us, for sure
Interestingly enough this is a similar problem that we have in lightning research, in the sense that you cannot get close to the object you are studying. So maybe their research can also benefit lightning researchers in their efforts!
I thought rocket induced lightning has been a thing for many years. Are you talking about the high altitude stuff?
@CKFYCoreni think they mean the fact that you can't put sensitive sensors right next to lightning bolts because they'll get fried
I suspect that the data gathered can be used to suppress or enhance explosions in the future. It is ever so. It’s also a constant that the researchers will present what the think sells the best.
I love how jealous Tom looked when he was told the camera recorded a quarter million FPS. Like, that was just as much a highlight for him as the explosion
If ever there was a Tom Scott video to collab with Slow Mo Guys...
And we run that camera all the way up to 10 million frames per second 😅
@Trit0n1 Holy crap! How many tenths of a second can you put in buffer at that rate?
@Marvin De Bot We can only put 128 frames in buffer.
@Trit0n1 I thought it would be small. that's an incredible framerate. So you get about a nanosecond of footage?
The "kick vs push" question is similar to the "what is a dot?" one. if you look far enough, everything is a dot (just like everything is a kick if you speed it fast enough). It becomes interesting if you zoom in the other direction. :)
Don't mind me, just stealing this explanation to use in the future ;-)
I feel like, as a result of so many encounters with so many different phenomena, Tom has begun to intuit some of the observations these scientists are making. A sort of "wait, wait, don't tell me! Let me see if I've got this right!" thing.
He probably does his research, too.
Tom Scott is the scientist whisperer.
It's just common sense if you're vaguely scientifically minded.
The last two utterances in this video encapsulate why I watch Tom Scott videos: his genuine desire not only to allow people passionate about interesting things to explain them, but also to *get excited along with them*.
Tom geeks out about learning new things, which lets the people he's interviewing geek out about their subject matter.
The dust coming off the large concrete pad is really interesting - shows how much energy is in even that 100g of explosive
0.0000001kilotons.
or 0.000000005 Hiroshimas.
Actually this only works if the explosive is tnt but I can't be bothered.
Last year I worked for a MACV-SOG/SEAL veteran, who works for the Department of Defense. He’s been mapping the surface areas of expanding blast waves as an engineer. I learned new applications of Brownian Motion from him.
damn, MACV-SOG and an engineer, that’s a hell of a career
@Jonathan Pfefferdespite the stereotype about soldiers being stupid you don’t become special forces if you’re dumb. Most of those guys could go get a college degree and be successful out of the military.
The reason they stay in and get shot at is because they want to.
Reminds me of the shock waves reflected by the ground during air bursts of nuclear weapons (albeit on a much larger scale), which then interfere constructively and largely increase the force of the blast.
Wish I had this video about 4 months ago, my dissertation was about simulating fires and part of the background was saying why we couldn't/ it's so difficult to simulate explosions! Nice video once again 👌
The multiscale/multiphysics and tiny timesteps required to simulate this stuff is so complicated. Data like this is used during validation and uncertainty quantification for models.
Now do a video of you going through Heathrow security. I once visited an explosion test site and then had a very interesting discussion at the Airport…
I'm a pyrotech, we put all clothing worn during blasting in sealed bags in checked luggage. Nothing (even boots) that was near explosives goes on you or in your carry-on. I pass the swab testing 95% of the time and we have ID to cover the times we don't.
I get that its built for different forces and that, but its quite funny seeing this box delicately lowered to the ground by the forklift before it's blown up by an explosive
Like protecting a perpetrator's head as they get in the police car, after being tazered and beaten.
Ooh! The HSE labs :) fascinating place. Built on top of RAF Harpur Hill, in its day it was the second largest munitions dump in the country - a honeycomb of concrete bunkers built in a disused quarry before being backfilled to look like a hill again. Also one of the locations where the MOD dismantled and studied the German vengeance weapons of WW2...
Shhhh...
Have you got any history about the area? This site is on top of hte hill and not near the tunnels. But we are very interested in the site and its history and always lookin for more information.
Have you ever covered how factories stitch books with thread? I'm trying to get my brain around it and just can't. I haven't found any videos that go into how it works, at least not as well or detailed or complete as some do for fabric sewing.
@Dave Rosser It might be an older method than you are looking for, but Adam Savage just recently did some videos on bookbinding at a bookbinding museum with historical equipment. The person explaining things to Adam went into detail about how the equipment sewed the signatures.
Look for medieval bookbinding videos, one just popped up on my recommended vids last week. I would imagine factories do it the same way just quicker..
Congratulations on 6m subs Tom, still going strong after all this time ❤.
I absolutely love watching you. so informational. I just set you up on my second monitor and work on my primary.. Keeps me entertained all day! Thank you!
It's amazing that we can understand so much about nature, yet be eluded by such basic things. Another example of this is the dynamics of a 2 wheeled vehicle such as a bicycle or motorcycle.
Humans 100% understand every aspect of how a bicycle works. Coming from a bike shop mechanic.
You should publish a paper describing how the wheels rotating increases upright stability then. It would be guaranteed to make waves.
@Brennan Crock Right. My bicycle has never done anything strange. Even when crashing into a BMW.
@Greg Blake already been done many times, my wave would be minuscule in magnitude and duration
@Brennan Crock I just looked it up and it has not been done. It looks like theory is that the moving wheel creates a gyroscopic effect which keeps it upright but they did an experiment to eliminate the gyroscopic effect and it it still remained stable soooooo
Would be very cool to see what that would do to a person standing a 1-3 meters away from it, like would the pressure damage the organs or would they be fine as long as they aren't within reach of the flames? Would love to see a test with a balastic gels simulated person with simulated organs
That's true! I'm an FX artist and the start of the simulation is pretty weird, it looks cool because it's the magic of the cinema, it's based on real life but the actual application is very weird indeed lol
Can we all appreciate how much a wonder nerd Tom is. He is all of us there
That was fascinating. Thanks to the reasearch team for showing us
Damn, filmed at about 250,000 fps, giving The Slow Mo Guys a run for their money.
5:10
These researchers have a camera that does 10,000,000 FPS
@longofire236 Damn that’s one strong camera
@Rock Steel Titan That's what millions in research funding pay for. Powerful research instruments and talents (of course).
2:15 Kinda cool to see 3D printed tooling used in an application like this! With heat set threaded inserts even
Cool to see the floor is immediately concealed by the raised dust at the point of explosion and then the dust near the floor rushes towards the explosion, which feels counter-intuitive and makes you think about what's really happening.
I wish I could go out and see something cool with Tom someday that would be the experience of a lifetime
I would have loved to see a comparison between the data for the rod withstanding an explosion, being struck with a regular hammer and a dead-blow hammer.
tom i want you to know that i love your podcast lateral and will be absolutely crushed if it ever goes away, mentioning it here, because i didn't know it existed until recently.
It's amazing how the black and white slow mo looks exactly like those still frames of the Trinity explosion, which was 186,000 times bigger.
You could say that it's those "bigger problems" that Tom mentions right at the start that this research is trying to solve.
As far as I know, there’s not really a distinction between a «hit» and a «push» in physics, besides the difference between a short vs long force impulse (Force * time). Its interesting to see how they go about measuring such strong forces that’s applied within such short timeframes.
This is the kind of thing I thought people would have figured out by now. It’s crazy how much we still don’t know about the world
It’s that classic thing of asking, “yes, but why…?” over and over again… get closer, get smaller, see things in more depth… answer the ‘Why?’ at one scale and then ask, “But what happens at the molecular scale?”
We've been blowing things up for a long time; it's reasonable to think that.
But anything chaotic is really hard to model. We don't really understand turbulent flow such as water in a stream either.
It's crazy?
You don't know what "crazy" really means.
i genuinely feel like insights in this research can be changing the future of humanity, control over the force exerted at that precise a scale lets us make new engines, reactors, materials
Awesome work Tom! as always!!!
Great video Tom - but please for goodness sake get the slow mo guys there with a phantom camera! They did an amazing video with an explosion where you could clearly see the shockwave, initial blast wave and negative wave pressure.
I'm always impressed by learning about times tinkerers, thinkers, and scientists had ideas long before the technology or economy was in place to support making them a reality, or at least practically ex[ploring them.
That’s what I’m working on currently for my masters. It’s a difficult line of research due to how much of it isn’t public knowledge.
I’d love to see how a deeper understanding of how an explosion acts and how the flame propagates will effect internal combustion engine design
Wouldn’t this be akin to the way a multi joint pendulum swing would work? As in the sensitivity to the starting conditions is high, so variability in the cascading effects would be extremely pronounced?
I wonder how an explosion changes when the detonation position is moved, even in something designed to pressurize it.
It's interesting how a slow-mo real explosion looks a lot like a movie one :-) turns out they were really onto something, haha!
I'd be curious to see if increases in knowledge could lead to major improvements in internal combustion engines.
There is a lot of chemistry teams involved in this as well. And you are right the burning and combusion side is interesting as well for things like combusion engines in a slightly different way.
I could easily observe an explosion up close in detail. At least once.
"Remember kids, the only difference between screwing around and science is writing it down."
I wonder how many things rapidly advanced once really good slo-mo became a thing.
I didn't know this was a mystery. I always assumed other people could sense the blast wave rebounds. Very interesting.
This video is pyrotechnically correct. The best kind of correct.
FASCINATING stuff, the possibilities are astounding of this kind of understanding
Now *THIS* is the kind of science I can get behind!
Felt the shockwave of a small explosion once at Nellis. It was a barrel of fuel that they detonated. It was kewl. Wasn't like the wind blowing, but your clothes vibrates.
That feeling when you're just graduating from Sheffield and you didn't even realise that your uni was doing thing.
It's odd how the explosion doesn't even look that dangerous
It almost looks like a fractal pattern when it’s exploding, as if it’s pushing in a set path.
This is relevant to the company I work for, Dynasafe. One of our product lines is Protective chambers that are used at Airports, by Bob Squads etc. for ieds that may be found.
That was absolutely fascinating and possibly the most interesting vid I’ve watched this year.
Tom... I know you say it can't be simulated but... I'm sure Todd Howard and maybe Circa 2010 DICE already has. It had something to do with two point of reference pixels overlapping and eventually multiplying the repulsion force exponentially and faster in a runaway logic train until an integer fails to post and then the anti lag code kicks in and reads the object as moving away from the other object. In which the object exploded outward. Sometimes into space.
The fact that we have the explosives we do right now with how little we actually know about explosives makes me fear for the future where we know exactly how they work.
I like how the title implies that Tom is going to directly cause an act of terror that will _MAKE THEM LEARN_
This looks like a job for the Slo Mo Guys 😁
It's understandable why observing the details of an explosion up close is challenging.
What about the direct flash at the top @ 5:18? I am curious about initial reaction. It seems much faster than the explosion itself... maybe as fast as the shockwave?
I thought that explosions were just myths and an explosion is what people see with all that energy. But this is lot more interesting and still as dangerous that only experts can experiment.
I wonder if data from this sort of experiment could help the quest for viable fusion.
The more I learn about chemistry, especially at atomic scale, the more I'm amazed other people aren't obsessed with this stuff. A wave of force that propagates within the barest fraction of a second applying so much energy to the enclosed system that a 10 square meter concrete pad is shaken hard enough to release dust clouds, and it's all caused by unusually energetic interactions happening at subatomic scale in an object with a mass of a less than a kilogram.
For those that are curious this was filmed at Health & Safety Executive Science and Research Centre near Buxton, Derbyshire (you can clearly see the tower on top of Grinlow Hill behind Scott). I once had a summer job there helping build dust extraction ducting systems on that very blast pad - and then blowing them up and analysing the data on Apricot computers; a ridiculously fun job for a 16 year old.
Fun fact the W3W location of the lab is somehow, implausibly safely.rules.eclipses
The slomo guys do this and have had some amazing results with reignited gasses from the pressure wave
They need to have a look at the transmission line method for simulating electromagnetic fields. A transient pulse fed in to a simulation like that looks very similar to the blast wave and reflections in this video.
if I am not mistaken it's taught in the military to stay clear of walls during explosions exactly because of this double pressure from the blast and the bounce.
What is sad to me is that a lot of this data is known to exist, but not accessible. Because, it was measured in the development of explosive lenses for imploding plutonium pits.
honestly, imagine having the imaginiation to have a theory that could only be proved 109 years later
As always a perfect video 🙂
At 05:13 : Tom's got the face of someone who's going to spend the next 12 hours searching for the right frame 😅. Fortunately, it didn't take that long.
It reminds me of high speed footage done of nuclear explosions. I bet there's a lot of explosion/fluid dynamics information locked away in nuclear vaults that these people would love to have.
It is amazing what you can do when you can record the speed of light! Wow!
doesnt seem so complicated to me. 2 things come in contact, react like theres no tomorrow. reaction causes a sudden rise in pressure pushing everything away from the epicentre. Just the pressure raises exponentially as you get closer.
I dont think anything fundamentally different happens at the beginning that will change our understanding.
Actually Tom, if your 5cm away from an explosion, you probably dont have any problems left at all.
Oh, that does look an awful lot like old test footage of nuclear explosions, doesn't it, mr Nolan?
:)
I wonder if they can add thin wires of some materials that can be used to make the characteristic fireball "legs" of tests where the nuke was up on a mast with support wires.
how awesome would it be to say you study explosions for a living
If only it would make me a hit at parties... 😮💨
What if we’ll get closer and closer to simulating an explosion, using a more and more advanced ai, until a self repeating loop generates a simulated explosion so dense and complex it turns out to actually be the big bang
It does make sense why it would be so "difficult" to measure and understand a concept so important to nuclear weapons.
The percent of videos recently where Tom is wearing a safety vest is through the roof.
Interesting stuff. I'll be sure to check out the paper you linked in the description.