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The Mystery of Impact Flashes - Smarter Every Day 307 (Patreon)

Published:
2025-03-31 15:24:19
Imported:
2026-06
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Thank you so much for supporting on Patreon! This was an absolutely awesome rabbit hole to go down. What do you think is going on? I'll be reading the comments here on Patreon (and commenting over the next couple of days). I'll definitely be planning for and updated video on this phenomenon. I'm thinking I need to do this in a vacuum FOR SURE.

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The Mystery of Impact Flashes - Smarter Every Day 307

A big thanks to Henson for sponsoring this video. Check them out at http://hensonshaving.com/smarter (Make sure the 100 pack is in your cart to get them for free.) Want to get an email when I upload? https://www.smartereveryday.com/email-list A big thanks to Brett from How Ridiculous and Gavin from The Slow Mo Guys https://www.youtube.com/@howridiculous https://www.youtube.com/@theslowmoguys ⇊ Click below for more links! ⇊ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ GET SMARTER SECTION Wowis this a deep rabbit hole you can go down! Here's some papers to get you started! "Survey of the literature on mechanoluminescence from 1605 to 2013" https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/abs/10.1002/bio.2647 "Using mechanoluminescence as a low-cost, non-destructive diagnostic method for transient polymer impact processes" https://www.sciencedirect.com/science/article/abs/pii/S0263224119310395 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Smarter Every Day on Patreon http://www.patreon.com/smartereveryday Ambiance, audio and musicy things by: Gordon McGladdery https://www.ashellinthepit.com/ http://ashellinthepit.bandcamp.com/ If you feel like this video was worth your time and added value to your life, please SHARE THE VIDEO! If you REALLY liked it, and would like to support Smarter Every Day by becoming a Patron I'd be grateful. http://www.patreon.com/smartereveryday Warm Regards, Destin

Comments

Ryan Massey

I'm about to go watch the video 🙂. But on a side note I just received my 2024 stickers 🥰. Thank you Destin 🤘🏻.

John Bonnin

Real cool one here, Destin!

The Higdons

okay, I watched the first 30 seconds of the video to make sure this was what I thought it was. I have not watched the rest of the video at all so if any of this gets covered, apologies. I believe what is happening is at the moment of impact enough force is imparted to atomize some bit of matter to (or beyond) its flashpoint. I believe this would be the same phenomena seen with Mantis Shrimp punches underwater where they strike so fast it causes cavitation within the water. The sudden change in pressure with such a small volume causes the temperature to spike. Also, I believe with those punches light is produced briefly as a result. This all happens so fast and on such a small scale that you do not get or risk a runaway chain reaction with the combustion of other nearby matter. While the effect seen is very similar to the Snap-Pop style of handheld combustible fireworks often given to kids around the Fourth of July, the physics of what happens is different enough and much more complex with high-speed impact/cavitation.

Ben V

I just re-listened to the baseball cannon NDQ. Great timing. Love this episode, epitome of "hey what's that" and going deep down the rabbit hole! Awesome stuff!!

Nicholas Kusch

Would love to know if there’s a pulse of energy expelled at moment of impact. Probably too fast to be metered and what meter to use? Emf, gauss, Geiger 🤷🏻‍♂️

ERROR 404

This is ENTIRELY unscientific, but i feel a hunch commin on. as i am watching the video i got to 30:45 and i see this very yellow color in the projectile for a little bit that reminds me of plasma cutting of all things. any time i have used a plasma cutter on steel it creates this thick yellow smoke that is very distinct from what ive seen. I cant help but wonder if much like a pistol shrimp/ sonoluminescence it is creating an extremely hot plasma and it is actually very slightly burning/evaporating/vaporizing your steel backstop

smartereveryday

I want to measure the light spectrum. Those spectrum analyzers are serious scientific units.

smartereveryday

Congratulations. I have you guys going all the way in my bracket.

Mark Wood

I think there are two different affects being presented here. One is combustion related, the fireball squirting out the side. and the luminescence affect from the disassociation of the molecules. Water is never single molecules but rather a long chains very similar to polymers. When the polycarbamate rod impacts the target both affects can be seen. The light blasting along the cylinder is from the breakdown of the polymers. This later is most likely from the shock propagation breaking the molecules. The physics of the transition is the energy of the shared electrons being released from the neighboring molecules. This means there is a energy state transition of the bound electrons which requires the release of photons. Should be fairly easy to calculate the transition energy. There could some contribution from other chemical reactions.

Craig Hansen

Destin - I am going to take a guess and say that an electromagnetic charge is responsible for initiating the sparks across all types of projectiles. Then the oil on the bullet or the oil on the leather glove, etc ignites for just a moment. A stretch - yes but it will be interesting to explore all possibilities.

Daniel Wisehart

The SloMo guys did a YouTube video where they were firing guns underwater. On some shots a bubble opened up and when it collapsed back together there was a flash of light. Water vapor and water and some dissolved air were all that were in the area of the flash at that moment (the bullet was long gone).

Phil

Love watching these. I think the compression theory is the strongest. Is it possible solids can ignite under compression if they get going fast enough and not just gasses?

Paul Tomblin

We used to do the wintergreen thing at summer camp. We’d go on a hike far away from the lights of camp, make everybody turn off their flashlights for a while (sometimes we watched the Persieds to while away the time) and then somebody would crunch a wintergreen lifesaver in their mouth and we’d all see the flash.

Keith Jensen

I'm a chemist and this is not my area of expertise, but I do know a bit about light. [You should be talking to researchers in this area.] Let's take a step back and first look at light. Light, or luminescence, is caused by excitation of electrons from their ground state to electronic orbitals with higher energy. Photons are released when the electrons fall back to lower energy states. You are likely exciting electrons with high heat caused by high compression and some friction. PV=nRT. You keep n constant (R is the gas constant) but drastically lower the volume which raises the temp and pressure. Electrons get excited from the high heat and when they relax they will emit photons. Neon signs, luminescence, work work similarly. The electrons in neon, a noble and very unreactive gas, gets excited by high voltage. When the excited electrons fall back to lower energy levels, that creates photons and you have neon light--also works with other gas combinations to give different colors. Besides heating, you can also have some other excitation events such as oxidation and other chemical reactions including breaking crystals. I think you are on the right path. Good stuff! If you have a stronger compression cylinder and are able to compress just gasses (no cotton), do they luminescence from just the high heat? I've heard you can get scorch marks in injection molding if you don't have a vent (only need some scratches to vent air) when injecting polymers at high pressures into well sealed molds. Your proposal of shooting in a vacuum is not going to be definitive. Even if you achieve a high vacuum, when you fire the gun you will generate lots of gasses. Your "bullet" will likely travel faster than most gases over greater distances but if you see light, the question remains did some gas beat or come with the bullet. You need a rail gun in a vacuum, lol.

Paul Tomblin

The plasma coming off the space shuttle when re-entering is red or orange. I think it depends of how hot it is. Also those recently discovered upper atmosphere phenomena can be different colors, like red sprites and blue jets.

Nashguy207

You're getting above my pay grade but a great video and very interesting

Sergio Gomez Damas

I aint no expert but my intuition tells me that: the base luminance is due to black body radiation due to adiabatic compression, then, on top of it we have plastics self-igniting. This is similar to having an aluminium marble against rusted iron marble. The shock causes the thermite reaction.

Petr Čertík

1) can you file grooves on the end of the rods, to see if the flashes follow their direction? 2) is there any way to get a spectrographic reading from these flashes, and see if it matches the gas mixture and/or the rod material?

Martin Brewther

What if you run it again with the chamber under pressure and/or with a vacuum?

Zoltán

There is clearly gasses involved, but the question is whether it's that only or not. I kept repeating "Do it in a vacuum!" in my head from the start, and was glad you mentioned in your closing section. :) Not easy at home, but a spectrum would also help. (Black body, or chemical.) The source of the heat is still not clear to me, and vacuum can help with that. - The first impact of the topmost layer of molecules when they first touch. - Initial compression. - Both. - Transferred to gas present. - Optionally igniting actual flames where they can. It may be a combination of all, and slightly different depending on the materials impacting, the gas present, and the shape of the surfaces. (e.g. polished surface vs grainy surface.)

Mike Taylor

I am super interested to see what would happen when you impact in a vacuum chamber! Also, probably a dumb question, but were you not worried about a bigger explosion with the oxygen running while you fired it? I don't have any experience with this stuff but I've always heard that oxygen is extremely flammable.

Jon Georg

I'm wondering if it's essentially compression/ignition of the air between the objects at impact. Doing it in a vacuum should be interesting for that very reason.

Joe A Powell

As a long time heat treater, hot forger and welder, I’m betting on the impacts causing the flash are Hydrogen gas (H2) atoms (which are everywhere) being excited enough to the point where some of these normally diatomic atoms are becoming two separate elemental Hydrogen atoms - that is (H2) splitting into two H1 + H1 atoms and then immediately giving off a flash of heat/light energy as the two unstable hydrogen atoms reconstitute themselves together again into H2 gas diatomic molecules. This exothermic flash from H2 to (H1+H1+ heat!) does not require any oxygen because it is not really the burning of Hydrogen atoms in the presence of Oxygen. Check out the YouTube videos on Atomic Hydrogen Welding where this antique hydrogen welder is using a high energy plasma arc between tungsten electrodes is generating a spark to generate a very high temperature around the hydrogen H2 splits into mon-atomic hydrogen and producing the exothermic reaction. See also my “Resources” page at

Joe A Powell

Check out your video on Solving the Mystery of the Prince Rupert’s drop has led Integrated Heat Treating Solutions to create high levels of beneficial compression in hardening of Martensitic steel and ductile iron raw materials.

Joe A Powell

A welding engineer who IHTSAkron.com’s consultants are working with has been working to update Atomic Hydrogen Welding for welding in the vacuum of space.

Greg

I suspect that you have both phenomenons happening here. Both the tripod, electric and shock heating. It would be super duper fascinated to see if you can figure out how to capture a spectrum of the flashes. That would tell us a lot about what's going on.

Florian

What about doing it in vacuum? Similar to this: "Making a Shockwave by Hitting Two Huge Steel Ball Bearings Together" by the Action Lab. If it's a gas thing, it should not flash.

sydhanful

This feels like a plasma. Like when the Space Shuttle reenters. But I have no clue, I am in no way a scientist. The video was great!

Michael

I would definitely try and get this done in a vacuum! I’d be willing to bet this is all due to compression of gasses. At least specifically in this case of these plastic tubes hitting steel or the glass balls hitting each other. That last shot, I think there’s a chance that fireball lasts longer not just because of how oxygen rich the environment was. With how perpendicular the impact is, I wonder if the oxygen is leaving through a lesser gap between the tube and the steel. Possibly meaning it takes longer for the pressure to level out from the “pocket” of compressed air and regular atmospheric pressure. Great video as always!

Potato

Hey Destin, this is my first time on patreon and I got on here because I was really hoping that you might respond to this message. Although no offense if you dont. ----- While whatching your video today I was reminded of how a similar thing hapens under water with cavataion bubbles. When the bubbles collapse they compress and form a bust of light. I think this may be similar to using the fire cringe. I went looking and found the original video that turnded me on to this idea years ago made by The Thought Imperium. Here is the link. https://youtu.be/puVxGnl_3y8?si=NXo5jxQPcH2KMftc In the video he talks about sonoluminescene which was the technique he used to study the phenomenon of creating light from cavitation bubbles. Using sonoluminescene he is able to capture a small bubble in a volume of water using sound waves and force it to expand and collapse multiple times causing a burst of light each time. I don't know if this is the same concept but I thought that it was similar and when reading other comments I didn't see anyone else expanding in this direction so I thought I would bring it up. I would be interested in seeing you discuss any similarities or differences between what you have shown in your video today vs creating light underwater using this technique or if you have already considered this idea and decided that it was too dissimilar to be relevant. I think that the repeatability of this experiment may bring insight that could be worth your time or would at least be good material for your viewers. Anyways thanks in advance for you time and considering my message.

Rick Corbitt

I think another important factor is the more it hits orthogonally, the higher the pressure for a larger volume of gas, as well as taking into account what others have said here, too. If the rod hits at a high enough angle it'll spark at the spot where it hits but the gas between the rod and plate may not be compressed enough to ignite; too easy for it to escape. I think you touched on this a bit, Destin.

Daniel Elliott

Might just be me but at a point would the pressure be high enough to make plasma which then possibly ignites due to extreme temperature, might be why the oxy environment gets a brighter flash. Would love to see this in a vacuum, I do think its gas based as well.

William Spalding

If you start with a really clean box and try to get mass balance you might be able to separate combustion from the luminecence processes. I think there may be more than one process happening. Great experiment and video!

Hayden Nelson

Hey Destin, I think your next step should be turning your high speed camera into a high speed spectrometer this will tell you if it is black body radiation from the heat or excitement of the electrons (I think that’s what is happening to the argon to make it brighter). You could do it with a simple prism or refraction gradient. You could tie it to the JWST and other astronomy topics. If you want quantitative numbers for it you could get a mini spectrometer from ocean optics or Thor labs (~$1000) that can do super fast acquisitions that should be able to show it. I think this would be easier than making a vacuum.

robert wallace

Destin, you seemed curious about the very orthogonal shot creating the best flash. If that shot was more effective due to there being better compression of the gasses you could remove some of the effect of your impactor angle by firing at a cavity that would confine some of the gas. The deformation of the impactor would seal and compress the gas in the cavity, kind of like a reverse of the NASA light gas gun sabot. This would most likely only be visible with the polycarbonate impactor (clear) but maybe this would ramp up the brightness of the flash.

robert wallace

I think so too. Purposely firing into a cavity that could trap the gas and compress it more might amplify the effect if it is truly gas related.

Rick Corbitt

I had the same thought; with a good chance of more than one thing happening causing a flash and many things affecting the amount of flash.

Karl

Similarly, perhaps a projectile with various shaped ends. Concave (dome and cone), convex (dome and cone).

Ms.Bach

I think this may be the same thing that happens continuously on the leading edge of atmospheric re-entry vehicles. If you could fire the object fast enough you wouldn't need the impact with another object but at these "lower" speeds the second object provides the compression needed to create the luminescence. The Shock Layer Gas Physics section of the Atmospheric Entry wikipedia page is a good read for those interested though it does have an unsettlingly large number of citation needed tags.

Troy Boulware

Just for the sake of testing, if you put regular printer paper in front of the target will it show a burn pattern ? You could also ‘ enhance ‘ the outcome by trying flash paper as that will ignite with low exposure to fire or the fart spark / spark fart you have already experienced.

David Harris

Awesome video. I also posted this as a YouTube comment: What if you used nitrogen as your gas? Wouldn’t they be more inert/noble and prevent any flash cause by gases? Also, how much unburnt powered makes it all the way to the impact? How much does the projectile pull ignitable debris or gas into the impact?

bolecut

As soon as i saw this video i thought of two more examples that i think could be key to understanding this! The first is a bullet through ballistic gel where you get a flash from the initial bullet impact at the face, but then a second flash inside the gel when the cavity caused by the bullet collapses in on itself and compresses the gasses. The second example is when you smack two steel ball bearings (by hand) and there is a large amount of heat created. This second one is usually demonstrated with a piece of paper inbetween and after the collision there is a burn mark/hole in the paper. Vsauce has a great youtube short on this where he creates a thermite reaction using two bearings (one rusted) and aluminum foil, see here: https://youtu.be/-hzue8KIS9M?si=HlXyhtyJKuNCpu87 From watching the vsauce video and considering the bullet/ballistics gel scenario, i think that the impact caused flashes are different from the flashes caused by the compression of gasses as with two spheres colliding, there shouldnt be much compression of gasses at all, if any. However, i do think they are related in that both introduce a lot of heat into the system in an extremely short amount of time. What i think is happening is in any case is a large amount of energy in the form of heat is being introduced into the system which is enough to spontaneously ignite whatever fuel maybe at the source of impact. And based on fire physics, this is affected by the surrounding gas composition.

smartereveryday

I had the gas there but basically I ran out of time. Lots of room to do more experiments in the near future.

smartereveryday

Spoiler alert... I've already ran that experiment... and it's going in the PhD.

smartereveryday

Thanks for joining Patreon! Yes, sonoluminescence is another area of interest that I haven't dived into yet.

David Bailey

You probably already know this, but there has been a lot of detailed research on hyper-velocity "impact flashes" in vacuum because it happens when small objects hit satellites, asteroids, the moon, …. Just search for "impact flash" on Google Scholar. Most of the research is for much higher velocities than your collisions, but still may be relevant. For example, "An experimental study of the impact luminous efficiency and vacuum level" (doi:10.1016/j.pss.2020.104921) reports that "Based on a high-speed spectroscopy, we find that the flash consists of blackbody radiation from hot ejecta and blackbody radiation from a vapor cloud together with emission lines and molecular bands. Spectrum analysis reveals that the initial luminous efficiency within the first few μs does depend on the vacuum level, whereas the luminous efficiency over several ms does not depend on the vacuum level."

David Bice

Hey, Destin. I have a fellow creator that I follow and support on YouTube that works with full size steam locomotives in Colorado. He’s been looking to do collaborations with creators, especially those with access to high speed cameras. Tried looking for your contact info, would love to send you some details.

Daryl

Can’t wait for part 2, I’ve always been curious about this. I used to have a mantis shrimp and also a pistol shrimp (not together 😅) and I feel like I could see the light with my naked eye. I’d love to see two life savers collide and see if it makes both forms of light. Also, I got my 2025 stickers, thanks! I especially love the eclipse one 🌙!

Peter Champlin

I wonder if it is similar to the flash you see when a bullet goes though ballistic gel.

Brad Keener

This was super fun. I'm a dentist. When I drill on zirconia crowns with a diamond burr, they spark pretty badly. The burr is spinning about 300-400k RPMs which makes the surface going about 55-60mph. Would be more than happy to provide you with supplies to try that out with high speed if you are interested. I'm AcTuAlLy(in internet comment voice) coming to Huntsville this fall for a Flying Dentist Association meeting.

Hayden Nelson

Super fast in this case would be sampling rate. This would help investigate if multiple things are happening(ie heat is sending the electrons into a higher state or if it’s just black body radiation). The Thor labs spectrometer has a minimum integration time of 10 uS, that’s probably too slow. You might need to get one with a university, you’re talking big money for something that could measure that quickly. But if you are clever you could use your high speed camera and a czerny-turner gradient to split the light into individual wavelength that shine on different parts of the high speed camera sensor.

Ben Riser

This video was a blast (pun intended). I'd love to hear more about the differences in the various types of luminescence you were exploring throughout this video.

Adam Willcox

I loved this video, it was like I was just hanging out with you while figuring this out. I'm here to shill for Hayden Nelson I think. After reading the replies I would love to see it repeated with normal atmosphere and a vacuum, both with a spectrum analyzer to figure out what the product of the flash is.

robert wallace

Lol, my head is spinning if the result ends up being a bang or a whimper! I can't wait to see either way.

Patrick Locke

Scott Manley put out a video about a month ago where he visited The JSC Hypervelocity Impact Test Facility (HIT-F). Since they have a giant machine for your null hypothesis (big gun into a vacuum chamber specifically to study impacts), thought it might be a good direction to look for next steps.

robert wallace

Well, it's not that oxygen is flammable, but having a higher concentration of oxygen around anything undergoing a Reduction/Oxidation reaction (burning most organic material is this type of reaction) will increase the rate of the reaction. So things that are burning will burn faster and hotter, things that may just smolder a little are suddenly going to be burning, a small spark suddenly has a much higher potential to light another thing on fire as well. So as long as he keeps fuel (and, ideally, heat) away from the oxygen, then he should be safe.

smartereveryday

OK... this is awesome. I'm working on this type of thing for the school stuff.

Brad Keener

It is where the diamond particles strike the surface of the zirconia. I could try to get a video of it sometime if you would like.

Daryl

It’s insane that they can generate that amount of speed through water. The gas theory makes sense since there’s a cavitation bubble on impact but maybe that’s just a flash boil? I’m just a curious normmie trying to gain a little knowledge every 24 hours 😆

robert wallace

Neon lights are plasma. Different gasses have different plasma colors.

Luke

Really cool video Destin! At first I was thinking that it could be something similar to when you get sparks when taking a grinding wheel to something metal (something related to the material properties of the two materials impacting and creating heat and light), but the fact that that it was happening with lots of different materials does seem to point to it being related to the compression of the air during the impact. I'm looking forward to seeing what you find out when trying other gasses or even a vacuum!

Carolyn Byars

You have been my favorite brain to experience for a long time! And I’ve told so many people about your curiosity and history that my husband is a bit jealous! But we’ve just found such joy in all of your adventures starting with the bicycle handlebar experiments. Our grandson now is a Patreon fan of yours! Yes, this smart video is as amazing as Tom Hanks Americas!!!

Steve Jones

Ok.. Hear me out.. A neon or fluorescent light works by exciting the electrons in an atom so they go to higher energy orbits, and then they release that energy as light when the electrons go back to their normal orbit, right? You have already proved that with the pressure, you are heating these objects to crazy temperatures.. Could it be as simple as the impact/compression, or even the friction in some cases, causing the same effect, where it is just electrons going back to their normal orbits after being excited? I am thinking that if I remembered more about chemistry and physics, I could think of a way to prove or disprove that by using different gasses that burn in different colors.. Maybe if it is the gas, then it should be a different color based on what is oxidizing, and if it's just photons coming from the decreasing energy of the electrons, it would be a constant color, which to me, it seems to be??? By the way, TWICE during that video, you said EXACTLY what I was thinking, exactly when I was thinking it.. First: He needs to shoot a marble so he can get the perfect contact with no angle.. and second: This needs to be done in a vacuum to prove it's not the gas burning!! Keep it up - Can't wait to see a follow up video!!

Steve Jones

By the way.. you can see the sparks from the lifesavers when you chew them.. Try it..

Matt Dickie

Dustin, very cool video. Could you try it with acetylene instead of oxygen?

Brian Mcduffie

Hey Destin! Listen to this!! A couple days ago I watched the most recent video on the Ballistic High-Speed YouTube channel titled “Tank vs Human!…” and funny enough before you posted this video (on these high speed impact flashes), I noticed in the Ballistic High-Speed video at exactly the 8:50 time stamp a tank round that weights about 17lbs hits a ballistic dummy head and I happen to notice it creates this same type of flash, and I’d even say it’s on a more pronounced scale. I think you would love to go watch the video and take a look at this situation where this “triboluminescence” occurs. It’s a very solid object hitting a very soft ballistics gel material.

John Cox

Theory 1: Not flash ignition, but flash ionization. The light in fire comes from energetic ions in a plasma. It's not just the atoms that are excited, but the electrons in the valence shells are too, and they will emit light when dropping to lower energy orbits. Argon doesn't burn, but it's very low heat capacity makes it susceptible to easy ionization under adiabatic compression. Early flash photography ignited single use argon flash bulbs, which would put the argon under a large presure-induced temperature spike. Due to to the noble gas' very low heat capacity (monoatomic is about as low as you can get) it got really really hot, ionized, and the highly excited valence electrons gave off a lot of light. For a moment. And then what's left is the smoke off the initial charge and the broken bulb on top of the camera. If this is correct (if), then you should see this in a vacuum too. I don't think that ignition has anything to do with it, but everything to do with flash ionization. Option 2: A tiny smidgen of matter peaced out in some kind of reaction. This isn't just a nuclear thing, but also occurs in exothermic reactions in general in which a very small fraction of mass is simply not there anymore in the product compared to the total mass of the reactants.

Simen Wright

If you could clap fast enough you’d light the air on fire 🔥👏

Tom Gidden

I love this. I'm definitely on the side of this being compression of gas at the target, as it's confined by viscosity of the surrounding atmosphere (and even the compressed gas's own viscosity and inertia) at this time scale. The whole time I was a little bothered by the limitations of the rig, though. The sabots and the stripping hole, while necessary in this design, seem like they're complicating it. Gravity's not helping with the obliquity and the side-parping either. And the target's being contaminated by unburned powder, gasses, disintegrated sabots, etc. So, I was thinking, would it be practical to build an indirect/transfer setup instead? Basically Newton's Cradle, but with guns and stuff. The shotgun fires a dense projectile -- tungsten? -- at a transfer device in the wall, say a drill rod pin with a sliding fit (or use O-rings, baby!) The transfer pin in turn would hit the stationary sample projectile waiting on the other side in a barrel, giving the sample its momentum and yeeting it at the target. If that was all mounted vertically, possibly with the projectile in a barrel for retention and alignment, it might hit the target head-on. There'd be complications of course, and you'd need to compensate for significant friction losses. Perhaps use foil at various points to seal the chamber while still allowing momentum transfer, if maintaining a different atmosphere or vacuum in the impact chamber. With enough indirection, eg. a _really_ long transfer pin, you could use something significantly more spicy than a shotgun to compensate for the friction losses. (Incidentally, I have issues with the "______luminescence" terminology for these phenomena, as I bet there's sound and heat being produced too, with my guess of the energies being conductive heat > infrared > visible light > sound.)

Brian Montgomery

Noble Gases are inert. If the chamber is filled with a noble gas then nothing is going to “burn”… If the gas itself is the source of the light then (as others have suggested) find a way to get the spectrum of the light produced and see if it matches the spectrum of the gas in the chamber.

Sinjid

This research is very interesting! My theory is that there are several different effects coming into play at different scales and environments. This effect where heated particles from the fragmented projectile (and compressed atmosphere if any) emit blackbody radiation is what I think would be the smallest magnitude light. Next on the scale would be the compressed atmosphere ionizing (like reentry heating?), like many other comments I saw suggest. These first two effects is what I think the tiny sparks are from all the small impacts seen in the argon-rich case. The large directional plumes accentuated by the oxygen-rich environment I think is autoignition with the oxygen and whatever else it can find in the atmosphere or projectile.

William Grant

Destin, please use a rubber mallet whenever you feel like smacking something with your palm. I loved this video but as a mechanic I winced every time you hit that air piston with your palm. A wise man once told me "your hand is the most expensive hammer you'll ever use"

John Allwine

This is what I came here to ask about. I was surprised there was no mention of black body radiation in the video. Anything that gets hot will emit light and if it's hot enough to do so, it's hot enough to then trigger side effect ignitions in an oxygen environment. https://en.wikipedia.org/wiki/Black-body_radiation Would love to know more about what you find out.

Mitch Rauk

As an engineering dork that loves listening to people smarter than me on topics I don't understand, your videos are entertaining. Everyone in this space, hats off to you as well.

Ben Brown

What if the plastic projectile had a concave or hemisphereical leading tip to either potentially trap and compress more or less gas. Also if you do it in a vacuum pull a vacuum then fill it with the gas of your choice. I also wonder if ambient atmospheres of pressure matter. Like was if it was 7psi of Argon. All the questions! Love your stuff got your stickers the other day!

Aqua Discovery

You should look up micrometeorite impact tests. These are done under a vacuum.

Aqua Discovery

Look at micrometeorite impact testing. Even noble gasses become ionized (plasma) You just dont get the "burning" of the gas but still will heat up hot enough to burn particulates including dust from the projectile.

Goblin

Another thing to analyze in this experiment is the energy of the projectile (1/2 m v^2), you could preform an experiment that analyzes the differences in either m or v^2 in a setup like the Adiabatic tube to observe the energy

Gryyphyn Crosthwait

I checked before you fired into the argon chamber and something I remembered was right: argon is used in "neon" lights to make the emitted light more blue. While argon is a noble gas, meaning it's not reacting as in burning, it does have a color emissivity spectra of a specific wavelength. A bit of research starting at https://en.wikipedia.org/wiki/Gas-filled_tube indicates that argon is used due to it's "low striking voltage". While the gasses are noble, the do have an activation energy required to cause them to emit light. In the case of argon, mercury vapor is used for the initial glow. The addition of argon shifts the overall frequency further toward the blue/violet range and is used for a more intense blue glow than mercury alone can provide. So I think there are three things happening here: 1. Rapid gas compression sufficient to reach the autoignition temperature of combustible materials. In the case of the plastics used in this experiment, I think it possible that you're hitting the autoignition temperature of the plastics at the high pressure front on contact. The same is possibly true of the wood sample. 2. Piezoelectric effect in the case of PETG. This one may be a stretch as the measured effect, per https://www.sciencedirect.com/science/article/abs/pii/S2211285517303063?via%3Dihub, was obtained with a PET film bonded to an ETA adhesive, so I'm not certain the effect would be truly present in a high speed projectile or high compression load event. 3. After watching the argon test, I think option 1 is still the most likely, as you've indicated throughout the process. As there is no sufficient electrical charge to reach the striking voltage of the argon atmosphere in either the fire piston or open chamber test, it's not surprising to not see a brighter flash. Since there was no combustible atmosphere in the fire piston, there was no actual burning of the cotton sample. This should also be expected. If you could truly, fully replace the atmosphere in the striking chamber ("very scientific" indeed lol), we may see the same effect with all of the projectiles. Something something SmarterEveryDay railgun something something experiment complete. I'd be super curious to see what a full spectrum converted camera would show. In theory, if you're reaching the activation energy required to make the noble gasses emissive, we may see a brighter flash but in spectra outside the normal visible range. If my theory about piezoelectric plastics is correct, it's possible.

Gryyphyn Crosthwait

This is correct. That's why we fill gas discharge tubes like neon lights with noble gasses to achieve specific colors.

William Strickland

What happens if the impact end of the rod is a different shape (point, bowl or ball). I would also like to see other materials like graphite or tungsten used to make the rod.

Houdini NFO

I am not a rocket scientist. But when I look at this, I’m asking myself the question, “Isn’t this just rarefied gas?” There is so much energy being transferred into that final instant of gas that it would be causing it to ionize. This wouldn’t be anything different than the ratification of gas around a heat shield of a capsule re-entering the atmosphere, or the rarefication of gas on the leading edge of a hyper-sonic vehicle in fight. Again, I’m the rocket scientist.

Daniel Turner

Is it feasible to use differentials in pressures to propel the projectile from the barrel to the target, which would also allow for different gas mixtures to be present. The very rapid transfer of kinetic through the objects impacting each other is covered in a video by @TheActionLab, i.e., "Newton’s Cradle Doesn’t Work the Way You Think", and so I wonder if the concurrent compression of the projectile is somehow interacts with internal shockwaves. Impact generating localised heat would certainly cause changes in electrons' energy states to higher ones that would rapidly return to lower levels by the emission of photons. Spectroscopic analysis of the wavelengths of light being emitted is certainly worthwhile exploring, as it should indicate if specific elements are responsible for the flash. Light emitted from cavitation collapsing is similarly linked to the instantaneous energy flux occurring when the gas is compressed uniformly by the surrounding liquid towards a single point.

Eric Lund

I don't know anything about this beyond what you taught in the video, but it feels to me like the amount of gas at the point where two balls would strike each other or where a ball would strike a plate is extremely small, since it is a point impact. It is hard to see how that would produce a noticeable flash. I was wondering, though, if the material itself is compressing it should also be heating, similar to sparks coming off of a grinder. Could it just be a bit of molten glass or plastic you are seeing? In the case of plastic, could it be the plastic vaporizing at a high temperature (hence the puff)? In the bullet video, it seemed like it could just be residual atmosphere (bubbles or slack space) inside the jacket. All total speculation, but maybe more fodder for experimentation? Also, curious what a pointed projectile hitting the plate would look like. Maybe print a cylinder with something like a pencil point on it? Another thought. Aluminum does not glow when it melts. Maybe try firing an aluminum cylinder at the plate?

Gene Wedge

I like the spectral analysis idea. This would distinguish between ionization (specific spectral lines) and black body radiation due simply to heating (a smooth curve spectrum), e.g. as we'd expect for sonoluminescence. Can you pull off a spectrum?

Mark Springston

Okay so what if is something like sonoluminescence (which only occurs in a liquid medium) I don’t even know if it is an actual term yet, but maybe “acoustically induced luminescence” or “sono-plasma luminescence”. I may be way in left field on this. But would love to hear your thoughts.

Tucker

If this is indeed a gas compression effect, then I would assume you could increase the size of the flash by increasing the amount of gas being compressed. To test this, I think you could have projectiles with convex, concave and flat ends. Assuming you could get solid orthogonal impacts, you would expect the concave projectile could trap more gas, which would hopefully be compressed and the impact crushed the cavity against the impact plate. By this logic, the convex (rounded) projectile would have the least amount of gasses trapped and therefore smaller flash. All speculation of course.

Tucker

I truly appreciate your willingness to post videos like this. The whole mentality of: “I saw something interesting I want to understand better. I’m going to test this idea. Maybe I figure it out. Maybe I don’t. “ Showing people it’s ok to not have the answer helps to make learning (and the risk of failure) more approachable. Great video. Thank you Sir.

Lance ==)----------------

Analytical chemistry uses a technique called flame spectroscopy. Assuming that the flash produces enough light to drive the spectroscope, you could find out what elements are being heated. From that you could infer what is participating to produce the flash.

Hayden Nelson

Hi one more comment, I think it would be interesting to put the acrylic rod between two pieces of steel and smash the sandwich with a hammer. I think you will see a bright flash of the whole rod. I think in the video we are seeing a few different phenomenon and this would isolate one of them.

Blake

If you want to do it in a vacuum you might want to look into a rail gun type accelerator. I can't imagine firearms are particularly happy in a vacuum but electricity dont care

Kieran Ludke

I'm really glad you're exploring this further because I watch all of these other channels you mentioned and have seen this phenomena many times and wondered, what is it, is it air in front of the moving object igniting as the pressure builds, is it forming some sort of plasma with the super heated air. I'm probably wrong because I'm not exactly smart enough for this kind of thing, but hey advancement in science either way is advancement!

Ian Nuñez

What should be ruled out is that these impacts aren't just fast enough to emit visible blackbody radiation due to friction. Projectiles heat up the objects that they hit at the impact point, increasing infrared radiation. Why can't these impacts be fast enough to create enough heat to be in the visible range? Some of the impacts are white/orange/yellowish and show the signs of this blackbody radiation. I am very excited for a possible test in a vacuum due to this.

Tyron Mascini

Love love loved this latest video Destin! I noticed you were using a macbook with windows operating system (31:30) I’m wondering how you managed to do that. I would love to know because I like Apple’s hardware but prefer windows Looking forward to your next video :)

Grant Skinner

This is a great one to get the brain turning over! Some of the way the flash moves about reminds me of a ball of plasma, this then makes me think of inertial confinement nuclear fusion where (to the best of my understanding) they're using the inertia of the impact to provide the energy to create the plasma and more. Could you perhaps fill the chamber with a few different types of gas known to produce different coloured plasmas? Neon: reddish-orange. Argon: lavender-blue. Helium: pinkish-white. Xenon: sky-blue. I know you tested argon but I would love to see a couple more impacts with slightly better axial alignment like the last one in oxygen. All food for thought! 🙂

Grant Robertson

The Slow-Mo guys have captured this effect when rounds contact ballistic gel when they filmed with Kentucky Ballistics. Great video Destin

Poker Chen

Looks like thermal radiation from air being compressed and superheated as a result. That's what Argon flashes are, and is seen in your videos. If true, the speed of projectiles must be greater than a significant minority of air molecules (mean speed 464 m/s at 293K, so 300m/s would be enough). With your polycarbonates, the cases where the whole tube lights up in both air and oxygen gas is due to refraction of the light from the combustion of polycarbonate at the interface, which is bright enough to light the whole tube. This is missing from the argon gas video since there is no combustion; the heated argon itself isn't bright enough. The cotton wool combustion inside the tube provides the essential explanation - thus same happens with the original glove and baseball example. In contrast, the polycarbonate polymer should be mostly amorphously and unlikely to have enough crystalline contacts to generate measurable fractoluminescence.

Poker Chen

Something like wood probably just wouldn't work at the same velocities since it's both a little porous, allowing more air to escape, and prone to fracture.

Timothy T.

I'm very convinced this is a combination of adiabatic compression of the gas, high reactivity at the moment of maximum compression, and affects of the impact, in that order. Im interested to see what happens in a vacuum, I think it's possible we still see high reactivity under pressure a-la those thermite reaction experiments with the rusty ball and the aluminum, and we may also see what id describe as the secondary effects like triboluminescence etc.

Brent Gourley

two ideas come to mind. One might be a subset of the other. Conservation of energy. The energy of the speeding object must "go somewhere" when the object quickly stops; it becomes an immense amount of heat and light upon empact. Rudolph Diesel knew about the gas laws. The bit of cotton hydrocarbon in the tube is heated to ignition by the compression of the gas. Every compression ignition engine; reduction of the volume of the gas raises the temperature high enough to ignite hydrocarbons; in that case, diesel oil.

ERROR 404

when i used plasma cutters the plasma itself waz blueish purple, but what i was reffering to was the brown/yellow color of the projectile the frame after the flash looking like the smoke that is produced when plasma cutting steel rather than the plasma itself. thats why i was going down the rabit hole of possibly vaporizing your backstop

Potato

Thanks for responding, it really means a lot. I'm always excited to watch your videos, please keep up the good work!

Eric Enslen

Reminds me of mantis shrimp punches in slow mo. I suspect like the mantis shrimp it’s causing very high temperatures in a very localized area for a brief moment, and the flash of light is primarily a result of those temperatures, but in an oxygen rich environment it additionally causes combustion.

Tyler Tel

The string example confused me a little but I think I get what you are saying. The example in my head to compute the tangential speed was a surfer on a wave, the difference in speed between a surfer going with the wave vs along it tangentially. Sailboat would be a similar example.

Frank Katzenberger

I do think vacuum and different gasses is important to explore the type of luminance type. One consideration should also be launching these projectiles at a point instead of a flat surface. There should be less ignition if this is that. I think you will also step up the frame rate extensively to see how the light is propagating. You may even might want to set up a schlieren lense to look at the mach waves of both the projectile and the explosion. If you control the gas mixture well enough you should be able to calculate out the changes in energy of the system.

20Q

Very similar to cavitation flashes. You are exceeding the speed of sound, hyper-sonic? The gas is ionizing, not burning, however, the heat might be high enough to have residual burning. I think it is creating a plasma. Also similar to banging two ball bearings together through a piece of paper, the contact point creates a sonic shock wave that burns the paper. It would be interesting to see a spectrograph of the flash, this should confirm ionization. Anyway, very cool.

Adam Haskin

As many have stated. I think this is simple pressure to heat leading to the combustion temperature of whatever materials are in line. I think that even under vacuum some materials will reach combustion temperature in the instant of impact because at the speed of impact they are acting like fluids. I've been doodling the math for gasses. You only have to compress a cubic center of air to 1/10th it's volume instantaneously to raise the temperature of the air to 600F in a perfect system. Which is coincidentally the estimated ignition temperature of leather. Given that this isn't a perfect system. I bet if you had the time to dump this into fluid dynamics you'd see enough compression to get up to that temperature no problem just in the gas. For solids it'll come down to how fluid they act when impacting. I'm wondering if that's why the Lead / Glass are able to get to ignition temperatures because they are probably plastic at these speeds/temperatures/pressures. That's what I'm thinking off the cuff.

Ryan Schweter

So I typed this up on YouTube before joining Patreon to jump in here, so I apologize if anyone else has said the same thing. But here's my take for what it's worth... So I have a different theory, similarly related. I'm a blacksmith, but I've always been passionate about understanding and learning, so needless to say I've spent a lot of time thinking about and researching impacts. I propose that it's adiabatic heating of the solid object at play, not the gasses. It's a well known phenomenon in the forging world that when you hit the steel, you can put heat back into it through adiabatic shear and actually extend your forging time. (it, as well as a few other things like fire welding, are topics I've wanted to reach out to you, for years ,about doing high speed study and investigation on, but I digress). There are a couple of reasons for my suspicion here. 1. On the topic of old classroom demos, you can burn holes in paper using two large ball bearings and just smacking them together. 2. The color of the ejected plume definitely looks "firey" ie incandescent. Short of being at plasma or electrically excited, I've never seen gas emit visible radiation, and only when soot or particles are in the stream does it take on that hue. 3. There always seems to be a dark cloud at the edges or after the "fire" is over, which I believe is the ablated material after it has cooled. 4. When cleaning metal with the laser at work, the ablated material seems to have a similar characteristic, though of course that's a different mechanism. 5. More of a suspicion, but I don't think, especially with the smaller pieces that flash, enough gas would be impinged to create a noticeable effect. Instead, I suspect that it is in fact adiabatic ablation of the impact surface of the materials at contact. I believe this ablated material is incandescing while effectively vaporized, and in the case of oxidizing environments burning after the fact. The amount of energy concentrated at the surface at the moment of impact has to be enormous, especially since the flash seems to happen before the Shockwave through the projectile can take the energy away. Testing : 1. Taking the spectrum of the flash should tell you what if any gasses are at play, but it certainly looks like a black body type of emission to me. 2. Marbles in a vacuum - I purpose building a vacuum cannon, where the impact happens inside the barrel. I suspect you will still see the red-orange-yellow ish flash and possibly a gas like cloud even in a nearly 3. If you can get an impact where the projectile is traveling faster than the speed of sound in itself, perhaps the flash will be continuous, or at least as long as it takes before the sound can take the energy away.

Ryan Schweter

Grinding metal creates sparks due to the pyrophoricity of the metal and the adiabatic heating from the plastic deformation of shearing, as well as friction. Metals with low pyrophoricity (typically non ferrous) won't spark, and others will spark different colors (titanium and zirconium are notable for their bright white). Source - I grind a lot of metal.

Ryan Schweter

Interesting perspective, as a blacksmith myself I suspect adiabatic shear heating the contact surface upon impact, but thanks for giving me a rabbit hole to go down with the atomic hydrogen welding!

Joe A Powell

Check out the rabbit holes on heating, quenching and tempering at my www.IHTSAkron.com “Resources” page.

Joe A Powell

Since the amount of energy concentrated at the surface at the moment of impact has to be enormous, especially since the flash seems to happen before the Shockwave through the projectile can take the energy away, that’s why I think it may be the high pressure that excited gases that are giving off the flash.

Ryan Schweter

While I'm sure there's impinged gas that's getting very hot, I believe the majority of the effect observed is from the vaporized contact surface, hence the sooty/flame like appearance. The fact the oxygen had a more energetic reaction seems to me that there is in fact a very finely devided and mixed cloud of substrate that is oxidizing. As with anything, there's always a lot going on and very well could be multiple things going on. But my money is that it's predominantly the solids interacting, not the gas compressing. The ball bearing demo is far slower but still able to generate enough heat at the impact zone to ignite paper, and I doubt there are any gas effects at play there. Therefore when scaling up the energies and speed, doubt that gas effects would surpass this, especially when the projectile is subsonic. I guess the other question would be, are there any visible effects of gas escaping at supersonic speeds from the impact zone? I really don't know, but would be interesting to look for.

Liam Brinton

Thought for next iteration. Fill the box with fog/smoke from a fog machine. May not show anything, but was thinking you could find a way to create a reverse wind tunnel and better look at what the air is doing in the leadup to the impact. Keep up the great work

Lance ==)----------------

Another consideration: if you want to minimize the possibility of conventional combustion, use a tungsten projectile against a tungsten backstop in a vacuum.

Octopus

This looks like ionization to me... Think of the electrons being pushed into a higher orbital... Kinda like fluorescence- noble gasses are used here because of their valence shells (you can make light by adding energy to any concentration of a specific noble gas despite their "inert" status, hence the proposed flash- maybe like a type of PLASMA. remember plasma is an ionized gas.. It must be enough energy to either knock an electron in each atom invlolden in the highest force of impact to add enough charge to the electrons in the valence shells to jump up temporarily to a new valence shell, only briefly though, as it makes the atom immediately unstable, and it then jumps down to its natural shell. It causes a release of energy in the form of light when this happens. OR it could be shedding the electron altogether, though (and I'm not entirely sure here) that that results in a different kind of radiation- not leading to visible light- I think of the electromagnetic spectrum here...And of course, when you have a clear "lensing type structure, like the glass balls or the plastic rods, it will light up much like a fiber optict lense- but also not as specific or direct, simply bent into different trajectories when one considers light as a particle...

MeshMasterMind

I believe this test need to be continued in a vacuum environment to eliminate the variables. This would give us the ability to see if the impact of the material is causing the flash vs. the gas that got compressed to a point that it exceeds the gas' flash point.

Alex G

I think it would be cool to try a "long exposure" of this in a completely dark environment. Since the brightest part of the flash is still so short, especially in the less than ideal gases. Maybe getting closer look with a very high resolution might reveal some extra details using the flash as its own lighting. Swap out the temporal resolution for some spatial resolution.

Adric Menning

Rusty ball bearings wrapped in foil struck together make a loud crack sound and a bright flash of thermite.

Adric Menning

if i was to guess he was remote desk-topped to another computer.

Adric Menning

My favorite Triboluminescence demo which may actually be piezoelectricity, is when you find the two most white/trance lucent dry river stones. and tub them together in the dark. you can get them flashing surprisingly bright just by hand. i think its the quartz dust being crushed. Probably does not help answer your problem, but you sound like someone who might enjoy it as much as smashing lifesavers.

Richard Glickman

I recently purchased a fire piston which compresses air to its flash point which ignites apiece of char cloth. Could the speed of the projectile produce a small volume of super heated air that gets compressed to its flash point just before impact? If so, you would get a flash no matter what the substance. 30 seconds after I posted this you started unboxing the fire syringe. What happens when the fire syringe has only room air in it. No cotton?

Lone Wolf Photography

I'm glad you finally mentioned the vacuum right at the end of the video. Try it with gas with no oxygen content and various pressures to see 1: if non oxygenated gasses will still flash, and 2: if the density of the gas has an impact on the brightness. Perform the rest of the tests with a glass marble to eliminate the variable from angle of impact and the possibility of the solid material combusting. My hypothesis is that the high energy transferred into the gas causes the gas itself to give off light, and the higher the density of the gas in the chamber, the brighter the flash. I think you won’t get any flash in a vacuum.

Johan Roux

So this got me thinking... What about the lightning that happens before earthquakes? https://www.youtube.com/watch?v=bYy-5-Pltec or https://www.youtube.com/watch?v=KzsRq9TjsyQ Could this be related? The shear pressure in the rocks, releasing electricity, snapping or compressing magnetic fields. This could translate to lightning being generated in the atmosphere. What about: https://www.youtube.com/watch?v=wcJXA8IqYl8 This is probably out of the box thinking, but similarities does exist, there must be some movement of energy at a more atomic level, translating into light. This could either be kinetic or electrical. the Life Saver Mints got me thinking this due to the color of the light.

Ryan Schweter

That effect definitely seems to be triboluminescence to me, as during an earthquake, fractures and friction in the rock are the mechanism at play. In the videos you linked, it was stated that 1% or less of earthquakes have the right conditions, which seems to me to point to the geologic composition of the region is critical, though I guess it could also be magnitude, fault depth, or other factors. The fact that the videos seem to show the clouds illuminated from underneath, would also point to this. I think the point you made about the color of the light is key, though. Without rewatching Destin's video, I don't remember any of the flashes being the distinct blues or other spectral emissions that I would expect from an electrical effect, or gaseous plasma. The handful of times where the image looks white, I suspect it's over exposing the sensor, especially since as the emission decays the plume appears to follow a black body sequence, going yellow -> orange -> red-> black/sooty looking. To me that says very hot particulates incandescing. The fact that the emission seems to follow the black body sequence nearly universally, regardless of composition also is mark against mechanoluminescesnce as from what I read, that is very material specific effect. I don't have time to try and pull and run the numbers, but I'd love to see what the energy density of the impact surface is, and compare the speed of sound in the projectile to the flash duration, both initial/peak and total to get an idea of the depth of the depth of the shockwave during the event. The only material that "knows" it's hit anything is between the shockwave front and the actual impact surface, and I suspect that the energy density there is more than enough to vaporize the surface, and create a particulate cloud.

William Beaty

Sometime physics teacher here. I recommend painting objects' surface with copper sulfate etc., or any other "fireworks chemical," to give desired line-spectrum colors. (re. 120V nails-in-potato with transparent agar block replacing the potato, include metal salts, strontium nitrate for magenta arcs etc. rather than sodium chloride.) I always assumed that this is just fire-syringe phenomenon, same as two ball bearings with tissue paper. Gas between surfaces is incredibly viscous because of boundary-layer physics, even behaving as a solid micro-layer. You want weird? I imagine that non-incandescent heating occurs everywhere constantly with this process. Perhaps only visible with NIR or with thermal cameras. How about raindrops impacting concrete or dirt? There should be immense shear-heating, immense velocities at micro-scale, and surface "asperite" materials aerosolized or even vaporized. But any flash might be invisible to humans. The raindrop surface wouldn't exceed 100C, but the solid surface below might heat far higher. Before wetting, do rainstorms produce sidewalk-flashes invisible to humans? What about hailstorm impacts? (I vaguely recall seeing reports of glowing hail-impacts at night!) And, the famous "petrichor" scent may require high temperatures, originating thermally? (Petrichor explanations never mention impact flashes or even include these micro-scale thermal issues. Today we think petrichor is well-explained, but maybe it isn't.) Nano-forests in the impact-heating zone easily vaporized, so perhaps a bit of copper nanopowder would always give blue-green flashes, with air or vacuum irrelevant. Or, impact two polished surfaces in vacuum, next compare with one being a soot-coated surface from burning paint-thinner flame. (Soot is a carbon nanoforest. Soot-coated Crookes Radiometer vanes, in hard vacuum, with IR laser shining, will incandesce. Analogous to impact-flashes! ) When messing with laser-sheets parallel to polished surfaces, I realized that boundary-layer gas is like viscous syrup, while the gas in direct contact with a solid, behaves as an actual solid, at least at the micro scale. Knowing this, all sorts of odd phenomenon become explainable. When solids collide, the sheared air layer *is* a shearing solid (like trying to shear aerogel.) Now try suspending some smoke plumes between two glass plates with 1mm separation, now try 0.5mm, 0.1mm, etc. The smoke is trapped in "low-Reynolds putty" made from air. (Now make a video display based on smoke particles moved by ITO transparent HV electrodes! Turned off, it becomes like an oil painting. Narrow-gap gas viscosity is WEIRD. ) PS To mix argon when air is present, your hose-tip MUST have a diffuser. Just a few layers of kleenex w/cable ties works great. That way the Ar is an expanding sphere, and not a turbulent jet which entrains the existing air. And, always let the air all escape out the top, since the tank provides cold heavy argon (treat it like a pool of CO2.) To test for 100% argon wo/air contamination, zap it with a little handheld tesla coil, to see the usual white-colored 6" lightning. Instead with a percent of air contam, you get obviously violet lightning, and it's far shorter than if you have straight Ar. (The infamous "1-ATM plasma globe" project of the 1990s was an open paper sack full of pure argon, with a handheld tesla coil stabbed into it from the top. Or, use an open glass flower vase of argon, excite it with an external tesla coil touching a piece of adhered foil, then stick your hand inside, so the lightning shoots out of your hand.) Remember "Hand-blaster balls," plaster balls coated with sulfur and potassium chlorate? Still sold!

William Beaty

Yeah, those "piezo quartz pebbles" sold by Edmund Scientific ...as a kid I realized that it had to be frictional heating, plus a transparent object to let the light escape from the crevice formed during impact. Also, it always produces a burning smell. Also, the flash is yellow-orange. Also, a direct strike produces very little light, while a glancing "frictional" blow makes a brighter flash. But I never tried it with glass spheres. Probably they need surface etching to work, #400 sandpaper-ground surfaces. Hmmm. For new colors, first paint yer quartz pebbles with copper chloride!

Justin Stockton

Can’t this just be ionized gas that was superheated when it couldn’t escape?

Arto Rantala

I don't think the effect requires combustion. The simplest explanation would be simply that the gas trapped in the impact gets compression heated to temperatures where it emits blackbody radiation in the visible spectrum, i.e. incandescense. It seems counter-intuitive until accounting for the incredibly short time period where it occurs. In an oxygen-rich environment, this heating can of course cause ignition of nearby available materials as a secondary effect.

J

I definitely think we need to see this in a vacuum! It really seems like it's got to be the compression of gasses to a superheated/ionized state. I wouldn't be surprised if combustion was not necessary to produce this effect. When pulling vacuum on the chamber, I assume you could do a burst disk or aluminum foil to seal the projectile opening? My gut says packing tape might foul things because of it's penchant for static electricity causing little bursts of light, but I've obviously never used it for this application before and it could work just fine.

Sergio Gingerich

I think that the flash common to all the materials is auto-ignition, this would explain the larger flash that was seen in the oxygen rich environment and the change in the argon atmosphere compared to air. Performing the shot in a vacuum could confirm this suspicion. With materials like the PC slug I think you might also be getting some triboluminescence, contributing to flash size. As for the "fart" that was most prevalent with the PC slug, could we be seeing some material combustion from effectively atomizing the face of the slug?

Gavin Sullivan

In simplistic terms the fire triangle is oxygen, fuel and heat. In my head I’m still wondering what the fuel is. The plasma hypothesis mooted below seems valid - but how do you prove that?

Gavin Sullivan

Also compression ignition is how diesel engines work no?

Ryan Schweter

That's a good thought, to try and quantify the flash brightness at peak.

Ryan Schweter

I hadn't considered boundary layer effects at the surface, and you're absolutely correct. All the more reason for a vacuum test. I still believe though that it is front surface ablation due to mechanical adiabatic shear in the time & zone before the Shockwave in the material takes the impact area away from the front surface, because of the charicteristics of the jet. I particularly love your idea of coating the impact surface with metal salts, strontium might be a good choice too because of its crimson emission is very distinct. That absolutely would be a telltale of whether the solid is contributing to the flash or if it is a purely gas effect. And on a sidebar, now I need to go dig into the atmospheric plasma globe you mentioned, it sounds so cool. I have a special place in my heart for cool science demos.

Josh Blevins

Has anybody already talked about the gases trapped in the things being compressed? All those things were manufactured/grown in an air rich environment. What happens if you take one of your resin printers and print those poly jobbers in a hydrogen rich environment? Or if you're too chicken to turn an expensive printer into the Hindenburg 2, use something else, but you'd be able to change the color of the full-body flash with different atmospheres in the printer chamber if it is, in fact, the trapped gases in the printed poly jobber being compressed to ignition. Print it in a vacuum and maybe no full body flash. (edit was the cat stepping on the enter key before I finished the thought)

Matt Holmes

Destin, I’m a LANL explosives scientist, shall I do a v7510 video of an explosively-driven argon flash for you? We haven’t used argon flashes for some time, but it wouldn’t be too hard to set one up for the heck of it on one of our shots and it would be good for us to dust off the capability. Sounds like fun. PM me. btw I think you're observing a shock interaction phenomena--the initial impact of the two solids generates shocks within the solids which, when they release into the adjacent free surfaces into the gas, raises the gas pressure high enough to be plasma for air, voila the light. An orthogonal shock by itself doesn't get the job done (sometimes it does, actually, on big/special explosives shots), but the two shocks at a close acute angle can cause mach stems and jetting, amplifying the pressure. Might be able to reproduce the phenomenon in a hydrocode, I'll ask my people. And careful filling a big box with oxygen man! Generally disadvised, especially if you're powdering wooden/plastic projectiles into the oxygen-rich environment with a ready ignition mechanism...

Chad Daulton

Is that a flame behind the baseball at 0:41?

JW King

Instead of a spectrum analyzer, couldn't you just use your existing video and analyze the spectrum using video editing tools?

Tom

The first thing I thought of when I saw this was the piezoelectric effect. I see other people have already posited that, though.

Marcus Hampton

I know very little about most of this, but here's my wild guess : Maybe the solid's own particles are the culprit, being compressed by the impact to their auto-ignition point, with a secondary effect being subsequently caused where the escaping air at the point of impact flashes a flame outwards based upon its oblique and surface topography along any path it can take. In the video, the first, clear polycarbonate seems to fully light-up, maintain its structure, then melt and splatter against the plate with the follow-through - something I can't see happening because of compressed gas alone, and certainly not transferring that heat through the entire volume, causing it to melt. Added to that, the plate does not appear to show the heated state necessary to cause this, though I suppose I'm not aware of the melting point of the polycarbonate used. In this same example, the light does not appear to be caused by fracturing but instead from superheating of the material. The glass balls in the "How Ridiculous" video show two interesting frames at impact. The 1st frame has a flash with a flattened lightning-bolt dividing the two halves of the right sphere, with the 2nd frame continuing that same flattened lightning-bolt as a more finely shattered glass section than the rear half. This further makes me believe that this may have nothing to do with compressed gas as the light seems to be emitted by an area within the volume and not along the surface nor as merely refracted light within the volume towards our eyes (as I first thought). Would be wonderful to determine the auto-ignition point of your specific, solid projectile and do the math to determine the amount of force required for compression to ignite the volume, taking into account that the plate will be bouncing back and supporting some of that heat. Then, you can test above and below that value to see whether the solid's compression is causing what you're seeing, though I'm still wondering if the flame isn't merely a secondary effect. Regardless, what a fantastic video, Destin! Greatly enjoyed watching and thinking through this one. So very thankful for you, my friend!

JW King

From studying the video, I'm not convinced that we are seeing a single source of light. I'm wondering if the initial flash on impact is from a different mechanism than the longer and more localized flame-like light seen later. I think your idea of trying a vacuum is excellent. Also, for all of your experiments where you are trying to fill the impact chamber with a specific gas, you might try sealing the sabot entry hole with plastic cling wrap. It won't slow the sabot down, but it will separate the gasses nicely. You can put a vent hole in the top or bottom of the impact chamber depending on whether the gas is heavier or lighter than air. As far a as a spectrum analyzer, any decent photo editing tool can analyze the spectrum of an image. So, you can just zoom in to just the area of the light and look at the spectrum of that image. Unscientific, but enough to show a change between different gasses. But yeah, to really nail down the science, you'll need a precise spectrograph to identify the fingerprint of the light source. For that to work, you'll need to thoroughly clean the chamber between shots to eliminate contamination. I've also been thinking about the problem you had with the wood sabot, and on other shots where the sabot was unstable. Can you lengthen and rifle the barrel? A little bit of spin would help a lot. Also, multiple barriers between the end of the barrel and the final chamber would capture more debris and keep the impact area clean.

Jeremy Grossman

Is this kinetic luminescence with a compressive luminescence factor? Or Compressive luminescence with a kinetic factor? Could you put an EM field meter in the box near the impact plate and show that next run? Curious what it picks up.

Ed Meredith

This may have been said and I am not knowledgeable enough to really comment but for my own education. All things made of atoms (everything) have either an electrical bit of energy, or if they do not…. They then can create energy with friction or impact. As small as flint and stone. I would love to see a possible episode about the green flash of a sunset because I have spent a majority of my life on the ocean and have seen in many places. So my question of the green flash would be, is it from a very short period of atoms in connection with our magnetic atmosphere, or is it something completely different. It seems like another impact flash to me. I would love to learn more of this

William Beaty

"1 atm plasma globe" started with my early-90s science listserver, when a user mentioned that the famous Radio Shack "Eye of the Storm" original plasma-globe wasn't vacuum. It was xenon. (Well, xenon at few tens Torr, to avoid unwanted heating and extra expense of 720 Torr xenon!) For those who could get argon, mine was a popular science-fair project in early internet years. 1998 page is http://amasci.com/tesla/heli1.html . Apparently helium works just as good, but the paper-bag must be upside-down! (We tried it with Ar-filled double-pane windows, but found too much air contamination. So, vent your argon windows, and purge it with pure Ar. Then zap with handheld tesla coil.) Every physics nerd needs a little 75KV "vacuum tester" bakelite tesla coil! They resemble a large-ish Dremel tool. Find on auction sites for under $100. Those recent Tesla-coil kits from china are more like 7KV, and I haven't tried them with the Argon-pool. Find a nearly-transparent trash bag. Add a tuft of steel wool, squeeze flat and purge w/argon a bit, squeeze again, then fill with pure argon, maybe one cubic foot ...then put it in a microwave oven. The resulting 20-second "light show" goes through several different stages. I've had it trigger standing ovations at physics lectures! I don't think it's yet on youtube anywhere.

Daniel Desio

So does this mean that you're modelling this phenomenon in your doctoral research of two bullets colliding? Obviously there's some kind of energy transfer going on, but I'm not sure if that's something you can model in FEA. Does the FEA occuring in a vacuum? Or are you making the assumption that all the energy of the collision goes into the two bullets and none is lost in other ways? Super interesting stuff, really looking forward to the next video on this!

Ben Kinney

I think we are seeing 2 separate phenomena simultaneously. I think the bigger cylinders are indeed shocking the gases to either burn or flash, but there were a few that didn't seem to ignite with a traditional burn, just a flash. I'm extremely curious if you could get a flash in a vacuum. And if so maybe we are seeing some kind of visible indicator of electron repulsion? Spheres and the curved edges of your cylinders impact with a lot of force on a nearly infinitismal surface area. I'd be curious to see some number crunches on that very first instant of impact and how it stacks up to all other nearby forces. I'm also curious you didn't bring up the ball bearing burning paper trick. I would assume something similar may be happening even at lower speeds and forces. Where just by the strength of your hands you can burn a hole through paper by slamming ball bearings together on either side. Maybe this holds a clue to what we are seeing in higher velocity situations with much more force. Edit: I thought about it some more. It is commonly known for electrons to produce flashes when forced to different energy states and since most of these flashes happen with curved surfaces striking it would mean a lot of energy in a very tiny area. I think another clue is how bright the How Rediculous glass balls were. Those were 2 round surfaces coming together at a single point, instead of your experiments being a curved edge of cylinder colliding with a flat surface. Once I thought of this I was reminded of yet another example of flashes of light from colliding bodies. Neutrino detection tanks rely on flashes of light produced by particles smashing into each other. Again, maybe this is a hint into what is happening.

Clay

Ohio has the worlds largest Vacuum Chamber 😏😏😏 God bless!

Andy Connelly

Destin - random thought at 2am… where do you store your supersonic baseball cannon? Does it sit just in your backyard? Lol

Daniel Michael

Short of doing this inside a vacuum chamber, please vary the tip design to make it better/worse at entrapping air at the tip. A slightly concave tip to prevent air escaping out the side; assuming a tangential impact. Conversely, holes drilled diagonally from the tip back out the side should provide an escape route for the compressed gas. Alternately, a large concavity, or hallow tube may have too much volume to build to sufficient pressures to produce light (via temperature & black body radiation?). With lots of design could you produce a hallow impactor who's walls roll inward, maintaining a seal until a larger volume reaches luminescence; effectively a shotgun powered fire syringe. To test whether or not this has to do with blackbody radiation, is it possible to do a spectrum analysis with something like a high speed camera? Put a diffraction grating in front of the camera?

Ryan Schweter

That's awesome! Gotta try that wool demo.

Alexander JB

It seems likely to me that there could be multiple phenomena happening simultaneously, though which ones Im not sure. Much of that hypothesis is based on the comparison between the polycarbonate in argon and polycarbonate in oxygen. While there is a speed difference, between the tests, those flashes were qualitatively very different. The argon flashes appeared to be localized to the material, while the oxygen seemed to ignite the gas. Perhaps, in an oxygen rich environment, the gas flash is brighter and overpowers the material flash?

omlet boi

Just a thought, In the transparent poly carbonate it seemed like the polycarbonate lit up before the impact flash. Im not sure if the transparency is truly acting as a lens like you said. I would love to see a round that was half opaque on the side of the impact and was transparent on the other side. If the transparent side still lights up then I dont think its acting as a lens. I think its possible it could be something called Bremsstrahlung Radiation; where an electron during a sudden deleceration losses enough kenetic energy that it produces a photon. Although im still not sure if that would explain why we only see it on transparent rounds and not the opaque rounds. I am by no means an expert on anything but I think it could be worth checking out.

omlet boi

This is excatly what I was thinking, as soon as I saw the polycarbonate light up on Impact I immedatly thought of Bremsstrahlung Radiation. I'm glad to see someone else who thought of it to.

Ashley

# Why I think this is happening I also think its the gas igniting from compression. I think the gas pressure goes up near the point of contact because it cannot move out of the way fast enough. # Schlieren photography I really wanna be able to see how the gas is moving around, you could try imaging it with schlieren photography. # Repeat experiment in vacuum method #1 You'll probably need to re-manufacture a box for that to get a good enough seal. Including the shotgun in all that may be complicated, but maybe you can avoid doing that by sealing the bullet entry point with some membrane, similarly to what you did with the supersonic baseball cannon. Except it'll be in reverse now with the bullet entering the low pressure environment not exiting it. # Method #2 Oh or better yet, just replace the shotgun with the same type of system you used for the supersonic baseball and expand the low pressure environment of the barrel to also include the box. # Method #3 Just make a scaled up fire syringe. Either by adding a transparent tube to the end of the shotgun and sealing that shut, or by changing the system to that of the supersonic baseball cannon, but made out of a transparent tube with the end shut closed. This seems a bit dangerous, I don't know how you could avoid the tube from just shattering from either the launch of the projectile or from it stopping. # Experimenting with different projectile shapes I think you might be able to get more consistent results if you machine down the end of the rods to be round. This way the contact surface will always be at 90 degrees and the immediate envorinment of the ignition zone will stay the same as the spheres shape isn't affected by rotation. Additionally you could try just sharpening it like a pencil, or hollowing out a conical cavity in a bid to increase the pressure even more by scooping up air.

jahr

I got my stickers today and they look awesome Destin! Crossing my fingers that this flash topic could be in the next batch

Robert Lund

im not sure if you've seen it but VSauce has a short about 2 metal balls colliding (https://youtube.com/shorts/-hzue8KIS9M?si=rL0Nk3Xkctu-aSAL) this may be a low-energy replica of the same event. but im with you on the belief that this is caused by the gasses between the projectile and the target surface. Keep being awesome!

Joe Schneider

Have you seen the latest Slow Mo Guys video where they shot panes of glass with 30-06? The flash correlates to velocity. And they caught the reflection on panes of glass behind the pane of impact. If you mimicked their setup, you could shoot a piece of glass that has a mirror behind it. If you set the focus to the mirror you could have a better view of the impact. You’d have to figure out a shooting angle that’s not obscured by the projectile. Would certainly add more data points. Link: https://youtu.be/05-ceCK5e9U?si=p_HUIn6FXjED1K8L

Chad Daulton

I am watching this video now and came here to make the same comment.

Nate Hoppes

Hey Dustin I know the odds of you seeing this are slim, But could you ever do a slow mo video and breakdown of welding processes. It is a part of almost every industry in some form or fashion and would be cool for the world to see/understand what is happening.

TobFal

The very first thing I thought of doing next is a spectrum analysis. A Planck Distribution would indicate that the flash is being linked to temperature related radiation. And emission lines could show which elements are maybe burning in there. I don't know if it is possible to do a spectroscopy of such a quick event with a standard spectroscope though.

AE5EZ

Some of the gas in the first of the polycarb shots, appeared to behave like plasma. one even had a jet to the upper right.

SqrlLrd

A good test of compression vs fracture would be to flood the tank with a gas that is not combustible and use the marbles again. That way you can rule out the gas’s burning and see if the fracture in the marbles is your light source. Also I believe that glass at this speed of impact will behave more like a crystalline solid than a liquid because it will not have the time to deform and will fracture along the silica structure of the glass. I am firmly convinced the yellow flame is the combustible gases being compressed to the point of ignition by the pressure wave in front of your projectile. To test this shoot slower and slower projectiles until the flame is not produced. I don’t know the math but I would see if there is a way to calculate the speed, surface area of the projectile and the density of the gasses to find the compression at point of impact, and use that to calculate the temperature this would produce. Does it hit the flash point for the gasses involved. I keep thinking that this is basically the way diesel engines work just without the cylinder walls using gasses with a higher ignition temp. A last thought is the heat at impact possibly creating a flash of plasma as the materials make contact, sublimating the material at point of impact if the energy involved is high enough.

Rosuav

Definitely wanna see this done in a vacuum! My thinking is that it's compressive heating, and it's not "igniting" or anything, just getting to the temperature necessary for blackbody radiation in the visible spectrum. If that's correct, there should be no flash in a vacuum, since there's no gas getting compressed.