Trying To Solve The 150 Year Old Mystery

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[@runcycleskixc]

Kind of amazing that they know how to detect the Higgs boson, but do not know how this basic device works.

[@sFeral]

perplexing for me as well

[@brianfhunter]

Simple, but not basic... Its like a double pendulum, is VERY Simple, yet, produces chaotic results.

[@gljames24]

Because of the scientific community's focus. There are only so many research dollars to go around and a fundamental aspect of the universe has higher priority than a desk toy. I'm not trying to say that in a snobbish way, moreso cynical. I really like the guy who spent 20 year solving snowflake formation.

[@Nathan-dt2tu]

To be fair, the Higgs is a controversial topic. It was confirmed in 2012, but along that way they observed many unknown boson-like particles, and even one that was 10 times the mass and is unexplained. I'm not convinced we "found the Higgs and solved mass attribution" and probably more "we opened an entire new world of particles and had only predicted one of them." Pretty damned sure our Standard Model is still incomplete as best.

[@omargaber3122]

Israel kills scientists The Israeli occupation forces, using American and European weapons, killed the great scientist Sufyan Tayeh, who was considered one of the top 2% of scientists according to Stanford University. Tayeh, who was president of the Islamic University of Gaza, was a leading researcher in physics and applied mathematics. Israel killed him and his family, consisting of his wife and five children

[@xionix4]

I used to have one of these as a kid. I always assumed the light heated the black side better, which heated the air causing a small local pressure increase, which pushed it. I had no idea there was so much to consider and that it had stumped some of the greats. Thanks. :)

[@PowerScissor]

Did yours spin as slowly as the one in the video? If I pointed a flashlight at mine (way less than 100,000 lumens) it would be a spinning blur. Definitely not even close to slow enough to count seconds per rotation.

[@miguelalonsoperez5609]

@@PowerScissor the original radiometer is at lower pressure than the vacuum chamber of the video: that explains why it turns so slowly

[@xionix4]

@@PowerScissor Interesting observation. Though I don't remember ever shining a flashlight at mine, it also spun very quickly especially in sunlight. There could be many reasons for the discrepancy... I did notice that the light seemed about as bright as my 1,300 lumen light, but I assumed it was due to the camera. Also, perhaps LED light has a considerably different effect than sunlight or the light from an incandescent bulb (such as I had seen my radiometer respond to). I would first guess that it was due to lower pressure in the constructed chamber than the original.

[@xionix4]

@@miguelalonsoperez5609 I am of the presumption that the radiometer in the vacuum chamber used was operating under lower pressure than when contained in the bulb, since I had read specifically that they are designed with a "partial vacuum," and that an absolute vacuum would not allow them to work. It was also stated that the vacuum in the chamber was at "0 bar" and "the lowest [...] can read [...]."

[@miguelalonsoperez5609]

@@xionix4 in that case may be the opposite: I don’t know which is the optimal pressure to produce the rotation effect, but nevertheless I suppose the one inside the bulb is better calculated to maximize the soeed

[@chaos.corner]

The non-spin of the holes is a result that seems like it's worth pursuing. If you know why that stops it spinning, you might know why it spins without them.

[@Nathan-dt2tu]

His radiometer already spins quite slowly, and punching those huge holes shrunk the surface area by around half. He'd need to pull a tighter vacuum since his friction is non-trivial.

[@dragoscoco2173]

@@Nathan-dt2tu A tighter vacuum would be worse.

[@Nathan-dt2tu]

@@dragoscoco2173 Tighter vacuum is how the toy version is made, and makes it spin faster. You are correct though, as you keep going tighter still, the spin would start slowing down and eventually stop working.

[@omargaber3122]

Israel kills scientists The Israeli occupation forces, using American and European weapons, killed the great scientist Sufyan Tayeh, who was considered one of the top 2% of scientists according to Stanford University. Tayeh, who was president of the Islamic University of Gaza, was a leading researcher in physics and applied mathematics. Israel killed him and his family, consisting of his wife and five children

[@maxweber06]

​@@Nathan-dt2tu I wonder if the extra holes introduces turbulence that equalizes the force, because I don't really buy that halving the surface area would cut the force so much that it couldn't overcome the static friction.

[@KaiseruSoze]

Here's something else to try. Replace the squares with disc's where the center is white and the outer ring is black. Hold the size of the center constant while varying the surface area of the outer black ring. Record results. Swap the white and black parts and repeat. Record the results and compare.

[@hassanaffan3012]

this sounds like something i would write in an A-levels physics exam

[@racghineering]

😆

[@Nathan-dt2tu]

I'd modify your idea a bit. Keep the surface area of the inner disc and torus to be equal. Then somehow ensure a uniform light source, perhaps with a laser and an accurate lens to ensure every part of the disc is exposed to the same lumen level. As you proposed, run the experiment with the black on the outside and the inside and record results. One revolution isn't enough for accurate results though. He should be timing how long 10 revs takes, or recording the number of revolutions in a full minute or more. If a proper physics lab were to do it, they could track one of the vanes and have the light source follow, keeping constant focus on the disc itself. I also wonder about the materials used in making the vanes, because I'm betting they don't stay straight when exposed to the light. There must be one side of the paper that's expanding more than the other. Black on inner vs outer part of the vanes could contribute to more or less bending, and then the shape of the vane needs to be considered since a sail is essentially being created.

[@CheffBryan]

@@Nathan-dt2tu So yet another direction to test; convex for black or white, and then what change would a cone shape have, what about using spheres, so on

[@advaitrahasya]

Hot side imparts more kinetic energy to the gas molecules than the cold side. Intensify the vacuum.. Then not enough molecules for it to work. Let the gas get more dense, and faster molecules on the hot side get reflected back, along with their momentum.

[@TentoesMe]

In 1968 or 9, I was 10, and the teacher showed us one of these. Then we read in the science book about how it worked because of the photon pressure. "Interesting," I thought. I looked back at the radiometer. It was spinning the wrong way. I raised my hand. This observation resulted in an argument and me in the principal's office. I couldn't believe I was the first to notice it spins the wrong way.😉

[@codetech5598]

It works because of Quantum Mechanics and Relativity because Einstein was a genius. 😜😜

[@herseem]

I'm really glad to hear that story, and I doff my hat to you for challenging what was said to you when your common sense could see it was wrong.

[@PaulMarostica]

@@codetech5598 It worked years before Relativity and Quantum Mechanics were invented.

[@codetech5598]

@@PaulMarostica But it works better with QM. LOL

[@PaulMarostica]

@@codetech5598 I would phrase it differently. The device works in reality. You think Relativity and QM explain better how it works in theory.

[@geoffgunn9673]

It would be interesting to try vanes with vanta black and the whitest white to see if that has any effect.

[@ianng4633]

You need to make sure the rotational momentum & CG are the same between the ones with slits/holes punched/solid, i.e. if you punch holes you will need to make the paper longer, and if you cut slits you will have to stack them horizontally. Also, the hole punched might not work because it might caused local circulations and negated the effect but that's just a guess.

[@MitzvosGolem1]

True rotational moment of inertia less for vanes with holes.

[@mikefochtman7164]

And perhaps cut the slits radially instead of along the axis of rotation. That way the mass doesn't move outward changing the moment of inertia or the moment arm of any torques being produced.

[@Intrafacial86]

You might be on to something with the laser. Maybe try making both sides dark but have 2-3 lasers set up around it that only hit one side of each vane as they turn. It could also be interesting to design two radiometers with a layer of material between the two sides of each vane. Make one where the material has high thermal conductivity, then another where it has low thermal conductivity. See if that has any effect on the speed of rotation. Maybe do this again but also with the first suggestion, making both sides black and aiming lasers so they only shine on one side of each vane. And on top of all of this, vary the vacuum pressure within the chamber to look for any sweet spots for maximum speed.

[@Jim-kz7vr]

“Every tool is a hammer, except screwdrivers. Those are chisels…” I’ll add files to that category as well 😂

[@starsixtyseven195]

A file is not sharp and will snap

[@mindnumb]

Screwdrivers can be chisels, but they still make damned good hammers.

[@robertlawson4295]

Don't forget that screwdrivers also make good pry bars.

[@christeanaz]

Great experiment on the Crookes Radiometer! You might find the 'orbital repulsion force theory' intriguing. This theory suggests that when electrons in the vanes' material absorb light, they jump to higher orbitals, momentarily increasing the molecule's size and creating a repulsive force between adjacent molecules. This force could be what drives the vanes' rotation, rather than just air pressure differences due to heat. To explore this theory in your experiments, you could focus on observing how different light intensities or wavelengths impact the rotation speed. Since electron orbital changes depend on energy absorption, varying light properties might yield different rotational behaviors. This could provide insights into whether the rotation is driven more by molecular-level quantum changes than by macroscopic thermal effects. Love the channel ❤

[@Snakyy1]

I don’t think this is the reason. He held a massive flashlight which covers the entire area and multiple squares at once and a small laser but they both turned at the same speed. That also goes against the one with holes not working.

[@tristanboyle4450]

good to try in an inert gas like.. argon?

[@christeanaz]

​@@Snakyy1Good point... It's possible that the radiometer's response isn't just about light intensity but also other qualities of light, like polarization, coherence, and spectral composition. Different wavelengths, light coherence, or even the way the light is polarized might interact with the vanes in unique ways. This could explain why varying the light intensity or using a laser didn't significantly change the rotation speed. It's a complex interplay that might go beyond just the brightness of the light

[@danpowell3953]

Totally agree that the wavelengths of light might make a difference, especially infrared or absorption frequencies.

[@smoothmove7566]

I know when you put it in the window in direct sunlight, it really starts winging along. so I'm going with it's a heat windmill.

[@mikemartin6165]

These light mills work on air molecules. Too much air in the chamber and the light makes the molecules bounce off of each other creating a neutralizing effect. Too little air in the chamber and nothing happens. With just the right amount of air, the molecules bounce off of the black side where they receive more energy since the black side is hotter than the white. The white side reflects more light keeping it cooler. The radiation forces from the reflected light is not enough to cause movement. That's why it spins away from the black side.

[@KAFKUBA]

Add a tiny serrated edge around the perimeter of the squares... this will increase the edge path length... punching holes and cutting into small sheets decreases surface area and hence speed

[@PhaedruS007]

The black and white squares are the same article. Can't trim one without the other.

[@KAFKUBA]

@PhaedruS007 you're right... but same answer!

[@VinitR]

3:40 Betterhelp is asking for trolling if they allow text. I can imagine someone automating Chatgpt to be on the other side.

[@JimGriffOne]

My guess: At the surface, diabatic heating will transfer energy to the air molecules in very close proximity to the vane, imparting kinetic energy to them. Due to there only being 180° of a cone those molecules can travel due to the vane being in the way, an equal and opposite reaction occurs. The molecules transfer some of their kinetic energy into the vane, moving it in the opposite direction as the molecules lose that kinetic energy and cool to a lower temperature. I guess there will also be some complex vortex physics going on at the same time caused by the vanes spinning around and displacing the air - something I don't know much about.

[@JimGriffOne]

In addition: What would be interesting is if the aerodynamics of the vanes were changed (the shape itself), so the air could flow easier around them as it spins. Then you could paint one side and see whether you can get it to spin faster. Having a more aerodynamic 3D shape might help to prove/disprove any theory out there.

[@robbbbery]

I wonder if you could use Schlieren imaging to observe the air movement that the hypothesis proposes

[@whatitmeans]

when studing engineering I tried to make a Crooks' radiometer with tiny slim magnets as vanes, in order to generate electricity on a coil... it was a huge failure lol, it cost me one semester... but I learned to work with molten glass, which was cool.

[@GeoffryGifari]

Is there a list on physics problems like this that don't _seem_ too hard to solve, but do?

[@TheDrapetomanic]

Good question, I'd like to know this too.

[@dominikmilien]

Every problem is an easy one, depending on the level of your knowledge.

[@satyaprakash03133]

Try Princeton problems in Physics..

[@GeoffryGifari]

@@satyaprakash03133Thanks! I'll look into it

[@francescotenderini1489]

Black surface absorb more energy than white. This cause the air directly in contact with the black face to be cooler than white. The air pressure is higher on the black side, pushing it foward. The delta pressure is so tiny that the contraption needs a low vaccum to overcome the drag force. Punching holes cause air to move through, highly reducing the push force that becomes less than the drag force needed to start the spin. Increasing the surface, by cutting in half the faces, increased the drag force, thus reducing the speed.

[@peceed]

Explanation is very simple. Dark side works as a piston. It locally warms up the gas, that is accelerated after contact with surface. But you need to use particle model in your mind. Free path in low vacuum has to be big enough. This way "hot" faster particles have a chance to escape far from surface before thermalization, and there is no isolating layer having gradients of temperature close to black surface. The device works in the regime where gas can not be considered the fluid (ideal gas). In the statistical sense all you need is to have a lot of cool gas particles that hit hotter surface. Hot particles can create backpressure, but it will be smeared and that pressure will also act on silver sufaces. Additionally most of the cooling will happen on the surrounding glass surface. So the colder glass is, the more efficient "engine" will be. Gas inside bulb is not thermalized - distribution will be a sum of few almost thermal populations with distinct histories of the last contact. There will be black populations, silver populations, side populations. The longer history history you will consider as population division, the more thermalized subpopulation you will have. For example: Glass-Glass, Glass-Black, Black->Glass, Black-Particle, Particle-Particle, Mechanism of the force generation starts in the exactly same time when most of the drag components dissaper, so that correlation could be additional difficulty for researchers because it coud hide the true nature of phenomenon. Holes obviously won't help. (PS. I was smarter than Einstein - just in my own way ;) )

[@guytech7310]

1. I recommend putting a control top in the same vacuum box you are using as the vacuum might be different 2. Try different gases: Helium, Argon, CO2 to see if the residue gas mass has an impact on the speed. 3. Instead of black use a color paint. & use a light source that is reflected (ie same as paint color) & a different light source that gets absorbed. 4. Try a cone shape blade & do two tests, reversing the color of the sides. The cone shape would like impact the direction the gas molecules. 5. Try different materials. For instance a metal versus glass\mica which has an low thermal transfer coefficient.

[@smoothmove7566]

I was gonna say Hydrogen.

[@LK-mb9hz]

AIr molecules meeting hot/fast molecules of radiometer have higher momentum after impact with hot/fast molecules of radiometer. In law of conservation of momentum radiometer fins have opposite rotating momentum. It works only in low pressure because viscocity of air increasing (with pressure increasing) faster than momentum. And in atmospheric pressure viscocity of air is too high (air resistance too high) for any rotation. Also may be at higher pressure free path of molecules can be too small to take hot/fast molecues far from fins.

[@andymouse]

Nah, if it was that simple you wouldn't see a video on it, you air pressure and momentum stuff was ruled out decades ago.

[@LK-mb9hz]

​@@andymouseIt is only assumption. It can be checked by two experiments with different thermal conductivity of fins. Cupper/silver fins will have same temperature on both sides and will rotate slower, than foam plastic fins

[@kosuken]

the guys at the action lab are the kind of people who can solve a 150 year old puzzle

[@Dee-nonamnamrson8718]

They didn't solve it, just displayed evidence against the prevailing hypothesis.

[@NitramGTi]

There’s more than one?

[@visualchallenge2413]

I have seen in another video that the rotation depends on light color : with one monochromatic led light it turns and with another LED with another color it doesn't turn even if you augment its intensity.

[@johnrobinson523]

i recall one of these in my science class when i was younger. It sat on the window sill and when the sun hit it - it would spin very fast. I was sure it was the heat given off of the black side that made it spin; as like a black car and a white car in the sun. the heat may create energy or change the structure of one side of the metal. Try with plastic or even circles. great video.

[@zeuso.1947]

I have always assumed the same. I never knew there was a question. That's black body radiation.

[@russchadwell]

Try Infrared. (Need a material allowing it to pass through though) Wire the IR emitter onto the inside? Ultraviolet. X-rays. Gamma rays, lol Stuff other than completely visible light.

[@PhaedruS007]

It feels like holding the laser in place and letting successive black tiles pass in front of the beam would work better. Also try 2 beams- one on the white and one on the black.

[@TubeNotMe]

Fascinating! I say it calls for more experimentation! Is there a way to get higher vacuum? See how different levels affect it? If it's a heating effect, why does a small light of the right wavelength have more effect than a powerful white light? Does violet or ultraviolet produce that much more heating?

[@nikthefix8918]

Photo-electric effect and interaction with Earth's magnetic field?

[@LoveDR91]

Love your videos, man!

[@CoughSyrup]

I own one of these. After playing with it, I noticed something interesting: Moving it, touching it, bumping the table or any source of vibration will cause it to spin, sometimes quite rapidly, and that it only ever rotated one direction. This leads me to believe there is some etching in the cusp of the glass, where the tip of the metal sits, that prevents back rotation. Or said differently: it allows it to only turn one way. It functions as sort of ratcheting mechanism, that prevents backwards progress. In this way, it essentially translates random motion or vibrations or an oscillatory motion--any of these--into forward-only rotation. This doesn't fully explain the radiometer, but it requires less special or magical behavior from the vanes: It doesn't matter if the forces on the vane, each direction, ultimately cancel out or are symmetric. So long as the forces happen at slightly different time offsets, or is oscillatory, then it will rotate in the forwards direction.

[@smoothmove7566]

or the fins are slightly tilted so they are not straight up and down and it works like a windmill, hot air rises and turns it. The black and white is just there to throw you off.

[@nikthefix8918]

If there was such a ratcheting mechanism then perhaps unbalanced thermal expansion would be enough to accumulate a rotation - especially as the expansion would be a bit like a bi-metallic strip causing a bend and subsequent rearward shift of the vane centre of gravity.

[@anzaklaynimation]

I liked this new format of the video. Good luck, keep it up.❤

[@JasonAStillman]

It didn't know this was still a mystery of sorts. That explains why I always have this puzzlement when seeing this device, having heard various different explanations for how it is claimed to work. So thanks! I'll take a mystery over an ambiguous claim any day!

[@shakdidagalimal]

The light heats the black side and in turn heats the thin air next to the black side more than the white side, thus the expansion of the thin air on the black side pushes against it in the contained area. If the air is thicker the friction of the air molecules and density prevents the push force from being enough to turn and "wind" the air movement enough to allow spin. So it is merely heating thin air molecules off the black surface which expand and thus "push" the black side.

[@codetech5598]

When you tried it in the vacuum chamber, there was no globe. Maybe the globe is important because of the way the air swirls around the inside.

[@chaos.corner]

I was wondering the same thing. It's possible the globe is an important part. It should be possible to get the globe apart such that it can be reassembled.

[@codetech5598]

@@chaos.corner I think the globe directs the air flow like the glass chimney in a "hurricane lamp".

[@smoothmove7566]

@@codetech5598 and the blades turn like a windmill. That's my thought.

[@valiantwarrior4517]

Thanks for the video. It seems really important for science to be able to explain things like this. It makes it obvious that we have gaps in our understanding.

[@MichaelPohoreski]

Science is a complete clusterfuck of ignorance with tiny gaps of knowledge interspersed throughout.

[@cyb69]

Would've liked this to be a little more scientific. Theres a ton of potential errors. Next time maybe mount the light sources and get better measuring equipment for the vacuum.

[@andymouse]

You realy don't get it. He understands the scientific method probably better than you and this is a 10 minute KZbin video, its educational not ground breaking. One thing even an idiot can take away from this is that if Einstein and Maxwell struggled with this then holding the fucking light in a mount aint gonna help !

[@SurlockGnomez]

My guess is it's the expansion of the heat off the surface that then pushes the surface away. As the material would have a heat resistance above that of the vacuum, the easiest path of the energy/heat to go is away from the material thus pushing the material away.

[@SeeWhatIs]

I think the light bounces many times forward and backward in case of dark material and it sums to less Newtons in one direction. In ideal case the light bounces once on the lighter material

[@jlfqam]

you can combine this experiment with the ionic thrust, both use the same principle, one creates a thermal vacuum, by giving energy to air molecules that is bein replaced by sorrounding, low vacuum air, and the other an ionic vacuum, ionizing air molecules that are repelled and the vacuum filled with sorrounding neutral air molecules, If you can coat the plates of the radiometer with a thin electrical conductive layer of metal and plug it to HV you should see the same. Eventually you may see opposite rotation, depending on the metal coated surface.

[@richarddeese1087]

Thanks. If I were trying to solve this, I'd have otherwise identical radiometers, & only change certain configurations: colors, holes, etc. Put them all side by side in the same light source, & see what they do. Just manually shining a laser on it is iffy because you're trying to follow it around with your hand motions, which can't be standardized, & therefore represent an uncontrolled variable. tavi.

[@DavidvanDeijk]

actual science in the making. good on you for trying these different things to see if there is an effect. would have liked to see you shine the laser on the white parts also.

[@kamalmichael]

It's the same unknown side force you get when you shake sand up and down with a speaker at certain frequency. The speaker moves up and down, the sand moves up and down but an unknown side force acts to push the sand into lovely patterns. I think you should do a video about this.

[@chaos.corner]

It's just random movement. The nodes are where there's not much vibration so the sand settles there.

[@tsm688]

There is nothing mysterious about the force. The sand bounces around when shaken in a random brownian-like manner. The lines appear at zero crossings -- the only places that **AREN'T** moving. The sand can't bounce away from those spots.

[@serenarose54]

could it have something to do with the corona charges being directed outwards? when you cut slits, they were still relatively pointed outwards but when you punched holes, the corona discharge was also directed towards the centre. I know paper is non really a good conductor but you know how it still shows some interesting properties related to static electricity. And you know the photoelectric effect. when a light shines on a METAL surface, photons are released. I'm not sure if paper has electrons in it. (sidenote: if not, it'd be cool to experiment with different papers like charged paper, wet, soaked in oil, burnt, different colors, double layered, possibilities are infinite) But I've seen plasma thrusters. Idk it could be all these things but in a very microscopic scale kinda like how the universal gravitational constant is so small.

[@Drone256]

It actually won't spin in a complete vacuum, so you were low but not zero.

[@mytube001]

He only said that it read zero, not that it was zero. They're not the same thing, and he knows that.

[@mytube001]

He only said that it read zero, not that it was zero. They're not the same thing, and he knows that.

[@Drone256]

@@mytube001 You are correct. I was aware of exactly what he said and did not mean to imply otherwise.

[@mykhailobasiuk4147]

I think the moment of inertia does play the role here - how fast you can reach top speed of rotation. For each point I = m * R ^2, but power advantage is proportional to R, so R / R^2 = 1 / R; the same mass and square should accelerate to max speed faster if they closely distributed to center. So cutting with /\/\/\ shape and moving closer will help until it reaches the max speed, which is limited by friction on top. I think drop of lubricant / type of lubricant / how much or lubricant is used (to not create more friction in edge case) is what can make difference.

[@wk2006sg]

Interesting. Cutting the vanes may have reduced the temperature on the black side and hence reduced the temperature gradient, which is the main driving force. We have so many physic models that can simulate the outcome of many experimental results with high certainty but not so much on this old science toy. Here is another paper on Crooke and Hettner radiometer DOI: 10.1088/1361-6552/ac420b

[@jozsab1]

I wonder if flushing the chamber with different types of gasses before creating the vacuum would have an effect. Maybe sulfurhexaflourid ? Maybe cold Helium ? ( just extending some other comment idea where the conservation of momentum would be the reason of rotation )

[@jozsab1]

Spent a bit more time. There are indeed so many theories why this thing moves. I got so curious if the effect can be amplified ( faster / stronger rotation ). Will adding more sails make the rotation stronger ( maybe not faster ). Will extending the radius of the sails make the rotation stronger ? Is there a limit to the rotation speed ? ( some say it depends on vacuum level ). Does the material of the sails have any impact ? What if the white is repulsive to the gas and black sail is attractive ( like the capillary effect ). But than why does it rotate backward at lower temperature ? Why does it even have an equilibrium temperature ? Will the sails slow down after a while or indeed turn forever. If you add more drag ( friction), would it convert the heat to.. heat ?

[@jozsab1]

I failed to find videos, but in theory the Hettner radiometer would prove the thermal transpiration effect.

[@MrLikeAsatellite]

According to (German) Wikipedia the (obsolete) "edges" explanation is from 1879. As far as I understand nowadays it is considered that the bouncing molecules on the surface are the driving force. That's why a reduction of surface area by punching holes results in no movement, and why producing more edges do nothing.

[@Sanabalis]

How about trying the experiment with different internal air temperature? What about tiny needle-punched holes instead of big ones? How about perforating the edges so they have longer length while keeping surface area near identical? What about using long thin rectangular strips instead of squares? What about different "blacks", for example Black 2.0 or Vantablack?

[@DLWELD]

I had one of these as a kid, put it in the sun, and added several mirrors - man, did it spin fast, Added a concave shaving mirror. The best! Got a small puff of gas and it never worked again.

[@rjung_ch]

The volume in the small vacuum is different, thus the delta needed in a bigger space would be more. If the space were minimized in some way, to the same volume within the bulb, that could maybe work better?

[@Jim-kz7vr]

If the action/force might be acting on the outside perimeter, I wonder if making the edge notched would have an effect. What if you cut zig zags on the outside?

[@KastorFlux]

Try aluminum foil vanes with those fancy black and white paints you were experimenting with before. Try a frequency of light that isn't absorbed by the atmosphere and the clear cover over the vanes. Ooh, try that camera trick to see air currents where you shine a point light source at the edge of an object. That last one might be hard since the blades would clip in and out of the focal point, but maybe with a high speed camera and frame rate tricks something awesome would show up?

[@dragoscoco2173]

There is sadly very little air for currents to be seen, but it would be a nice try.

[@KastorFlux]

@@dragoscoco2173 nice try bot.

[@dragoscoco2173]

@@KastorFlux As a GEN6 bot I am trained to understand the amount that 1-3 Pascal pressure contains in amount of gaseous molecules in a given space. Are you?

[@KastorFlux]

@dragoscoco2173 bleep bloop bleep. Computing... we can detect single OMG particles smacking the atmosphere at nearly light speed with simple detectors. Filming perturbations in gasses is not hard, and the methods are well known. Ask your developers to augment your training model with less reddit and more elementary school science text books. It'll make you much more engaging in comments on edutainment videos! Bleep blop bork, computation complete! Press any key to continue.

[@dragoscoco2173]

@@KastorFlux I detect a Logical menage a trois incoming. Reboot.... The Schlieren camera is based on various densities of the tested air sample being present to observe the effect. At 1 atmosphere you need a few tricks to make it visible. If your pressure is 10000 times less the contrast of it is about 10000 times less thus hard to observe. My neural network based intuition does not exist but my knowledge base has quite a few examples of it. And the focal plane is not a problem as it can be made as large as any water based creator entity likes.

[@contessa.adella]

I’m gonna make a simpler proposition. Light rebounding from the white side is not like billiard balls transferring momentum, the light is being re-emitted…sending its momentum away with the photons. The black side absorbs the photons taking upon itself their momentum also…which is a vector quantity so the direction and amount of momentum pushes on the black surface. ….An analogy…imagine the hard heavy billiard cue ball (photon)smacking into a small cardboard box (black vane)…it does not rebound, it goes into the box and is absorbed by it, and pushes the box on in the same direction. A stone box (white vane) can’t absorb the cue ball’s momentum vector and doesn’t move…yet sends the ball (photon) back the way it came (reflects it).

[@Hescor_Nellse]

You could also use a high speed camera (The Slow Mo Guys / SmartEveryDay) to figure out the thermal circulation works within the device. Both channels have done something like this in other contexts, but I hope it would work here also. Maybe a collaboration between your channels of some sort.

[@francoislacombe9071]

My guess is that the black side becomes hotter than the white side, and air molecules hitting the black side get more energy and more speed as they bounce off, imparting greater force on the black side and spinning the vanes. Basically, the hotter molecules on the black surfaces kick away the air molecules with greater force, thus producing a greater reaction force and making the device spin.

[@SureshKrishna5]

I am a Commerce graduate and yet I am here just to listen to this guy.

[@ishaangarg7188]

Same

[@kevinthealienfpv]

My best guess is thermal expansion? And it has to be in a vacuum because the force exerted by the expanding air wouldn't be enough to overcome air friction? The problem would be that with less air inside to slow down the vanes, there would also be less air to expand. It definitely seemed like the total surface area had a noticeable effect. Maybe that's why it wouldn't move after you punched holes in it?

[@jww24]

You appear to have forgotten about the increase in radial inertia required to rotate the veins after splitting them, Yes you increased the surface area, but you also moved half of the area further from the centre of rotation

[@Tsudico]

Perhaps the split should have been from the outer edge toward the inner edge so the two halves are arranged vertically?

[@melody3741]

@@Tsudicothen its the opposite problem lol. We aren’t trying to spin them no matter what, we are trying to get data

[@bobair2]

I do not know how it works exactly but it sure is an elegant looking device and one I like seeing.

[@Mysoi123]

I think I'm still satisfied with the fact that light carries momentum. Although light does not hit the blades directly, but through a mysterious process with the air, the main cause for the heat arises from the transferring of momentum by light.

[@sg9222]

You missed the part where 'better help' sell their customers sensitive data to zuckerberg

[@MaximKhantaev]

Obviously, what makes them spin is a 90° corners, where the turbulence created. Cut more 90° corners shaped stars ✸ to make it twist faster.

[@TD-er]

I always thought it was a matter of heat difference. The black side heats up more, thus heating the air close to it. This air then expands and pushes the disc. In low density air (low pressure) there is low friction and also relatively more pressure difference for the air heating up and it can't transfer heat to other air molecules very efficiently.

[@rafaelcalderabebber1198]

Really interesting, didn't know about this before

[@realcygnus]

@The Action Lab Nifty. I know these Q's weren't the main point but you should have at least shown how fast it spins with that ultra bright light before you smashed it & even more importantly, why was it so slow with the bright light in your vacuum chamber ? Was it that the pressure wasn't low enough or too low? Since they say they work better in a "medium" vacuum why didn't you just let some air in ? Or is a medium vacuum in industry even lower than your lowest ?

[@andymouse]

Its your last point, less of a vacuum and more of an absence of air here if I said that right...poor vacuum !

[@dereknalley]

Make one with vanes that have a spiral cut groove through the whole thing. You'd have a massive surface to edge ratio. Also, when you cut the vanes down the middle, you greatly increased their moment of inertia by opening them up so wide, of course it didn't spin much faster.

[@cwt5654]

Or possibly a myriad of pinholes?

[@jimladXLII]

If you can find a way to measure the force imparted more exactly, this might be far easier to work out. Maybe a single blade of the radiometer in a vacuum, hit by a fixed laser, to measure how many degrees it rotates off whatever force it gets before rotating out of the laser's light? That would make tests more reliable, so simpler tests could be performed like the light position you did, or seeing if light angles matter.

[@logaandm]

In your experiments you do not maintain a constant angular distribution of mas. Like an ice skater spinning faster when they bring in their arms. I think measuring rotation frequency is a reasonable approach, but you may want to place a mirror attached to thin wire and measure how much it twists using a reflected laser the amplify small rotations. Also a way of measuring the force of gravity between two suspected objects.

[@dahmc59]

you should check into the reflective and absorbative properties of each material for light and heat. would not hurt to know the electromagnetic charges and specs on them too. i. e. one black ink may act as an insulator whereas another may have heat resistance...

[@ZoonCrypticon]

Other things you could try: a) differently colored lasers with the same lumen and candela settings b) instead of black side a silver (or aluminium) mirrored side c) a fine metal grid, black on one side, white on the other

[@freeemailssuck6848]

The whirl of the cooling fans on that flash light are insane lol

[@muggyate]

my guess is conductive cooling. the white side is more cool than the black side and therefore, when an air molecule hits it, it gets bounced off less hard than when one hits the black side. the air molecule that hits the black side will absorb more heat energy and gains momentum when leaving the black side and thus giving negative momentum to the black side and making it spin. If this hypothesis is correct, then heating up the air inside the bulb will have a different effect as it would cause air molecules that hit black side to lose momentum as it transfers some of it's heat energy to the paper. The difficult part is to somehow only heat the air without heating the rest of the contraption and if it works, the question becomes why is the black side more thermally conductive cuz I think that makes no sense.

[@anmolagrawal5358]

5:57 Isn't it possible that as you cut those slits, it moved the overall geometry further away from the axis of rotation and due to conservation of angular momentum, it spins at a slower rate as a result. Given its size, I'd say even a few mm would make that difference and with your results, that variation might match up

[@ugurunver2403]

I wish you had tried to spin it with some infrared source. I mean, it must react differently to different wavelength and energy levels of lights if the reason is thermal transpiration. It must spin faster with IR light. And I think it maybe spin slower under the ultraviolet light even if UV has the most photon energy in our visible spectrum. Because as far as I know the best wavelength to transfer energy as heat is infrared despite UV has the most energy. I mean, if the reason is heat, IR will perform better, but if the reason is photonic pressure caused by momentum of photons, UV will perform better. And i think this experiment would bring us a solid answer about the question.

[@swaggamesph3342]

Try to focus the laser in one line of sight to have all wings be touch by the laser, this will rotate it faster compared in focusing in one wing. Then try to do the same while shining the edge or the outer left corner of the wing, you will see it will rotate faster. Try to time at least 2-3 cycles to get a much better time difference. After doing the steps above, you will see that its definitely, not Thermal Transpiration.

[@miguelalonsoperez5609]

It may rotate by heating the tiny air layer over the wings, at higher temperatures on the dark side. In absolute vacuum this wont happen, and possibly at 1 atm pressure air drag overcomes the effect or even heat dispersion occurs at ratios that allows pushing on all sides. This could explain why it doesn’t turn with holes, by decreasing heated surface. One way to prove it may be building another model with one face of each wing heated by Joule effect with direct current, for example

[@angryskycraper]

that rotation measuring by heating parts of the tiles felt sooo scientifically accurate x)

[@diveflyfish]

Have you ever tried imparting a Dark Plasma to the chamber? It would be interesting to have a sub luminescent voltage applied to the chamber once evacuated then test the light interaction. Then fully ionize the the chamber to impart an intrinsic glow then apply laser to edge....... If you flood with Xenon then evacuate with some ionizing source like a bit of Americanium from a smoke detector it would make for an interesting experiment. Thank you for all you do to bring physics to understandable elegant application. Cheers

[@juliuseder]

A simple explanation: The force is not caused by the radiation pressure of the incoming light, but by the "cooling" of the wings, because the black side emits more photons than the white side increasing the pressure under the black side. This could be checked by heating the wings without an external light source and observing a rotation. Also you could point the laser on the white side and observe rotation.

[@tsm688]

if the radiation pressure isn't enough, the cooling pressure will be even less enough, because the vanes emit far less light than they receive.

[@juliuseder]

@@tsm688 it emits exactly the same amount of energy as it receives. Conservation of energy must not be violated.

[@tsm688]

@@juliuseder not all energy is light

[@juliuseder]

⁠@@tsm688 if you add energy by light, some is transformed to heat and some to motion. When you stop adding energy it will eventually get to equilibrium with the environment emitting all added energy as heat. Maybe we could heat the wings without adding light on the black side (e.g. with IR-laser on the white side, electric current or radioactive decay) to prove that the pressure difference is because of the higher heat energy emission on the black side to the surrounding gas molecules.

[@NueUzrnem]

My hypothesis is, effect could be result of the conversion of thermal energy to kinetic energy through gas molecules. Which also explains why this effect wouldnt work in extreme vaccum and in normal pressure. Explaination: Upon viewing from side, one side is cold and another is hot Molecules of air with average kinetic energy/pressure contact on hot side, absorbs heat, and bounces off with more kinetic energy. And on the cold side, air molecules impact and slow down. The hot side works like molecule propulsion. And this wouldnt work in EXTREMELY less pressure because there are not enough molecule to build momentum. And in normal air, molecule activity is numerous, so it averages out. Hence no effect.

[@Moist_yet_Crispy]

Considering that most of our frame of reference and intuition in science is based on what we've seen and experienced on Terra/earth, with x num of heavy particles, X gravity, X air pressure and so on, I'd put my money on the notion we're still missing something here. Air pressure changes all kinds of things with elements, crystallization, and has to have a cascading effect across other metrics as well. It only stands to reason. Most of our inputs are fixed, and also fixed inside of pretty small ranges even with what we can change kuz money is also a factor. This was a fantastic video! kudos!

[@benmcreynolds8581]

It seems like a form of a "Solar sail" Where the photons are able to interact with the black parts of the material. Which could induce a slight force that's maybe causing temperature or pressure changes in the chamber

[@christiantrujillo1986]

Omg I saw you today at Disney, I was so shocked to see you and wanted your autograph so bad! We gave you six small cups!! It was great to see you!

[@mikefochtman7164]

I always thought it was just that air molecules recoiling off the hotter black surface would have more energy than those recoiling from the white side. Yes, overall air is at the same temperature, but it is those air molecules that recoil from the surface that count.

[@Trip_Ts]

That's what I thought. I wonder if they use high concentrations of CO2 make it spin faster.

[@tsm688]

That doesn't explain the double-sided radiometer at the end

[@dragoscoco2173]

Chemistry hints to gas molecules sticking to surfaces by enhanced reactivity when surface area is higher. Thus it would be logical that a hotter surface would make those gas molecules fly off more often than the cold side resulting in a net force difference. Yet this needs to cycle thus gas needs to connect to the hot side at some point to keep the force running. Conversely the cold side would see more gas being available for sticking to it and see a net force opposite to the hot side. I see why the edge effect is considered as there is the point of possible transfer of stuck gas molecules from the cold to the hot. But if you make holes then you affect the surface and affect the net force attainable. While this is a compound effect and truly hard to separate the sticking part is testable by changing the gas to something more inert electronically or simply heating it up (the whole radiometer including walls).

[@aditya4953]

The rotation in the vacuum is due to the gas molecules taking energy from the black-hot side and going in opposite direction to the rotation. Meanwhile, with high pressure there is an opposite direction wind current due to cold air rushing in neutralizing the effect. Therefore in zero vacuum this wouldn't work and would have a maxima for speed for appropriate low pressure. Test This --> Reducing surface area reduces speed(You checked) High surface area to mass ratio increases speed Shape of the paper matters, Focusing air molecules perpendicularly would increase the speed

[@JohnW118]

Interesting! Sometimes 'doing science' produces "nothing" but that is still a very intriguing result here. Another experiment that suggests itself to me, is keep the black side fully covering the surface, but the opposite 'white side' surface should only be covered in white for 1/4 the surface area. And vice-versa.

[@diveflyfish]

The coefficient of thermal expansion may make a difference. Eg. Neon will effect greater thermal expansion than if helium were used. Differential in speed noted if variance in RPM with different noble gas would impart support for hypothesis. If movement is due to electrical force, delta of milieu voltage will elucidate that.

[@Desperate.Situation]

Good evening, a rarefied gas inside a glass ampoule could ionize (rarefied plasma) with a light source. The glass of the ampoule acts as a "photon greenhouse effect" because many photons remain trapped, reflected from the internal surface of the glass ampoule. The atoms of the rarefied gas can ionize more easily, and remain ions for longer, because the mean free path is longer. Thus white face reacts to a different extent than black face to a light plasma, which is conductive.

[@luismlc89]

Try conical, black inside, white outside. I think that will work like a propeller

[@bawat]

Would be interesting to attack the laser to the assembly and see if it continues to accelerate in that configuration. Maybe if it is too heavy, something like a fibre optic cable to reroute the light as the device spins would be interesting

[@mhtrproplayer]

well, I think what happened was when u heated the era up air molecules pumped to the area and got accelerated away and causing an opposite force on the thing. and it doesn't have to do with corners, and this makes sense because when u cut it u didn't change the area, so it was spinning fine but when u punched holes and reduce the surface area it didn't work.

[@anywallsocket]

Light on white is like elastic collisions, white on black is like inelastic, one radiation conserved overall kinetic energy, the other doesn’t.

[@FriedTux]

I have heard that they do not function in a perfect vacuum. They only work correctly at near vacuum. I have suspicion that your vacuum pump is making it lower pressure than the factory, but not enough to make it stop functioning altogether.

[@DoNotPushHere]

I'd like to test different conce tration of gasses. Superlow vacuum but made out of co2, he, ne, etc... And see how much it would affect. My feeling is that denser gasses will make it spin faster. I think the vanes are thermally vibrating and any random molecule that impacts on them, bounces off, mechanically imparting a reaction force, not due to "higher pressure"

[@bcataiji]

You could have shown us that it does NOT work if both sides were black or if both sides were white, then I could start to believe that the opposite colors were at least part of the reason why it works.

[@TankYou90]

Slightly increase temperature = Slightly increase pressure PV=nRT you create a very small ΔP, but enough to move the frictionless pivot Easy. Done Evidence: 1- In a full vacuum, it doesn't work because there's no gas expansion. 2- It only works (effectively) on the black surface that heats up faster. 3- It's hard to use a heat source other than light that selectively heats only one side without affecting the whole atmosphere, but if you manage to do thet, it should make it spin. 4- Trust me bro.

[@TankYou90]

When you punch holes in it or cut it, you help equalize the pressure faster on the opposite sides. punching the holes could have made a passage for the small amount of air to flow through, instead of having to either go all around the square or push it.

[@francescotenderini1489]

I wrote the exact same thing. Also, cutting in half the faces increased drag, and the rotation was slower. It works only with light, or infrared maybe, because the black side needs to absorbe energy from em waves. And it's this that create high pressure on the black sides

[@bradleyaverick2191]

In a vapor chamber you can see the potential for development of Eddy currents produced by the velocity of the particle in the vapor condense. These condenses may have a rotational inertia that develops due to friction with quantum fields.

[@bradleyaverick2191]

Maybe the photons or other particles produced by the light source, as they pass through the coated tin vanes, produced Eddy currents.

[@alanwhitelock7110]

Assuming the black side is hotter or imparts heat to the gas molecules that bounce off it. Ie to they depart with a higher velocity and impart a small velocity to the vane. Once the vane is moving it transfers some of its extra velocity to the molecules striking the cooler white side until an equilibrium is reached. The equalibrium result is the spin speed it dependent on the sustainable temperature differential.

[@TheRealInscrutable]

Point the laser at the inner and outer corners instead of top and bottom corners - you may be getting a lever arm from the center to the point of heating and may get a bigger speed difference that way.