You should definitely make one with 1.5 cm vanes and then one with .5cm vanes and see if there is a linear link to the gas molecules. That'd be very interesting!

@Roerco

Жыл бұрын

3cm^2 vanes

Mister, this is the best, simple explanation of this phenomenon I have ever seen, heard, or read. Old video. Hope you're still out there.

So in the argument I had with my high-school science teacher 30 years ago, I was right. Huh. I wonder if I can find him to say 'told ya'.

@unsignedmusic

3 жыл бұрын

I was taught that it was photons as well.

@TrystansWorkbench

6 ай бұрын

SimoWill, I think your high-school teacher will be more impressed that you still have that vibrant enquiring mind of yours.

@LEARN-UNITY3D

2 ай бұрын

The phenomenon where a radiometer rotates in the opposite direction when refrigerated or cooled is often attributed to the gas inside the radiometer. When the radiometer is heated, the gas inside the bulb expands, creating a pressure imbalance that causes the vanes to rotate. Conversely, when the radiometer is cooled, the gas inside contracts, generating a pressure difference that leads to the rotation in the opposite direction. This effect is primarily due to changes in gas pressure rather than changes in light intensity

These radiometers are neat. I vividly remember when I was a kid going to a planetarium and looking at one of these. Nice video!

How can one resist such temptations? You truly are a man of iron will

Very interesting! This is the best example of describing what's going on I've found yet. Thank you for deep diving into it!

This is very thorough and informative. Thank you for taking the time to give this a proper explanation.

Fascinating as always! Thanks Ben!

@pratwurschtgulasch6662

3 жыл бұрын

i recognize this guy w2aew :) i guess you're a little bit famous then :)

This is a great experiment Ben, thank you. I enjoy all your videos, explanations and analyses, but this one really got my mind *spinning*. Thumbs up

The first time I saw one of these I was told that the force was delivered by the photons. Great video man.

I was told in science class in 2003 that this was due to light hitting the sides not heat. I remember being confused at the time of the direction it spun. Good to know. thanks for the video!

I’ve just watched this and practically jumped up when you said you might try to make a radiometer with larger blades. I’ll be looking for that right now, but if you haven’t *please* do! Loved this! Subscribed.

I'm very curious to see the results of the larger one. I hope you decide to make it! Great video!

@geekyoyd

Жыл бұрын

I don't quite understand why the effect just happens at the edges.

Thanks for your explanation. Very nice! What would happen if the center of each vane would be removed? It would seem it would spin faster as there would be more "edge" to affect.

Very interesting. I've owned one of these for many years, ever since my Physics teacher demonstrated one. However, aren't the vanes slightly tilted? Like a fan? I always thought the effect was the black areas heating more quickly, then heating air molecules which then rose, further colliding with the tilted vane and causing it to spin. Similar to the little devices people place over candles to ring bells.

The spin is caused by the temperature gradient you're creating. Very cool.

Wait wait wait!!!! You never ever explained how it moves Backwards when cold!!! And you really skipped over how the "second " way it turned works!! Thank you for the video but we NEED MORE!!! Thanks!

Fascinating exposition Ben. Great. :)

Been watcing a few videos on this, glad to see you made one as I trust you on such matters the most.

I haven't even watched the whole video and I have clicked the like button.......... This is amazing stuff.........and the experiment is making it more interesting.

Blown away with the freezer spray cooling even repeated that one at home to see it again. Did not expect that to work still thinking about it.

Very clever device. I liked the experimentation and investigation. Very cool physics demonstration, this radiometer

Great video. Way better explanation than the other suggested video. And a good demonstration!

Fascinating, I've always wondered what made it turn, ever since middle school. I really would like to see this taken a step further, even to the point of measuring torque?? How big would it have to be to turn a 10kw generator?

I love your explanation on radiometer, especially using oscilloscope. :D

What effect do different light sources have on the speed of rotation? Do different wavelengths have different effects? It would be interesting if it responded well to a non visible part of the spectrum like infra red. You could make it rotate with no visible means of adding energy.

Data is beautiful, as they say. Great stuff. Would be very interested in the larger vanes and other possible variable tweaking. Gas composition? energy wavelength? Do the black and white faces need to be bonded thermally?

Fascinating. I always wondered how these worked.

Best explanation I've heard. Thumb up, Captain. Liked and subscribed.

Well done. Operation clearly explained. Very engaging by using a vacuum chamber and oscilloscope to collect data from sensor.

Very good experiment, thank you! I read a theory that the gas or air curls/coils around the edges of the flags and pushes from opposite side, i imagine like the air flows around the back end of a semi truck when driving down the highway.

Always love your experiments. I can remember hundreds of radiometers on a big table for sale, at Disneyland.

I first saw this thing on an episode of Mister Wizard. Great show. =)

I think it was James Clerk [pronounced 'Clark'] Maxwell who, in a lunch break, elucidated the workings of these things. When I go my first vacuum system I used a naked radiometer as a rough indicator of vacuum. I now use a Pirani and a Penning gauge. Was that Volts/vacuum table for an ion gauge? I have one that I must get around to fitting. The naked radiometer now sites on a shelf as a 'curlometer' for the air field in the room. My old baseplate had expensive Edwards feed-throughs, and I needed more, for which I used RF feed-throughs soldered into a plug that replaced a single HT feed-through. I was thinking of sparkplugs. Do you use their standard seals? Do you plugs a good solution? I am envious of the turbo-molecular pump; I still use diff pumps. I note that the TM pump's maw is off centre. My original baseplate had it in the centre, but that gave little space for experiments, so I made a baseplate with an offset hole. Now that the Technology Connections channel pointed to this video I must keep an eye on the channel.

Very cool and interesting video, really enjoyed your explanation.

Hi Ben, Really nice video. Do you have the data on rotation rate vs pressure?

Sweet, very cool way to test this. I wonder if having vanes with a large edge:surface ratio would spin faster? My Radiometer slowly lost its tenancy to spin after I left it in a sunny window for an afternoon. I'm not sure if something gassed off or if the needle/glass bearing experienced wear. It still goes but only with very strong light sources.

@markbell9742

9 жыл бұрын

Possibly by sitting in full sun for a while the temperature of the whole system has warmed and the temperature difference between the two sides of the vans is less resulting in less of an affect. I don't know, maybe? Cheers, Mark

@NickMoore

9 жыл бұрын

I thought that initially but it has stayed the same since then. Without a 500w light it refuses to get going :/

@chronos1002

9 жыл бұрын

I think your pivot point has warn down. Think about it, to make the vanes able to spin with very little force exerted, the whole thing is suspended on a needle fine point; and as the vanes rotate, the two surfaces will wear each other down. So after a very long period of use, the turning motion of the vane assembly would wear down the needle fine point to become more blunt. The more blunt the needle, the more force must be exerted to induce motion. Hence the requirement for a brighter light. More light = more force.

@whitcwa

9 жыл бұрын

The glass may have a very small hole which is causing air to leak in. It happens sometimes with electronic vacuum tubes. Also, you can test the worn bearing hypothesis by getting another radiometer and testing how much the vanes rotate when the radiometer is rotated. If the bearing is worn, the vanes should move more than an unworn bearing.

@Swanicorn

3 жыл бұрын

@@chronos1002 I think like UV rays from the Sun affect many materials, it might have made the metal react and kinda corrode in some way making its surface rougher. Or maybe the vacuum might have reduced which then again lowers the RPM.

It would be great to see you make vanes of all different shapes, and sizes, and compare the performance. If you could make them light enough, you could even 3D-print some designs and test them, too.

Thanks for sharing! I love this channel. I am curious, was this whole experiment mainly for your viewers or were you curious yourself or did you have some other motivation to do all this? Also, I would love to see more experiments that involve the vacuum chamber :-) Thanks again!

@AppliedScience

9 жыл бұрын

Thanks! I really appreciate it. I am motivated quite a bit by basic curiosity, however having this youtube channel causes me to be more focused and productive. So, it's a win for everyone.

+Applied Science - Can you put that spreadsheet somewhere online so I can download it? That would be awesome. Thank you

If you do think of revisiting this. I'd love to see if different gas effect RPM. Also, different wavelengths of light. Would UV create more heat than IR? And of Course Vane size!

Very nice! Something I've always wanted to try.

Thanks for sharing, Would you please describe what kind of electric valve you have used and what are the specs ? I am trying to find a suitable gas flowmeter for like 1 to 10 sccm of flow.

As always, very interesting. Thanks for sharing.

Hi Ben, I like the way you have used regular spark plugs to get signals in and out of the vacuum chamber. Very novel idea! I must have missed that "Vacuum chamber build update" on that ;-). Did you also made those red wire passthroughs?

In the first part of the video you applied cooling to the surface of the radiometer, which had an effect. Then, when you transferred the spinner to the vacuum chamber, you effectively had a chamber with more volume. Is the volume of the chamber relevant at all? I suspect this is not easy to test, although, perhaps you could introduce different sized containers into the vacuum chamber. What about repeating the experiment at various ambient temperatures? Apparently, the outer surface of the chamber serves as a heat sink. If you could repeat the experiment at very high or very low ambient temperatures, would you see a difference in rotation speed? Which would be faster, and why?

Excellent vid! Thanks for sharing!

I think I'm picking up what you're laying down but A: What info is given with the packaging? You just did a really cool experiment to find out info that I feel like the makers could easily include or even print onto the base. It's a learning tool for Pete's sake. B: I am now angry at every science teacher I had that had one of these on the shelf (almost all of them) and never brought it up or just had it so we could look at the spinny thing and not bother them for awhile.

Nice! I do have a question though. You say the ideal is 1 milla- tore (spelling) If you pressurized it to the same point the other side of room temperature would it also spin? Thanks I love watching these videos. Dave

The scientific term for the force is "Photophoretic force". Your observation is very interesting because in micro particles the force peaks when the mean-free-path of the gas is the same as the diameter of the particles. This force can be used to trap and guid particles which absorbs light.

What I find interesting is how he happened across this. he was trying to make a perfect vacuum to get any air influence out of the picture. Because he accidentally did not make a perfect vacuum but only a partial one is why it even spun at all in the first place. Does this work with round veins or do they need to be squares? Also normal air pressure is 760 torr or 1 atm. The pressure in the tube is less than 1 torr. So its pretty close to a vacuum. I wonder if it could be done using a excitable gas one can be visualized? That way you could maybe see the currents in action.

Excellent experiment. Your physics teacher would be much pleased.

interesting effect & explanation/demonstration. enjoyed it.

Question: What would a practical application of a Crookes radiometer be? I seem to have memories of seeing them from time to time at roadside installations in southern California in the 1960s - 70s or so, in remote areas, and in the presence of what may have been utility cabinets. I never knew what or why they were. (Admittedly, my memory may be totally wrong. That was a long time ago.)

@louistournas120

7 жыл бұрын

Perhaps to measure intensity of sunlight? I have never see these radiometers on roadsides in Quebec or Ontario. Measuring sun intensity can be done with a photoelectric cell and a voltmeter.

@ObjectsInMotion

7 жыл бұрын

Craig Bass Those were probably wind meters, not radiometers.

I would love to see the difference between two radiometers at the same pressure, but one with say helium, and the other sulfur hexafluoride, or another dense gas, and see the difference between them at varying pressure levels.

You should try adding a fractal edge to the vane (increasing the perimeter for thermal transpiration).

Nice. Can you get it spinning then turn off the light and film it with a night vision camera to see exactly where temperatures vary? Thx.

So I had been fooled to believe all this time that it was radiation pressure. Now I understand why I couldn't understand it...because it couldn't be radiation pressure! Thanks for the clear clarification.

Thank you for this amazing video

very interesting experiment, thx for sharing with us

This is cool! I am trying to recreate the experiment for my school project. @Applied Science, What is the name of the equipment at the bottom? Did you buy or assemble it? How did you have the turbo machinery pump connected to the bell jar with electronic controlled valve? Also, how did you seal the tachometer wires inside the bell jar and connected it to the oscilloscope? I am trying to rebuild it but these things are a puzzle in my mind. It would great if someone could answer it.

Did you ever make a large one. Curious to see if the rotation peek speed follows some specific size . My other thought is what if you could make one large enough to be a solar type generator...maybe crazy but Hay that's one big glass ball huh? Or what if atmospheric pressure and speed correlate to a specific size? If its creating a pressure differential from hot and cold off its edges is the propelling force would it not change the perimeters? Wondering if a wind generator that still spins in sun light or assisted by it would be even feasible?. Don't call me crazy, its the ones with seemingly crays ideas that are usually the one getting locked in an a tower until proven right.

Hello! I love your channel. Just wondering, did you ever get to do the changes in vane sizes? I'm rather curious about that. Thanks!

@AppliedScience

8 жыл бұрын

+Doxie Lain Thanks! No, I haven't returned to the radiometer project since making the video. I have a long list of things to do.

@rhynoorhyon5291

8 жыл бұрын

+Applied Science There's also the corollary to consider: is there a smaller length at which a radiometer would work at a pressure that's closer to what we're used to? Testable by going bigger, rather than smaller, of course.

@keegreil

8 жыл бұрын

+Applied Science Hi! Love your channel too! Would you be willing to share the Excel data that you collected? I'm thinking about trying to duplicate your experiment, maybe test the different sizes of vanes.

it would be interesting if you use infra-red camera to observe, also i would use 4 light positioned in all directions to determine the heat cycle.

Great video (again), but why the spark plugs in the vac chamber??? Are you drying them out???

It would be interesting to see how it responded to different wavelengths of light

I think you should switch the colors so we can have more data. It cold be related to the vibration of the atoms that can absorb kinetic energy from one place and releases to another, just like a sound levitation but in a form of radiation. The energy travels through the gas molecule in certain frequency, if there's no gas,the eneryt can not be transferred, if there are to much gas, it cancels each other out. Try with magnetic sheets, cover with black and white and see if works in a vacuum.

Could you make the veins magnetic or conductive. Then as it spins detect and draw on the moving magnetic field to produce a current? Because if you could solar power would have a new meaning.

OMG, you are my new hero.... awesome video

heat means basically IR right or whatever it is, it must be Electromagnetic radiation right? if yes why does it need gas to propagate I also remember reading the heat dissipating radiation sheets used on satellites of some GPS satellites affect them which is why they are mounted symmetrically

I wonder if the size of vane would affect pressure required for peak spin speed. Although i cant see how, as if you scale then a a 4cm vane would require little vacuum, which makes no sense. I also wonder if theres a correlation between amount of light to vacuum for peak spin rate.

Thank you sir for sharing you knowledge with the world. Just wondering, If data exists. You said you let air in to see what pressure was optimal. I'm assuming you were using ambient air while letting air back into the system. Is there a gas or gas combination that is/are more optimal than our atmosphere that you and I experience on a day to day basis. For example Random with Argon? Reason I ask, this could be an ingredient for a extremely high efficient electrical generator.

@uploadJ

5 ай бұрын

Hydrogen might prove to be optimum? Used around large-scale rotary generating equipment ...

Ben, is that spreadsheet data available anywhere? Would like to see the exact numbers if possible :)

Was there ever a continuation to this video ? I can't seem to find it. I'm really curious about the details how the effect can be amplified and what are the parameters that influence the rotation effect.

What happens with variation of brightness of narrow beams of light, sprctrum and temperature of light, and different color laser light on the vanes? Does moon light run it, how about a larger outdoor solar version?

I would have liked to have seen how fast the radiometer spun at the optimal pressure! Though I'm guessing that's very close to the pressure that the sealed unit from the gift shop is made at.

My guess is that the light is absorbed by the black face and re-emitted as long wave IR. This transfers heat to the air molecules in front of the black face, causing a slight increase in pressure and making it move. It has to be low enough pressure so that there is less air resistance so all the vanes can move easier.

Is it running faster with CO2 atoms or slower? Actually it should be slower right? Simply, it just moves because the black side is heating up the molecules and they in turn move faster away from the black side thus creating the force? Therefore with CO2 the gas will absorb more heat and there will be less heat coming from the black side? Or will it be the same? This is confusing! Never saw this thing before, great video!

I own a 5 year old radiometer. But about 2-3 years ago it stopped working. Sometimes it was sitting in bright sunlight without moving. Flicking the glass would make it go for a few minutes. This behavior increased over time. Nowadays I rarely see it moving. Why ist that? There is no information on that online but I came up with 2 possible answers. First one is the needle bearring. It is possible to be worn out over time. But after close inspection it seems to be fine and since it spins perfectly for a few minutes when touched I dont think thats a problem. Another possible answer is that air diffuses through the glass into the radiometer. The increased drag could slow down the Blade bringing it to a stop. However these are just best guesses. I am genuinly curious whats happening.

Hi Ben. This is interesting to me. I built a LED strobe light of about a dozen 100W LED panels for fun. I noticed some very strange things during each pulse. Holding something like a black piece of paper in front of the array of panels caused it to jump a bit in ambient air. I thought at first it was maybe the metal sheet I bolted the LED panels to since the high current travelling through the wires creates a magnetic field which interacted with any metal/magnets nearby, I thought maybe it was making the metal sheet vibrate because of this. Although this /was/ a contribution, I noticed the effects were greater on a black piece of paper in front of the array than on a white piece of paper (same paper, different colour). I know the variables are different, I used a ridiculous amount of current, and ridiculous light output. I presume this is the same kind of effect as demonstrated in this video? Enjoying your videos as always, keep it up!

OMG! As a child I was lied to! Excellent!

If it's an edge effect, I'd be interested to see what a grid or screen shape does!

What is the material of the vanes? In the older one that I have (made in 90s), I'm guessing that they're painted aluminum. I'm trying to find what materials are typically used to make them and what else can be used.

I think sir it's both, it's being moved more by photons at the same time, slightly with heat, specifically with heat differential (much like how earth's wind works, when there's warm and cold air, cold air on the other side) because I tested it with bright LED light vs. 100 Celsius SMD heat gun (about a few centimeters), it spun faster with the bright LED light (almost touching the LED reading lamp) than with just heat. A laser pointer may make it spin very fast without melting the bulb (it might explode). I wonder if a very high laser is shown, like blue laser but not intense enough to damage it?

@uploadJ

5 ай бұрын

Were the sources inside the glass vacuum vessel, or outside? The glass will intercept some IR ...

Please demonstrate a Hettner Radiometer, which has horizontal vanes with black and white zones.

Rockin that 2014 eeePC

Did you get a chance to test your observation about 1 centimeter travel with larger veins? Thanks

Can you fill the chamber with different gasses and see how that effects speed?

Fantastic, super interesting super profesional thank you very much for shering your knowledge..

As the effect depends on a thermal gradient between the two sides of the vane, making the vane of ceramic or other insulating material should enhance the effect.

@geekyoyd

Жыл бұрын

Yes, I wondered about that. If the vanes are thin sheet metal one would have thought black and white sides were almost the same temperature but the black side is radiating more heat and heating the nearby air molecules thereby setting up a heat gradient in the air and hence a pressure gradient.

Is there an angle to the vanes? Drag, lift, aerodynamics?

Best video describing this

If there was a hole in the center of each vane, would the vanes spin faster since the total length of edges would be increased?

My high school science teacher told me 'porky pies', photons indeed, made him sound smart. Thanks for clearing that up Ben. catch ya. Triggy.

So, does this work with a lightbulb that doesn't generate, or at least generates much less, heat? For example an LED lamp? Great video as always, love your style of making videos!

@AppliedScience

9 жыл бұрын

Tungsten lamps produce a lot of far infrared, which is just as effective at heating the radiometer vane as visible light. I was using a 40W bulb, while LED and CFL lamps do not put out as much total power (eg 15W or less). So, it is just a question of total output radiation in the far IR to visible spectrum, which is much higher for a typical tungsten lamp.

Can you write to us the full name of the: 1. Tool of measuring the pressure 2. Vacom ( the air pump) ??

Please do the experiment with radiometers with different vane sizes!

The plethora of spark plugs in the vacuum chamber has me very curious!

@scienceprimo

9 жыл бұрын

They are probably high voltage feedthruoghs.

Awesome video!!

If the vanes are larger, and the optimal pressure is lower, then you need much more light to make it spin?