Risking My Life To Settle A Physics Debate

Publicerades den 29 maj 2021
Everyone will say this craft breaks the laws of physics. This video is sponsored by Kiwico, For 50% off your first month of any subscription crate from KiwiCo (available in 40 countries!) head to www.kiwico.com/Veritasium50

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A HUGE thanks to Rick and Neil for letting me drive Blackbird. Check out Rick's SElists Channel for more in depth videos and explanations on going faster than the wind downwind -- ve42.co/Rick

Gene Nagata made the shoot possible. If you’re a video nerd like me, check out his channel, Potato Jet: selists.infof... .

Xyla Foxlin for made the model cart used in this video. Xyla builds amazing things like rockets and canoes, check it out! selists.info

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References
Jack Goodman's SElists video -- ve42.co/Goodman
Rick's treadmill footage -- ve42.co/Treadmill
Rick's multiple explanations of how Blackbird works -- ve42.co/DDWFTTW
Forum discussions -- ve42.co/forum Blog -- ve42.co/blog1 and retraction ve42.co/BlogRetraction

Gaunaa, M., Øye, S., \u0026 Mikkelsen, R. F. (2009). Theory and design of flow driven vehicles using rotors for energy conversion. In EWEC 2009 Proceedings online EWEC

Md. Sadak Ali Khan, Syed Ali Sufiyan, Jibu Thomas George, Md. Nizamuddin Ahmed. Analysis of Down-Wind Propeller Vehicle. International Journal of Scientific and Research Publications, 3, 4. (April 2013) ISSN 2250-3153. (www.ijsrp.org)

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Special thanks to Patreon supporters: Bill Linder, Paul Peijzel, Crated Comments, Anna, Mac Malkawi, Michael Schneider, Oleksii Leonov, Jim Osmun, Tyson McDowell, Ludovic Robillard, Jim buckmaster, fanime96, Juan Benet, Ruslan Khroma, Robert Blum, Richard Sundvall, Lee Redden, Vincent, Marinus Kuivenhoven, Alfred Wallace, Arjun Chakroborty, Joar Wandborg, Clayton Greenwell, Pindex, Michael Krugman, Cy 'kkm' K'Nelson, Sam Lutfi, Ron Neal

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Thanks to James Lincoln for building the initial prototypes for a model blackbird.

Written by Derek Muller, James Lincoln, and Petr Lebedev
Animation by Mike Radjabov and Iván Tello
Filmed by Gene Nagata, Derek Muller, Trenton Oliver, AJ Fillo and Emily Zhang
Edited by Trenton Oliver
Music from Epidemic Sound epidemicsound.com
Additional video supplied by Getty Images
Produced by AJ Fillo

Kommentarer

  • If you want more detail on the explanation here it is: 1. The car is powered only by the wind. There is no motor or batteries of any kind. 2. The propeller does NOT spin like a windmill. The wind does NOT push it and make it turn. 3. Instead the wheels are geared to the propeller to turn it the opposite way, like a fan, so it pushes air backwards. 4. To start the vehicle the wind simply pushes on the whole vehicle (like a block of styrofoam) and gets it moving. 5. The wheels are turning so they turn the propeller in the opposite direction to how the wind is pushing it. 6. The prop is pushing air back so air pushes the prop forwards, accelerating the car. 7. Once you get up to wind speed there is no apparent wind on the vehicle. If the prop were spun like a windmill this would mean no more thrust. But, since the prop is operating like a fan, it still accelerates air backwards, generating thrust. 8. You can go faster than wind speed continuously because even when going faster than the wind, the prop can still accelerate air backwards (in the car's frame of reference) generating thrust. In a stationary frame of reference you would see that the wind behind the propellor is slower than the surrounding air. So it's clear that the energy is coming from the wind. FAQ: If power is coming from the wheels to turn the prop, why doesn't that slow down the wheels more than it gets the prop to push back? A: Because the wheels are moving over the ground much faster than the prop is moving through the air (because there's a tailwind). Example: Let's say the car is going 12m/s in a 10m/s tailwind, so faster than the wind (note the prop will be moving through an apparent headwind of 2m/s). Power = Force x Velocity Let's say the chain applies a drag force of 100N on the wheels to drive the prop. This means we're taking power from the wheels = FxV = 100N x 12m/s = 1200W If we apply this power to the fan, it can create a force of F = P/V = 1200W / 2m/s = 600N Admittedly I've assumed no losses, but even if we waste half the power, we'd still get 300N of thrust which is more than the 100N of drag the prop adds to the wheels. The key is that we're harvesting power at higher speed, lower force, and deploying it at lower speed, higher force (which is only possible because we have a tailwind - in still air this wouldn't work because the relative velocity of the wheels over the ground would be exactly the same as the relative velocity of the prop through the air).

    • I'm mind blown

    • @дмитрий иванов >> How does the structure behave in calm weather? It just sits still in no wind. Or if you prefer - it can go 3X wind speed in 0 wind. :)

    • @eyytee "MIT aerodynamicist Mark Drela : "In my view, the most closely controlled and unambiguous DDWFTTW demo is the cart climbing up the tilted treadmill." in the article: "What I’ve Learned About Wind Carts" by Mark Frauenfelder" Here's what I think "could" also work, though some people would still think that there are too many potentially hidden energy imputs being applied to the vehicle. Use the treadmill apparatus, sure, but in a different way, completely level. Just to prevent the vehicle from rolling forward, at first, when a fan starts to apply wind velocity/pressure from behind (I mean there is only a limited amount of runway on a treadmill). At some point as the fan is being ramped up in output air velocity/pressure, the vehicle is going to start rolling forward. At this very precise moment, stop the fan speed increase and hold it at that point (showing the audience that the fan is no longer being ramped up). Now also at this very precise moment start the treadmill to keep the vehicle in the center, by gradually ramping up the belt backward rotation in unison with the vehicle's tendency (now that the wind is pushing it forward) to NOT roll forward. At a very precise belt velocity, we will witness that the vehicle is not continually accelerating indefinitely, that the fan is set at a very precise velocity. We will be able to measure and record the vehicle speed in relation to the belt's m/s. We will be able to measure and record the velocity of the wind in m/s and compare the two. Simple. But, again, some people will think there is hidden inputs. This is why a tunnel/pipe with nothing but a fan, a vehicle on a rail (keeping it straight and giving it the wheel to ground contact required for rotation) would/should sooth these people's suspicions.

    • @Fred Meister look up mechanical doping in cycle racing then tell me he checked properly, science-hating crackpot.

    • It still does not explain why the speed of the prop is accelerating instead of decelerating when the vehicle is slowed down.

  • This thing is made of 50 % spite and 50 % duck tape.

  • you should connect the propeller with a pedal powered foot

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  • Still way better and make more sense to work though not practical as a vehiclular solution but better than the hype vaporware of Elon's HYPERLOOP. Ya I said it.

  • Show me the experiment how you can show , Chicago skyline visible at 57 mi from Michigan coastline. Duplicate the The mirage that's supposed to be happening?

  • I want to see your gravity experiment? I want to see Bend water around the globe experiment? I want to see your experiment to show how an airplane that's in let's say Canada's whether there's only spending 200 mph cruises over to the equator we're spending 1,038 miles an hour, show me that experiment

  • It's like swimming down stream

  • law of physics is a LAW. I'm not a scientist, but this is very trivial. There are flaws in this experiment. 1. To start the vehicle from 0, it already used so much wind power and convert it to kinetic energy to move that propeller. There's where you get the "extra" energy. So, it is not free. 2. Do you consider the elevation? 3. is the wind constant? If not, then you're just moving faster than the wind when it becomes weaker. And that's completely understandable

  • Now imagine the device with rare earth magnet frictionless hubs ... what kind of speeds could you get up to? And I'm sure the propellers could be tweaked for even greater efficiency to tack Against the Wind

    • I think friction loss at the hubs is probably tiny compared to losses due to wind resistance at 2.8x wind speed. A full cockpit might help significantly. A larger diameter prop would probably help, but at some point the efficiency gained with size will be balanced out by added weight of the prop and the frame that holds it plus balance issues.

  • So it's creating a vacuum.

  • the beginning of the video and the animation with the cylinder earth and sailboats all made it seem like the prop was being used as a sail to drive the wheels. sort of confusing to make it that the wheels are actually driving a push prop.

    • It's supposed to be sort of confusing. That's what makes it a great brain teaser. But the wheels are in fact driving the propeller at all times.

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  • You are so high, look at you're eyes 😂

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  • The vehicle relies on wind shear, ie low down the wind goes slower due to ground friction than higher where the propeller is located. So when the vehicle gets up to the speed at the ribbon height, it droops down or switches direction while the prop keeps turning, generating power from the higher wind speed at it’s height. No free lunch!

    • No, it relies on the fact that wind blowing over a surface is a potential source of energy. After the wind passes through the rotator disc of the prop it is moving more slowly relative to the ground the energy that the wind loses goes into the cart.

  • I wonder if the slower wind speeds behind the vehicle creates a vacuum, or lower pressure, that sucks air from the higher pressure in front.

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  • Could this apply to solar wind? Light? Hmmm... thinking, yes? tho... isn't lightspeed a hard limit?

  • now that the muon accelerator exists our laws of physics are gone maybe more things like this exist

  • The air pushes on both sides of the propeller or sail

  • The air colum the prop making is pushing the cart. Think of it as a 1stage rocket. Only 1 stage because the air pressure doesn't change no differnt nozzles needed

  • So effectively there is a vacuum being produced on the headwind side of the fan which is pulling the cart forward. It would be the same thing as when you get in the vortex behind a semi truck on the interstate and you can reduce acceleration of your own vehicle yet the semi pulls you down the road behind it.

    • No the air that the propeller interacts with loses energy. That energy does into the cart. Just like a sailboat on a downwind reach. Does a sail make a vacuum in such a case?

  • Wheels turn prop, prop pushes air back towards forward moving air. Absolutely logical. Great vid.

  • Isn't this video older than just a few weeks !??? I have the impression i already have seen this, do am I right ?

  • I just hear a sound looks like that a diesel motor gets out of fuel in 12:24 .why it should make sound look like this. it has no air compress system.

  • What happens when you point it into the wind?

    • @subductionzone Nevermind, I think my mental model had the blade speed much lower than it is in reality.

    • @subductionzone but by moving faster than the air, all force applied by the air is on the front of the vehicle, as if it were traveling up wind. At that point, it seems like the sailboat analogy should be flipped around, because as it is, sailboats are able to sail up wind by using the sail to generate force sideways, and using the rudder to redirect that force backwards, much like this vehicle is doing when it goes faster than the wind.

    • @Eric Ruhl No, it is just going faster than the wind. The prop merely extracts energy from the air. The wheels drive the prop, so the faster that the cart goes the faster that the prop spins. It is a feedback system. If there was no friction it would keep going faster and faster indefinitely, but in the real world friction is an increasing factor. It eventually keeps the cart from going any faster.

    • @subductionzone but isn't that effectively what it's doing when it goes faster than the wind? I guess the way that it's geared to the wheels would have to change. Hrm... Maybe a 1/3 to 1/5 gear reduction to compensate for the lower land speed?

    • It goes backwards. Much harder to steer in reverse. And the propeller would not be as efficient. It might not reach wind speed.

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  • So is the cap speed when the air is left behind, still in reference to the ground, or would the fan just start blowing the air behind it at a headwind speed ?

    • Yes, one absolute limit would be when you reduce the wind speed to zero in the column of air swept by the prop. The prop (or a prop actually capable of doing that in this configuration) would become highly inefficient long before that though.

  • Is this the beginning of a real warp drive?

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  • how is it any different than a prop on a boat, the air is essentially a fluid too so I don't see why it would be possible

    • Yes, but the equivalent would be water/land, not water/air. So something that rides astride a canal with roadway on both sides and has a prop on a beam in the water. Water/air may be possible, but in that case you have a lot more losses.

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  • before the video hitted to minutes i understood the clue, it's brilliant

  • Wonderful!!! Fantastic!!! Funny how these so called scientist are so quick to doubt something new...

  • The Dyson dude gonna visit you

  • I really do love this channel.

  • Now apply this to the Alcubierre drive so that we can go faster than the speed of light in the direction that the universe is expanding. And then go for breakfast at Milliways.

  • @Veritasium Build the same vehicle with 4 propellers with Carbon Frame and use a GearBox with 6 Gears. So when you have 20km/h Wind with the 6th GearBox can get up to 120km/h. :)

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  • The way the video was set up and presented, there is no pushback. When he said he expects pushback, he knew there will be virtually none.

    • @John Borton OK, give me the percentage. I'd say maybe 1%. If that's a lot, then you have a very strange understanding of "a lot".

    • @sevencolours Never made that claim at all, but I have examined them all

    • @sevencolours Given that I've read every comment, I have a much better idea as to the percentage of pushback than you do. If you were smart you wouldn't assume so much.

    • @John Borton The comments are overwhelmingly positive. You don't know anything about statistics. You made the noob mistake, claiming all comments must be examined.

    • @John Borton You don't know anything about data sets. In orders to see the percentage of push back comments, only a subset can be examined. If you were smart, you'd know that that.

  • Think of it this way, wind energy is being converted into wheel energy right? As the vehicle approaches the same speed as the wind, the wind energy plateaus, but the wheel energy keeps on providing (by driving a propeller). This is because the wheel energy depends on the vehicles speed relative to the ground (which is always zero) whereas the wind energy depends on the vehicles speed relative to the wind. So it works by converting wind energy to another form of energy that can keep on providing a speed increase even after the wind energy no longer can.

    • @John Borton I should have worded it better. I meant that the ground is always zero. Meaning the delta V between ground and vehicle keeps growing unlike the delta V between the wind and vehicle.

    • In operation, the vehicle's speed relative to the ground is most definitely not zero.

  • It may sound dumb but would this be considered infinite energy? Like would it just keep going

    • No because you still need the wind and it is powered by the sun which despite how long lasting it is does not by any means have infinite energy.

  • It needs more blades on the propeller

  • So, when the vehicle is at wind-speed the prop acts like a wing spinning in stationary (relative to the vehicle) air. This lift pulls each prop blade forward and that force is translated to the mast of the vehicle. Gearing the wheels to the prop is just to get the prop spinning so the blades can start generating lift.

    • Gearing the wheels to the prop provides the Blackbird the same kinematic constraint that the keel provides on a sailboat. Remove the keel on a sailboat and it merely drifts downwind at something less than windspeed. Same with the Blackbird. This constraint it required at all speeds.

  • it would have been even more impressive to have it so the prop could be oriented at various angles, to allow different directions, and, see him turn instead of stop, and turn across the wind, and then, back at an angle into the wind, back towards where he started.

  • Does this have any analogy to a helicopter falling without an engine? Just in the other direction

    • Nope -- the Blackbird is utilizing a garden variety propeller and never autorotating.

  • Newton's mind is blown

  • Now it makes sense ... Love this kind of stuff... Bravo for the team ... Hello from Romania.

  • add a generator to it and make a wind powered perpetual motion device.

  • Let me ultra simplify it: The wind slaps that thicc Pixar Mom Ass of the cart pushing it forward. But it's hot out and there's no humidity and the breeze feels like an oven. So she is waving a fan in her face which helps push the hot air off her neck. But also makes her move forward slightly faster. Nice

  • Your videos are great...

  • It doesn't seem so unintuitive to me since it only works for moving objects (relative to the surface), given that the wind speed is greater 0 relative to this very surface. The vehicle is just a very clever idea of sucking the energy out of the wind but it requires the wheels having ground contact to work. Change your point of view into the inertial system of the wind. At the point where in our inertial system the vehicle is moving at wind speed all you see in the winds inertial system is the ground moving under a standing vehicle. Now of course you can transform the energy of the moving ground to power a propellor on the vehicle to push the vehicle in the direction you would want it to move. The propellor creates wind by itself so this only works as long as there is a velocity difference between the wind created by the vehicle and the moving ground. The max speed results from movement of ground in downwind euqilibrium + velocity increase by the propellor moving air at ground speed which can be greater than the velocity of the air moved by the propellor. I don't know if the diameter of the rods makes a difference but I would think it should not?

  • If that Propeller is blowing backwards, why did they positioned it IN FRONT of the holding tripod?

    • @John Borton I ll start developing when i stop going to work/paying taxes for the migrants in germany!

    • Build one that breaks the Blackbird world record of 2.8x the windspeed, and demonstrate your design is better. Perfectly simple. Weird how 99.9% of airplane designs have the entire airplane/wing/engine 'interfering with the push stream', don't you think?? Turns out, 'puller' props generally run at a better efficiency than pusher props because they run in undisturbed air.

    • @nitraM L. nesredeP So turn it and the driver other way round? just drive backwards? I mean, they don t want to interfere the push stream....

    • Stability. It would tip pack because of the weight

  • The added animation really increases the value of the video.

  • That’s a great video - I think the reason here is that the propeller is not 100% impulse type …..it has some reaction element as well …..so we need to consider the delta Pressure component powering it.

    • It's a plain Jane, garden variety propeller operating as any other.

  • 11:28 i wonder what would happen with different gear ratios

  • Question pourquoi ne pas mettre un moteur qui produit un souffle d'air puissant et une voile devant? Ainsi l'élément pourrait être autonome. Stéph. Question why not put a motor that produces a powerful blast of air and a sail in front? That way the element could be autonomous. Stéph.

  • Has anyone thought about liking a video twice , cause this video definitely made me wanna do it.

    • @Rick Cavallaro absolutely.😂😂😂

    • So you "like liked" it!?

  • Gosh, Papa Legba really is asking for a kick in the brain. @The Guy also wants it, but I think is wrong to Kick mentaly disable people. Anyway, I know Veritasium will make another video to spit on these Conspiracy theorist.

  • I propose we use the same principle to spin solar sails on our interstellar probes ;)

  • 4.7k people understood this video.

  • Either way, one or BOTH will expose their Dunning-Kruger Syndrome. :D

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  • It seems to me that the debate/controversy revolves around not so much whether or not this breaks the laws of physics but rather what the definition is of a vehicle moving straight downwind. We know that in the example of a sailboat cutting on a diagonal through the wind (and moving faster than windspeed), the craft is moving partially downwind and partially across the wind, giving the sailboat its angular direction with respect to the direction of the wind. It's obvious to us that the sailboat is not moving straight downwind. So the question becomes: is the wind-powered vehicle travelling straight downwind? It seems to me that the correct answer to that is: only part of it. While the body and tower of the vehicle (along with the driver) are travelling straight downwind, the propellor is not. When the vehicle stops moving, the propellor has certainly finished downwind of its starting point, but what of its motion during travel? Each blade of the propellor is angled, which means that as it rotates (due to the spinning of the wheels and not the motion of the wind), the propellor is moving both downwind and across the wind at the same time, just like the angled sailboat is, which is why the double sailboat on a cylindrical earth analogy works. In both the case of the sailboat and this wind-powered vehicle, the component of the vehicle which interacts with the air and generates a forward-moving force (the sail and the propellor) is angled across the wind. In both cases, this means that the vehicle is moving partially downwind and partially across the wind, which makes this wind-powered vehicle completely analogous to a sailboat moving diagonally through the wind at a speed greater than that of the wind. In the case of the sailboat, the entire craft is angled, while in the case of this vehicle, only the propellor is. But in neither case can you say that the entire vehicle is moving uniquely downwind. If the propellor were swapped out for one with perfectly vertical blades, not angled ones, then the rotating of the wheels would spin the propellor but not generate any additional forward force, and that would indeed be the same as a sailboat moving directly downwind. But as soon as those propellor blades are angled, then as they spin, they are cutting through the wind on an angle, and that vehicle is now doing precisely the same thing as an angled sailboat, even though it doesn't look like it. What it boils down to is that this isn't an issue with the laws of physics; it's an issue of comparisons. To compare this vehicle to a sailboat moving straight downwind is unfair because while that sailboat moves straight downwind, this vehicle moves only partially downwind. If this vehicle were instead compared, as I believe it ought to be, to a sailboat moving diagonally across this wind, then all controversy disappears.

    • >> So the question becomes: is the wind-powered vehicle travelling straight downwind? It seems to me that the correct answer to that is: only part of it. Try and think of a land based vehicle that could even theoretically have all its bits moving straight downwind? Keep in mind it can't have wheels. Pretty much the only thing it could have is a longitudinally oriented abacus.

    • // "If this vehicle were instead compared, as I believe it ought to be, to a sailboat moving diagonally across this wind, then all controversy disappears."// Except the controversy doesn't disappear. As Rick is fond of saying 'There are something like 12 different ways to correctly explain it. One of those will provide the 'Eureka!!" moment for someone and they will say 'those other 11 explanations are stupid - you should have used this one first'. That's all well and good, except for the fact that that it's never the same one that does it.'

    • Unfortunately the controversy doesn't disappear, even if you point out that the propeller blades are not moving directly downwind. People (including physics professors) still claim it is impossible.

  • What a cool contraption! Would it be hard to have more than two blades? That would help keep vibrations in check.

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  • I love how you say in the end "that's how education should be". Interesting to see that most of us who do hands-on things have that opinion. Still at the same time school is so different. Wouldn't it be time to change that? A school full of engineers and practical physicists teaching how the world works. Imagine how motivated and creative children would be there.

  • Truly speaking, i am unable to wrap my mind around this idea. Also i am no expert on machanics, so i will not go to the point of criticism. But what i would like to understand is that, if we take the same experiment and change one variable i.e. instead of the vehical getting power from wind, if it get powered by a constant power generator. Then the additional power generated by the Propeller in the top can be converted to electricity and again feed to the wheel in addition to the constant power that we are supplying. Which will make the Propeller go more faster and the loop can go on. Now just for theory, even if we do this experiment in vaccum, i.e. there is no air drag on the propeller, still it seems like there is energy being generated out of no where. I may be missing something here and would really like to be corrected. Please explain this process in a bit more detail and correct me where i am going wrong. Thanks.

    • Read the pinned comment.

  • for how long can you go faster than the wind?

    • As long as the wind keeps blowing.

  • Was just thinking about this and wonder whether it's a similar concept to: If you had a river flowing at x speed and put a sheet against its flow. No matter how large you make the sheet (assuming it still fits within the river) it'll end up going at the same speed as the same force is acting on each square inch of surface area. So if you have a small object it'll go the same speed as a large object. If you instead funnelled the river water into a small area you'd create a much greater pressure. If you hit the spurt coming out the other side against the small object it'll go way faster than the small object that was simply flowing against the water. I've probably missed stuff there, for instance the fact your funnel had to be quite large compared to the small sheet for it to work. But it would work for the big sheet as well I guess if you imagine them to be weightless.

  • hey, can u add a normal propeller (a normal windmail) in front of the one u already have.. I am thinking that could add more burst energy when u start the vehicle (accelerate faster) but will be useless later on when u speed up more then wind cause the wind wont reach it then... i am thinking to ad it in front of the first one because like u said the wind behind the first one will be slower... what do u think..?

    • and I think some (switch direction sails) can be add for the vehicle to be able to go even faster and not only downwind.. [like in the example with sailboats] (this way I think you (or a person mastering the motion control) could at some point surpass [5X power of the wind]).. that would be exciting... [and yeah maybe need to be add more safety measures(especially is the speed successfully increashes)]

  • So essentially, this is the manifestation of "You don't need to know how something works to use it"

  • Don't understand

  • I don't know

  • Here is a more intuitive proof that you can build something that goes faster downwind than the wind. You build a car like the one seen, but instead of connecting the prop to the wheels, it is connected to a dynamo that charges a battery. The wheels are powered by an electric motor. First, you apply the brakes so that the car is stationary and allow the battery to charge. Once charged, you fold the propeler away and use the battery to drive the wheels. If the propeler is big enough and the car light enough there is no reason why you can't generate enough energy so that the car can go so fast that it catches up and overtakes where it would have been if it had just gone at the same speed as the wind. I see no physical law that can prevent this from being possible. Once the battery runs out, you just stop and repeat. So it is clearly possible to go faster than the wind on average at least. If this is possible, then there is no conservation law being broken by going faster than the wind by being powered by the wind.

    • @The Original Planet I'm not certain that you got it right and I got it wrong, but I'm definitely leaning that way. I guess I need to learn to stick with my initial intuition no matter what! :)

    • @Rick Cavallaro I am glad I did't get it wrong. It was a really great video and experiment. It really made me think. Thanks!

    • @The Original Planet I was telling myself that it's not possible to do that because it should be possible to come up with a mechanism to do it steady state - even if we couldn't think of that mechanism. And I reasoned that that's impossible without working the turbine against the ground. But you are doing that by applying the brakes. So it's quite possible I spoke to soon.

    • @Rick Cavallaro Thanks for the reply! I am happy to be proved wrong on this and learn something. My thought experiment was based on the idea that there were not many theoretical constraints on the size and weights of the components (although for sure practical ones). I could build an arbitrarily large wind turbine (maybe limited by the tips not exceeding the speed of sound) of some arbitrarily light material. The car and motor and similarly arbitrarily light and the mass of the battery is limited only by e=mc². When my car is anchored to the ground, the time I need to wait to charge my super-battery can be extremely short with a big enough turbine. I can then fold the turbine away and accelerate to over the wind speed. This only requires that the energy gathered from the wind is greater the ½mv², where m is the mass of the car. But this mass does not affect my ability to harvest energy. It is not in the equation, so I can make m as small as I like (apart from the battery) until the kinetic energy is smaller than the energy harvested. Furthermore, if my car is arbitrarily well streamlined and has frictionless wheels, if I am going faster than the wind then even when the battery runs out I can coast for as long as I like until I overtake the point where the wind has got to. I am not sure where the logic is wrong. To be clear, I was just trying to show by another argument (in addition to the boat-on-a-cylinder) there is no theoretical barrier to going downwind faster than the wind using a propeller. Obviously the Blackbord shows us that is the case in practice.

    • Simply generating electricity from turbine blades, and using that stored energy to drive the wheels, could get you above wind speed in spurts, but not on average.

  • The thing is these concepts are indeed mind wobbling but they are theoretically sound, what's sad is that it's kinda overwhelming to imbibe these concepts in these small videos....we need to pick out own paper and pen and think about it....by the time video has already ended leaving you dazed...you keep thinking that people have understood what is being demonstrated in the video... I don't know, all this might appear fancy but the question is, can people really get that sound understanding of the underlying physics just completing this video? PS: I am your patron and your videos are real delight to watch!!

  • PhD in physics here ! Love how we think we know but we actually we don't. This is just another proof that we have so much to discover, rewrite and advance.

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  • What about using the car backwards and going straight against the wind? The propeller would be used as a windmill and power the wheels. The faster the car goes, the stronger the wind gets. Would that work as well?

    • It did work in 2010 when we set the record going directly upwind at 2.1X wind speed.

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  • Would this work for a solar sail in space?

  • your explination kinda confused me by saying the air molecules behind the fan were giving energy to it. wouldnt it be the air in front of the fan giving kenetic energy to the sails (props/fan) and thats why there are slower behhind the fan? the props are the sail boats, the air in front is generating wind like they are tacking. they even can be adjusted to go faster or slower w/ the angle they attack the actual wind. so its not a perpetual motion machine. its a giant land sailing boat. which requires more than 10mph to go faster than wind apparently, and caps out at 2.8 times actual wind, from their testing. its cool they made it but it obviously doesnt break the laws of physics or establish new ones. and its obviously not a perpetual motion machine. not sure which forum they were posting on that trashed them before tho

    • >> not sure which forum they were posting on that trashed them before tho Literally dozens

  • I have an objection sir. the air particles behind the propeller are slow but particles in front the fan are still have the same speed. so the stick with clothe on it have to show its direction as the wind original speed because clothe is there, where the particles have the original speed nat the slower speed like particles behind the propeller.

  • The issues I have is that there's no mention of the props motion relative to the air (the air speed the surface of the prop sees is going to be faster because of the rotation of the prop) and also the aerodynamics of the prop acting like a sail (or rather an aerofoil), generating suction (i.e. thrust) on the front surface of the prop. The analogy of pushing air particles behind the vehicle isn't really how the aerodynamics work...

    • @David Marshall You aren't professionally involved with aerodynamics at all. I can tell.

    • @David Marshall But again - it DOES. They are two different, and equally accurate, ways of looking at and analyzing the same problem.

    • @Rick Cavallaro But again, following the aircraft wing example, it doesn't fly because the wing is pushing air particles down resulting in an equal and opposite force upwards, it's flying because of a pressure differential acting on the wing surfaces producing the lift force.

    • @admacdo2009 Well that's how an aeroplane flies and they tend to be pretty aerodynamic ;). Wing profile results in high velocity air over the upper (suction) surface, creates low pressure (=suction), resulting in the lift force being generated.

    • >> The analogy of pushing air particles behind the vehicle isn't really how the aerodynamics work... It really is. We can analyze lift using either Bernoulli or Newton. Just two sides of the same coin.

  • I actually understand how it works but not in terms of energy conservation

    • @Ujjwal Singh The effective surface of the prop blades is moving backward with respect to the air, so it slows the air with respect to the ground.

    • @eyytee ya , but how

    • The wind loses energy. The car gains it.

  • everyone gangsta until the prop starts shaking

  • I think it’s possible to drive a vehicle faster than the speed if the down wind, it’s called: a car.

    • @Francisco Garcia But Even the highest performance sailboat can't do that while going directly downwind. The Blackbird can. That's the point.

    • @John Borton to me suffice to know that a sail boat can go faster than a balloon being dragged by the wind.

    • @Francisco Garcia It's most practical application has turned out to be as a science education tool.

    • @John Borton but what's the practical use of this? A bicycle it's way more practical.

    • @Francisco Garcia Given the task, if your car is not wind powered, then your point most definitely does not prevail.

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  • Net positive seems to be the nature of this universe.

  • Turbine?

  • if we can use light as the resource, we can easily travel faster than the speed of light 😂! when someone travel same as speed of light, his/her time will stop! which means time can be manipulated! even though the pilot doesn't feel the change of time because the pilot's time had stopped when he reach the speed of light, but we can still expect to see the pilot come back after million of years later(for the pilot, it just feels like 1 second passed)! and the main problem is, anyone else who didn't travel as fast as speed of light would be dead within 100 year... so only something that can live forever is able to carry out this time travel experiment. therefore, only A.I. is the best participant for inventing the time travel machine 😂

  • Look at the sail size. That much force can make this light cart faster than the air it's harvesting energy from. Obviously it can't fly lol. That will break the laws of physics.

  • I wonder how many people figured out that this isn't about transportation but energy generation.

  • We thought the demonstration was well done and provided adequate detail to form an opinion.

  • warp drive hints here.

  • For me it made it a bit easier to understand how this is possible by knowing how turbines in a hydroelectric power plant are designed. The blades of those are most efficient when they aren't straight but have a w shape. This way looking from the point of the blade itself you push yourself forward by pushing the water back. But looking globally the water won't be reflected against the stream but loose all movement relative to the surroundings. With a flat blade design the water will continue flowing in the direction of the stream and thus still having some energy left. The turbines are most efficient, if the water doesn't move anymore (and just drops straight down because of gravity). With this vehicle it's very similar. As the driver you get pushed by the wind an "deflect" it back again. But looking from the outside you'll see the wind behind the vehicle still moving in the same direction. It will be the fastest and most efficient when the wind pushed back by the prop will be stationary relativ to ground.

  • There's a difference between a sail and a propeller that gives thrust 🤦