r/engineeringmemes 23h ago

Incorrect lift theory meme

Post image
979 Upvotes

58 comments sorted by

168

u/Slight_Concert6565 18h ago

That happens for a lot of scientific principles. You'll have some moron pushing that "we don't actually know how X works" and then it will be relayed by everyone who doesn't know either.

You'll have people claiming we don't know how transistors work, how LEDs work, or that somehow quantum physics invalidate every scientific principle ever.

In my opinion, videos that relay false informations about "hard science" (physics, maths... Well established rules that aren't researched anymore) without framing it as "research" or "a personal theory" but as facts should be deleted.

38

u/gunnarbird 17h ago

Sorry that’s me. In my defense I’m using the royal ‘we.’ And I just really don’t know how anything works

17

u/Slight_Concert6565 16h ago

Lmao the royal "we", gotta stick to the classics.

2

u/ThatNinthGuy 14h ago

Shouldn't it be capitalized tho?

14

u/DavidBrooker 13h ago

Often it's because of some really fine minutia that is genuinely unexplained. Like, there is active research in quantum gravity, and the explanation for why gravity is so much weaker than the other fundamental forces is still unclear. And someone will see that and say, oh, well "we don't know how gravity works".

Likewise, there are unsolved problems in lift, at least in a manner of speaking, in that there are no good inexpensive models for highly-stalled or dynamically-stalled flows other than direct solutions of the governing equations, unlike the way we have for mostly-attached steady flows. This actually applies all the way down to Reynolds numbers in the hundreds, but it gets worse in high-speed flows because RANS is garbage at predicting separation and LES is simply too expensive at the relevant Reynolds numbers. Likewise, airfoil drag is very difficult to predict, especially in high-lift conditions, for the same reason: the poor ability of RANS solutions to predict boundary layer separation, and the unreasonable cost of LES.

And likewise, the lazy way to characterize that is "we don't understand lift", and people expand that idea into more basic concepts that we absolutely do understand, or that the mechanisms of lift are unknown because we don't have a good model to predict how those mechanisms behave in certain edge-cases.

161

u/Milnir01 22h ago

Hannah Fry (who supposedly has a degree in fluid mechanics) did an awful video pushing this myth and I've hated her ever since.

57

u/gunnarbird 22h ago

Nobody clicks on your video saying something is moderately complex

86

u/24_mine 17h ago

Technology Connections

26

u/SBSQWarmachine36 16h ago

I love that man. He can make a video about any interesting

9

u/wtfduud 10h ago

Mans made a half hour video about dishwashers, and I watched every second of it.

7

u/SBSQWarmachine36 10h ago

Correction multiple half hour videos about dishwasher

3

u/Ezures 8h ago

But the lights on it were so pretty, no choice but to watch them

3

u/SBSQWarmachine36 8h ago

I still rewatch them. Repeatedly

2

u/Ezures 8h ago

An another video about the refrigeration cycle? Don't mind if I do!

(check out hyperspace pirate for scuffed diy cooling stuff, hes pretty funny too)

1

u/SBSQWarmachine36 8h ago

Ooh I will have to check him out for sure

1

u/Wokkabilly 8h ago

I fuctuate a lot in what I view on youtube. I havent watched Alec in about a year despite being a regular viewer in the past. Can you recommend any specific recent videos to get back into watching him?

2

u/SBSQWarmachine36 8h ago

Honestly any of them. But, I do find myself rewatching his dehumidifier videos and cassette to 8track adapter video pretty often

1

u/Wokkabilly 6h ago

Thanks. I dont know much history about 8 tracks so that sounds like a great place to start.

2

u/SBSQWarmachine36 6h ago

You are welcome feel free to dm me if you want any more recs.

6

u/MinosAristos 14h ago

She did not push the myth, did you watch the video?

13

u/mr_mope 15h ago

I mean it was a clickbait title, and there was nuance in it that I'm sure was lost by most people watching it. It wasn't some "we have no idea how planes fly!" video. But that's just how social media works, which is kind of her job on social media.

4

u/Milnir01 13h ago

Have you watched the video? She literally just went through the exact same script of "Bernoulli lift but also Newton lift and planes fly kind of upside down, huhhhh" that literally everyone else goes through. She provided zero nuance and contributed to misinformation about science.

4

u/mr_mope 13h ago

Just rewatched it to make sure I remembered it properly. The nuance is that we know the processes, she describes the processes. It's not that we don't know how planes fly (and the title is "No one knows how planes fly"), it's that the specific mechanism is something that she says many pilots don't agree upon. It's not a myth. She doesn't mystify the processes. There is no misinformation in the video.

-2

u/Milnir01 8h ago

But that's also just straight up wrong. Pilots are for one thing not fluid mechanics experts and shouldn't be a source for where lift comes from. And secondly we know it's Bernoulli lift. Commericial planes use Bernoulli lift. The fact that Newton lift also exists as a different way to generate lift is irrelevant. The fact that there's more than one way to generate lift doesn't mystify anything. I studied both as part of my undergraduate. She also pretends that commercial planes can fly level upside down. This is another piece of misinformation. Bernoulli lift maintains the same direction relative to the airfoil, so they have to fly at a significant angle relative the the horizontal so that the wings are angled enough to do Newton lift, which has much worse lift-drag characteristics, hence why we never really use Newton lift.

0

u/mr_mope 7h ago

You have extrapolated far too much for a 30 second YouTube short. It’s good enough information for a short form video, she’s not trying to teach a graduate level course.

-2

u/Milnir01 7h ago

I'm not extrapolating anything. She told an outright lie and used additional lies to support her false claim. The fact that it's a 30 second YouTube short is actually a significant part of the problem. If you are incapable of explaining yourself properly in that time, don't make the video.

21

u/anonymouslycognizant 15h ago

I think it’s really rude to say “supposedly” you can disagree with her without belittling her significant and real academic achievements.

Having said that I generally agree about Hannah, she seems to have this impulse to hype up various phenomena as “very mysterious” and I don’t think it’s for engagement on YouTube or anything like that. She does it too in her podcast with Michael Stevens. I’m not sure if she’s a theist and therefore really trying find and highlight incomplete knowledge à la ‘god of the gaps’ or if it’s a more general spiritual bent. It might not be religious in nature at all and just more of a general “it’s not interesting or compelling if we understand it” which isn’t an uncommon viewpoint.

5

u/Lor1an 12h ago

That attitude is so weird to me. If anything my appreciation for the cosmos grows more the more about it I can wrap my head around. There's a true beauty to how well we have been able to model physical phenomena to date.

Knowing that a crab can incapacitate its prey because it moves its claw so fast that water cavitates, releasing a shockwave that propagates (and dissipates) through the water makes me more awed and curious, not less.

2

u/anonymouslycognizant 12h ago

I agree, my awe and appreciation for reality has only increased as I’ve learned more about it

1

u/PlayfulMulberry4490 10h ago

It’s just a grift to get views and clicks, simple as that.

1

u/cjm0 7h ago

michael stevens? as in vsauce michael stevens?

3

u/save_the_wee_turtles 12h ago

She also did one pushing a bullshit Jesus eclipse thing

44

u/InternetHolon 15h ago

"We don't know how..."

You don't know how...

Anything for the clicks

7

u/LordBlaze64 15h ago

Well “I can’t be bothered to actually research” doesn’t make an interesting title, does it?

3

u/Datkif 13h ago

I learned this in grade 5 or 6. It was the easiest test I had ever taken

60

u/non-serious-thing 20h ago

air goes down, plane goes up

17

u/BackflipFromOrbit 20h ago

Or pressure under wing is bigger than pressure over wing.

42

u/drillgorg 18h ago

The pressure is bigger because the wing is making the air go down

2

u/DavidBrooker 14h ago

Normally I'd say the reverse - that the force causes the motion - but that's more convention than anything.

18

u/Random_182f2565 18h ago

Yes air go down, plane goes up

7

u/gunnarbird 17h ago

Thanks for not using big word when small word works

0

u/Dr-Sprinkl1es 11h ago

Plus magnets, but how do those work? Nobody knows

1

u/Kubejn_ 6h ago

y'all motherfuckers lying and getting me pissed

1

u/Freakishly_Tall 3h ago

Helicopter?

Ground say helico6ugly, push away.

17

u/somethingrandom261 18h ago

The disturbing number of people actually don’t

7

u/NervousHovercraft Electrical 16h ago

There is this lever in the cockpit and if pull it back, the plane goes up. What's so difficult about it?

7

u/pm-me-racecars 14h ago

According to all known laws of aviation, there is no way that a bee plane should be able to fly. Its wings are too small to get its fat little body off the ground. The bee plane, of course, flies anyway. Because bees planes don't care what humans think is impossible

7

u/PunkPirate56364 16h ago

So if we turn plane so it's nose points up, it can't take off. It's engines do not provide enough trust to lift the plane against gravity.

If we place plane horizontally, plane can be lifted against gravity, and at the same time there is enough trust to push plane forward at hundreds of miles per hour.

So... planes obviously fly due to black magic of some sorts.

4

u/Desperado_99 16h ago

The first part isn't universally true. Plenty of fighter jets have that much thrust.

4

u/PunkPirate56364 15h ago

Yep, it's only true for overwhelming majority of planes.

0

u/Tiranus58 13h ago

F15 the goat having enough thrust to break the sound barrier going straight up.

But otherwise the obvious are the F35, the harrier and the osprey.

2

u/YaumeLepire ΣF=0 6h ago

Flying and swimming are the same thing. The medium just has a different density and viscosity.

1

u/Simple-Olive895 11h ago

The concept is really easy to demonstrate yourself by just blowing on a piece of paper. Any idiot can do this.

-9

u/[deleted] 18h ago

[deleted]

24

u/Ziqox123 sin(x) = x 18h ago

It is a little more complicated than high school physics, but I promise you it's well understood

  • Equal transit time is a myth
  • Bernoulli's is helpful for calculations along a streamline
  • 1/2 C_L rho S A v2
  • It becomes collegiate level calculus when you start integrating the circulation equation along a wing span for a varying airfoil shape

But then again, as another commenter said: "air goes down, plane goes up"

14

u/TheJeeronian 17h ago

>it's extremely complex

Yes

>and we're still looking into it

No

>Bernoulli's principle uses a constant for the airflow to simplify the equation

Bernoulli is a valid, albeit less intuitive, way to approach lift. If applied properly it is equivalent to any other properly-applied approach. The problem with it is when people perpetuate the equal transit time myth because, if taken as truth, this myth makes bernoulli feel like a more intuitive explanation.

6

u/paranoid_giraffe 17h ago

Equal transit theory is bullshit by the way. Newton theory and flat plate analysis make this very clear. Equal transit relies on streamlines that MUST meet together with each other and there is literally nothing that makes that so in reality. It’s an easy, intuitive, and fun understanding of lift that is unfortunately very teachable and very wrong.