What’s one myth you cannot believe was confirmed?

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Adam was actually approached by a young 10ish old child if memory serves, and they speculated that it was because the mouse was white as opposed to brown like it would be in the wild. Adam said that was a plausible reason that none of the adults had considered. I love when people can admit they might have been wrong. Especially an adult to a kid.

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wesleyweir@reddit

Also the fact that the mouse popped out of a hollow piece of poop! That musta been pretty freaky for the elephant!

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IOrocketscience@reddit

They tested with just the hollow poop rolling over to make sure that wasn't what they were reacting to, and they ignored it. It was specifically the mouse that freaked them out.

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badbirch@reddit

Shouldn't they have run a third test with a different thing hiding in the poop. Maybe something that looks scary but doesn't move.

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424Impala67@reddit

Need to rewatch, but did they try just a white toy mouse just sitting there to see if they reacted to having amy strange object by their feet?

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badbirch@reddit

No just moving the poo without anything in it. They really don't test it super thoroughly. But that is understandable, it's hard to get elephants to do anything and it's probably best to not try and scare them over and over.

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chemtiger8@reddit

Control experiment! Science!!

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Protiguous@reddit

That's the best part about science.

"Wow, that was unexpected. Fascinating!"

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benglescott@reddit

Came here to say that. It was so weird. Although I thought it looked like they were more afraid of stepping on the mice vs. actually fearing them.

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Protiguous@reddit

Agreed. Like they did not want to cause unnecessary harm.

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RedShirtCashion@reddit

I always found that using liquid nitrogen on C4 as in Lethal Weapon 2 being possible to be particularly interesting. Even more hilariously that the need to yank the person on the toilet into the bathtub is completely unnecessary, it delays it enough for you to just carry the guy out of there.

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soulreaverdan@reddit

Perhaps not quite that I didn’t believe it, but seeing the Monty Hall Paradox laid out and fully tested with a large sample size and an actual full experiment highlighted it much better than I ever had heard it.

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Thefirstargonaut@reddit

I gotta go watch that, I hate the Monty hall problem vehemently and entirely disagree with everyone on it.

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justme46@reddit

The best way to imagine Monty hall is to think of a scenario with 100 doors.

You pick one door and the host opens 98 doors leaving your pick and one other closed. Surely youre changing your mind this time right? The chance you got it right the 1st time is 1/100 but the chance the new door is correct is 99/100

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Thefirstargonaut@reddit

The probability is the same for both doors remaining in your example. They both have a probability of 1 in 2. There’s two doors. One is correct.

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justme46@reddit

No. In my 3 door example all 3 are still closed. You pick door 1. Then the host gives you the option of sticking with your original or choosing to open door 2 and 3. Of course you would switch in this case right?

In my 100 door example yes there are only 2 doors left but you understand the chances of you picking right the 1st time is 1/100 right? The host knows which door the prize is behind. If you have picked incorrectly (which you will 99/100) then the prize has to be behind the other door

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Protiguous@reddit

The host knows which door the prize is behind.

That part is almost always left out, and it changes the outcomes.

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datalaughing@reddit

So if we’re not in that situation. Let’s say instead of Let’s Make a Deal we’re playing Deal or No Deal. The contestant, with no foreknowledge makes all the choices. In the end he has $.01 and $100,00 left and has to decide to either keep his own case or switch. Have the odds changed?

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Protiguous@reddit

he has $.01 and $100,00 left

I'm sorry, I do not understand this part. (I don't know, "Deal or No Deal".)

Is this another game similar to the Monty Hall one, in that the contestant has 3 choices?

Low, Medium, or High rewards? ($0, $0.01, or $100,000?)

And can only pick one?

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datalaughing@reddit

In Deal or No Deal there are something like 20 cases. Each case has a different amount inside. The player starts by picking a case for themselves. Then they gradually eliminate other cases, finding out how much is inside each, until they’re left with only the case they chose at the beginning and one unopened mystery case. Then they’re given the choice to keep their original or trade for the remaining case. The 20 different amounts are all known ahead of time, but you don’t know which one is in which case. So if at the end there are two possibilities left, a very low one and a very high one, is there a benefit to switching vs keeping at that point?

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Protiguous@reddit

Oooh, interesting! (Let's see if I follow correctly.)

Start with 20 total cases, each of a random $$ reward?

Player picks 1 (first) case. Do they know the contents yet? I'm guessing that's the mystery case #1, so they don't know?

Do they basically open all other 18 cases, and then know those amounts but only one at a time?

And then that leaves the remaining final case, contents unknown?

So, the choice is to stick with the very first case they picked or switch to the final remaining case. Contents of either, still unknown.

Along the game, as they uncover the 18 cases, if they see what they think is a 'high' reward, at that point do they have the option to stop and keep that reward?

I would venture a guess that people would tend to keep the one they think is going to be their 'highest' reward, rather than risk getting a lower reward case?

I'd like to see the data of their choices all graphed out. I'd bet there are some unique variations in their choices among different types of people!

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datalaughing@reddit

Yes, you’ve got the process mostly right. And yes the contents of the first case does remain a secret until the end.

The only thing I left out is that after they open a few cases, the host gives them an offer, calculated based on the remaining possible case contents. They can choose to accept the offer (take the Deal) or else say No Deal and continue opening cases potentially raising or lowering future offers depending on what amounts are revealed. If they keep choosing No Deal until the end, that’s when they decide whether to trade in their mystery case for the one remaining mystery case on the board.

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bradygilg@reddit

The math is extremely simple and does not need to be explained. The reason that Monty Hall is so overblown is that it's primarily an issue of communication, not math. The result is critically dependent on the assumption that Monty knows where all of the prizes are and acts in the best interest of the competitor. Alternative formulations of Monty's behavior lead to any other probability distribution you desire.

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AtreidesOne@reddit

You're right that in some cases, the fact that Monty knows where the prizes is and ALWAYS reveals a goat isn't spelled out, and that definitely hurts people's understanding of the problem.

HOWEVER, this is certainly not the reason it's so controversial. If it was, everyone who was presented with the clearly explained version would get the right answer. But that's not at all what we see. Very many people who have the problem clearly explained to them still insist that it's 50/50 because you are picking 1 from 2.

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IOrocketscience@reddit

right, it's an example of "the gambler's fallacy" - people tend to think that any time there are multiple possibilities, they all have an equal chance of happening, which leads to the assumption that any event with 2 possible outcomes is a 50/50 coin toss. but that's not the case. For example, if the New York Yankees played the Little League world series champions in a game of baseball, there are only 2 possible outcomes, but it would be insane to believe that the Little League team has an equal chance of beating the New York Yankees. Ironically, the one place where people stop believing in equal chance is in coin tosses! they tend to think that if you get a bunch of tails in a row on coin tosses, then the next toss is more likely to be heads, because the heads toss is "due" after all the tails. but each coin toss is still exactly 50/50 and is independent of what happened before.

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DesolationRobot@reddit

Gamblers fallacy is erroneously tying the probability of an independent occurrence to the outcomes of previous occurrences.

“I’ve flipped 5 heads in a row. The next one has to be tails.”

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lionseatcake@reddit

What a narcissistic thing to say. Like you speak for all people or something. "Does not need to be explained" as you then go on to prove that you do need to offer some kind of explanation 🤣🤣🤣

Fuckin reddit, man.

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bradygilg@reddit

The math doesn't need to be explained. Reading comprehension does, apparently.

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lionseatcake@reddit

Right, "I'm rubber your glue" keep proving me right, please.

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bradygilg@reddit

You have emojis in your reddit comment.

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Protiguous@reddit

The result is critically dependent on the assumption that Monty knows where all of the prizes are and acts in the best interest of the competitor.

Thank you! I've been saying this for years!

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AtreidesOne@reddit

Yes, it's important that "he opens the door to reveal a goat" is explained as his consistent behaviour, not just something that happened one time.

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TheGloveMan@reddit

That’s a good approach actually.

Month is on your side and helps you. Do you want to pick before he helps you or after?

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FrickinLazerBeams@reddit

FYI you can't really "disagree" over a matter of fact. Like, you can be wrong, or not be wrong, or just not understand; but disagreements are for opinions. Mathematical facts are not opinions.

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Thefirstargonaut@reddit

Lol. My opinion (due to my poor understanding) is that others are wrong. I disagree with what they tell me. Although, this round I am disagreeing with others less. I want to test it out, though.

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FrickinLazerBeams@reddit

Then you think you're right but either you're wrong or you don't understand. You'd be better off saying you don't know but you're confident enough to claim you're right even though you probably aren't. In any case there's no room for an opinion about facts.

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tactical_waifu_sim@reddit

What do you mean you disagree with everyone?

The math doesn't lie.

Switching increases your chance. Watch the episode and you'll see it happen in real time.

Here is the easiest way I've ever been able to wrap my head around how it works.

First, Monty knows what is behind each door. This is key.

You pick one of three doors. You had a 1/3 chance of picking the correct door. Or said another way, there is a 2/3 chance it is behind one of the other doors.

Monty now opens a door. It will never be yours, or the money.

He asks if you want to switch. This feels 50/50, but it isn't. When you switch you are effectively flipping your odds.

When you selected your initial door you had 2/3 chance it was in one of the other 2 doors. Those odds didn't change just because Monty opened one of them.

By switching to the other closed door you gain those 2/3 odds.

Basically, by switching you are really selecting both of those doors. Not just the one that isn't open.

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Extreme_Priority_170@reddit

As I said below the Monty Hall problem only works with two conditions assumed and one of these is not what actually happened in “The Price is Right” TV show. In the problem Monty KNOWS what is behind each curtain AND he will always eliminate all other outcomes so that ONE OF THE FINAL TWO CHOICES IS A GOAT. If Monty doesn’t know where the goat is OR he doesn’t eliminate all other possibilities so that the goat is one of the two final outcomes the problem doesn’t work.

In other words if Monty is selecting at random then it doesn’t improve your odds. If Monty doesn’t care if he reveals the goat or a new car behind the curtain you don’t improve your odds. These two factors HAVE to be explained in the problem because to my recollection this isn’t what would actually happen on the show.

This was what would happen on the show as I remember it as a kid watching in the 70s. In the three curtain situations there were three prizes. A great prize, an OK prize and a non prize. For example the three prizes could be $100, a new car and the goat. Monty knew what was behind each curtain BUT if you were to pick the $100 curtain SOMETIMES he would chose to reveal the goat and SOMETIMES he would reveal the new car because sometimes missing out on the big prize made for better TV then getting the goat. If he is just as likely to reveal the new car as the goat then switching doesn’t improve your odds of getting the new car.

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Protiguous@reddit

Monty knows what is behind each door.

That part is almost always left out, and it changes the outcomes.

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Extreme_Priority_170@reddit

Right AND he will always eliminate all other outcomes so that one of the two final choices are a goat. If Monty doesn’t know where the goat is OR he doesn’t eliminate all other possibilities so that the goat is one of the two final outcomes the problem doesn’t work. In other words if Monty is selecting at random then it doesn’t improve your odds. If Monty doesn’t care if he reveals the goat or a new car behind the curtain you don’t improve your odds. These two factors HAVE to be explained in the problem because to my recollection this isn’t what would actually happen on the show.

This was what would happen on the show as I remember it as a kid watching in the 70s. In the three curtain situations there were three prizes. A great prize, an OK prize and a non prize. For example the three prizes could be $100, a new car and the goat. If you were to pick the $100 curtain sometimes he would chose to reveal the goat and sometimes he would reveal the new car because sometimes missing out on the big prize made for better TV then getting the goat. If he is just as likely to reveal the new car as the goat then switching doesn’t improve your odds of getting the new car.

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Thefirstargonaut@reddit

You’re like like 15th person to explain it to me on Reddit. I hate the Monty hall problem. Probability doesn’t carry forward, though. Like, if there are two doors, and there is a prize between one of those two doors, the probability is 50/50. I have a one in two chance with either door.

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AtreidesOne@reddit

Here's something that might help with the 50/50 thing.

Consider two sports teams: the Bears and the Eagles. Say they are playing each other tonight. I ask you who would win. You have no idea who these teams are. One may be a lot better than the other. but you don't know this. So you can only flip a coin, or some other arbitrary method, and you'll have a 50% chance of getting it right.

And THAT is the situation if you just brought a random person into the Monty Hall situation at the last minute and asked them to pick a door. They see two doors, and they have no history or past knowledge, so they have to pick randomly, and they'll have a 50/50 chance of getting it right.

However, the actual contestant in the Monty Hall problem DOES have some history and knowledge. They know how the doors were chosen. So it's like asking someone who's been following the Bears and the Eagles all season and knows that the Bears would win a match-up with the Eagles 2/3 of the time. They would know to pick the Bears, and they'll be right 2/3rds of the time.

So why is one door more likely to win than the other? Because it essentially has already "beaten" another door. The door you initially selected had a 1/3 chance of winning. The pair of doors that you DIDN'T pick had a 2/3 chance of winning, since there were two of them. If you could pick 2 doors instead on 1, you'd do it , right? Because picking 2 doors gives you a higher chance of winning. Well, by switching after Monty has opened a door, you essentially ARE picking 2 doors. Because Monty "threw away" the door he knew was no good out of those two doors. So by switching after he's opened a dud door (and always a dud door) you increase your chances just as if you'd been allowed to pick the other two doors from the start. You know the history of how the doors were chosen, so you have a better than 50/50 chance of picking the right door.

Does that help?

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AtreidesOne@reddit

Speaking of "throwing away", I find it helps to imagine it as a card puzzle:

—

The Dealer lays out three cards face-down on the table. You both know that two cards are black, and one card is red. If you end up with the red card, you win.

You pick one of the cards, but you aren't allowed to look at it yet. You keep it face down on the table in front of you.

The Dealer picks up the two remaining cards, looks at them, and discards one of them face up. He always discards a black card. You still don’t know your card, and you don’t know the dealer's card.

Now you have the option of keeping your card, or switching cards with the dealer. Which would you choose?

Since the dealer had a 2/3 chance of drawing the red card initially and you only had a 1/3 chance, you’d always want to swap hands with him. The fact that he discarded a black card doesn’t affect his chances of winning.

—

The same applies to the doors. You only had a 1/3 chance of being right the first time when you first picked a door. The remaining doors had a 2/3 chance. And that 2/3 chance is now contained solely in the 1 remaining door. So pick that one!

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Thefirstargonaut@reddit

Your sports analogy doesn’t help.

This one is making me think, which is better than most analogies. Imagining pulling out a card from three and holding on to it kind of helps. This helps more than any other analogy. Thank you for sharing this.

I’m a teacher and I want to test this with my students. I want to see if I could shoehorn it into a probability unit, but my students are upper elementary. I don’t know.

I hate this thing. I’m a relatively smart guy, but I just get stuck with this. Your card analogy helps more than any other.

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Unlikely-Rock-9647@reddit

Think of it this way. This is a mathematically equivalent way of looking at the problem.

You pick one of the doors. Let’s say you pick door A. Now, before opening any doors, Monty looks at you and says “You can keep door A. OR. You can switch to BOTH doors B and C. If you switch and the prize is behind B OR C you win, because I’ll open the one that doesn’t have the prize and you open the other one.”

Obviously the pair of both door B and door C have a 2/3 chance of having the car behind them because it’s 2 doors, not 1. You’re not picking between two doors. You’re ultimately picking between Behind Door A, and Not Behind Door A.

The math gets even more obvious if you picture a hundred doors. You pick door 1, and Monty gives you the option nod either Door 1, or Door 2-100. If you pick 2-100, you win if the car is behind any of those 99 doors, because he will help you and open the 98 doors that don’t have a car.

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AtreidesOne@reddit

I'm glad! Yes, the card one was what helped me the most too.

Analogies are funny like that - some will click and some won't. The main point of the sports was highlighting that choosing 1 out of 2 is only 50/50 is you don't have any other information. The statement that "if there are 2 things, the probability is 50/50" doesn't hold, generally. That ONLY holds for random picks. If you have more information and aren't just picking randomly, you can get a higher win rate.

You should definitely try it with your students! It's absolutely probability and wouldn't be shoehorning at all. And sometimes you have to see things to believe them. It's very easy to test and it will be fun to get them to make predictions beforehand too. And it's appropriate for huge age ranges.

Don't feel too bad about it. It's tripped up many, very smart people! The only sin here is if you start insulting others for what you see as the wrong answer, which many smart people have done (see the interesting and embarrassing history in the link below) but you haven't.

https://priceonomics.com/the-time-everyone-corrected-the-worlds-smartest/

Personally I LOVE this kind of thing. It fascinates me that our strong intuitions can fail at basic reality so badly.

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KeterClassKitten@reddit

The host eliminates a wrong option, that's key.

So, if you choose the correct door from the get go, he eliminates one of the two others. But if you choose the wrong door, he eliminates the only other wrong door. This means that if you choose 2 of the 3 options, the remaining door will be the correct answer. The probability remains based off of the first choice.

By switching, you're "betting" that the first option was the wrong choice, and it is 2/3 of the time.

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soulreaverdan@reddit

It’s one of the viewer request episodes, S9E21

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jayhawk88@reddit

The “Dive under water to be protected from gunfire” one blew my mind watching it the first time. Completely logical, but still, watching .50 cal bullets fail to do any damage at like 3 feet or whatever it was…incredible.

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Safe_Increase_4099@reddit

That in the movie "Titanic" only Jack or Rose could have survived on the board, not both.

I love the fact that James Cameron commissioned a study that used stunt people and hypothermia experts to recreate the scene. The study found that only one of them could have survived.

Side note: after viewing the movie Dr. Neil DeGrasse Tyson observed that the night sky Rose was looking at would have been different. He contacted James Cameron who then had Dr. Tyson generate the correct star field so that he could re-edit the scene and incorporate it into the 10th anniversary re-realease.

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NandroloneEnanthate@reddit

TO this day, i still do not understand how they were able to prove that an airplane could take off on a conveyor belt when the plan was clearly moving forward and therefore producing lift. I thought the thought experiment was a STATIONARY plane on a conveyor belt couldnt take off.

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drakeallthethings@reddit

I remember how pissed off Jamie was that they were even doing that myth.

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THE_CENTURION@reddit

I was also tricked by this one at first. "Stationary" isn't actually part of the myth, you assumed it was because your brain just locks in "vehicles on treadmills don't move forward" as a fact and then moves on with the rest of the question (can a plane take off without moving forward). But that rule doesn't apply to planes, since they don't need the ground to move forward.

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lieutenatdan@reddit

FWIW in many version of the myth, including the graphic that makes the rounds on Reddit, it does say the treadmill “exactly matches the speed of the wheels”… which, unless you try to say that means something other than what we typically mean by those words, would indeed mean “stationary plane.” It’s also an impossible scenario that the mythbusters would have no way of producing and testing. But technically…

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THE_CENTURION@reddit

"exactly matches the speed of the wheels”… which, unless you try to say that means something other than what we typically mean by those words, would indeed mean “stationary plane.”

I don't understand what you mean by this/I don't see why that would lead to a stationary plane.

The plane does not care what the ground is doing in in terms of movement. It can move forward with no ground at all, because it can fly. (I mean, assuming that we ignore wheel bearing friction/overheating).

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lieutenatdan@reddit

But a plane cannot move down the runway with the brakes on. Takeoff is dependent on the plane moving to generate lift. The movement of the plane is not caused by the wheels like a car, but it is indeed dependent on the wheels (which are attached to the rest of the plane) being able to move down the runaway until the plane generates enough lift to fly.

The verbiage “exactly matches the speed of the wheels” means the wheels cannot move forward, at least if we’re using the common meaning of “speed or the wheels”: rotational speed.

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THE_CENTURION@reddit

I still don't see how it would have any effect. The wheels don't really need to move forward, they just need to remove friction between the airplane and the ground so the engines can do their job, and they do that no matter which way they're spinning.

Again, assuming it's not a trick question about wheel over speeding or bearing friction, the wheels can do whatever they want, the ground isn't even part of the equation.

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lieutenatdan@reddit

The ground is part of the equation until the plane takes off though. The plane needs to move through the air to generate lift, and until it has enough lift to takeoff, the wheels facilitate the movement of the plane. Not propel the plane, but facilitate the movement. Ergo, if the brakes are on, the plane can’t take off (that’s by design, btw).

In the common version of the prompt, this treadmill-runway “exactly matches the speed of the wheels.” Unless you interpret that to mean something other than the common meaning (rotational speed), that means the wheels cannot move forward. Any rotation of the wheels is countered by the treadmill. The plane effectively has the brakes on.

And as I said: that’s not realistic and it’s an impossible scenario. IRL, or course the plane takes off from a treadmill. But IRL we can’t match the requirements of the prompt. And if we’re going by the requirements of the prompt, the plane can’t take off because its movement against the air cannot be facilitated by the wheels.

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THE_CENTURION@reddit

The engines create a force pushing forward. If the plane is going to stay still, there will need to be a force pushing the other way.

Just step by step;

1: Ground moves backward

2: Wheel spins to match

3: A force is imparted on the plane that contracts the engine force, keeping the plane in place.

How do we get from 2 to 3? How does ground movement exert a force on the plane? Because that's what it would need to do, to stop the plane from taking off. Again, assuming bearing friction is zero, there's no way the ground can exert a force on the plane body.

Having the brakes on is a completely different thing. That's a flawed leap in logic.

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lieutenatdan@reddit

No you’ve got it backwards. Step 1 is the wheels spin, step 2 is the ground moves backward to match.

IRL, the plane takes off from a treadmill because the wheels can always spin faster than the treadmill can move backwards. So the plane can still move forward through the air and generate lift.

But in the hypothetical prompt, the wheels cannot spin faster than the treadmill moves backwards. I recognize that’s not realistic, but that’s what the prompt says. The treadmill exactly matches the speed of the wheels. Ergo the wheels are stuck in place, which means the plane is stuck in place.

The engines will still push, but unless the engines can exert enough force on the body of the plane to break off the landing gear, the plane can’t move through the air to generate lift.

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THE_CENTURION@reddit

Nope, still just can't get there. I am still having trouble wrapping my head around the wheel rotation, but fundamentally I just cant get past this;

If the ground is going to somehow prevent the plane from taking off, it needs to exert a force on the plane. Since the wheels are perfect bearings*, it is impossible for the ground to exert a force on the plane.

* I guess this isn't technically specified in the prompt, but it seems logical given that we're talking about an ideal scenario.

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lieutenatdan@reddit

I don’t claim to know all the forces theoretically involved, but my hang up is that in the prompt (unlike how it would work in real life) the wheels can’t just spin faster than the treadmill when the plane engines push. Wheels have to “out-spin” the surface to facilitate movement, and if they can’t (again, not realistic) then the wheel can’t move. So similar to the brakes being on: the plane can push forward, but the wheels can’t facilitate movement.

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AtreidesOne@reddit

I do agree that the wording is confusing. But it makes sense when you realise that speed isn't a vector.

At take-off, the treadmill surface will be moving backwards (relative to the ground) at (say) 180mph, while the wheels themselves are moving forwards (relative to the ground) at 180mph. If you hooked a speedo too the wheels, they would think that the plane is moving at 360mph, which is correct as this is the plane's local "ground" speed. But the plane's airspeed will be 180mph, and it will take off.

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lieutenatdan@reddit

I don’t think that’s a fair reinterpretation of what “speed of the wheel” means. If the mechanic shop puts my car on a lift and then revs the engine so the wheels spin while it’s not touching the ground, and someone says “what is the speed of the wheels?” we all know the answer we’re looking for is not 0mph.

Or if a car is sliding on ice at 5mph and you’re flooring the gas pedal and the wheels are spinning like crazy (despite not propelling the car because you’re on ice) and someone says “what’s the speed of the wheels?” we all know the answer we’re looking for is not 5mph. No one says “speed of the wheel” and means “speed relative to the ground.”

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AtreidesOne@reddit

You're right, it's a very strange way of saying it, which is part of why the problem is so problematic. However, it's the only way to interpret it that makes physical sense. If the conveyor belt matches the speed of the wheels as displayed on a speedo, how would that actually work?

Your aircraft is sitting there at rest. Wheel (speedo) speed = 0, conveyor speed = 0, all good. Now what happens when the engines start up? There's nothing holding the plane back, so it starts moving forward at 1mph relative to the ground (and stationary treadmill). So wheel (speedo) speed = 1mph. So now the conveyor has to be moving at 1ph backwards. But since this doesn't actually slow the plane down (how can it?), the wheel (speedo) will now be saying 2mph. But that means the conveyor is now moving at 2mph. So now the wheels are moving at 3mph, so the conveyor is moving at 3mph, etc. etc. You see the problem? As soon as the plane gets any movement at all, the only solution is for the plane and conveyor belt to be moving at infinite speed. There is no solution, other than all speeds being zero. But this has 2 problems:

How exactly is this treadmill resisting the force of the engines? This is a physics problem after all, not a maths problem. Somehow the engines are blasting away and the plane is sitting there on a stationary magical treadmill.
If the treadmill can magically hold the plane stationary, then yes, we all agree that the plane can't take off. But again, this is not a physics problem any more.

That's why in many versions of the problem, they don't use the vague "speed of the wheels" terminology. They use something like "the plane's groundspeed". You'll notice that the Mythbusters avoided this mess too by testing the myth of a conveyor belt moving at the take-off speed at the aircraft. So they allowed it to move backwards for a bit while it got up to take-off speed. Even in this simplified case, people (including the pilot in the myth) still wrongly predict that the airplane wouldn't take off.

So yeah. A real treadmill can do nothing to prevent a plane from taking off. You'd need a magical treadmill that can somehow fix the plane in space.

And in case it helps, I have degrees in Physics and Mechanical Engineering, so I do at least know what I'm talking about.

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lieutenatdan@reddit

Yes, it’s not a realistic prompt. But when a prompt says “how many Toyota Highlander’s do you have to stack end to end to reach the moon?” people don’t seem to mind answering the prompt as asked, when the “realistic” answer is “this prompt makes no sense, you can’t stack anything from the earth to the moon, it’s physically impossible” you know what I mean?

IRL the plane will take off, no denying it.

And I do believe your credentials! Admittedly I am not a physicist. At the end of the day, we know that the prompt is intentionally divisive and misleading.

I appreciate you taking the time to spell out the physics problem!

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AtreidesOne@reddit

I get what you mean. But I think it's reasonable to assume things are as realistic as possible within the scope of the question. E.g. if you don't assume your Toyota Highlanders have infinite crush strength, it's not really within the realms of answerability. But if we assume the physically possible "speed of the wheels" interpretation, you still have a relatively realistic scenario. Sure, you still have to assume you can build a runway-length conveyor belt that can hold an aircraft, which is also pretty unrealistic. But it's still an interesting question because it makes you really think about how an aircraft flies.

I'm not sure it's intentionally divisive and misleading, though it certainly could be. One thing that could be contributing is that people aren't always great all posing problems unambiguously, even when they are trying to. The other is that the divisive and controversial answers are likely to be the ones that get the most attention. As Hanlon says, "Never attribute to malice that which is adequately explained by stupidity." :)

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lieutenatdan@reddit

It’s definitely fascinating, and tbh I’ve found my position to be somewhat unique (in the sea of “planes don’t need the wheels to fly!!!” and “but planes can’t fly without the wheels turning!!!” shouts). I even read a breakdown someone wrote on the problem, and when they broke down the options of what “speed of the wheels” means, option 1 was:

”the treadmill 1:1 matches the rotation of the wheel… But no one holds this interpretation so let’s move on to interpretation 2 & 3”

And I’m like… why does no one hold that interpretation? That’s exactly what the common use of the phrase would mean! It doesn’t make much sense (even less sense than a runway length treadmill) but if that’s what the prompt is telling us, why not entertain the hypothetical?

But alas, most replies are “nooooooo the plane’s ability to take off is completely unrelated to the wheels, end of story!!!” (which is only half true, because until the plane is generating enough lift its movement through the air is facilitated by the wheels, that’s why planes can’t move with the brakes on, after all)

All that is to say, I echo back your thanks for a reasonable response! Thanks!

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Siggy_23@reddit

I think the assumption is that as the wheels start to rotate, the treadmill speeds up which of course causes the wheels to speed up, whic cause the treadmill to speed up even more until both the treadmill and wheels are running so incredibly fast that the friction of the wheel bearings is greater than the force of the propeller pushing the plane forward.

The people ive talked to about this take it to mean that the wheels and treadmill are always going exactly the same speed which is only possible if the plane is stationary for some magical reason.

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AtreidesOne@reddit

> going exactly the same speed which is only possible if the plane is stationary for some magical reason.

Speed doesn't have a direction (unlike velocity). So you and I can have the same speed even though you're running north and I'm running south.

Here, the the wheels (and the plane) can be moving forward at 400 mph, while the conveyor can be moving backwards at 400mph. The plane's speedo will say they are moving at 800mph, but assuming they can handle that speed, there's nothing stopping the plane from taking off. And both the wheels and the conveyor belt have the same speed.

(Yes, if you try and get the conveyor to match the plane's speedo, the only solutions are speed = 0 or speed= infinite. But that's no longer a physics problem, as there's no physical way the conveyor could actually stop the plane form accelerating from 0 to 1mph. It would have to be a magical treadmill.)

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lieutenatdan@reddit

I did say up front this was not a realistic scenario, but if the prompt says “the treadmill exactly matches the speed of the wheels” then yes, for some magical reason the plane is stationary (the wheels cannot facilitate the forward movement required to generate lift). IRL the plane will always take off, but if you’re given a physics prompt you’re kind of supposed to answer the prompt as given, even if it isn’t realistic, right?

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lieutenatdan@reddit

Is this a helpful simplified version?

Roller skates on a treadmill, treadmill matches your speed. I’m NOT talking about propelling yourself, that would just be the “planes be cars” discussion. But imagine that the treadmill doesn’t just “match your speed” but rather “exactly matches the speed of your wheels.” That is, if your wheels spin, the treadmill spins exactly the same amount. In the car scenario, those may be interchangeable. But consider:

With you in skates on the treadmill, your friend (not on the treadmill) throws a rope and tries to pull you forward. Can they? The force to move you is coming from a separate place, unaffected by the treadmill. But you are still on your skates, and every movement of the wheels is exactly matched by the treadmill. The treadmill doesn’t stop your friend from pulling, but it doesn’t stop your wheels from moving in the direction of the pull. And you are attached to your skates.

In that hypothetical scenario, your friend is going to feel a force pulling back, yes. That doesn’t really sound right, but for an impossible treadmill that exactly matches the speed of wheels to function, that appears to be how it would work. In the hypothetical, the only way you are moving is if your friend gives a bit tug and pulls you out of your skates entirely.

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NerdIsACompliment@reddit

Airplanes push against the air to move, not the ground.

The wheels are free spinning. Like moving on a skateboard by pushing yourself with a leaf blower.

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NandroloneEnanthate@reddit

I understand the wheels have nothing to do with lift. But correct me if I’m wrong but if a plane is moving in an opposite direction equal to the conveyors belt speed, thereby making the plane stationary in relation to the observer, then the plane is not creating lift. If a plane is moving twice the speed of the conveyor belt, then it is moving forward in relation to the observer and creating lift.

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IOrocketscience@reddit

The airplane isn't going to be affected by the speed of the conveyor belt once it turns on its engines. You're thinking that the asked the wheels rotate at it's the speed that the cost is moving at, because that's how cars work - because cars use their wheels pushing against the ground (or conveyor belt) to move the car forward. But airplanes don't work like that. The airplane uses its propeller to pull itself through the air, and the wheels spin freely against the ground, just to allow the airplane to move forward until it lifts off. So if it's on a conveyor belt when the propeller is spinning, the airplane's air speed will be the same as always and the wheels will spin twice as fast as the conveyor belt pulls them in the opposite direction. There is no way to keep a powered airplane stationary with a conveyor belt. The only way to do what you are talking about would be to lock the wheels down to the ground so that the airplane can't move forward. So, yes, if an airplane is stationary, it doesn't generate lift, but an airplane on a conveyor belt isn't going to be stationary, no matter the speed or direction of the conveyor belt. The airplane's engines move it relative to the air, not the ground.

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NerdIsACompliment@reddit

I actually have the same degrees. Bs ME, MS aero engineering.

I guess we're both saying the same thing with different wording. Airplane is unfettered and will take off.

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1NqL6HWVUjA@reddit

I thought the thought experiment was a STATIONARY plane on a conveyor belt couldnt take off.

Of course a stationary plane cannot take off (barring a headwind that matches takeoff speed, but that's a different matter).

The myth is ultimately about whether a conventional airplane sitting on a running conveyor belt, with its means of propulsion (e.g. a propeller) operating as if it was trying to take off, can ever even be stationary. And it can't, regardless of how fast the conveyor belt moves.

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IOrocketscience@reddit

Because an airplane on a conveyor belt wouldn't be stationary, that's not how plains work. They don't drive with their wheels like a car, they pull themselves through the air with their propellers or jet engines. Even when they are on the ground, all the wheels are doing is allowing the engines to pull themselves through the air. So the conveyor belt has no effect on how the airplane takes off. The question is sort of a trick question. It implies that airplanes drive with their wheels and so they wouldn't be able to get up to speed while on a conveyor belt going in the opposite direction, but that's not the case

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SerendipitySchmidty@reddit

Either way, the plane would take off. The plane taking off has absolutely nothing to do with the wheels or the runway (in this case the conveyor belt). Its starting speed being 0 or 20mph makes no difference what so ever to it's ability to take off. Still a fun myth, though. Seems counter intuitive, but that's physics for you.

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Blessed_tenrecs@reddit

I still can’t get over the fact that you can bend a shot gun into a ‘U’ and it’ll still shoot. So simple and yet I didn’t believe it would work.

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RedHelvetiCake@reddit

Defeating a motion sensor with a bedsheet. I wonder if the people who develop motion sensors have patched that out by now.

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levidurham@reddit

That was passive infrared (PIR). A newer technology on the market is mmWave preference detection.

Look up the Aquara PF2. It can do all kinds of neat things; fall detection, sleep respiration rate, etc.

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sir_thatguy@reddit

And how easily thumb print scanners were defeated.

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tobor_a@reddit

what happened there? Was it like the second SCooby-Doo live action that Daphne uses some make-up + a pore strip to use an old print?

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An_0riginal_name@reddit

They literally used a copy machine to print off a picture of Adam’s fingerprint on regular copy paper and that unlocked it lol

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tobor_a@reddit

wtf that easy? damn wtf lol

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AtreidesOne@reddit

For some devices they had to lick the paper first. Many of them sense moisture (or probably resistance or capacitance).

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Moakmeister@reddit

Ive never heard of this episode. What was it?

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bradygilg@reddit

My experience with the Lockpicking Lawyer tells me that most security companies don't give actually give a shit about security.

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Malakai0013@reddit

Exactly. The several lockpicking accounts online have made me realize those locks are mostly for show and to prevent curious eyes. If someone wants in, they're gonna get in. Usually by just slapping the lock in just the right way.

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bargle0@reddit

This is how you open a Masterlock with a Masterlock.

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wpmullen@reddit

Pirate vision

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Just_a_Lurker2@reddit

What's that?

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Justacynt@reddit

Sailors used eye patches to preserve night eye in one eye for when they go below deck

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Hazard-SW@reddit

I had a scar on the cornea of one eye, so when I get tired I would just close that eye unconsciously (it’s just my brain conserving processing energy because interpreting information from that eye is just harder). When I’d get up to pee at night I started noticing that my night vision was wildly different between my two eyes. I thought there was something seriously wrong with my vision…

Until I watched this episode and realized that I was essentially just naturally eyepatching my one eye, particularly when I was close to sleeping.

Fascinating stuff, it really is dramatically different.

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Just_a_Lurker2@reddit

Awesome, and pretty plausible! Confirmed?

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Justacynt@reddit

Indeed confirmed!

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Just_a_Lurker2@reddit

Awesome! Also def gonna check out that episode now

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revtim@reddit

The mouse scaring the elephant

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Moakmeister@reddit

I just watched the Exploding Steak episode, where they tested if explosives can tenderize a steak. I thought this was such an obviously stupid myth and a pure, distilled excuse to just do more explosions. No way it could work.

Confirmed.

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Nights_Revolution@reddit

Im still mad about the plane lifting off the ground despite a treadmill - there was no treadmill and it was a bad attempt at one. Yes, flight is achieved through the thrust of the propeller or turbines, but still

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AtreidesOne@reddit

There's no way a physical treadmill can hold a plane back, nor prevent it taking off. The only way it would happen is you imagine some sort of magical treadmill that can hold the plane stationary. But a treadmill can't do that.

The moving runway they used wasn't quite the same as a treadmill, but it served the same function. It meant that the wheels were spinning twice as fast as usual when the plane took off. But that doesn't affect the plane's motion. The wheels are only there to reduce friction with the ground. Planes can and do take off with skis instead.

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Nights_Revolution@reddit

Who in their right mind assumed it was SPINNING WHEELS that makes a plane take off? O.o

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Plus-Ad1061@reddit

Phone book friction. If it ever came out that there was an episode they had done as an April Fool’s joke, this is the one I would assume was it.

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wesleyweir@reddit

Yes! That one completely blows my mind. The fact that they literally needed two tanks to pull apart books held together by only friction! 🤯

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AtreidesOne@reddit

I wonder if air pressure plays a part at all, even a small one. I know it's not the same setup, but you can break a ruler by smacking one end while it's hanging over a table and the other end is under a sheet of paper. I wonder if anyone's ever repeated this test in a vacuum chamber?

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raaustin777@reddit

Actually just saw Adam talk about this on YouTube and how they would do a stunt at live shows where they'd have a couple of folks from the audience weave the phone books together and then Adam would hang from the ceiling from the books at the end of the show

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AtreidesOne@reddit

I really doubt they got the audience to leave the phone books together though. In the episode where they did it, it took AAAAGES and they had to hyperlapse it. That would be a really boring thing for them to subject a paying audience member to. And they didn't do it when I saw their show. They used a pre-whacked book.

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AtreidesOne@reddit

I've seen them do this. They put an air mattress under Adam, as if that would do much if the phone books failed.

Here's a photo someone took: https://www.flickr.com/photos/yelpar/15062531645/

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Moakmeister@reddit

As a kid, O was convinced that it was the tape holding them together. I refused to believe that the friction of the pages could possibly produce any force.

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jsabo@reddit

Video game weapons. I figured that a strong enough guy would be able to carry it all, but not that they'd be able to move around so easily.

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Plus-Ad1061@reddit

Ok, but now I’m going to need Adam to carry 64 blocks of cobblestone up and down these stairs all day.

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Sudden-Wash4457@reddit

Keep in mind that the average soldier carries somewhere between 70-120 lbs on a combat mission

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Whiteguy3Stars_Sun@reddit

What possible gear do you need that takes 100 pounds up in a backpack.

Like I have seen tribes in Amazon jungle get everywhere with next to nothing and a blow dart

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Brilliant_Snow8822@reddit

Man lemme tell you something about "ranger school"

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Sudden-Wash4457@reddit

https://s3.us-east-1.amazonaws.com/files.cnas.org/hero/documents/CNAS_Super-Soldiers_4_Soldiers-Heavy-Load-FINAL-2.pdf

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Whiteguy3Stars_Sun@reddit

Cool thanks 🙏

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ianvoyager@reddit

Golf ball car!

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Walraptor@reddit

Homer simpson on a wrecking ball can save a house

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Zoeloumoo@reddit

I just watched that episode! I thought I had seen them all but apparently not. Such a good one!

I feel like they didn’t have a way to measure if Homer would be, like, dead, but still very good.

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