Originally posted by Javaman: Ummm . . . that's what we've been saying all this time.
Bull$#!t. You've been saying that the Mythbusters interpreted the myth as though the plane SHOULD BE HELD MOTIONLESS, and thus that the question is "Can a plane take off while being held motionless?" I've been arguing that they did not interpret the myth this way, and that the question is "Can a conveyor/treadmill hold a plane motionless?"
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Originally posted by Javaman: You are the one telling us that the myth says that the plane is moving forward.
Read the riddle as posted on the physorg forums. It says, in explicit terms: "The plane moves in one direction"
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Originally posted by Javaman: The starting point is with the belt and the plane moving in opposite directions in matched speeds. The immediate results are that the plane will move forward as soon as it throttles its' engine. That, however, is not the starting point of the myth.
The plane is already moving, it's throttle is already at full. This is the starting point, and the immediate result. It's not my problem that you and everyone else refuses to see this, and continues to make an issue out of it.
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Originally posted by Javaman: Your responses confuse me. You argue vehemently with us that at the beginning of the myth, the plane should be moving forward in relation to the ground at the same speed as the conveyor belt.
Yep!
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Originally posted by Javaman: Then you tell me that the "clear intention" of the myth is to fool people into thinking that the belt can keep the plane from moving.
Absolutely! And it's obviously working, otherwise this conversation wouldn't be happening, would it?
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Originally posted by Javaman: If the starting point is where the plane is already moving, then no one would be fooled into thinking that the belt could hold it in place.
The fact that this debate is ongoing proves you wrong.
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Originally posted by Javaman: The myth would already be busted before it began.
Yep! And yet, here we are...
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Originally posted by Javaman: On the other hand, if the plane were moving in relation to the belt, but stationary to the ground, then there would actually be something to test. Can the plane move forward in relation to the ground? The answer is obviously yes, but that is the condition set by the myth so that people would be tricked into thinking that the belt could hold it in place. Again, your answers seem to contradict each other.
The ONLY way to have the belt be moving and the plane not is if the plane is anchored in some way. No such anchor is mentioned in the myth, therefore it is not there.
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Originally posted by Javaman: Your interpretation of what is said in the video is ridiculous. Read it or show it to anyone you know and ask if they think Mark is agreeing with the myth presented in the episode or if he is believing something other than what the episode presents as the myth.
One more time... just because Mark believes X, and the Mythbusters show Mark saying he believes X, DOES NOT mean that the Mythbusters also believe X!
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Originally posted by Javaman: Then show them the other quote - "If a manned airplane is on a conveyor belt, and both are going at the airplane's takeoff speed, but in opposite directions, will the plane be held where it is, or will it take off?" and ask them if they think "held where it is" means moving forward in relation to the ground. I would be interested to hear what you think the point of reference is when the plane is held where it is.
Obviously "held in place" means "motionless relative to the ground". The myth is designed to take advantage of your natural, but incorrect, assumption that two speeds going in opposite directions will counteract and result in a motionless object. My point in linking that clip was to show definitively that the Mythbusters interpreted the myth as asking the question "Can a conveyor/treadmill hold a plane motionless" - and I think that it proves this point quite well: "will the plane be held where it is, or will it take off?"
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Originally posted by Javaman: In order for it to be "held in place," it needs to start in that condition, which is what I have been saying this whole time.
Once again, you are applying the hypothetical result of the test as a condition for the test. The myth DOES NOT specify that the plane has to be held in place. The HYPOTHESIS is that the plane will be held in place - this IS NOT a constraint on the test, this is the expected RESULT of the test! The fact that the plane IS NOT held in place is the proof that their hypothesis was incorrect! It's all part of the scientific method, which they do follow, albeit loosely at times
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Originally posted by Javaman: By the way, we are not scrambling to make a case for the plane not flying. I whole-heartedly affirm the mythbusters' results from the physical stand point. I'm not trying to make a case for no-fly, I am making a case for the mythbusters not staying within the parameters set by the myth. I could care less if the plane flies or doesn't fly. What I care about is being true to the myth. They were true to the intention of the myth, but they were not true to the letter of the myth.
If you feel that they missworded the myth in such a way that they led viewers to believe that the plane speed should be measured relative to the belt, then I would agree with you that they were not true to the letter of the myth as they presented it. I disagree, however, and I believe that looking at the method by which they tested the myth makes it perfectly clear that they did not intend for the plane speed to be measured relative to the belt.
Javaman I see that you are trying to do some serious semantic spinning of the myth to get to come out the way you want. Previously you were talking about the plane being "'held where it is'", and then measuring the speed of the plane relative to the conveyor belt. Right there you are mixing two different frames of reference. So can the conveyor belt hold it in place, moving or not? No, the plane can roll on the conveyor belt. So obviously we have to measure the plane's speed relative to the ground, not relative to the conveyor belt. And though it may seem trivial the myth is busted.
Originally posted by Javaman: Now, it is never stated in direct terms that the plane is required to be held in place to test the myth, but with a little thought, that is exactly what will happen if you follow the condition that they must always be going the same speed in relation to eachother.
Nonsense. The plane and belt are ALWAYS going the same speed relative to each other, whether the plane is moving relative to the ground or not.
What you're asking for is for the speed of the plane to be measured relative to the belt, and the speed of the belt relative to the ground.
But seriously... I've been reading over the Mythbusters wiki, and the specifics of the myth as they posted it, and I'm willing to concede that the Mythbusters got the right answer by doing it all wrong. They stated the problem incorrectly, their method did not actually test what their stated problem was. and the hypothesis presented was incomplete and invalid.
This concession relates ONLY to the Mythbusters' actual presentation and testing of the myth, and NOT to the validity of any interpretation of the myth. I still maintain that it is invalid to measure the speed of the plane relative to the belt.
I will also agree that the appropriate starting conditions for this myth should be with both plane and belt motionless relative to the ground, but I hope it is clear that as soon as the plane generates any thrust, it will begin to move relative to the ground, and there is nothing short of rational's theoretical infinite acceleration that the conveyor/treadmill can do to stop it.
No, it is never stated in direct terms that the plane is required to be held in place to test the myth, but with a little thought, that is exactly what will happen if you follow the condition that they must always be going the same speed in relation to eachother.
That condition isn't explicitly stated, either - they vaguely refer to the "speeds" of the plane and belt, leaving the details out because, in the end, the plane takes off regardless of how you interpret it.
If you want to be precise, though, and the choice in interpreting ambiguous terms in the question leaves with one result being intuitive, simple, and logical (which it is) and the other being physically and theoretically impossible (which yours is), the choice is easy.
Again, your only argument left is that the answer is too simple once you know the answer, and that's not a valid argument.
I see where you all are not understanding exactly what I am trying to say, I am just at a loss how to better articulate my real thoughts. I am not pulling things out of the air. What I have to say is absolutely valid. I just haven't figured out how to get you all to track with me.
it's not that the answer is too simple, it is that it is pointless. A body in motion is in motion, not held in place. In order for it to be held in place, it has to be in place. To ask if a moving plane can move or not is . . . whatever.
Originally posted by Javaman: I see where you all are not understanding exactly what I am trying to say, I am just at a loss how to better articulate my real thoughts. I am not pulling things out of the air. What I have to say is absolutely valid. I just haven't figured out how to get you all to track with me.
I wish you would figure it out, because it honestly doesn't sound like you have a valid point other than that the Mythbusters didn't do a great job presenting the myth.
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Originally posted by Javaman: it's not that the answer is too simple, it is that it is pointless. A body in motion is in motion, not held in place. In order for it to be held in place, it has to be in place. To ask if a moving plane can move or not is . . . whatever.
Exactly. It's pointless, once you see through the riddle. The problem is that you're too hung up on there being some significance here when there simply isn't any.
it's not that the answer is too simple, it is that it is pointless. A body in motion is in motion, not held in place. In order for it to be held in place, it has to be in place. To ask if a moving plane can move or not is . . . whatever.
It's as pointless as asking where they bury the survivors of a plane crash, or which side of the barn the rooster's egg will roll down, to use my previous comparisons.
Once you know the answer, the question is trivial, but that obviously doesn't keep it from stumping some people. You and -rational- obviously have issues with overthinking things.
Originally posted by Javaman: Then you tell me that the "clear intention" of the myth is to fool people into thinking that the belt can keep the plane from moving.
quote: Originally posted by EnderGT: Absolutely! And it's obviously working, otherwise this conversation wouldn't be happening, would it?
Yes it would because I don't think the belt can keep the plane from moving. I'm not that dense. It is the limitations set by the wording of the myth that keeps the plane from moving in relation to the ground. I was talking about what fools other people.
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Originally posted by Javaman: Then show them the other quote - "If a manned airplane is on a conveyor belt, and both are going at the airplane's takeoff speed, but in opposite directions, will the plane be held where it is, or will it take off?" and ask them if they think "held where it is" means moving forward in relation to the ground. I would be interested to hear what you think the point of reference is when the plane is held where it is.
quote: Originally posted by EnderGT: Obviously "held in place" means "motionless relative to the ground". The myth is designed to take advantage of your natural, but incorrect, assumption that two speeds going in opposite directions will counteract and result in a motionless object. My point in linking that clip was to show definitively that the Mythbusters interpreted the myth as asking the question "Can a conveyor/treadmill hold a plane motionless" - and I think that it proves this point quite well: "will the plane be held where it is, or will it take off?"
quote: Originally posted by Javaman: In order for it to be "held in place," it needs to start in that condition, which is what I have been saying this whole time.
quote: Originally posted by EnderGT: Once again, you are applying the hypothetical result of the test as a condition for the test. The myth DOES NOT specify that the plane has to be held in place. The HYPOTHESIS is that the plane will be held in place - this IS NOT a constraint on the test, this is the expected RESULT of the test! The fact that the plane IS NOT held in place is the proof that their hypothesis was incorrect! It's all part of the scientific method, which they do follow, albeit loosely at times
The myth begins with the plane being motionless in relation to the ground while both plane and belt are moving. Every version of the myth indicates this. How do I know? Because they all set up the stage with them moving. You argue that this means relative to the ground, but if that were the case, then there would be no point in asking if the plane would be held in place because it wouldn't be held in place to begin with. Being held in place is one of the conditions set by the myth. The question then asked is whether or not it will continue to be held in place. You are confusing the results with the initial set up. If the myth was posed the way you interpret it, it would have to read something like this - "A manned plane is sitting on a conveyor belt which has the ability to instantaneously match the speed of the plane but in the opposite direction. When the plane throttles up, will it be held in place, or will it take off?"
This is almost exactly the same as what the myth actually says except for one very important thing. The original myth includes this BEFORE asking the question: "and both are going at the airplane's takeoff speed, but in opposite directions," "ARE GOING." THEN it asks if the plane will be held in place. The belt and plane are ALREADY moving before it asks if it will be held in place. This would make absolutely no sense by your interpretation. The only way it makes sense is if "are going" is in reference to eachother and "held in place is in reference to the ground. It's really just simple English and sentence structure, but you apparently don't get it. This holds true with every version of the myth that has been presented here.
As to pilot Mark. You are still wrong. They are saying that Mark believes that the myth is true. Then confirm that his interpretation of the myth is what they believe the myth says, NOT that they believe the myth. BIG difference. Believing the myth and believing what interpretation of the myth is intended are two different things.
Subduction, I am not twisting the myth to make it fit my beliefs. I am reading and taking it literally as it was written which is quite opposite of making assumptions and trying to distort things to make them seem to be the way I want them. I am reading and taking it by the letter.
Originally posted by Javaman: The myth begins with the plane being motionless in relation to the ground while both plane and belt are moving.
Which is exactly what happened with the model plane on the real treadmill. The belt was moving, the plane was held motionless by Adam while Jamie throttled up the plane, then Adam let go and the plane took off.
The question was: Can a moving conveyor belt stop an airplane from flying. Obviously, proven it will fly.
The wheels of an airplane are there for one purpose only - To keep the airplane clear of the ground while waiting to fly. They are free wheeling. (Braking excepted) As mentioned many times, the speed of the wheels do NOT do anything to the takeoff speed of the airplane. The propeller does not have any conection to the ground. It doesn't know where it is, or how fast it is moving. It only acts on the air. So, it produces thrust. That moves the airplane. When the airplane moves through the air fast enough, it can lift off. The speed of the ground under the wheels has nothing to do with this. And the engine power that is used for a normal takeoff? All of it. The amount of engine power used on the ultra light in the program? Probably normal takeoff power.
What is the problem? The program proved the concept well enough to have put this to bed.
The problem is that some people here have chosen to interpret the 'myth' in a way that it's required that the plane to be held motionless by the belt during the test to see if the plane is held motionless by the belt, even though they're fully aware that the plane can't be held motionless by the belt. They also claim the mythbusters believed this, too, even though everything about the way they performed the test says otherwise.
quote: Originally posted by Javaman: The myth begins with the plane being motionless in relation to the ground while both plane and belt are moving.
quote: Originally posted by EnderGT: Which is exactly what happened with the model plane on the real treadmill. The belt was moving, the plane was held motionless by Adam while Jamie throttled up the plane, then Adam let go and the plane took off.
Myth busted per your conditions.
OK, we are finally getting somewhere. Yes, that is exactly what happened with the model airplane. So, to answer several questions here, let me clarify. I have not been arguing that the intention of the myth was for the plane to be held motionless in relation to the ground during the entire test. The intention of the myth was to do it just like Adam and Jaimie did. I also have not been saying that they believe it should be held motionless during the entire myth, just the starting point. In other words, they believe, like I do that the speed of the plane should be measured in relation to the belt, not the ground. From there, my thoughts have gone beyond what Adam and Jaimie did, which was the whole purpose for my argument. That argument being: if the intention of the myth is for the planes' speed to be in relation to the belt, then the moment it throttled up and moved forward in relation to the ground, it was moving faster than the belt. That works great except for the fact that the myth clearly states that the belt will always match the speed of the plane. In order for that to remain true, the plane could never throttle up and move forward in relation to the ground. Ender, I know you get this concept because you demonstrated it a few posts ago. Your argument that a myth with that intention would be pointless and ridiculous is absolutely correct. But I'm not saying that this was the intention of the myth. I have said that many times. The intention of the myth was do be done as Adam and Jaimie did it. I just think the author of the myth (and Adam and Jaimie) missed the problem created by having a belt that could instantaneously match the speed of the plane. It effectively prevents the plane from throttling up and taking off even if that wasn't the intent of the myth.
I think I have given enough proof in both the written myth as well as in the episode, that the speed of the plane is supposed to be in relation to the belt. If that is true, whether you agree with that or not, then let me ask two questions: 1) If the plane moves forward in relation to the ground, is it moving faster than the belt in relation to the belt? My answer is yes. 2) If the speed of the plane in relation to the belt is faster than the speed of the belt, then isn't that breaking the condition stated by the myth that the belt can instantaneously match speeds with the plane? My answer is yes.
That is what I am arguing.
Uncivlengr, yes, that is what I am saying the myth requires, but I am not saying that it's intention was that, nor am I saying that the myth busters believed that. Quite the opposite in fact. If they believed it, then they wouldn't have tested it like they did and I wouldn't have a case for them doing it wrong. All I am saying they agree with me about is that the plane's speed should be measured in relation to the belt, not the ground.
Originally posted by Javaman: In order for that to remain true, the plane could never throttle up and move forward in relation to the ground.
So... you think the myth is asking "If a plane isn't allowed to throttle up, would it be able to take off?" And you think MY interpretation is ridiculous and pointless?
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Originally posted by Javaman: I think I have given enough proof in both the written myth as well as in the episode, that the speed of the plane is supposed to be in relation to the belt.
I do not think that you have given enough proof. Here's why:
Planes move by displacing a mass of air in one direction, and depending on Newton's Third Law of Motion to displace them in the other direction. Unless the plane has some externally provided velocity, the plane will never move unless it is displacing a mass of air, etc. When the plane is motionless relative to the ground, the belt will have to be relative to the ground also. Remember, the wheels don't turn unless the plane moves in relation to the surface the wheels are touching, and with no thrust and no externally provided velocity, this plane isn't moving relative to anything. Therefore motion = notion, motionless = motionless, and never will you have motion = motionless.
Here's the bottom line: If the plane ISN'T ALLOWED to throttle up, it WON'T take off. If it IS ALLOWED to throttle up, it WILL take off.
Which is the more realistic question to be asking?
What the myth is really asking, whether you want to admit it or not, is whether or not the treadmill can prevent the plane from moving. Clearly, the answer is "NO", and this is what the Mythbusters demonstrated.
EnderGT, Did you happen to read what I wrote or just look at it and come up with your own thoughts to put in my mouth?
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So... you think the myth is asking "If a plane isn't allowed to throttle up, would it be able to take off?" And you think MY interpretation is ridiculous and pointless?
Well, let's refer back to what I just posted:
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Ender, I know you get this concept because you demonstrated it a few posts ago. Your argument that a myth with that intention would be pointless and ridiculous is absolutely correct. But I'm not saying that this was the intention of the myth. I have said that many times. The intention of the myth was do be done as Adam and Jaimie did it. I just think the author of the myth (and Adam and Jaimie) missed the problem created by having a belt that could instantaneously match the speed of the plane. It effectively prevents the plane from throttling up and taking off even if that wasn't the intent of the myth.
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What the myth is really asking, whether you want to admit it or not, is whether or not the treadmill can prevent the plane from moving. Clearly, the answer is "NO", and this is what the Mythbusters demonstrated.
I almost agree with you here. I would add, "what the myth is really WANTING to ask . . ."
I still have to disagree with you about what the speed of the plane is in relation to. I understand all you said, but you have to realize that there is relation between the belt and plane and if you get down to it, ground speed has nothing to do with a plane's ability to take off either. Air speed is what is critical. I have seen videos of planes tethered to the ground during a hurricane and they were flying even though their ground speed was zero. You never did address what I had written previously as my proof:
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The myth begins with the plane being motionless in relation to the ground while both plane and belt are moving. Every version of the myth indicates this. How do I know? Because they all set up the stage with them moving. You argue that this means relative to the ground, but if that were the case, then there would be no point in asking if the plane would be held in place because it wouldn't be held in place to begin with. Being held in place is one of the conditions set by the myth. The question then asked is whether or not it will continue to be held in place. You are confusing the results with the initial set up. If the myth was posed the way you interpret it, it would have to read something like this - "A manned plane is sitting on a conveyor belt which has the ability to instantaneously match the speed of the plane but in the opposite direction. When the plane throttles up, will it be held in place, or will it take off?"
This is almost exactly the same as what the myth actually says except for one very important thing. The original myth includes this BEFORE asking the question: "and both are going at the airplane's takeoff speed, but in opposite directions," "ARE GOING." THEN it asks if the plane will be held in place. The belt and plane are ALREADY moving before it asks if it will be held in place. This would make absolutely no sense by your interpretation. The only way it makes sense is if "are going" is in reference to eachother and "held in place is in reference to the ground. It's really just simple English and sentence structure, but you apparently don't get it. This holds true with every version of the myth that has been presented here.
The way you see it, the belt and plane start out motionless altogether. The myth clearly has them moving before asking if the plane will be held in place.
Why do you keep arguing physics with me? I understand all that. I thought I made it clear, but apparently you just skim what I write and don't give it much thought. As I have said, the plane is motionless to the ground while moving in relation to the belt. I am not saying that motion = motionless. I am saying that something can be in motion in relation to one thing while being motionless in relation to something else.
Originally posted by Javaman: I am saying that something can be in motion in relation to one thing while being motionless in relation to something else.
Obviously.
As I understand it, this is your interpretation and conclusion:
Since the belt cannot exert the same amount of force on the plane as the engines of the plane can, a plane exerting full thrust WILL move relative to the ground. If the plane moves relative to the ground, it violates the conditions of the myth. Therefore, the plane is not allowed to exert full thrust. A plane without thrust will never gain airspeed, and thus will never take off.
Do I have that right?
Here's why it's wrong:
If the plane IS NOT ALLOWED to exert full thrust, then it's not allowed to TRY to take off. However, the myth says "will the plane BE ABLE to take off", implicitly stating that the plane IS ALLOWED to TRY to take off. Since the plane exerting full thrust WILL move relative to the ground, by extension it IS ALLOWED to move relative to the ground. Therefore, measuring the speed of the plane relative to the belt IS NOT the appropriate frame of reference.
I understand that you think my interpretation of the myth is just silly and pointless, but you need to get over it: it's a riddle, and riddles are frequently nonsensical once you think about it. uncivlengr has provided a few examples.
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