there we go hey everybody adam savage in my cave uh and i'm answering some questions about my time
as a host of mythbusters on the discovery channel it's been uh officially almost exactly five years
since the last episode aired and it feels like about 18 months to me it doesn't feel like
a half a decade has passed um it still feels quite fresh today's question is a really awesome one
jordan freeman says do you think the controversy called by plane on a conveyor belt will ever end
this is great um first of all let's talk about what plane on a conveyor belt means and then let's
talk about the controversy and then i'll address whether or not i think it's ever going to end
the myth of airplane on a conveyor belt the myth is that if a plane is on a runway trying to take
off my hand is this plane and it's trying to take off and it's moving down the runway to take off
and the runway is itself a conveyor belt under the plane running in reverse matching its speed
if the plane is trying to take off and the runway is a conveyor belt running the other direction
can the plane take off that's the question it's like a physics question right
if a plane is attempting to take off on a runway while the runway
is a conveyor belt running in reverse can the plane take off this question
generates reams of controversy on the internet when we first started looking into it i remember
bringing it to jamie and him going why would we test that it's totally stupid and i'm like
it may be painfully obvious to you heinemann but check out this stack of arguments we found and we
like thousands and thousands of websites devoted to people arguing about this this is a while
back but yeah this is a a a a a deeply fought over passionate debate can the plane take off
now the way i have laid that question out to you that's the question and now the controversy where
does the controversy come from you're already have probably formed an answer in your mind
as to whether or not you think the plane can take off and it all hinges on whether or not the plane
can actually operate like a plane i.e can it move forward
so a lot of people say the plane will never move forward because the conveyor belt's matching its
speed it's stationary and a stationary plane can't take off well that's true a
stationary plane cannot ever take off sorry unless it's a vtol right sure that but we're
talking standard airplane with a propeller can never take off if it can't move forward
to create its own headwind i mean okay sorry it's a small qualifier i guess if there was a headwind
that matched the plane's takeoff speed yes the plane could take off but that's we're not talking
about that we're talking about standard plane on a standard runway taking off in its standard fashion
if it can't move forward no it can't take off and lots of people make that argument
it never flies because it can't move forward and then all these
other people say they can totally move forward and fly and they're arguing with
the the funny thing about the controversy about this story is it's a disagreement over
the basic principles of the question
the reason i'm being slow about this is because i want to kind of give you an
idea of how complicated the question actually is um to make to make it clear why it took us
so long to understand why it's complicated it took us forever what it felt like took
about three weeks of production before we understood people's confusion with the story
enough to actually explicate and speak to that confusion in the episode
and the confusion that we discovered is the question itself has this verbal trickery in
it when i say to you that the plane is attempting to take off but the runway is a conveyor belt that
matches its speed in reverse you are thinking of the plane before it's taken off like a car and
it's very similar to a car in its large components there is a body and you sit in that body attached
to that body are wheels this is the same for a car that body is moving forward on those wheels and if
the road is matching the speed in reverse well the car won't move forward but what about the plane
i mean the plane's the same as the car it's got wheels it's moving along the road it should also
not move forward but it does because while the superficial similarities between a car and a plane
i.e a capsule for a person and wheels to move along the ground those things are similar
the medium that those two machines move through are totally different the car's
mode of locomatio the car's mode of locomotion is its tires contact with the ground the way it
moves forward is because of the friction tires contact to the ground and that friction means
that each place the tire is touching the ground um there's a little bit of inertia to get past that
friction as the tire moves well now the car takes advantage of that inertia and moves forward and so
that point on the tire changes the next point and keeps on moving the car and the car moves forward
the car moves forward because of the tires relationship to the ground
on an airplane the car moves forward for an entirely different reason on an airplane the
car moves forward because the propeller which is a pair of wings bolted to a spindle because
their propeller is moving wind this way and thus it's pulling the plane in the opposite direction
the wind is the propeller is pushing wind into the plane
and because it's doing that for every action there's an equal and opposite reaction
the plane is moving forward so both the plane and the car are moving forward because of
the first law of thermodynamics but they're exploiting totally different versions of it
the car is using friction with the ground and the plane is using friction with the air
all this is to say the confusion around airplane on conveyor belt is
all about that little relationship between a car and a plane and their similarities
and their differences because the answer is the plane will always take off because it's pushing
itself through the air not along the ground so no matter how fast the the conveyor belt
of the runway is moving the opposite direction to the plane the plane will always move forward
because it's the air it's not the ground that is hope that the plane is moving through
this myth is so controversial we actually in order to do it we took a tarp that was half a mile long
and put a bar at the end of it and dragged that tarp behind a pickup truck at 25 miles per hour
which was the takeoff speed of this ultra light fully covered canvas plane we hired for the day
and so that's their takeoff speed was 25 miles an hour we had a pickup truck pulling the runway
and reverse at 25 miles an hour and that plane took off same exact time it would have every
other time the runway moving in reverse made no difference to it and the pilot of that plane
he thought it wouldn't take off that's how pervasive the confusion in the question is so
when you ask about the controversy the thing i always want to say is
go easy on people who have trouble with the controversy of this story
it's not because they're dumb and it's not because they don't understand it's because the question
is devilishly clever in its ability to confuse the human mind cars and planes seem very similar
in this question on a superficial level and that superficial similarity is what confounds everybody
so i'm here to say that that that story is going to be complicated for a long time because it's
hard to communicate i just took me what 10 minutes to talk it through that's the result i can't even
tell you we argued about that like stevo and i argued about it stevo and jamie jamie and i
you know the whole crew went through all these different mechanisms to come around to
understanding where this confusion was it was not immediately obvious and we really had to kind of
sort of look over all of our our proclivities and all of our biases to
understand where that confusion was and then speak to it but it was completely iterative so
no i don't think that controversy is going away funny story when that episode was supposed to
air discovery had it up on their schedule and for some reason it didn't air that night like
there was just some east coast west coast feed problem with discoveries channel listings and crap
oh good um sorry i just thought i noticed something um there was some like snafu with
the with the television listings and so people thought airplane on a conveyor belt was going
to air one night and it didn't air that night and people went bananas this is the reason jamie got
rid of the landline at m5 he still had a landline at the point in which we made this episode but he
came in the next morning that episode was supposed to have aired and his answering machine of m5
was filled with people yelling at him for the controversy of somehow not airing this story it
was crazy how involved people got later on when the episode finally aired and we checked in with
some of the forums where people were arguing with us the people who argued against the plane taking
off still said that it would never take off we just did the episode wrong isn't that funny
what they're literally saying is oh i watched those two guys conduct an experiment to prove
this and they proved that the plane would take off and because i disagree with the that the plane can
take off i'm just going to ignore their experiment i can't help people like that um yeah no that that
that that's not going away soon but it's not because people are dumb not at all it's because
language is confusing and people can get caught up in that confusion
yeah thank you so much for that awesome question i love talking about that controversy it was a
fun story and it was fun to be part of such a fervent kind of passionate discussion um
tested patrons keep submitting your wonderful questions and i will keep answering them hopefully
uh wonderfully as well thank you guys so much stay safe and i will see you next
time