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Which Way Will The Water Go? (ft. Steve Mould)- Smarter Every Day 226

– Hey it’s me Destin. Welcome back to Smarter Everyday. This is Steve Mould. – Hi. – You’ve seen him, you’ve seen his face, when he did the chain, what’s the deal? – Well, it’s called The Mould Effect. – [Destin] Is it really? – [Steve] Honestly? Because yeah, some scientists
named it that in a paper. – I have always wanted
something named after me. It would be something stupid, if it was like the Sandlin, anyway, long story short,
we are in an argument. And we are gonna settle it
with internet physics videos, which is the appropriate
way to settle an argument. If you’ve never seen a nerd fight, they look just like this. Steve has proposed the building of a spiny water apparatus and he’s telling me he thinks the water’s gonna sling out
of it in a certain direction. Now, Steve seems like a pretty smart guy, if you can look past the
British accent and all that, but I just don’t agree with it. Somewhere along the argument we decide that it’s going to take a phantom camera to figure out exactly
what’s going to happen with this device. But at the end of the discussion, I started to think that maybe Steve has already built this thing and I’m just getting played. Anyway, this is how that discussion ended. – We made an agreement. And what did you say
about being in Alabama? – If you make a handshake in Alabama– – Yeah. – It’s a contract, all right. – And we already did this, right? – Shut up. (Steve laughing) I am on a train in London, about to go see Steve Mould. I have the high speed camera. I’ve been tricked, I’m pretty sure. Whenever I visit someone whose
videos I watch on YouTube, I’m always really excited to see where they film in real life. Okay, so this is the studio, right? (laughs) It looks so
much bigger on YouTube. – [Steve] Yeah, where’s the red pipe? – [Destin] Everyone always
says it looks smaller but- Once we were in Steve’s back garden, we set up the slow motion camera and finalized the terms
of our disagreement. – To state the question simply, if you spin it and then
you take a snapshot, what does the snapshot look like? – [Destin] Okay, so which
direction is it spinning? – So your description was this. You said that, “The water would come out, and then it would kind of go like this, and it would be back
here like that,” okay? So we take a snapshot
and it looks like that. – [Destin] Well, I think that happens but I think it also goes in
the direction of rotation. – Okay, this is just a
way to think about it in two steps, okay? Because if the question
is too complicated, just simplify it and
then you might get there. Okay so this, the jets are just
coming out like this, okay? – [Destin] Okay. – And so we’re going to spin it this way. And then now, maybe, you have
an intuitive understanding of what’s going to happen. And when you take a snapshot, Destin, what do you think? – [Destin] So we have angular momentum. Angular momentum there, right? – [Steve] Yeah. – [Destin] And so I would think that as a particle comes out here, it has some sidewards velocity. That’s the term, right? Sidewards? – Sidewards, yeah. – [Destin] Yeah, yeah, yeah (laughs). – [Steve] Let’s say tangential. – [Destin] Well, I’m
just gonna say sidewards. (Steve laughing) I’m from Alabama. So it’s got some sidewards direction here. And so I think what’s going to happen is you’re going to see a curve
get thrown out like that. – Okay, so you think that it’s
spinning in this direction, the curve is going to go like that? – [Destin] Yeah, I think so. – Okay (laughs). – [Destin] Am I wrong? – That’s like the opposite
of most people’s intuition. – [Destin] Why? – Because, okay well,
most people would say, look, it’s going to come out here, and it’s going to trail behind. – [Destin] Oh. – That’d be most people’s intuition. – [Destin] Well, I think it’s- – Well, should we see what happens? Let’s do this then. Like this is the simpler puzzle so let’s just try this one. – [Destin] Yeah okay, let
me set the phantom up. (Destin laughing) Am I wrong? – I think so, yeah. – [Destin] You think I’m wrong? – I think you’re wrong even about this (laughs) the simpler version. – Okay so here we go, the first question is what happens with just straight water coming out? And you think what’s going to happen? – So I think you’re going
to get this curve of water that trails the motion of the spouts. – But, yeah, I think it’s going to trail the motion of the spout, but
it still has motion going in the direction of rotation. – It does, but, it does– – You’re trying to make me look stupid, is what you’re doing. – [Steve] I just gonna
get absolutely soaked. (both laughing) – [Destin] I’m going to get my feet up. (both laughing) Okay I’m ready. – [Steve] Ready, Ready? – [Destin] Yeah. (Steve laughing) Oh that’s pretty. – All right, there you go. – [Destin] That’s really pretty. Okay, so let’s take a
look at that slow motion, and see why Steve and I
both agree, and disagree. – [Steve] So yeah, it’s
kind of, it’s trailing. That’s what I meant by trailing. It’s behind the direction
of motion, right? – [Destin] Okay, granted. Granted. But any individual particle is actually going out and away. – Yeah, it is yeah. – So I’m not wrong. (both laughing) So this is a language problem. If you look at it from the snapshot view, you could say it’s trailing. But I’m an American, and I
think about what that particle is seeing and experiencing on its own, and Steve’s wrong, in a British sorta always right, kind of way. As water exits the spout, let’s track any one droplet, and try to draw what it does. There are two things happening here. Number one, it’s being
shot out of the spout. That gives it an initial
velocity in this direction. Number two, it’s being slung
around the wheel by rotation, which means when it exits the spout, it also has this velocity
going in this direction. Now that we have those
two components laid out, if you add the arrows together, that gives you the final
direction of the water when it leaves the pipe. And if you’ll notice, it’s not
actually trailing the pipe, it’s moving in a straight line forward. If you were to draw a circle in your mind around any drop that’s
on the screen right now, and follow it, you’ll see that it’s
moving in a straight line forward from the direction
that it left the pipe. It looks like it’s trailing, but it’s not. That’s an optical illusion. – So, we’re now going
to have the water jets firing into the center. – [Destin] You made this just
to, just to get on to me. – [Steve] Yes. This was just to get onto
your YouTube channel. (both laughing) – [Destin] Well it worked. (both laughing) So, my guess is, if we follow the same
logic that we had before, and we have the rotational
velocity, omega, times the radius, ‘r’, then that’s going to make
this go in this direction. But the water jet is going to be coming up and at you like this, so I would expect the snapshot. Oh god, I see the problem now. (both laughing) So when we start it, it’s going to all go to the middle, but as you start to accelerate, I think it’s going to, the snapshot’s going to look
like it’s lagging behind, and then as we get faster and faster, it’s going to look like its going forward? – Okay, that’s interesting. So at some, there’s a certain
speed you think where, the speed of rotation, where it’s going to come back to the middle. – [Destin] We’re talking
about the snapshot right now? – Yeah, yeah. – [Destin] I think that’s possible. – Okay, yeah. What I like is, and what most people’s intuition is, you would expect it to lag behind, right? – [Destin] I think it’s going
to start lagging behind, for a snapshot, and then
it’ll speed back up. – Okay, well let’s find out. Okay I’m going to turn the water on. Are you clear? – [Destin] Oh that’s beautiful. – [Steve] Is it hitting in the middle? Nice. – [Destin] Almost. It wants to. We can tune it right? – [Steve] Yeah. – [Destin] Oh that’s pretty. (Steve laughing) All right. – [Steve] You ready? – [Destin] Yeah. – [Steve] Okay. – [Destin] Oh, that’s pretty dude! – Yeah, it’s cool, huh? – [Destin] Ah! That’s awesome. It feels weird, like it looks– – [Steve] It just doesn’t
look right, does it? – [Destin] No. It doesn’t look right at all. – Okay, I’m just going to
try and go as fast as I can, just with my hand. – [Destin] But if you go really slow, does it lag at all? – No as soon you start to move it. – [Destin] It always go forwards. – As soon as you start to move it, it goes forward. – Okay, I was wrong, but, Steve was right (laughs). Let’s run the slow-mo. (creepy upbeat music) Okay what we’re seeing
here is fascinating. Part of it’s obvious, part
of it’s not so obvious. You remember before when we said you had two velocity components, right? Number one, we have the water that’s shooting out of the spout, which gives it a velocity in this direction. And number two, it’s being
slung around by rotation, which gives it velocity in this direction. Just like before, let’s
add those arrows up, and again, the water is still
moving in a straight line. Just like before, you can track
any particle and follow it, and you’ll see that it’s
moving in a straight line, away from the nozzle. The fun thing about this device for me, is that it’s tricking my brain
into thinking that the water is actively curving out
in front, but it’s not. Your brain tricks itself into
thinking the water is turning. And here we are, at the Smarter Everyday moment for me personally. When I’m presented with a problem, often times I get pretty head strong, like maybe even arrogant because of my education on the topic, or because I have a life experience that makes me think I
know all the answers. And when that happens, in my heart, I am less likely to hear the other person. At times during this experiment, Steve and I were communicating the exact same physical truths, from two different perspectives. And because we weren’t saying
it exactly the same way, I misinterpreted that to mean that one of us had to be wrong. As I look back at this footage, it was obvious to me that Steve clearly
understood my perspective, but I can’t say I took the
time to do the same for him. Because of that, when I was really wrong, and he was trying to explain it to me, I was already shut
down, I couldn’t see it. I just looked like an idiot. Here’s the takeaway for me, when I disagree with someone, or at least I think I
disagree with someone, it is imperative that I stop, I listen, and I don’t move on until
I completely understand the other person’s perspective. Because it’s possible you’ll find that you don’t actually disagree. – [Steve] It doesn’t feel right, does it? – [Destin] It doesn’t feel right at all. But it makes perfect sense. Real quick, this video
is sponsored by Audible. You can get any audiobook
of your choosing, plus two free Audible Originals by going to, or texting the word ‘smarter’ to 500-500. Speaking of disagreements
with the British, I want to try to convince
you to listen to a book. I have discovered biographies. I want to direct your
attention to this book. It’s called “The Marquis,” and it’s about Marquis de Lafayette. It’s written by Laura Auricchio, I think that’s how you say her name. It’s a fantastic look at
a Frenchman’s activities during the American Revolution, and how those unfolded and transformed into his role in the French Revolution. It is fascinating stuff. Go get “The Marquis:
Lafayette Reconsidered”, by going to, or texting the word ‘smarter’ to 500-500. There’s also tons of
other titles you can get. There are Audible Originals which are exclusively
available on Audible. I reclaim my time in the car,
by listening to audiobooks. Okay, let’s go back to Steve’s garden, and thank him for building
such a wonderful contraption. He makes incredible physics videos, all kinds of really neat stuff. You need to check out his channel. You want to tell people a couple of videos that you recommend? – I wanted to explain gravitational waves, but I wanted to build something to say, “This is what gravitational waves are.” Involves a Lycra sheet and a
drill with wheels attached. So I used that to explain– – [Destin] So you feel like
you’ve nailed it on that one. – I feel like I got like
as close as I could get. (Destin laughing) And I’m really proud of it. – [Destin] So, I will
leave links over here, so you can check out these videos. They’re in space, you can’t see them, but they’re in space. So go check those out. And you’re hoping to get
to a million subscribers, that’s the goal, right? – That’s what I want, yeah. – [Destin] Let’s just be
real, that’s the goal. – That’s what I, I’d feel really proud if
I got the gold play button and all that. – All right, that’s the goal. Let’s just be real here,
let’s don’t fake it. So anyway, that’s it. Go check out Steve’s channel. He makes great stuff. I’ve watched your stuff for years, man. – Aww, thanks. – So this is really fun to
be in your back garden, man. Thank you very much. – Cool. – I appreciate it. I’m Destin, this is Steve. Getting Smarter Everyday. Have a good one, bye. (twinkling music)
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