The Science of Curveballs 

Steve Smith and David Warner liked this

I find this person quite relaxing.

2:30 This is why in baseball you will sometimes see the catcher hand the ball to the umpire who will look at it and give it back to the catcher, or more usually, give the catcher a replacement ball.

This professor is so good all sports leagues have banned him

I tend to think it has to do with capillary action (or something like it). For a mechanical pump there should be no difference because pressure is independent of area.

I know it's cheesy, but this video filled me with joy!!!

Rod is just so full of charisma and smarts, must be an excellent person to hang out and chat with. Thanks for the awesome video!

that's looking from the back - it's curving toward the rough side on the front.

This video made so much sense! Cricket seems more sensible now!

@bibabuzze No, they're due too the Magnus Force - check out our earlier video on this topic.

@c3vzn Oh, the complications. Rod and I discussed this but you always have to limit the scope of a video. I think it involves the flow on both sides becoming turbulent.

@jonasianbuddy Rod Cross, Emeritus Professor at the University of Sydney

This was a great video. Thank you. It would have been nice to have "reverse swing" dealt with. In cricket, with an old ball, some bowlers can get it to swing the opposite way. Any idea why this might be?

Special appearance by zahir khan and R Ashwin

ashwin? 1:46

i recently realized that this described a curve i throw in slow pitch softball... you finally helped me solve the riddle of why this pitch curves since i don't crank it at all... i knew something else was at work and now i know what it is... i started out to hold a clinc to teach what i do without knowing why it works... and in researching it i found your video which i had seen before but didn't realize what it meant to me... once i realized... i started figuring out what i could do to make it work better and more consistently... and it assisted me in teaching it to others at the clinic... you should look into this... thanks again... 8|

@tanner9449 The diameter shouldn't matter but it did seem to be easier with 3mm (when we did the 6m attempts). For the 10.3m attempt, we tried the 5mm because we felt that was more in line with a standard straw.

golf balls and ping pong balls curve due to the Magnus force (check out our video on this) and the reverse Magnus force (haven't made one on this yet).

this guy seems to so positive, I just want to listen to him for ages.

When I used to play baseball, I had a lot of movement on my slider. I am right-handed and I had my fingers such that if you hold the baseball in front of you, so the seams makes a "U" shape, I positioned my fingers together just on the inside of the right part of the U and threw the ball with a slight wrist tilt on release, which produced the rotation shown. At the time, I didn't realise what it was I was actually doing. So I'm glad this video finally explained it to me many years later!

And as a further aside. I am Australian, that played baseball, that also went to Sydney Uni and this was one of my Physics lecturers while there. So this video really resonates with me.

wow, as someone who played baseball for most of my life, this blew my mind. The different baseball pitches and how they worked always seemed pretty straightforward, but then there were times you'd hear about a particular pitcher having a lot of movement on the fastball or having "late movement". And this effect could probably partially explain why. So many intricate air flows going around a baseball.. this also sheds some light on the knuckleball, too. And it's making me think of the long-derided "gyroball" from japan..

Brilliant - you said you'd do this and you have! I think at last I'm understanding how Shane Warne produced his ball of the century and it seems that swing (Seam bowlers) and Drift (Spin Bowlers) both optimise the laminar flow and boundary layer factors to get the ball as Grimmett would have called it to "Swerve".

Great youtube channel. I subscribed a few months ago, and since then there have been several gems. Keep them coming.

Just to get the baseball jargon correct: The "curveball" that they talk about at 2:07 is actually not a curveball but a slider, which breaks mostly laterally. The curveball's dominant movement is downward, due to the top spin imposed on the baseball by way of the pitcher's delivery, which basically pulls down at the front of the ball when he throws it. Some curveballs do have lateral movement, but the essential break is downward.

What you explained with the cricket ball was the conventional swing. Can you please provide an explanation for reverse swing that happens once the ball gets older?

The purpose of a knuckle ball is to give very little spin to the ball. So the perfect knuckle ball initially has no spin. If the ball is perfectly round and smooth it would move normal. A ball isn't perfectly round and smooth, it has all sorts of bumps, scrapes or seams. This, together with drag, will make the ball rotate. Also the bit from 2:50 on is still valid. So the ball will swing away from the smooth side, which will change as the ball is rotating. Which makes for a erratic flight path

Science + excellent presentation x amazing guest speakers + epic beard = fantastic show !

Can’t believe you’ve been doing it for 10 years! Amazing

High five, Derek! Great job!

This is excellent. We will use this in future BallsAustralia exclusives.

Great video. The professor is a joy to watch and learn from.:-)

How is this doens't have 1 million views😌👏 just brilliant👏👏👌👌👌👌👌

Really interesting! Excellent explanations for a complicated phenomenon. Btw, in the presentation text: defelected -> deflected

how to curve a ball? simple. just throw it like you normally would. the coriolis effect will curve it either right (on the northern side of the globe) or left (on the southern side of the globe)

I used to play baseball all the time and they told you at least how to hold it to get it to either be a slider or a curve, etc.. but they never explained why. Cool video.

Swing is a subtype of fast bowling swing bowling is to get the cricket ball to deviate sideways as it moves through the air towards or away from the batter

@DreJr a football ( i am assuming you mean the spherical one, if not then its just aerodynamics i think ) then the magnus effect is responsible for 'swerve' , air has friction, and the side spinning with the headwind is the direction of motion. (im 17 so sorry for poor vocabulary and explanation)

Plus with an aircraft's wing in a wind-tunnel it can easily be demonstrated that NON-laminar air detaches from the surface quicker (hence stalling and so on).

Found your channel tonight. Love it. Thanks for putting something educational out there. I love science and physics... I’d like to get my daughter in love with it too.

reverse swing is caused by the rough side of a cricket ball becoming lighter than the shiny side because of the material lost off the ball. he ball will fall towards the shiny/heavier side

Totally agree with you still, but check out a knuckleball in slowmo! That's where it gets truly mindblowing to me.

Your videos are awesome. Just need to be more clear on left and right otherwise it does get confusing. I have seen this in more than just this video of yours. Let's not invoke the classic "why does a mirror switch left and right but not up and down"....no wait, lets do! Make a video on that for fun.

You talk to such interesting people over interesting thing!

What is the ideal angle for a spin bowler (in cricket) to spin the ball on to get optimal swing/drift? How does the amount of revolutions on the ball affect the amount of swing/drift?

although at the point in the flight where the arrows are displayed the forces may be about equal, and as the orientation of the ball changes later in its trajectory the side force increases causing the ball to curve "late".

I'm sorry if I sound dumb, but what about the Bernoulli's principle? If the air passes through the rough side of the ball, then it will meet greater resistance, right? (I'm actually not sure about it). Then, according to Bernoulli's principle, the fluid(In this case, air), must exert a greater force on the ball than the smooth side. This should make the ball swing towards the smoother side. Could anyone please tell me why this approach is flawed or if the assumption I've made is wrong?

I could watch this all night xD It's almost 1:30 pm... Alright, last video! :D

Bernoulli's Theorem works off the streamline flow of an ideal fluid, which air definitely isn't. If it were, the air would just pass straight over the ball, seams and all, and carry on as it was out the back. And due to the balls symmetry, there is no real difference in distance, and therefore pressure on either side of the ball. Any effect from Bernoulli would be outweighed by the large amount of drag produced by the seam.

We need more scientists like this nice gentleman!

Rod seems a really nice chap and very intelligent too!

Curveballs generally do not have lateral movement. While there are a ton of breaking pitches and even more ways to blur the lines between all of them, the curveball is generally meant to mean a pitch that breaks from 12-6. It is thrown by providing top spin and making the laces tumble consecutively. As proven by a ton of other ball mechanics, top spin provides more drop off in trajectory. The pitches shown and discussed in this video are more akin to sliders. This difference is the reason why curveballs are what ruin pitchers rotator cuffs more so than any other pitch. To produce the top spin, you align your index and middle fingers on a single seam and as you throw the ball, you turn your wrist sideways and yank downwards. Very few curveballs have perfect top spin and are usually rotating at an angle. This leads to the famous "red dot" that batters will see while the pitch is on the way.

Okay, the pitcher at the end of the video clearly has a splitter grip, and the action is what you'd expect from a 3/4 or sidearm split-finger fastball. I always thought, though, that the splitter did what it did because there was less backspin (magnus effect) keeping the ball afloat than a usual fastball, without too much dip in speed. However, that seems like it only explains the action from a 12-6 overhand throw. Or is the action more similar to the gyroball? I'd love to hear from a pitcher about what I'm seeing there. Fascinating stuff nonetheless!

Found it (using Shazam) for anyone wondering, the song is Opus Magnum Phase - Le Dernier Orage

Very cool!

It's called a xistera. It's used in the game "Jai alai". en. wikipedia. org/wiki/Jai_alai

Lol, this video is right at the intersection of my interests: mechanics and baseball. Derek obviously knows a lot about the former, but probably not much about the latter. As such, here are some corrections: 2:06: A curveball doesn't usually spin on a vertical axis. Though every pitcher is a little different, the term "curveball" refers to pitches that have some degree of topspin. So, with some variation, the axis is horizontal, and because they have topspin, they fall faster than gravity pulls them. They also move in varying degrees to the pitcher's glove side, so to the left if thrown by a right-handed pitcher. A curveball that moves to the pitcher's arm-side is called a "screwball". I think they are called "curveballs" because their movement is most noticeable, because their movement is consistent with gravity. The fastball, on the other hand, resists gravity, due to backspin. 2:33 In major-league baseball at least, they put a new ball in play if virtually anything touches the ball, other than the pitcher and catcher. Pitchers don't have much opportunity to scuff or smooth a baseball, because they're almost always using a new ball. 3:18 lol "baseball match"

3:39 lol. Dude your vids are great. Thanks for the good job you do!

Waseem Akrim is famous for roughening up a side of a cricket ball and using it to achieve reverse swing. Most world class fast bowlers also have a specific gripe for reverse swing. When we play a cricket match, our team makes sure the ball bounces as little as possible and we always shine the side with the logo. I am curious as to how this effect would affect a spin bowler. Anyone have any idea?

Let me c it this help me in my game... Tnx for the info Prof.

i think he's explaining why the cricket ball swings, ping pong balls and golf balls are made from different materials and dont have a seam around the equator of the ball and requires a lot of force to create sidespin. Its an apples and oranges kind of deal.

this was put up on my b-day :D great vid btw

golf balls and ping pong balls both show curvature due to spin and neither have a rough surface. The symmetry of a baseball is such that the seam makes no difference. I went through every comment and nobody is questioning the science in the video. Am I crazy? (I liked the video)

could you explain how reverse swing works? wasim akram and waqar younis were the first to demonstrate this very effective tactic in the 1980's

@pinkybrain6 I would of thought it would be due to the fact that more friction is caused by air running over a rough surface e.g its hard to walk on ice due to lac of friction so you "pass over quickly" whereas its easier to walk on a pavement as there is more friction as it is rougher so you "stick" to it. I hope that makes some sort of sense.

Hey Derek, who is your go to cricket player?

please correct it.. for cricket ball, the rough surface side generates high air pressure, smooth surface side generate low air pressure, so high pressure pushes the low pressure, and ball swings in air in smooth surface side.

OMG! This man, is awesome

The explanation takes more room than a RU-vid comment allows. Follow the link under the video, click on the picture of the baseball then the link to an article on knuckleballs.

In regards to Cricket, which way should I spin the ball, (I am a Leg Spin Bowler) with the shiny side facing the batsman or the rough side?

this bloke is so australian

In the sister video to this one, you used the term "parabolic" when you described the tennis ball falling. So much of this universe ends up following a parabola or shaped liked one. Why not have a video about what they are and how so much ends up having one or moving in its shape?

3:40 that was so wholesome

Hooray for learning!

I love your whitecaps FC jersey. One question I have is what about curling stones. Because they rotate the same direction as the spin. Is this from having a smooth side or because of a different effect?

@SteinPapier Because the flow of particles is deviated and less smooth :)

The side of the ball you scratch is the side the ball moves to when you throw it? Is that how it works? Sorry, didn't understand.

did I hear them correctly? If the seam is not rotating parallel with the motion of the cricket ball the ball swings to the smooth side and if the seam is rotating parallel the ball swings to the rough side? 1veritasium, can you put annotation arrows on the diagrams? I'm confused.

thank you for sharing this amazing video

Soccer Ball swings because of bernaulli effect. And it swings towards the laminar flow. You seem to suggest that cricket ball has opposite effect.

people still asking about "reverse swing" clearly didn't pay attention to the video. It's all the same effect, just that in the reverse swing case, your seam is not as prominent, and the swing is caused by one side being rougher than the other.

Awesome accent :) Love it ^^

1:42 Zaheer Khan with the ball. 1:46 R Ashwin with the ball.

nice whitecaps fc jersey. are you from vancouver?

@bibabuzze Remember Jabulani, from 2010 World Cup? That ball was tricky...

I have that same fusion poster @ 3:14 !!!

Which game is Dr Cross referring to at 3:30? I'm fairly certain it's from a Yankees/Blue Jays game April 19th, 2011. I'm simply curious, not trolling for ©

My Aussie pride just went up a notch...even though I didn't actually discover anything.

That guy is a genius!

There is a diamond back

I'd imagine the turbulent air is moving slower than the smooth air. Would this create a pressure difference on the ball causing it to curve?

A few people have mentioned that a pitch with a vertical spin axis is a slider. Actually, that's not quite correct. Most sliders have an axis that is parallel to the direction of motion, sort of like a corkscrew, or a bullet. This makes them move somewhat close to how a thrown ball would move in a vacuum, at least more so than any other pitch. A few pitchers throw sliders/curves with a vertical spin axis, like Sergio Romo or Adam Ottavino, but they tend to have nearly sidearm deliveries. It's very hard for a pitcher who throws overhand to get that kind of spin. However, there is another pitch that tends to have a vertical spin axis, but with the spin oriented the other way: a circle changeup. Most circle changes move way more to the arm side than sliders move to the glove side.

My dad is a huge baseball junkie, and I would love to out-trivia him with some facts regarding the physics of the throw that was mentioned, and its actual usage. Could you please help?

I'd say it'd depend on weight, fabric, speed of the ball thrown.

Bancroft has entered the chat.

could you investigate higher dimensions in one of your videos?

This old guy is a genius.

With the Magnus force, why would the "speed" (or spin) change how much curve the baseball has?

i love cricket

Thanks Sir