This is Tom Brady. He's the greatest American football quarterback of all time.

Can you hear it go by you?

(laughing) Yeah, it's scary.

He's won seven Super Bowls and has thrown the most touchdown passes in history.

Ooh.

Ooh, that one hurt the chest, I heard that.

Right in the chest.

I'm like glad I'm not catching those.

Every quarterback takes pride in their ability to throw a tight spiral. The tighter the spiral you throw means the more control you have of the football.

We analyzed his throw in detail.

Have people shot you in really slow motion for the release and everything?

Never.

And discovered something surprising. Even Tom Brady can't throw a perfect spiral. Just look.

Said hut.

On his deep passes, no matter how hard he tries to spin the ball cleanly around its long axis, if you look closely enough, you'll notice this little wobble. Not only that, there's a slight drift to the ball, which means even Tom Brady can't throw straight. Virtually all his long passes curve to the right.

But these aren't mistakes, they're actually fundamental to the physics of throwing a football accurately. To find out why, we ran a full computational fluid dynamics analysis, tested spinning balls in a wind tunnel, and even embedded sensors in real footballs.

That's crazy.

Now, admittedly, who are we to tell Tom Brady anything about football?

(Derek grunting) I've never really played much football. I grew up in Canada. I'd be much happier to be playing hockey. Like why can't I throw at all? That is so rough.

Okay, well, he'll walk you through it, I'm not gonna bother doing it (laughing) right now.

Yeah, yeah, yeah, yeah.

Try to do this, over-exaggerate the tilt. So instead of standing straight up-

Yeah, lean forward?

lean like you're almost like a shortstop, right, and like you're falling over, and then you're just here, like that.

(Derek grunting and laughing)

Good catch.

So lean over a little bit.

I feel like I'm like not ready for it.

So get down like a shortstop.

Yeah, yeah, like this?

Even more.

Even more?

Yeah. Now throw it sidearm.

Yeah? I feel like this is weird. There you go, that was a better throw.

That is a better throw.

It was really good.

What's the key to throwing like a really tight spiral?

The key to me is, first of all, you gotta have very light grip pressure on the football. I learned over a period of time that I had to be really efficient with my mechanics. I had to have all my energy going right toward the target with a very relaxed posture. And then it's a really smooth, efficient throwing motion.

And then how are you actually imparting the spin to the ball?

So you're really popping your wrist at the end. So I can even go really slow and just pop my wrist at the end. And even that little bit of wrist pop will create a little snap on the ball as it releases from my fingertips. Henry, you can't drop the easy one.

That snap and the spin it creates is the key to Brady's record-breaking throw. But the big question is why? I mean, what does the spin actually do to the football?

It seems like such a simple question, but the physics turned out to be much more complicated than I initially thought. In fact, physicists studying the problem didn't get close to the real answer until just five years ago. So let's break it down from the start.

A question for Tom is, can he throw the ball without spinning it.

Like a knuckleball?

Yeah, can you knuckleball a football?

Yeah, I could try. Can I throw it underhand?

Yeah, yeah, yeah.

Yeah, however you wanna toss it.

Even overhand, there's no way to do it without getting a spin on it or it's just gonna mess with you?

I mean, you'd have to almost throw it sideways.

Yeah, yeah.

Oh, that spun a little bit.

When you launch a ball without spin, perfectly aligned with the direction of motion, it seems like the air flowing over the ball will be totally symmetric. But this is unstable. Any slight disturbance, like a tiny bit of wind, will cause more air to hit one side than the other, and that starts to change the ball's orientation. And now more area on that side is exposed to the oncoming air, so it deflects even more.

So drag on the ball increases, it's pushed off course, and it can begin to tumble. The total drag force on the ball is proportional to the area presented to the airflow and the drag coefficient. That's just a measure of how streamlined an object is.

Pointed straight in the direction of motion, a football is pretty streamlined, with a drag coefficient of just 0.14. That's better than a bullet. But on its side, the drag coefficient is 0.85, which is worse than a cow.

Man, I'm learning a lot today. That's what I'm gonna use with all the quarterbacks, going, "Man, your drag coefficient sucks." (laughing) "What are we doing? We need .14. .85, no good.

To make matters worse, when a football is going sideways, it exposes nearly 70% more area to the oncoming air. And combined with the higher drag coefficient, this means that the drag force is 10 times greater than when the football is aligned with the throw. So an un-spinning ball can end up going sideways, meaning it decelerates up to 10 times faster. Plus, as it tumbles, the air pushes on it in different directions, making it move unpredictably.

Now, in some cases, you actually want this. Like when kicking the ball back to the other team, punters sometimes intentionally kick the ball end over end so that it gets pushed around erratically. That makes it far harder for the opposing team to predict where the ball's gonna go and get under it. But when you're passing to your own team, you want the ball to be predictable and go as fast and as far as possible. And for that, you need spin.

The benefits of spin really became clear in the mid 1800s during the Crimean War. Back then, soldiers were armed with muskets that fired round lead balls. And to make reloading faster on the battlefield, these musket balls were made significantly smaller than the barrel. But when the gunpowder was ignited, some of the expanding gases would then escape around the bullet, making the bullet's exit velocity unpredictable.

This, combined with inconsistent manufacturing and the round ball's poor aerodynamics, meant that muskets were somewhat unreliable.

There was a British army musketry instructor who famously said, "I'm willing to stand and be shot at all day long, as long as whoever's shooting at me with the smoothbore musket promises to aim at me every single time."

Because he knew the bullet's never actually gonna go (laughing) where the gun is being aimed.

All of that changed in the fall of 1854. Russian troops huddled in Sevastopol under siege by French and British forces. The soldiers watched as British troops set up on a distant hillside. They were far out of standard musket range, so the Russians weren't worried, when suddenly a window shatters.

They were shooting through the windows of the Russian barracks at their naval base in Sevastopol, 900 yards away, they're shooting bullets through the windows.

But these were no ordinary bullets. Eight years earlier, an enterprising French army officer, Claude-Etienne Minie, made a breakthrough. He developed a conical bullet with a hollow base and an iron plug that would fit into it. So when fired, the gas pressure drove the plug into the base, which expanded the bullet, pressing it firmly against the barrel walls so no gas could escape. This made the bullet's muzzle velocity much more predictable.

But it also enabled something else. The expanded bullet could grip spiral grooves carved into the inside of the barrel, called rifling. This imparted spinned the bullet as it shot out. And this is key because all spinning objects have a fundamental quantity they can serve, angular momentum. This helps them resist changes in their orientation. It's just like the spinning top.

Now, without spin, the top just falls over like you'd expect. But if we add a little bit of spin, we can see that it resists changes in its orientation. So if I give it a little touch, it reorients itself in the direction of its angular momentum.

A similar thing happens with a spinning bullet. Its angular momentum resists changes to its axis of rotation. So even if wind applies an unbalanced force to the bullet, it maintains its orientation. This reduces drag and helps the projectile fly further, faster and more accurately. The exact same thing is going on when Tom Brady throws a tight spiral.

The important part of a spiral is you feel the wind blown at us. If the ball wobbles at all, it's gonna catch a lot of resistance in the wind, and it's gonna slow the velocity of the ball down a lot and the accuracy. The tighter the spiral and the more it spins, the more it can just rotate through the air and the wind will have a less effect on the ball. So for any good quarterback, the ability to throw a tight spiral is really important when you play in windy conditions.

A spinning ball will maintain its orientation, and therefore cut through the air with a smaller frontal area and a lower drag coefficient. This all makes sense, but here's where things get weird. If the ball is maintaining its orientation then on a long Hail Mary pass, it should stay pitched up like this the whole time, just like when it was thrown. But that is not what happens.

There's kind of a paradox in football, which is, when you release the ball, you're angled say positive 30 degrees.

Okay.

And when your receiver catches it, it's angled negative 30 degrees.

Perfect, I love that.

So what we just said was, angular momentum makes the ball hard to pivot.

Okay.

But what we saw was it pitches from this to this in four seconds.

Right, turnover-

Yes, exactly.

is what we would call that. Now, turnover is essential to a good throw because it means at every point along the arc, the ball's orientation stays closely aligned with its direction of motion. That means it stays pointed directly into the airflow, which minimizes drag.

Now, sure, you might think this isn't that crazy? I mean, arrows and birdies align themselves along the path of the arc as well. But that works in these cases because the objects are front weighted. The feathers catch the air and get pushed behind the heavier tip, which leads the way. But a football's totally different. I mean, it doesn't have feathers or fins, and its weight is evenly distributed along its axis. So it just can't use the same mechanisms to align itself.

So in 2020, the editor-in-chief of "The American Journal of Physics" decided to figure it out.

I was surprised at how many bad explanations that were easy to debunk got published. When you think about it, it doesn't make any sense, because the air resistance would push the nose of the football up, and you want the nose of the football to go down. So it's pretty curious.

So Price put together a theoretical model to explain the football's turnover. And today, we're gonna see whether his findings hold up by simulating Tom Brady's own throws in a wind tunnel.

The idea of having anything to do with Tom Brady, whom I greatly respect, not only because of his skill, but because of his work ethic. It's otherworldly.

We have these sensors in these balls. So we should be able to see how fast the balls are actually going from inside the ball. And just to be sure, I'm measuring the speed of these balls the old-fashioned way, a decision I might regret.

Do you wanna go right on the side of the dummy with the gun? I'll throw it right over your head.

(Derek laughing)

I won't hit you, trust me. Yeah, right there, perfect. Ready?

Yep. 45.

Maybe scoot just a smidge more that way. Perfect.

Holy (bleep). 46. You gonna do another one?

49. My God, that's scary. That's like 80 kilometers an hour. But would you actually use that speed in a game?

That'd be a good speed. That's a normal pass.

That's like terrifying.

And that's just for a regular throw. For his long throws, the speed jumps even higher, over 60 miles per hour, that's almost 100 kilometers per hour. Now, I'm not about to step in front of that cannon. I was not built for being an athlete.

You're built for analyzing the. (laughing)

That's right, I'm here for the data. And that's why I've got Henry here.

Ooh.

Ooh, that one hurt the chest. I heard that.

Sure you don't wanna swap in, Derek? (laughing)

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Have people shot you in really slow motion for the release and everything? Did you ever watch that back?

Never.

You guys ready?

I'm ready.

Three, two, one.

Oh my God. Are you good? You good, Ricky?

Yeah, yeah, I'm good, I'm good.

Is that plexy or is that real glass?

That's plexiglass.

That's incredible.

You get one shot at these things.

Oh (bleep), all right, I'd have given it my best. Should we try one more, even if the camera breaks?

(Henry and Derek laughing)

I don't see the cracks-

Wow.

so we can go again.

Let's try one more.

Are you kidding?

Let me just throw a little harder.

All right, let's go again.

I'm gonna throw a little harder.

Aw.

Now we're broke down.

That went right there. Are we able to watch the throw back?

Good spiral. (laughing) Oh, that's so cool.

The sensors show Brady's maximum spin rate on this day was 628 revolutions per minute. So armed with this data, let's analyze Brady's throws in a wind tunnel.

How much data are you used to getting?

Zero.

Really?

When I played?

Yeah.

None of it was available.

So this is the low-speed wind tunnel here at the university. This wind tunnel facility can get up to about Mach .2, so 20% of the speed of sound.

Typically this wind tunnel is used in the development of advanced wing geometries for innovative sustainable aircraft design. But today, it's being used for football.

We have just a sting mount mounted to a turntable. We actually have a six-component load cell here. And with this six-component load cell, we can measure all three components of force and torque. We then have an electric motor, right, that we can spin to basically simulate the spiral.

First, we're gonna simulate one of Brady's throws where the ball travels straight into the airflow with his classic spiral. And everything proceeds as we expect, no significant forces or torques develop. But during a game, a ball doesn't travel like this in a straight line. During any throw, its center of mass follows a roughly parabolic trajectory.

So let's say you align the ball perfectly with this parabola when you launch it. Well, then, from the ball's perspective, just a moment later, this parabola starts to curve down away from the ball, which means more air will be hitting the underside of the ball than on top. Now, you would expect this would tilt the ball back, but that's only what happens if the ball is not spinning. If it is spinning, then the situation is very different, which you can see with this amazing demo. Imagine this ring of golf balls is like a cross-sectional slice of the football.

Here's what happens when I try and push it back with this leaf blower. I mean, it tilts back just like you'd expect. But if I do the exact same thing, but this time, get the wheel spinning, tilts out to the right. And you can see why if we slow it down. So as the ring passes the leaf bar, that's where the force is applied. But each ball still has momentum in the direction of rotation. So it actually reaches its peak 90 degrees further along from where the force is applied, and this is known as gyroscopic procession.

So if the wind was hitting it, it's gonna keep the point up.

So you'd think that it would just push it back.

Right?

But because it's spinning, when you push up, it actually tilts to the right.

Oh, interesting.

But it doesn't stop there. As the ball tilts right, it exposes more area on that side. So now, because of gyroscopic procession, the ball pitches downward. And with more air hitting the top of the ball, well, it's going to deflect to the left. And that is going to make the ball deflect back up. And now we're back to where we started. So this cycle is going to repeat, but since this is happening continuously, the nose traces out a circle around the direction of airflow. So we get a slow wobble.

We used to joke, whenever you would not throw a tight spiral, you would call it a tight wobbler. That was a Brett Favre-coined phrase. He let it go and have a little wobble to it, and he'd go, "Oh, tight wobbler."

(Henry laughing)

Now, if the ball were just traveling straight, this would be the whole story. But remember from before, the ball's path is a parabola, meaning that from the ball's perspective, the oncoming air is constantly dipping down away from it. So the ball is trying to process around the airflow direction, but that direction is constantly changing.

For example, by the time the ball has reached the bottom of the procession, the airflow has moved down too. And what that means is the ball is not gonna tilt out to the left as much as you'd expect. So when it processes back up, it doesn't go as high as where it started. And over time, it is this that gradually pitches the nose of the football down, keeping it aligned with its parabolic path.

I can visualize it all, your fancy science words.

Okay, okay.

I'm going all the way back to my high school days. I was a very average science student, so. But you're teaching me a lot.

As the ball goes through the air, there's gonna be more air resistance on the bottom of the ball than on the top.

The front of the ball, not the back, 'cause that's hitting the wind first.

The front bottom of the ball.

And so what that means is, it creates this processive effect that pushes it out, pushes it down, pushes it right. It creates a wobble no matter what you do.

Very cool.

So wobble is actually not only impossible to avoid, but it's essential to make sure that the ball follows the path that you want it to follow.

You can see this in the wind tunnel. We've tilted the ball up by three degrees and it's free to pivot in any direction.

Yeah, you're definitely seeing a pitch. Oh, that's awesome. What we're seeing is, it's starting out aligning itself about three degrees off. You know, 'cause that's how we spin it up. But as the airflow starts, it's pointing itself in the direction that minimizes drag. That's so cool. I mean, that's exactly what we were expecting, but it's still incredible to see it in person.

If you look at a real football flight, you'll notice that it spends more time angled slightly to the right when thrown by a right hander. That is what creates the force, which, through procession, gradually pitches the nose downward. It creates the turnover effect that Tom Brady was talking about.

Just wanna reframe the wobble as not necessarily a bad thing.

Okay, good.

(laughing) Yeah. Peyton Manning had a good wobble on the balls, but he found a way to complete a lot of touchdowns that way.

But the right-ward lean of the ball also has an unintended side effect. Something we've heard is that for right-handed throwers, the ball will drift right, and for left-handed throwers, the ball will drift left. Do you think that's true or is that something you notice?

So I wouldn't necessarily agree with that.

So we got Tom to throw straight down one of the lines on the field. Is the drone set? That's a pretty straight throw.

Henry, don't move, you're making it look bad.

(Derek laughing)

I'll stay planted. The more still you go, the better it looks for my throw. It's like a catcher. when you frame the pitch.

I'll frame it, I'll frame it. (laughing)

From ground level, his passes looked amazingly straight. But from the drone, if you watch closely, just at the end of the pass, the ball does drift off to the right. This is because up until now, we've been ignoring a very important aerodynamic effect, which is lift. When the ball is tilted to the right, it generates lift out in that direction. The more it's tilted, the larger this force is. The rightward tilt is required to get the ball to turn over during its parabolic path. But it does mean that right-handed throws tend to drift, right?

The effect is subtle, but some players notice it intuitively. In the fall of 1991, Jerry Rice, generally considered the greatest wide receiver of all time, changed quarterbacks. In place of the right-handed Joe Montana, he was now catching passes from the left-handed Steve Young. And for Rice, something felt off. He wasn't sure exactly why, but he said the throws were coming up short. Of course, what was actually happening was that the ball was drifting away from where he expected it to be. Joe Montana's right-handed throws drifted to the right, whereas Steve Young's drifted left. It's a subtle effect, but it's all part of the procession that minimizes drag on the ball and lets it fly farther, faster and more accurately.

So it's not because you're a bad quarterback throwing it with a wobble, it's because wind, you know?

Okay, so what if you're in a dome and there's no wind?

See, that's a great question. So I'm just saying this is just air resistance. So even in a dome, the same thing would happen.

Whether in an outdoor stadium or a closed-top dome, the ball will always wobble. But outdoor stadiums are significantly harder to throw in because of the wind. With the ball being thrown at 50 to 60 miles per hour, most of the airflow over the ball is due to its own motion, but in winds gusting over 15 miles per hour, the weather starts to play a major role.

We commissioned the NFL data team to do an analysis of completion percentage in outdoor stadiums versus indoor domes. And they found that throws in indoor stadiums are consistently more accurate, no matter the distance. So maybe Brady was hard done by Foxborough, New England's stadium. Do you prefer to throw in a game when it's no wind? Do you prefer wind, rain, snow? Does it matter?

I preferred outdoor, 70 degrees, humid, tiny little breeze, just to keep you cool.

Right, but why did you like being outdoors as opposed to being in a dome?

I felt like my depth perception was a little better outside. I liked just the natural feel of the natural air. The dome always felt like a vacuum.

Do you think you had an edge if the weather was bad compared to other quarterbacks?

I would say yes. And the reason why is I'd say I practiced in it all the time. And I think getting used to the conditions and the familiarity of the wind, of the humidity, of the rain, of the snow, you know, grass field, turf field, I knew exactly what to wear for every single condition. I played 23 seasons, 100 to 120 practices a year.

You saw everything.

So that's over 2,000 plus practices. You know the thickness you want your sleeves, you go, okay, "What's the temperature? It's 50 degrees. Okay, this is the shirt I wear when it's 50 degrees. Oh, it's 35 degrees, this is the two shirts I wear when it's 35 degrees. You know, this is the muff that I wear. You know, this is how many heat packs I put in the muff to keep my hand warm when it's 30 degrees versus 50 degrees."

You had it all dialed in.

You just have to, I mean, you just observe over time, and you, you know, get better and better. It's a lot like an F1 car. You know, everything is just fractions of, you know, things to do to make yourself feel the most comfortable.

So maybe Brady is a bit more scientific than he gives himself credit for. Over 383 career games, more than 7,700 completed passes and tens of thousands of hours on the field, Brady intuitively understands all the physics we've just analyzed. Plus he knows how to harness these effects to get the ball where he wants it to go with just a few seconds to throw it. In a game where perfection is impossible, he's internalized all the complex physics, the kinematics, the aerodynamics, and he still makes it look simple.

Yeah, I don't have to move. (laughing) So we actually made a video together with Tom Brady teaching us how to throw a football. And if you wanna learn more about that, you can check it out right here.

Now what we got for you are some balls that you've never thrown before.

Oh God, what have you guys got cooked up?

But we're not done yet.

What the heck? In other sports, surfaces are engineered down to the smallest detail to control airflow. But footballs, they've hardly changed in decades. So we tested whether a football's design is really optimal. And to find out, we had Tom Brady through a series of custom balls, including one built to eliminate his spin entirely.

I don't even know how you could throw that.

Now, in investigating this, we actually uncovered a secret technique that teams are using to modify their balls and give their players an advantage. But we'll get to that in a future video. So make sure to subscribe and stay notified, and we'll see you then.

That's insane.

(Henry laughing)