The Wobbly Truth: How Fluid dynamics Explains Tom Brady's Throw
Recently, we contributed to a new Veritasium episode with the one and only Tom Brady on the aerodynamics in play during American’s most popular sport. Our team was happy to support the project with a deep dive into the "why" of football flight – specifically, the crucial role of aerodynamics and gyroscopic motion in maintaining the ball's alignment with it's trajectory. It was fascinating to discover that, like so many other things in this universe, it is almost impossibly serrendipitous that the laws of physics work in a way that have made it possible to throw a prolate spheroid with any accuracy what-so-ever. We'll never play on the moon!
The same methods we used here to create this digital twin (below) linking flight trajectory simulations with CFD simulations are being used by cutting edge aerospace companies. We relied on Siemens Amesim and STAR CCM+ to do so.
Heads Up… we love computational fluid dynamics, so this blog article is very science-ey (no, that is not a word, but it gets the point across). Scroll down to the bottom for a simplified version.
The Perfect Pass: A Masterclass in Applied Fluid Dynamics
The spiraling football is an icon of American sport, a symbol of precision and power. For decades, quarterbacks have been judged by their ability to throw a "perfect" spiral, with Tom Brady often cited as the master of the craft. However, a deeper analysis reveals that the concept of a flawless spiral is a misconception. Even Brady's most celebrated passes exhibit a distinct wobble and a slight lateral drift—characteristics that are not flaws, but rather the signature of complex fluid dynamics at work.
Through computational fluid dynamics (CFD) and wind-tunnel testing, we can deconstruct the physics of the pass. These so-called "imperfections" are not only unavoidable, they are fundamental mechanisms for achieving accuracy and distance.
CFD Simulation of football aerodynamics using Simcenter STAR-CCM+
The Aerodynamic Challenge: Mitigating Drag and Instability
The primary engineering challenge of a pass is to overcome aerodynamic drag. An un-spun, or "knuckleball," pass is inherently unstable. Any minor disturbance from airflow can induce tumbling, which dramatically alters its aerodynamic profile.
This instability presents a significant problem. A football is highly streamlined when aligned with its trajectory, registering a low drag coefficient of just 0.14. If it turns sideways, that coefficient increases to 0.85 as its cross-sectional area expands. This combination creates a tenfold increase in drag force, severely reducing the pass's velocity and predictability.
The engineered solution is spin. Imparting spin generates angular momentum, creating gyroscopic stability that holds the ball's orientation nose-first. This minimizes drag and allows the projectile to travel farther and faster with greater accuracy. The importance of this stability is well-understood by elite players; Brady himself notes the critical role of a tight spiral in mitigating the effects of wind.
Facing a headwind, a quarterback can choose to increase velocity or launch angle to hit the same target distance.
Velocity: 55 mph to 61 mph Launch Angle: 20º to 30º
The Turnover Paradox: Harnessing Gyroscopic Precession
The role of spin extends beyond simple stabilization, leading to a counter-intuitive phenomenon known as the "turnover paradox." A long pass does not maintain its initial launch angle; instead, it "turns over" to align with its descending parabolic arc. This continuous realignment is essential to minimize drag throughout its flight.
This turnover occurs not in spite of the ball's angular momentum, but because of it. The mechanism responsible is gyroscopic precession.
As the ball moves along its trajectory, the surrounding air generates a lift force on its underside. On a non-spinning object, this force would simply push the nose up. Due to the gyroscopic effect of the spin, however, this upward force is translated into a lateral movement—a tilt to the right for a right-handed quarterback.
This lateral tilt then exposes the side of the ball to the airflow, which in turn generates a new force. Through precession, this sideways force is translated into the desired downward pitch of the nose. This constant, cyclical procession creates the slight wobble and allows the ball to trace its trajectory perfectly. The wobble, therefore, is an essential component of the turnover mechanism.
Inherent Consequence: Aerodynamic Lift and Lateral Drift
The physics responsible for the turnover has another inherent consequence: a slight, lateral drift. The persistent rightward tilt required for precession also generates a small but constant aerodynamic lift force in that same direction.
This explains why nearly all of Tom Brady’s deep passes drift slightly to the right. This effect is validated by anecdotal evidence from professional players. Hall of Fame receiver Jerry Rice, after transitioning from the right-handed Joe Montana to the left-handed Steve Young, noted a change in the ball’s arrival point. Young's passes drifted left, consistent with the physics of a left-handed spin.
Therefore, what appears to the spectator as a simple, powerful throw is, in fact, a complex ballet of physics. The wobble and drift are not imperfections to be eliminated, but evidence of a quarterback subconsciously harnessing the intricate laws of fluid dynamics to achieve the perfect outcome.
Interested in a simplified explanation? Keep Reading…
Why a Perfect Football Throw Isn't Really "Perfect"
When you watch a great quarterback like Tom Brady, it looks like he throws a perfect spiral. But scientists who studied the flight of a football found a surprise: even the best passes have a slight wobble and float a little to the side. It turns out these "imperfections" aren't mistakes. They are actually a necessary part of the physics that helps the ball fly straight and true.
Why a Spiral is So Important
First, why spin a football at all? The main reason is to fight against air resistance, also known as drag. If you throw a football without spin (like a knuckleball), it will start to tumble and flop around in the air. A tumbling ball has very high drag, which slows it down and makes it hard to aim.
Spinning the ball makes it stable, like a spinning top. This helps it stay pointed forward, which is very streamlined and has low drag. This allows the ball to fly much farther, faster, and more accurately.
The "Turnover" and the Wobble
Here’s where it gets interesting. For a long pass, a football needs to change its angle as it flies. It starts by pointing up, but it needs to point downward by the time the receiver catches it. This is called "turnover," and it helps the ball stay aligned with its path.
This turnover happens because of the spin, through a cool physics trick called "gyroscopic precession." As the ball flies, the air pushes up on its underside. Because the ball is spinning, that upward push makes it tilt slightly to the side. This small tilt to the side is what then helps the nose of the football aim back down. This constant process of tilting and aiming down is what creates the "wobble" you can see in slow motion.
So, the wobble is actually what helps the ball turn over correctly during its flight.
Floating to the Side
That same sideways tilt does one more thing: it creates a small amount of lift that pushes the ball sideways. This is why a pass from a right-handed quarterback like Tom Brady will almost always "drift" a little to the right. For a lefty, the ball would drift to the left.
In the end, the wobble and the drift aren't mistakes. They are key parts of the physics that allow a quarterback to throw a long, accurate pass.
Watch Veritasium’s full episode below!
