How to get better at snooker… with physics

The 2025 World Snooker Championship recently wrapped up, with China’s Zhao Xintong beating former champion Mark Williams in the final to become his country’s first world champion. However, earlier in the nail-biting tournament it was another player who made world news—Northern Ireland’s Mark Allen. Allen compiled a rare perfect break of 147 points, making him only the 11th player to do so during a World Championship match, and earning him a roughly $53,000 (£40,000) bonus. A perfect break! 147 points! If you’d like to know what that actually means—and/or how snooker turns out to be a great demonstration of Newtonian physics—read on!

How snooker works…

First, the basics. If you’re familiar with snooker, you can probably skip this section—but if not, here’s why 147 is the magic number.

A game of snooker (called a frame) starts with 21 balls on the table, not including the white cue ball. These are called object balls, and they include 15 red balls, along with one of each of the following colors: yellow, green, brown, blue, pink and black.

Like pool, the aim of the game is to use the cue ball to push the object balls into the six pockets that line the table’s perimeter. This is called “potting” the ball, and if a player does this successfully, they get to take another shot. If not, the other player steps up. The game continues until all the balls have been potted.

a detailed view of a person holding a cue and going in to break snooker balls. most of the balls are red, with one pink, one blue, and one yellow — A detailed view of a cue and snooker balls during the Final of the Dafabet Masters between Stuart Bingham and Ali Carter at Alexandra Palace on January 19, 2020 in London, England. CREDIT: Alex Davidson/Getty Images. Alex Davidson

There are two key things to note here. The first is that balls in snooker are worth points, and need to be potted in order of ascending value. First, the 15 reds (worth one point each), then the yellow (worth two), the green (three), the brown (four), the blue (five), the pink (six) and finally the black (seven). Secondly, after each red ball is potted, the player who potted it gets the chance to pot a colored ball. If they succeed, the value of the colored ball is added to their score, and that ball is returned to its starting position. The red remains off the table.

Skilled players can chain together long strings of successive pots. Such a streak is called a break. And as sharp-eyed readers will have noted, there’s a maximum possible score from a single break: all 15 red balls (one point each), each followed by the black ball (worth seven points every time), then the colors in order. This adds up to 147: (15 x 1) + (15 x 7)) + 2 + 3 + 4 + 5 + 6 + 7.

…and why it’s really, really hard

It’s hard to overstate just how difficult it is to compile a 147 break. For starters, there’s the simple fact that it requires potting 36 balls in succession, without missing. As anyone who has spent any time playing pool will attest, that kind of streak is no mean feat in and of itself.

However, your average barroom pool shark might be startled by the size of a snooker table: they’re huge. A regulation snooker table is 12 feet long by 6 feet wide, which is basically the same size as getting four average bar-size pool tables and arranging them in a two-by-two configuration. In fairness, professional pool tables are larger—9 feet by 4.5 feet—but still have significantly less area than a snooker table.

In addition, despite the snooker table being so much larger than a pool table, the pockets are smaller, and they also open at a narrower angle than those on a pool table. This makes snooker less forgiving than pool; if a ball isn’t traveling straight into a pocket, it’s just as likely to catch the corner and bounce out again.

All these factors make chaining together several shots difficult enough, let alone clearing the table, let alone clearing the table and setting yourself up to pot the black ball every time you pot a red..

Controlling the cue ball… with physics!

So if snooker is really, really difficult, how on Earth do players ever make 147 breaks? A big part of the answer is… physics!

Astrophysicist and snooker fanatic Simon Goodwin, from the University of Sheffield in the UK, tells Popular Science that in principle, snooker is a pretty simple game.

“You’ve got your cue ball, and your main goal is to get an object ball in the pocket. And when, when you don’t play very well, like me, usually you just go, ‘Yes! Got one!’” he says. However, the key to making pot after pot, is maneuvering the cue ball to set yourself up for the next shot. “You’ve got a very particular order in which you have to pot the balls: you’ve got to get it red, then you’ve got to get a color. And so cue ball control is absolutely crucial.”

Controlling the angle

Cue ball control starts with understanding what will happen when two balls collide. Consider the most simple case: a cue ball moving in a straight line, and striking the object ball perfectly square on. The cue ball carries a certain momentum, which is calculated as its mass times its velocity. As the ball is moving in a straight line, this is referred to as linear momentum.

Goodwin says this simple case is pretty straightforward to model: “You have the cue ball coming in. It hits the object ball. And if it’s a head-on collision, exactly along a straight line, you pass all the momentum on. [The incoming] ball stops, and the other one just carries on. So it’s very, very simple.”

In other words, all the cue ball’s momentum is transferred to the object ball. This is because momentum is a conserved quantity. All other factors being equal, the amount of momentum carried into a collision will be the same as the amount carried away.

However, it’s pretty rare for a cue ball, object ball and pocket to be perfectly aligned, so most snooker shots involve the cue ball striking the object ball at an angle. In that case, momentum is still conserved, but now it’s split between the cue ball and the object ball, and the sharper the angle at which the cue ball hits the object ball, the more momentum it retains.

The one constant is that the balls fly apart at a right angle. Well, almost. “If this was a classic idealized physics problem,” Goodwin says, “the balls would [diverge] at a perfect right angle.”

However, of course, snooker is not a classic idealized physics problem. The cue ball loses some energy to friction as it travels, the collision between the two balls is not perfectly elastic, the contact between the two balls also generates friction and the loss of kinetic energy to heat, and so on.

But to work out what the cue ball will do once it’s impacted an object ball, you can do a lot worse than starting with the knowledge that they’ll fly apart at pretty much a 90° angle, and that momentum will be conserved between them.

Mastering the spin

Linear momentum is only half the story–and arguably the less interesting part. If you watch some snooker highlights, you’ll see that the best players can do all sorts of insane things with a cue ball: make it stop on a dime, turn at an apparently impossible angle, or swerve violently after impact. Goodwin says that even he finds himself shaking his head in disbelief at times. “There’s things you watch and you go, ‘That is breaking the laws of physics!’”

All this wizardry depends on another form of momentum: the ball’s spin, or more formally, angular momentum.

“Watch the really, really, really good [players],” says Goodwin. “They manage to get the [cue ball] exactly where they want it to, When somebody’s on a really nice break it looks so, so natural. And the way you control the cue ball is by giving it spin.”

Spin is imparted to the cue ball by striking it with the cue somewhere other than perfectly in the center. Hitting the ball above its center point imparts topspin, while hitting it below the center point imparts backspin. Both of these send the ball spinning around an axis perpendicular to its direction of motion.Topspin rotates the ball in the same direction it’s travelling, whereas backspin does the opposite. Hitting the cue ball to the left or right, meanwhile, will send it spinning around an axis perpendicular to the plane of the table.

And that’s not all. As Goodwin points out, “You can combine [multiple forms of spin] and set the ball spinning in a complex way.”

So what happens when a spinning cue ball hits an object ball? Angular momentum is also a conserved quantity, which means that the amount of spin imparted to the cue ball is distributed between cue ball and object ball in a collision. A cue ball carrying topspin will follow the object ball after the collision, while sufficient backspin will cause the cue ball to screw backwards, moving in the opposite direction to the object ball. Sidespin will alter the direction of both cue ball and object ball.

Understanding the table

Up until now, we’ve looked at idealised models of how snooker balls interact, but the real-world imperfections of the actual game itself are important when considering spin. The cue ball’s interaction with the table, in particular, is a crucial consideration.

“The ball can gain or lose spin as it travels across the cloth,” explains Goodwin. The degree to which the ball grips the table is somewhat dependent on its speed–the faster a ball is travelling, the more it will skid across the table, rather than rolling. This explains how shots like the below piece of sorcery from snooker icon Jimmy White are possible. At first, the cue ball is traveling too fast to grip the table. As it slows down, the extreme spin White has imparted takes hold, and the ball just … stops.

Every individual snooker table is different, too, with some creating more friction than others.“Quite often,” Goodwin says, “you’ll find the first couple of frames [of a match] are a bit scrappy. Even if [a frame] is clearly won, the other player will play on for a bit, even though they have no chance of winning, just to get the feel of the table.”

In addition, he says, “The cloth has a nap, so it’s got a direction it goes. So it’s actually slightly different potting a ball up the table than down the table. And again, if you don’t get that quite right, and you’re not quite attuned to how the table’s running, you can under hit or over hit shots.”

There’s one final aspect of the table to discuss: the cushions. Again, in principle, the way a ball interacts with the cushion is pretty simple. This time, it’s helpful to borrow a concept from optics: angles of incidence and reflection. “In an ideal situation, [the ball] is just reflected,” says Goodwin.

Basically, if you draw a line perpendicular to the cushion at the point where the ball contacts it, then the angle the ball’s trajectory makes with that line (the angle of incidence) will be the same angle at which it bounces off (the angle of reflection).

However, add a little spin to the ball and it will start behaving very differently. Watch how the ball travels straight down the table, but then bounces off the cushion at an unexpected angle:

Forgetting everything

Do professional snooker players think about angles of reflection or the difference between linear and angular momentum? “Of course not,” laughs Goodwin. “They just have an instinctive understanding that if I do this, this happens.”

Such an understanding is built up over a lifetime of practice. A professional will have spent “thousands of hours on the practice table,” according to Goodwin.

For those of us who can’t do that, it can be surprisingly helpful to understand why the balls behave in the way they do. A theoretical understanding of the physics of cue ball-object ball interactions can only take you so far–but it might just provide you with an edge next time you’re playing pool at the local bar.

This story is part of Popular Science’s Ask Us Anything series, where we answer your most outlandish, mind-burning questions, from the ordinary to the off-the-wall. Have something you’ve always wanted to know? Ask us.