Beyond the day job
One degree,half a millisecond
Why grown adults volunteer to be humiliated by a 45.9-gram ball that isn't even moving. Half an hour of golf: history, physics, radar — and a handful of things you get to break yourself.
Navigate with ↓ ↑ or scroll
Why I got hooked
Four reasons that have nothing to do with the ball
Anyone can win
The handicap system cancels out the skill gap. A beginner can beat a good player in a genuinely fair match. No other sport does this — we'll do the maths later.
Your opponent is you
The course doesn't move, doesn't defend and never has an off day. Everything that goes wrong, you did. Confronting, and strangely addictive.
Four hours offline
Eight to ten kilometres of walking, no phone, no notifications. The closest thing I know to genuinely thinking about nothing.
It's never finished
You cannot complete golf. There is always one shot that could have been better. That is precisely why you go back next week.
Origins
Banned three times, played anyway
Golf is old, and the question of who invented it is exactly the kind of argument golfers can sustain for four hours.
Loenen, Netherlands
Earliest known reference to colf: hitting a ball toward a target with a stick. No hole in the ground yet.
Banned in Scotland
King James II outlaws golf. His archers were practising their swing instead of their shot, with a war on.
First written rules
Thirteen rules committed to paper in Leith. Most of them are still recognisable in today's rulebook.
Eighteen holes
St Andrews drops from 22 holes to 18. For no deeper reason, that became the world standard.
The Netherlands
First course in The Hague in 1889, first club four years later. Today: 445,009 registered golfers.
Ninety seconds of vocabulary
Everything you need to follow along
Par
The number of shots a very good player is expected to need on a hole — usually 3, 4 or 5. Eighteen holes add up to par 72 on most courses.
Birdie, bogey, eagle
One under par is a birdie, two under is an eagle. One over is a bogey. The words get worse from there, and so does the mood.
Low score wins
Count every shot, including the ones you'd rather not. Fewest shots after eighteen holes wins. There is no defence, no clock and nobody to blame.
Handicap
A number describing how far above par you typically play. It gets subtracted from your score so different players can compete fairly.
The bag
Maximum fourteen clubs. Driver for distance, irons for accuracy, wedges for the last hundred metres, putter for the ground game.
Fairway, rough, green
Short grass, long grass, and the smooth bit with the hole in it. Which one you land on decides how the next shot feels.
Demo · click the map
What you're actually looking at
One par 4, roughly 380 metres. Two shots to reach the green if everything behaves, which it will not. Click any part of it.
A par 4: the architect expects two shots to reach the green and two putts once you're there.
Demo · what the differences look like
Eight heads, eight jobs
Side profile on the left with the loft drawn in, the face straight on with its usable area on the right. The whole design space is a trade-off between how far it goes and how much it forgives.
- Loft
- 10.5°
- Typical carry
- 250 m
- Forgiveness
- high
Demo · one contradiction, solved with layers
The ball has to do two opposite things
A ball that spins little off the driver goes straighter and further. A ball that spins little off a wedge won't stop on the green. Those are the same ball. The entire industry exists to break that trade-off.
- Driver spin
- 2,400 rpm
- Wedge spin
- 7,000 rpm
Compression is largely marketing except at the extremes. Practical rule: play cheap balls until you break 90, then urethane earns its money
Demo · why the little pits
A smooth ball goes half as far
Dimples keep the airflow attached to the ball for longer. That roughly halves the drag, and together with backspin it generates lift. Without them the ball simply falls out of the sky.
- Dimpled
- —
- Smooth
- —
A modern ball has three to five hundred of them. Their shape, depth and layout is some of the most closely guarded engineering in the sport.
Fixed drag coefficients of 0.27 and 0.54, ball speed 67 m/s, launch 14° — 195 m against 99 m
Demo · hit a shot
What one degree costs
A 150-metre shot to a green 14 metres wide. Move the only two things that actually steer the ball: where the clubface points, and where the club is travelling.
- Start direction
- 0.0°
- Curve
- 0.0 m
- Off the pin
- 0.0 m
Dead at the flag. Enjoy it, this won't happen again today.
Face angle accounts for roughly 80–85% of where the ball starts; the gap between face and path bends it from there
Demo · click the clubface
The sweet spot is the size of a coin
Click anywhere on the driver face to strike the ball there. Miss the centre and two things happen at once: you lose ball speed, and the clubhead twists — which spins the ball the opposite way. That second effect is called gear effect, and it is why a heel strike hooks left.
- Ball speed
- 241 km/h
- Carry
- 225 m
- Curve
- 0 m
Middle of the face. Maximum ball speed, no unwanted spin, and a sound you remember for a week.
Demo · click any of the nine
How you actually hit a draw
Two numbers produce every shot in golf. The face decides where it starts. The gap between face and path decides which way it bends — always away from the path, towards where the face points.
- Face
- 0.0°
- Path
- +3.0°
- Finishes
- at the pin
The rule that covers all nine: face and path on the same side of the target gives you a workable shape. On opposite sides gives you the ones that end up in trees.
Demo · your turn
Half a millisecond
The clubface touches the ball for 0.0005 seconds. After that, everything is decided. The bar below sweeps at downswing speed. Stop it dead centre — that's a square clubface.
- Face error
- —
- Off the pin
- —
- Best attempt
- —
- Attempts
- 0
Let someone else try it too. It rarely goes better.
Demo · the short stuff
Even the best miss most of them
Pick a distance and let the two hundred best players in the world putt twenty times. Everyone guesses these numbers too high — golfers included.
- PGA Tour make rate
- 50%
- This set of twenty
- —
2.4 metres is the length of a desk. It goes in half the time.
PGA Tour make rates from Mark Broadie's ShotLink analysis: 96% at 3 feet, 77% at 5, 50% at 8, 40% at 10, 23% at 15, 15% at 20 and 7% at 30 · putting is roughly 40% of all shots in a round
Demo · 108 millimetres
The hole is only just big enough
The hole is 108 mm across and the ball is 42.7 mm, so a perfectly centred putt has 32 mm of margin on each side. But the ball also has to fall in. Arrive too fast and it runs across the front edge and out — even dead centre, even perfectly struck.
- Speed at the hole
- 1.0 m/s
- Result
- drops
Capture speed after Holmes (1991); green speed assumed at stimp 10, roughly 0.55 m/s² of deceleration
The infrastructure behind every number in this talk
Every shot, by every player, since 2003
Strokes gained, the baselines, the make percentages, the dispersion patterns — none of it exists without a measurement system nobody watching on television ever sees.
Lasers on towers around every hole, surveyed to the centimetre. Hundreds of volunteers with handhelds. Every shot gets a start position, an end position, and a lie — walked to and recorded, one at a time.
Roughly 32,000 shots in a single tournament week, each one a coordinate. Over two decades that becomes the most complete performance dataset in any sport, and it is why golf analytics overtook every other sport's despite golf being older and slower.
Once you know where every shot started and finished, you can compute the average number of strokes needed from any position. That single table is what every modern golf statistic rests on — and it could not be estimated, only measured.
The lesson is not about golf. A century of opinion about what makes a good player was replaced within a few years, and the thing that replaced it was a boring, expensive, painstakingly maintained dataset.
How the prediction actually works
Five numbers do all the work
Everything a launch monitor tells you about where the ball ends up is derived from five measured quantities. Once the ball is a metre off the clubface, its entire future is already fixed — the rest is arithmetic.
What the sensor sees
Ball speed · launch angle · launch direction · spin rate · spin axis
Outdoors a radar reads these directly off the ball. Indoors, spin axis is often computed from club data instead, because there isn't enough flight to observe. That single substitution is where a lot of indoor disagreement comes from.
What gets filled in
Air density · drag and lift curves · spin decay · gravity
Air density comes from temperature, pressure and altitude. The drag and lift curves are the manufacturer's ball model. Nothing here is measured on your shot — it's a set of assumptions about a standard ball on a standard day.
What appears on the screen
Apex · hang time · curve · landing angle · carry · side · total · descent
Every one of these is an output of the simulation, not an observation. Outdoors the radar can check its own homework by watching the ball land. Indoors it never finds out whether it was right.
So "carry 218 metres" is a prediction with error bars, presented as a fact with three digits. The next two panels are about how big those error bars really are.
Demo · put error bars on it
Where the ball probably lands
Give the five measured inputs a realistic uncertainty and run the same shot three hundred times. A single predicted landing point becomes a cloud — and the cloud is the honest answer.
- Carry, 95% range
- —
- Lateral, 95%
- —
The honest part
Carry is predictable. Total distance isn't.
The unmodelled half
Everything so far ends the moment the ball touches grass. What happens next depends on turf firmness, moisture, grass type, mowing direction and slope — none of which any launch monitor can see. On a soft morning a drive stops dead; on a baked August fairway the same shot runs thirty metres.
The wind you can't feel
The model uses one wind value. A real ball climbs thirty metres into air that is moving faster and often from a different direction than the breeze on your face. This is the single largest unmodelled term outdoors.
Not the ball in the model
Drag and lift curves are fitted to a specific premium ball. Range balls, a scuffed ball or a cold ball behave differently. A two-degree change in ball temperature is worth real metres.
Spin axis is the weak link
Curve depends on spin axis, and indoors that's frequently inferred rather than measured. Miss the centre of the face and gear effect makes the inference much harder — which is exactly when you most want to know what the ball did.
Which is why tour players don't aim at flags. They aim at the centre of a distribution, accept the ellipse, and pick the target that makes the bad half of it survivable. The prediction was never a dot.
Exhibit A through D
My own evidence
Four photos, four stories. This is the part people actually remember, so use pictures only you could have taken.
And finally
I am, incidentally, still looking for a sponsor
Bronze
€ 500
Your name on my bag, in a font of your choosing. I say it out loud after every bad shot, so you will get considerably more airtime than you were hoping for.
Silver
€ 1,000
Your name on my sleeve. Visible in every photograph of me looking up in disappointment, which is most of the photographs there are.
Gold
€ 2,500
I name my driver after you. Permanently. It gets sworn at by name roughly fourteen times a round, and I will send you the video.
Platinum
€ 5,000
All of the above, plus a round with me. I carry your bag, read your putts, and explain everything in this talk again — in person, over four and a half hours, whether you ask or not.
Terms: returns are not guaranteed and visibility depends heavily on how often I am in the trees. Payment in golf balls accepted.
- 01Golf isn't a game so much as a precision problem: one degree and half a millisecond decide the whole thing.
- 02The technology around it is real engineering — defence-grade doppler radar reading dozens of parameters per swing.
- 03And because of the handicap system, anyone can play. Including you, including next week.
Questions? · The sponsorship offer stands