If you drive down a certain stretch of highway in the California desert, you will hear music.
It's supposed to sound a little bit like this:
[William Tell Overture, by Rossini]
but instead, it sounds like this.
[William Tell Overture, by Rossini, but badly out of tune]
That was the musical road of Lancaster, California.
And as you may have heard, it's a little bit out of tune.
A lot of money was spent on that road.
It was a publicity stunt for a car company who wanted to show off how clever they are.
And doing the calculations for something like that isn't really difficult.
A musical note is a vibration in the air at a particular frequency.
And those vibrations can be made by a violin string or synthesised by a computer
or - in this case - made by vehicle tyres hitting grooves in the road.
The closer the grooves are, the faster the vibrations, and the higher the note.
So take the speed limit,
divide by the frequency of the note you want,
and that's how often there should be a groove in the road.
And if people travel at the wrong speed, well, it shouldn't really matter.
It'll just be like slowing down or speeding up any other piece of music:
it'll be in the wrong key, but it'll still sound right to most people's ears.
It won't sound like that mess.
So what went wrong?
At this point, I am indebted to David Simmons-Duffin,
an assistant professor of physics at Caltech,
whose interests include Quantum Field Theories and playing baroque violin.
Because he was, as far as I can tell,
the very first person to figure out what went wrong:
and the problem was probably the English language.
Whoever did the calculations said that the grooves should be so far apart.
Let's say, four inches for the first note.
And they meant there should be a groove every four inches.
But whoever gave the instructions to the work crew
said that the grooves should be "four inches apart".
And that was interpreted as four inches between the end of one groove
and the start of the next one.
They didn't include the width of the groove itself.
But your ears definitely do include it.
The highest note on that section of the William Tell Overture
should be one octave higher than the lowest.
That means the frequency should be doubled,
and that the grooves should be half the distance apart.
And they are: if you don't include the width of the groove itself.
That error means that every note is distorted not by a fraction of its value,
like if you're travelling at the wrong speed,
but by a constant amount: by the width of the grooves.
The higher the note, the greater the effect of that distortion.
And the result is the mess that you are about to hear for a second time.
And the really strange part?
This is the second musical road built in Lancaster, California.
The first one, built by the car company, was too close to residents,
who complained about the constant noise.
And probably this note here.
So the city paved over it and rebuilt it...
to the exact, same, wrong blueprints.
That's a take.
That is a take.
Right there.
And in order to celebrate that take, I am going to put my foot down.
This is an SUV.
It doesn't, er... it doesn't do that.