Cambridge is very good at making intelligent people feel momentarily stupid.

The Mathematical Bridge manages it without saying a word.

Stand beside the Cam and look at the wooden bridge connecting two parts of Queens' College.

Clearly an arch.

Except the main timbers creating that sweeping shape are straight.

Look again.

Still looks curved.

That's the trick.

The bridge uses straight timbers arranged through geometry so that together they create the appearance and strength of an arch.

It's clever.

But apparently that wasn't quite clever enough for Cambridge.

Somewhere along the way, Sir Isaac Newton got dragged into it.

It's a brilliant story. Shame about the dates.

The legend has several versions, but the best-known goes something like this:

Newton designed the bridge and constructed it without nuts, bolts or nails.

Later, students - or sometimes fellows, depending on who's telling the story - took it apart to discover how he'd done it.

Then they couldn't put it back together.

So they had to use bolts.

Wonderful.

There's just one fairly substantial problem.

Isaac Newton died in 1727.

The Mathematical Bridge was first built in 1749.

Twenty-two years after his death.

Newton was undoubtedly clever, but designing Cambridge bridges from beyond the grave would have been an impressive late addition to the CV.

The actual design was by William Etheridge, with the bridge built by James Essex the Younger for Queens' College.

And the original wasn't mysteriously held together without any form of fixing either. Iron pins were used at the timber crossings.

The truth is actually more interesting

Forget Newton for a moment and look at what Etheridge really did.

Your brain sees a curved bridge.

The structure gets there through the positioning of straight pieces of wood.

That's why the name Mathematical Bridge feels so appropriate, even though it wasn't its original official name.

You don't need an equation written beside it.

The geometry is the thing you're standing there looking at.

And once somebody points out the straight timbers, it's difficult not to start following them individually with your eyes.

Straight.

Straight.

Another straight one.

Yet step back and there's the curve again.

That's a much better Cambridge trick than pretending Newton built it with magic.

Is it still the original bridge?

Not quite.

A wooden bridge exposed to English weather for more than 275 years was never going to escape without some attention.

It has been rebuilt during its lifetime, notably in 1866 and 1905, while retaining the historic design.

So you're not looking at untouched wood from 1749.

You're looking at an idea from 1749 that has survived.

And perhaps that's why the Newton myth refuses to disappear too.

It's a story people enjoy telling.

Cambridge has plenty of those.

Some are true.

Some are nearly true.

And some require the main character to have been dead for 22 years.

Which Cambridge Story Have You Been Told?

Maybe somebody told you the Newton story. Perhaps there's another Cambridge legend you've repeated for years without ever checking it.

Tell us in the comments. What's the Cambridge “fact” everyone seems to know and should we investigate whether it's actually true?