How 2…

9 March 2014

How 2...


No more? No, more!

18 February 2014


The editors wish to point out that we no longer display pictures of self-referring signs, such as the one above.


28 May 2013


As so often, xkcd says it so much better than anyone else could:

"Model Rail", a recursive cartoon from

Original cartoon here:  But well worth sitting down and reading through the whole archive: laugh out loud funny about the interface between science and… people, plus plenty of nesting, recursion fans!


3 April 2010

If TLA is a recursive acronym, it must also be allowed that T-shirt is a self-describing word. And just look at this T-shirt:

T-shirt with droste-effect picture of the wearer in a T-shirt...

photo credit: paulandstorm

Beware of the Sign

4 March 2010

Lushlush writes:

Owwww, my head….”

self-referential warning sign over escalator

Describing a warning sign hanging over an escalator: “..the sign is comical in itself: stick figure rides up the escalator and bumps his head on a hanging sign, the impact causing VIOLENT RED RAYS OF PAIN. Beware! All is well and good until, armed with a newfound caution, you look around for the offending object and realize that IT’S A SIGN ABOUT THE SIGN ITSELF”

Full story and other pictures – including a photoshopped infinitely-recursive version here

When I was a child, I thought up a joke and I did it all by myself. Alas, no one else seemed to understand how funny it was. It went a bit like this:

I phone up my mum from a call-box to say that I am going to be late home.

‘Why are you going to be late?’ she would ask me.

Photo: Keven Law

‘Because I have to walk home’ I would reply.

‘Why don’t you take the bus?’

‘I don’t have enough money.’

‘Why not?’

‘Because I spent it on this phone call’

‘But, why did you phone then?’

‘To tell you I was going to be late.’

‘But why are you going to be late?’

(& so on)

Of course I never  actually did this but when I told my friends my joke they just looked at me funny and said, ‘but that’s just stupid. Why would you phone your mum in the first place?’.

But that’s the whole point! Recursion means never having to say why you did anything…in the first place.

Post Script

In no way connected to this site, the students of Norwalk High School (Ohio?) have produced their own fantastic projects on recursion. I hope that for at least some of them it will be the start of a never-ending love affair with never-endingness.