# Flip-Flops and my Dzhanibekov problem

Hey. This page is more than 7 years old! The content here is probably outdated, so bear that in mind. If this post is part of a series, there may be a more recent post that supersedes this one.

## I walk the dog on the beach – I take my flip-flops off.

Why? Somewhat irrelevant to this post, but flip flops may be the best shoe-wear there is (I mean, even Jesus wore them, right? And walked on water in them) but flips-flops do have Achilles heel(s?):

• Walking on dry sand is irritating (possibly why Jesus took to the water).
• Wet granite paving is lethal

## I finish walking the dog on the beach. I put my flip flops back on.

### – End of (a shit) story? –

Not quite.

I want to put the jandals back on with FLAIR, so I fling them out in front of me onto the pavement nonchalantly, and hope they land exactly right so I can just step into them in my stride ‘just like I meant them to’

This doesn’t happen work quite right, quite often – they land upside down. And now I know why: The Dzhanibekov effect

Even with all the practice in the world (or out of it – Dzhanibekov was a cosmonaut), the way I was flinging the shoes (around the second principle axis of rotation) means there was an unpredictable instability in the flip-flips’ rotations. I could throw the same shoe exactly the same way and the outcome would be unpredictable.

So my fling might be perfect, in terms of the rotation around its secondary axis, but who know what ‘random flips’ will occur between leaving my hand and hitting the ground (invariably upside down).

Whew! And I thought it was just me.

### – End of story –

PS I have not changed my method, I just relish in the futility of it when I do it now.