There’s been a fair amount of talk over how unsuitable a bunch of touch-sensitive areas down the sides of a screen would be, to replace the traditional iPod clickwheel.

I’m not-so-sure that that’s a valid criticism - quite apart from the patent clearly showing virtual clickwheels on the main display area, it ought to be possible to use a vertical strip of touch-sensitive areas as an input mechanism

The crucial part is the “infinite length” of a circular motion - you can describe a really-rapid motion with your thumb/finger and it’s always going in the same direction (clockwise or counter-clockwise). My point is, though, that a circle is just a particular style of ellipse. Imagine squeezing an ellipse so it’s very thin and very tall - you could still run your thumb up and down that ellipse by making your thumb go in a circular motion, but having the sensors on a line.

Physicists call this the vertical component of the motion - it’s still the same, no matter how the horizontal component is changed. Try it: hold a pen in your non-favoured hand, and with your favoured hand, put your index finger at the top of the pen then move your thumb in a circle. Et voila, your thumb slides across the pen surface, and sensors there (in a line) could detect that cyclic (it’s no longer circular, but it is cyclic) motion, and do the same as a clickwheel would do.

It seems obvious once you’ve thought of it - and I wonder why no-one else has come out with anything like it before Apple filed this patent. Perhaps it’s not-so-obvious after all...