# Spirals

Swirls and spirals appear in nature in all kinds of places. In the seeds of a sunflower, in the vortex of a hurricane, in the horns of a goat, in the shell of a snail, in the curling fronds of a fern, in this guy's beard.

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In this totally naturally occurring jetty:

## Spirals in Logo: 2 different ways

One of the classic shapes to construct in turtle logo is the Spiral.

The first way you write this program, is as a variation on a polygon. You go forward, you turn a bit, you go forward, you turn a bit. But you make it recursive, so that the amount you go forward can become smaller and smaller each time. Technically, this is called a 'spirangle'

If you look at that last example, we turned it around completely.

Instead of making a smaller and smaller line each time, we made a bigger and bigger line. (A ratio of 1.005) This created a spiral in the opposite direction! (Opposing chirality)

## Spirals are Chiral!

It's worth nothing that spirals are chiral. And if you're ever stuck trying to remember that word for things have handed-ness... just remember the rhyming phrase: "Spirals are Chiral" and you'll be all set.

What is this "chiral" business you ask? There's a page for that.

Essentially every spiral can be either left-handed on right-handed. It can get smaller as it turns clockwise, or counter-clockwise.

## Using Arc to draw a spiral

There is also an 'arc' function in Turtle graphics, that lets you draw smoother curves.