Spiraalisuus

Spiraalisuus, or spirality, refers to the property or appearance of being spiral-shaped. It appears across nature, science and human design, wherever a curve or form winds around a central point with changing distance from the center.

In mathematics, a spiral is a curve described in polar coordinates by a function r = f(θ) that winds around the origin. Common examples include the Archimedean spiral (r = a + bθ), where spacing between turns is constant; the logarithmic spiral (r = a e^{bθ}), which has a constant angle between the tangent and the radial line and exhibits self-similarity; and the Fermat spiral (r^2 ∝ θ). The logarithmic spiral is often called equiangular, and a related example is the golden spiral, a logarithmic spiral whose growth factor is the golden ratio and which is connected to Fibonacci numbers in some natural patterns.

In nature, spirality explains patterns such as phyllotaxis in plants (for example sunflower seed arrangements and pinecones), shells like the Nautilus, and the spiral arms observed in many galaxies and in weather systems such as hurricanes. In technology and design, spirals appear in antennae, spiral stairs, and various decorative and architectural motifs.

Spiraalisuus thus describes both an abstract geometric concept and its widespread manifestations, bridging mathematics, natural phenomena and human creativity.