A fractal is a geometric shape exhibiting self-similarity at various scales, often found in natural and cosmological structures.A fractal is a set with a fractional dimension and self-similarity at all scales. For example, the Koch snowflake is constructed by replacing each line segment with a broken line, and after infinite steps its length is infinite but its area is finite. The fractal dimension quantitatively describes how densely an object fills space.
The term 'fractal' (from Latin fractus, meaning 'broken') was coined by Benoit Mandelbrot in 1975, but its origins lie in the work of Pierre Fatou and Gaston Julia (early 20th century), who studied iterations of complex mappings. Lewis Fry Richardson noticed in 1961 that the length of country borders increases as the measurement standard becomes smaller. Mandelbrot generalized these ideas, describing the fractal geometry of nature in his 1982 book.
The fractal structure arises from the recursive application of a simple rule. For example, the Koch curve: each straight segment is replaced by four segments forming a protrusion. After an infinite number of steps, the length of the curve grows without bound, and its dimension is log 4 / log 3 ≈ 1.26. The fractal dimension d is defined by the power law N(ε) ∝ ε^{−d}, where N(ε) is the minimum number of balls of radius ε needed to cover the object (box-counting dimension).
Fractal antennas in mobile phones receive signals over a wide frequency range, and computer graphics create realistic landscapes.
Human lungs pack about 100 m² of surface area into a volume of a few liters thanks to the fractal structure of the bronchial tree.
| Ω_* | variable | breakup angular frequency — angular frequency radian per second |
| M_* | variable | mass of the rotating body — mass kilogram |
| R_* | variable | radius of the rotating body — radius metre |
| G | constant | Universal constant of gravitation — gravitational constant = 6.67430e-11 cubic metre per kilogram per second squared |






