Everything about Archimedean Spiral totally explained
An
Archimedean spiral (also
arithmetic spiral), is a
spiral named after the 3rd-century-BC Greek mathematician
Archimedes; it's the
locus of points corresponding to the locations over time of a point moving away from a fixed point with a constant speed along a line which rotates with constant
angular velocity. Equivalently, in
polar coordinates (
r, θ) it can be described by the equation
»
with
real numbers a and
b. Changing the parameter
a will turn the spiral, while
b controls the distance between successive turnings.
Archimedes described such a spiral in his book
On Spirals.
This Archimedean spiral is distinguished from the
logarithmic spiral by the fact that successive turnings of the spiral have a constant separation distance (equal to 2
πb if θ is measured in
radians), while in a logarithmic spiral these distances form a
geometric progression.
Note that the Archimedean spiral has two arms, one for θ > 0 and one for θ < 0. The two arms are smoothly connected at the origin. Only one arm is shown on the accompanying graph. Taking the mirror image of this arm across the y-axis will yield the other arm.
One method of
squaring the circle, by relaxing the strict limitations on the use of straightedge and compass in ancient Greek geometric proofs, makes use of an Archimedean spiral.
Sometimes the term
Archimedean spiral is used for the more general group of spirals
»
The normal Archimedean spiral occurs when
x = 1. Other spirals falling into this group include the
hyperbolic spiral,
Fermat's spiral, and the
lituus. Virtually all static spirals appearing in nature are
logarithmic spirals, not Archimedean ones. Many dynamic spirals (such as the
Parker spiral of the
solar wind, or the pattern made by a
Catherine's wheel) are Archimedean.
Applications
The Archimedean spiral has a plethora of real-world applications.
Scroll compressors, made from two interleaved Archimedean spirals of the same size, are used for compressing liquids and gases. The coils of
watch balance springs and the grooves of very early
gramophone records form Archimedean spirals, making the grooves evenly spaced and maximizing the amount of music that could be fit onto the record (although this was later changed to allow better sound quality). Asking for a patient to draw an Archimedean spiral is a way of quantifying human tremor; this information helps in diagnosing neurological diseases. Archimedean spirals are also used in
DLP projection systems to minimize the "Rainbow Effect", making it look as if multiple colors are displayed at the same time, when in reality red, green, and blue are being cycled extremely fast.
Further Information
Get more info on 'Archimedean Spiral'.
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