Asymmetry
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Template:Cleanup-date Template:Otheruses4 Asymmetry is both the absence of symmetry, and a fundamental basis for symmetry. Symmetry analysis may result in the identification of a fundamental region that is the smallest element required to explain the repetition that forms a pattern. The fundamental region is asymmetrical.
While symmetry is a characteristic of geometrical shapes, equations, and other objects; as well as things that are in nature (left/right brain, sun, crystals, ... ), asymmetry is fundamental feature of natural processes. Asymmetry of time, thermodynamical processes, vertical asymmetry of bodies, cosmic asymmetry breaking, molecular asymmetry, etc.
Louis Pasteur believed:Only products originating under the influence of life are asymmetrical, because the cosmic [i.e. generative, life] forces that preside over their formation are themselves asymmetrical. Asymmetry differentiates the organic world and the mineral world.
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Asymmetry in organisms
Due to how cells divide in organisms, asymmetry in organisms is fairly unusual, with biological symmetry clearly being more common. There are a number of reasons asymmetry may occur though.
- Certain disturbances during the development of the organism, resulting in birth defects.
- Injuries after cell division that cannot be biologically repaired, such as a lost limb from an accident.
- Essential assymetry and important evolutionary traits, such as the left human lung being smaller than the right to make room for the heart. Humans in turn only have one heart, but this is likely due to a shift from a more central position during evolution, since it is still a bilateral symmetry (it has two ventricles and two atriums), like e.g. the nose, albeit slightly distorted, with some parts of the heart larger than others.
Among many organisms, since birth defects and injuries are likely to indicate a poor health of the organism, defects resulting in asymmetry are often looked as negative traits when it comes to partnership and reproduction.
Examples of asymmetry in nature
- Clausius' Second Law: There is no thermodynamic process whose sole effect is to extract a quantity of heat from a colder reservoir and deliver it to a hotter reservoir.
- Pasteur's molecular asymmetry: The lack of some elements of symmetry is necessary to have left- and right-handed molecules.
- Asymmetric cell divisions. [Yuh-Nung and Lily Yeh, 1999]
- Charge-symmetry breaking in physics, the mechanism responsible for protons and neutrons having different masses.
- Distribution of income in economics.
Images
Image:Tangram.png Image:Atomoxetina.png Image:Southern eagle ray.jpg Image:Procyon lotor 7 - am Wasser.jpg Image:Hourglass drawing.jpg Image:Vesta-HST.jpg Image:The Earth seen from Apollo 17.jpg
References
- Yuh-Nung Jan and Lily Yeh Jan, 1999. Asymmetry across species. Nature Cell Biology 1, E42 - E44
See also
- Kepler, (1611) Strena sue de nive sexangula (On the Six-Cornered Snowflake) - discusses (among other things) symmetry properties of minerals and trees.