Hubble captures interacting galaxies NGC 5410 and UGC 8932

A pair of small, interacting galaxies shine in this new NASA Hubble Space Telescope image. The larger of the two galaxies is named NGC 5410 and was discovered in 1787 by British astronomer William Herschel. It spans 80,000 ...

Studying the mechanisms of water transport along a fiber

How fast does a droplet flow along a fiber? It depends on the diameter of the fiber, and also on its substructure. These are the findings of a study conducted by researchers from the University of Liège who are interested ...

Lianas found to have large vessel dimorphism

The determination of plant vessel structure is fundamental for further understanding vascular function in different plant groups. Vessel dimorphism may be an important hydraulic strategy and ecological adaptation of plants. ...

Size of X-ray beams successfully evaluated with mathematics

X-ray fluorescence analysis allows elemental analysis in a variety of environments without destroying the sample. The smaller diameter of the X-ray microbeam, the more accurate the elemental distribution can be. Because X-ray ...

Creating the world's largest SiC aspherical mirror

Aspherical components in optical systems can increase the free design variables without introducing new aberrations. That brings improved imaging quality and reduced size and weight. Aspheric components are widely used in ...

First quadruple asteroid system detected

A trio of researchers from the National Astronomical Research Institute of Thailand, Université de Lyon and Sorbonne Université, respectively, has made the first sighting of a quadruple asteroid system—an asteroid with ...

Nondestructive testing of optical fiber diameters

The increased use of optical fiber has seen a greater focus on the precise control and measurement of its diameter. That is due to the diameter being vital for a wide range of fields, from high-speed optical communication ...

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Diameter

In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle. The word "diameter" derives from Greek διάμετρος (diametros), "diagonal of a circle", from δια- (dia-), "across, through" + μέτρον (metron), "a measure").

In more modern usage, the length of a diameter is also called the diameter. In this sense one speaks of the diameter rather than a diameter, because all diameters of a circle have the same length, this being twice the radius.

For a convex shape in the plane, the diameter is defined to be the largest distance that can be formed between two opposite parallel lines tangent to its boundary, and the width is defined to be the smallest such distance. For a curve of constant width such as the Reuleaux triangle, the width and diameter are the same because all such pairs of parallel tangent lines have the same distance. See also Tangent lines to circles.

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