rotationphysics
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linear transformations algebra, linear
...sends each vector to c times itself, where c is some constant. Thus, every vector remains in the same direction, but all lengths are multiplied by c. Another example is a rotation, which leaves all lengths the same but alters the directions of the vectors. Linear refers to the fact that the transformation preserves vector addition and scalar...
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relativistic mechanics relativistic mechanics
...x/dτ) make up the 4-momentum of the particle. According to Minkowski’s reformulation of special relativity, a Lorentz transformation may be thought of as a generalized rotation of points of Minkowski space-time into themselves. It induces an identical rotation on the 4-acceleration and force 4-vectors. To say that both of these 4-vectors experience the same...
astronomy
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asteroids asteroid
The rotation periods and shapes of asteroids are determined primarily by monitoring their changing brightness on timescales of minutes to days. Short-period fluctuations in brightness caused by the rotation of an irregularly shaped asteroid or a spherical spotted asteroid (i.e., one with albedo differences) produce a light curve—a graph of brightness versus time—that repeats at...
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galactic structure ( in Cosmos: The Milky Way Galaxy
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Detailed information can be gleaned about the distribution of mass in the Galaxy if one possesses a knowledge of the rotational speeds of disk matter at other radial locations in the Galaxy. The most common measurements are of atomic hydrogen in its spin-flip transition at 21-centimetre wavelength and of the carbon monoxide molecule in one or another of its rotational transitions at millimetre...
in galaxy: The spheroidal component )...long-term effects of close encounters between stars. These models of the spheroidal component (appropriately modified in the presence of other galactic components) fit the observed structures well. Rotation is not an important factor, since elliptical galaxies and the spheroidal component of spiral systems (e.g., the Milky Way Galaxy) rotate slowly. One of the open questions about the structure...
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Great Red Spot Jupiter
The rotation period of the Great Red Spot around the planet does not match any of Jupiter’s three rotation periods. It shows a variability that has not been successfully correlated with other Jovian phenomena. Voyager observations revealed that the material within the spot circulates in a counterclockwise direction once every seven days, corresponding to superhurricane-force winds of 400 km...
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Halley’s Comet nucleus comet
There is some uncertainty concerning the rotation of...
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baseball baseball
Of the 25 players on a major league club’s normal active roster, usually 11 to 12 are pitchers. The manager usually designates 5 of the 12 as starting pitchers, or the rotation starters. They take their turn every four or five days, resting in between. The remainder of the staff constitute the bullpen squad or the relief pitchers. When the manager or pitching coach detects signs of weakening on...
the successive cultivation of different crops in a specified order on the same fields, in contrast to a one-crop system or to haphazard crop successions.
Throughout human history, wherever food crops have been produced, some kind of rotation cropping appears to have been practiced. One system in central Africa employs a 36-year rotation; a single crop of finger millet is produced after a 35-year growth of woody shrubs and trees has been cut and burned. In the major food-producing regions of the world, various rotations of much shorter length are widely used. Some of them are designed for the highest immediate returns, without much regard for the continuing usefulness of the basic resources. Others are planned for high continuing returns with protected resources. The underlying principles for planning effective cropping systems began to emerge in the middle years of the 19th century.
Early experiments, such as those at the Rothamsted experimental station in England in the mid-19th century, pointed to the usefulness of selecting rotation crops from three classifications: cultivated row, close-growing grains, and sod-forming, or rest, crops. Such a classification provides a ratio basis for balancing crops in the interest of continuing soil protection and production economy. It is sufficiently flexible for adjusting crops to many situations, for making changes when needed, and for including go-between crops as cover and green manures.
A simple rotation would be one crop from each group with a 1:1:1 ratio. The first number in a rotation ratio refers to cultivated row crops, the second to close-growing grains, and the third to sod-forming, or rest, crops. Such a ratio signifies the need for three fields and three years to produce each crop annually. This requirement would be satisfied with a rotation of corn, oats, and clover...
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description of symmetry symmetry
...within the solid. Inversions move every atom to another position in the crystal; the old and new positions of the atom lie upon a line, at the middle of which is the centre of inversion. So-called improper rotations are rotations followed by reflections (known as rotoreflections) or rotations followed by inversions (called rotoinversions).
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