A ball is a round, usually spherical but sometimes ovoid, object with various uses. It is used in ball games, where the play of the game follows the state of the ball as it is hit, kicked or thrown by players. Balls can also be used for simpler activities, such as catch, marbles and juggling. Balls made from hard-wearing materials are used in engineering applications to provide very low friction bearings, known as ball bearings. Black powder weapons use stone and metal balls as projectiles.
Although many types of balls are today made from rubber, this form was unknown outside the Americas until after the voyages of Columbus. The Spanish were the first Europeans to see bouncing rubber balls (albeit solid and not inflated) which were employed most notably in the Mesoamerican ballgame. Balls used in various sports in other parts of the world prior to Columbus were made from other materials such as animal bladders or skins, stuffed with various materials.
Other articles related to "ball, balls":
... Using the Banach–Tarski paradox, it is possible to obtain k copies of a ball in the Euclidean n-space from one, for any integers n ≥ 3 and k ≥ 1, i.e ... a ball can be cut into k pieces so that each of them is equidecomposable to a ball of the same size as the original ... These results then extend to the unit ball deprived of the origin ...
... The Quarter seam is the tiny seam which runs around a cricket ball at 90 degrees to the large, raised seam ... be 'picked at' - loosening the threads - in order to create conventional swing when the ball is relatively new, more recently, an understanding has evolved that the quarter seam can ... Lifting the quarter seam during an over alters the balance of air pressure surrounding the ball as it travels through the air and help it reverse ...
... is a theorem in set-theoretic geometry which states the following Given a solid ball in 3‑dimensional space, there exists a decomposition of the ball into a finite number of non-overlapping ... different way to yield two identical copies of the original ball ... that given any two "reasonable" solid objects (such as a small ball and a huge ball), either one can be reassembled into the other ...
... Computed tomography of a football (soccer) (Video) Baoding balls Baseball Basketball Billiard balls Bowling ball (and pin) Lacrosse ball Cricket ball Golf ball next to a hole ...
... the paradoxical decomposition of S2 then yields a paradoxical decomposition of the solid unit ball minus the point at the ball's centre (this center point needs a bit more care, see below) ... and like the point at the centre of the ball, it is possible to patch the proof to account for them all (see below) ...
Famous quotes containing the word ball:
“It may be possible to do without dancing entirely. Instances have been known of young people passing many, many months successively, without being at any ball of any description, and no material injury accrue either to body or mind; Mbut when a beginning is madewhen felicities of rapid motion have once been, though slightly, feltit must be a very heavy set that does not ask for more.”
—Jane Austen (17751817)
“But the ball is lost and the mallet slipped long since from the hands
Under the running tap that are not the hands of a child.”
—Louis MacNeice (19071963)
Big as the ball of my thumb, and dumb as eyes
Ebon in the hedges, fat
With blue-red juices. These they squander on my fingers.
I had not asked for such a blood sisterhood; they must love me.”
—Sylvia Plath (19321963)