From Wikimedia Commons
Sunday, August 29, 2010
Thursday, August 26, 2010
Faster Than Light Travel
Faster-than-light (also superluminal or FTL) communications and travel refer to the propagation of information or matter faster than the speed of light. Under the special theory of relativity, a slower-than-light particle with nonzero rest mass needs infinite energy to accelerate to the speed of light, although special relativity does not forbid the existence of particles that travel faster than light at all times (see tachyons).
On the other hand, what some physicists refer to as "apparent" or "effective" FTL is the hypothesis that unusually distorted regions of spacetime might permit matter to reach distant locations faster than what it would take light in the normal or undistorted spacetime. However, according to current theories, matter is still required to travel subluminally with respect to the locally distorted spacetime region.
Apparent FTL is not excluded by general relativity. Examples of apparent FTL proposals are the Alcubierre drive and the traversable wormhole, although the physical plausibility of these solutions is uncertain.
From Wikipedia
On the other hand, what some physicists refer to as "apparent" or "effective" FTL is the hypothesis that unusually distorted regions of spacetime might permit matter to reach distant locations faster than what it would take light in the normal or undistorted spacetime. However, according to current theories, matter is still required to travel subluminally with respect to the locally distorted spacetime region.
Apparent FTL is not excluded by general relativity. Examples of apparent FTL proposals are the Alcubierre drive and the traversable wormhole, although the physical plausibility of these solutions is uncertain.
From Wikipedia
Thursday, August 12, 2010
Randori
Randori (乱取り) is a term used in Japanese martial arts to describe free-style practice or sparring, sometimes with multiple attackers. The term literally means "chaos taking" or "grasping freedom," implying a freedom from the structured practice of kata.
The exact meaning of randori depends on the martial art it is used in. In judo, jujitsu and Shodokan Aikido, among others, it most often refers to one-on-one sparring where partners attempt to resist and counter each other's techniques. In other styles of aikido, in particular Aikikai, it refers to a form of practice in which a designated aikidoka defends against multiple attackers in quick succession without knowing how they will attack or in what order. This form of randori is not sparring, and the attackers are usually not allowed to resist or attempt to counter the defender's techniques. The term is used only by Aikikai dojos outside Japan. In Japan, this form of practice is called taninzu-gake (多人数掛け), which literally means multiple attackers. In kendo, jigeiko means "friendly" free combat as in competition, but not counting the points.
Although in karate the word kumite is usually reserved for sparring, some schools also employ the term randori with regard to "mock-combat" in which both karateka move very fast, parrying and attempting acts of extreme violence with all four limbs (including knees, elbows, etc.) yet only ever making the slightest contact. Total control of the body is necessary and therefore only the senior grades can typically practice randori. In these schools, the distinction between randori and kumite is that in randori, the action is uninterrupted when a successful technique is applied.
Randori is also practiced in bujinkan ninjutsu and usually represented to the practitioner when he reaches the "Shodan" level. In ninjutsu, randori puts the practitioner in a position where he is armed/unarmed and being attacked by multiple attackers.
Randori may be contrasted with kata, as two potentially complementary types of training.
From Wikipedia
The exact meaning of randori depends on the martial art it is used in. In judo, jujitsu and Shodokan Aikido, among others, it most often refers to one-on-one sparring where partners attempt to resist and counter each other's techniques. In other styles of aikido, in particular Aikikai, it refers to a form of practice in which a designated aikidoka defends against multiple attackers in quick succession without knowing how they will attack or in what order. This form of randori is not sparring, and the attackers are usually not allowed to resist or attempt to counter the defender's techniques. The term is used only by Aikikai dojos outside Japan. In Japan, this form of practice is called taninzu-gake (多人数掛け), which literally means multiple attackers. In kendo, jigeiko means "friendly" free combat as in competition, but not counting the points.
Although in karate the word kumite is usually reserved for sparring, some schools also employ the term randori with regard to "mock-combat" in which both karateka move very fast, parrying and attempting acts of extreme violence with all four limbs (including knees, elbows, etc.) yet only ever making the slightest contact. Total control of the body is necessary and therefore only the senior grades can typically practice randori. In these schools, the distinction between randori and kumite is that in randori, the action is uninterrupted when a successful technique is applied.
Randori is also practiced in bujinkan ninjutsu and usually represented to the practitioner when he reaches the "Shodan" level. In ninjutsu, randori puts the practitioner in a position where he is armed/unarmed and being attacked by multiple attackers.
Randori may be contrasted with kata, as two potentially complementary types of training.
From Wikipedia
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