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A picosecond (abbreviated as ps) is a unit of time in the International System of Units (SI) equal to 10 −12 or (one trillionth) of a second. That is one trillionth, or one millionth of one millionth of a second, or 0.000 000 000 001 seconds. A picosecond is to one second as one second is to approximately 31,689 years.
The speed at which the individual crests and troughs of a plane wave (a wave filling the whole space, with only one frequency) propagate is called the phase velocity vp. A physical signal with a finite extent (a pulse of light) travels at a different speed.
- Etymology
- Definition
- Standard Units
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The unit is named after Blaise Pascal, noted for his contributions to hydrodynamics and hydrostatics, and experiments with a barometer. The name pascal was adopted for the SI unit newton per square metre (N/m2) by the 14th General Conference on Weights and Measuresin 1971.
The pascal can be expressed using SI derived units, or alternatively solely SI base units, as: 1. 1 P a = 1 N m 2 = 1 k g m ⋅ s 2 = 1 J m 3 {\displaystyle {\rm {1~Pa=1~{\frac {N}{m^{2}}}=1~{\frac {kg}{m{\cdot }s^{2}}}=1~{\frac {J}{m^{3}}}}}} where N is the newton, m is the metre, kg is the kilogram, s is the second, and J is the joule. One pascal i...
The unit of measurement called an atmosphere or a standard atmosphere (atm) is 101325 Pa (101.325 kPa). This value is often used as a reference pressure and specified as such in some national and international standards, such as the International Organization for Standardization's ISO 2787 (pneumatic tools and compressors), ISO 2533 (aerospace) and...
The pascal (Pa) or kilopascal (kPa) as a unit of pressure measurement is widely used throughout the world and has largely replaced the pounds per square inch (psi) unit, except in some countries that still use the imperial measurement system or the US customary system, including the United States. Geophysicists use the gigapascal (GPa) in measuring...
Amyotrophic lateral sclerosis ( ALS ), also known as motor neurone disease ( MND) or Lou Gehrig's disease in the United States, is a rare, terminal neurodegenerative disorder that results in the progressive loss of both upper and lower motor neurons that normally control voluntary muscle contraction. [3] .
Robert James Fischer (March 9, 1943 – January 17, 2008) was an American chess grandmaster and the eleventh World Chess Champion. A chess prodigy, he won his first of a record eight US Championships at the age of 14. In 1964, he won with an 11–0 score, the only perfect score in the history of the tournament.
In mathematics, the Fibonacci sequence is a sequence in which each number is the sum of the two preceding ones. Numbers that are part of the Fibonacci sequence are known as Fibonacci numbers, commonly denoted Fn . The sequence commonly starts from 0 and 1, although some authors start the sequence from 1 and 1 or sometimes (as did Fibonacci ...
Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei (⫽ ˌ ɡ æ l ɪ ˈ l eɪ oʊ ˌ ɡ æ l ɪ ˈ l eɪ ⫽ GAL-il-AY-oh GAL-il-AY, US also ⫽ ˌ ɡ æ l ɪ ˈ l iː oʊ-⫽ GAL-il-EE-oh - , Italian: [ɡaliˈlɛːo ɡaliˈlɛːi]) or simply Galileo, was an Italian astronomer, physicist and engineer, sometimes described as ...
