UnitFact's profile picture. Units of measurement, constants, dimensional analysis, etc. From @JohnDCook

Units

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Units of measurement, constants, dimensional analysis, etc. From @JohnDCook

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Why dimensional analysis matters

UnitFact's tweet image. Why dimensional analysis matters

SI unit names are not capitalized, except for Celsius. Unit abbreviations are capitalized if and only if they units are named after people. So for example, Pascal is the man, pascal is the unit, and Pa is the abbreviation.


A batman was a traditional unit of weight used in the Ottoman Empire, equal to about 17 pounds.


The constant G in Newton's law of gravity is only known to between 3 and 4 significant figures. en.wikipedia.org/wiki/Gravitati…


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A span is nine inches.


Converting between loudness units of phon and sone johndcook.com/phon_sone.html


A warhol is equal to 15 minutes of fame.


Standard SI prefixes are single Roman letters with two exceptions: the prefix for deca uses two letters, da, and the prefix for micro is μ.


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An electron volt (eV) is the amount of energy gained by a charge of one electron moved across an electric potential difference of one volt.


Standard SI prefixes for factors of 10^6 and higher use upper case letters. Smaller factors and fractions use lower case letters.


Informally, an astronomical unit is the distance from the Earth to the sun. Officially it is 149,597,870,700 meters.


The name SI comes from French: Le Système international d'unités.


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A fortnight is two weeks. It is a contraction of 'fourteen nights.'


In typography, a pica is 1/6 of an inch, and 12 points to a pica.


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Diagram of relationships between derived SI units physics.nist.gov/cuu/Units/SIdi…


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