Zetta-

Zetta is a decimal unit prefix in the metric system denoting a factor of 10²¹ or 1000000000000000000000. The prefix was added as an SI prefix to the International System of Units (SI) in 1991 and has the symbol Z.

Zetta is evocative of the Latin numeral septem, meaning seven. Therefore it was used to denote the seventh power of 1000.^[1]

A prefix of the same value, hepta, was informally introduced a few years before the promulgation of zetta. It was formed from the Greek ἑπτά, (hepta), also meaning seven. Hepta never received official sanction and is obsolete. Zeta (Ζήτα), although being the 6th letter of the Greek alphabet, denotes a value of seven (7) when used as a numeral.

Examples:

• The mass of Earth's atmosphere is approximately 5 zettagrams (Zg).^[2]
• The volume of seawater in the Earth's oceans is approximately 1.369 zettalitres (Zℓ).^[3]
• Avogadro's constant is 602.2 zettamol^-1 (Zmol^-1).^[4]
• A zettabyte (ZB) is a quantity of information or information storage capacity equal to 10²¹ bytes, 1000⁷ bytes, 1,000 exabytes or 1 sextillion bytes. The zebibyte (ZiB) is a related unit that uses a binary prefix, and means 1024⁷ bytes.

1. ^ The metric system was introduced in 1795 with several metric prefixes, of which, however, only six were adopted as SI prefixes by the 11th CGPM conference in 1960, whereas myria (10⁴) as well as double and demi were not adopted. In 1873, micro and mega were recommended by the British Association for the Advancement of Science. The other dates relate to recognition by a resolution of the CGPM.

See also

• Metric prefix

Footnotes

1. ^ "Resolution 4 of the 19th CGPM (Conférence Générale des Poids et Mesures)". BIPM (Bureau International des Poids et Mesures). Retrieved 2009-05-16. Les noms zepto et zetta évoquent le chiffre sept (septième puissance de 10³) et la lettre « z » remplace la lettre « s » pour éviter le double emploi de la lettre « s » comme symbole. The names zepto and zetta are evocative of the numeral sept (seventh power of 10³) and the letter 'z' is substituted for the letter 's' to avoid the duplicate use of the letter 's' as a symbol. 
2. ^ http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html
3. ^ http://hypertextbook.com/facts/2001/SyedQadri.shtml
4. ^ http://physics.nist.gov/cgi-bin/cuu/Value?na

External links

• BIPM website