Strange SI prefixes
Strange SI prefixes
(OP)
Has anybody ever considered that the electron-volt (eV), a unit of energy as are the calorie and the Btu, equals 160.2 zJ ? The z is for zepto = 10-21.
Or that the fusion of pure Deuterium yields 0.33 PJ/kg ? Where the P stands for peta = 1015 ?
Strange SI prefixes, aren't they ? Does anybody know the etymological origin of the SI prefixes yetta (10E24), zetta (10E21), exa (10E18), peta (10E15), zepto (10E-21) and yocto (10E-24) ? Thanks.
Or that the fusion of pure Deuterium yields 0.33 PJ/kg ? Where the P stands for peta = 1015 ?
Strange SI prefixes, aren't they ? Does anybody know the etymological origin of the SI prefixes yetta (10E24), zetta (10E21), exa (10E18), peta (10E15), zepto (10E-21) and yocto (10E-24) ? Thanks.





RE: Strange SI prefixes
Everyone knows that micro means small and that nano means dwarf. And pico is small, again. Spanish pequeño is small, I think. Then, there are femto (10^-15) and atto (10^-18), which stem from the Danish language (fifteen = femtan and eighteen = atten). This is in hommage to Niels Bohr, the guy that introduced the modern atom theory.
There seems to be a similar connection between zetta and greek for seven, exa seems to be a variation of hexa (six) and so on. It seems that the naming of very large and very small numbers has a fundamental principle where the number of zeroes or decimal places is expressed as a multiple of three. Peta (penta in disguise?) for 15 zeroes and yocto (octo in disguise?) for 24 decimal places and so on.
RE: Strange SI prefixes
TTFN
RE: Strange SI prefixes
I really wanted to know. Interesting.
RE: Strange SI prefixes
RE: Strange SI prefixes
That means that a very, very small unit of inductance is called a ChiciHenry.
Must go and talk to one of my electronics colleagues ......
RE: Strange SI prefixes
Cyril Guichard
Mechanical Engineer Consultant
France
RE: Strange SI prefixes
RE: Strange SI prefixes
http://www1.bipm.org/en/si/si_brochure/appendix1/d...
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Strange SI prefixes
BT
RE: Strange SI prefixes
Cyril Guichard
Mechanical Engineer Consultant
France
RE: Strange SI prefixes
So if you want to be pedantic, I suppose you could talk of "decimal" units rather than SI when you want to use decimetres or whatever.
Actually, it has proven very useful to me to be "multi-unitary" - I'm quite at home with most weird units (including megashekels per fortnight - actually my pay feels more like microroubles per fortnight sometimes!)
Bung
Life is non-linear...
RE: Strange SI prefixes
Powers of ten that the SI has prefixes for:
1,2,3,6,9,12,15,18,21,24 (and negatives thereof)
Litres, on the other hand, are non-SI (and so are hectolitres).
Hg
RE: Strange SI prefixes
According to NIST SP 811 Guide for the Use of the International System of Units (SI) , liter is a unit accepted for use with the SI, similar to minute, hour, day, and degree (plane angle). This document is available at:
http://ts.nist.gov/ts/htdocs/200/202/mpo_pubs.htm
Regards,
Cory
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Strange SI prefixes
Hg