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From Yotta to Yocto
Dateline: 04/17/00
By Alan Bruzel
What Is a Yotta?
Yotta and yocto (along with zetta and zepto) were adopted by the Conférence Générale des Poids et Mesures in 1991 as permissible prefixes used to modify SI units. (SI is an abbreviation for Système International d'Unités.) The seven base SI units are: the ampere, candela, kelvin, kilogram, meter, mole, and second. Other SI units are derived from these base units.
One yotta of some unit is equivalent to
1,000,000,000,000,000,000,000,000
of those units. For example, the mass of asteroid 1 Ceres is about one yottagram.What Is a Yocto?
On the other end of the measurement descriptive spectrum is one yocto, which is
0.000,000,000,000,000,000,000,001
of a unit. One hydrogen atom, for example, has a mass of almost two yoctograms.
As illustrated in the table below, scientific notation (powers of ten) makes the writing of these numbers manageable. Keep in mind that 100 is the number one.
| Numbers Above One | Numbers Below One | ||||||
| Prefix | Power | Symbol | Number | Prefix | Power | Symbol | Number |
deka |
101 |
da |
ten |
deci |
10-1 |
d |
one tenth |
hecto |
102 |
h |
one hundred |
centi |
10-2 |
c |
one hundredth |
|
kilo |
103 |
k |
one thousand |
milli |
10-3 |
m |
one thousandth |
|
mega |
106 |
M |
one million |
micro |
10-6 |
µ |
one millionth |
giga |
109 |
G |
one billion |
nano |
10-9 |
n |
one billionth |
|
tera |
1012 |
T |
one trillion |
pico |
10-12 |
p |
one trillionth |
|
peta |
1015 |
P |
one quadrillion |
femto |
10-15 |
f |
one quadrillionth |
|
exa |
1018 |
E |
one quintillion |
atto |
10-18 |
a |
one quintillionth |
|
zetta |
1021 |
Z |
one sextillion |
zepto |
10-21 |
z |
one sextillionth |
|
yotta |
1024 |
Y |
one septillion |
yocto |
10-24 |
y |
one septillionth |
What the Web Has to Say about:
From Yotta to Yocto
Beyond
Extra Large (and Ultra Small)
Outlining the necessity of numerical descriptives. From Ivars Peterson's
MathTrek, Science News Online.
Defining the Meter, the Second, etc.
An article from this Web site describing past and present SI units of
measurement.
How Low Can You Go?
Zeptomolar and yoctomolar detection limits in analytical chemistry. From science
writer David Bradley.
SI Prefixes
Proper usage of these numerical modifiers. From the U.S. National Institute of Standards and Technology.
Speed
of Light Is Independent of Frequency
Physics News Update by Phillip F. Schewe and Ben Stein reports on Bradley
Schaefer's observation that different frequencies of light don't show
differences in their speed down to the zepto level.
The Sum of
Human Knowledge?
Printed pages, words, bytes and other packets of information may be handily
itemized using the proper numerical prefixes. Scientific American article
by Philip Morrison and Phylis Morrison.
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