Ask A Scientist© General Science Archive

name        Sarah
status      other
age         50s

Question -  What's the word for the smallest designated unit of 
time-- equivalent to .000000000000000000000001 second (decimal, 23 
zeros, >> 1)? Thanks!


Hello, It is good to know someone is wondering about those small 
numbers... For a moment I thought you were calculating return on the taxes 
we pay!

Anyway, for completeness, here is a list of all the prefixes I know of. I 
do not know what 10e+27 and 10e-27 are called, so I made them up. The 
first one, Taxo, is a very large number, as in our taxes. The last one, 
empto, is a very small number, and that is what we get in return!!!

Symbol     Unit       Value 

Tx        Taxo       10e+27        (unofficial)
Y         Yotta      10e+24 
Z         Zett       10e+21         
E         Exa        10e+18
P         Pento      10e+15 
T         Tera       10e+12 
G         Giga       10e+09 
M         Mega       10e+06 
k         kilo       10e+03 
c         centi      10e-02 
m         milli      10e-03 
u         micro      10e-06 
n         nano       10e-09 
p         pico       10e-12 
f         femto      10e-15 
a         atto       10e-18 
z         zepto      10e-21 
y         yocto      10e-24 = 0.000,000,000,000,000,000,000,001 
e         empto      10e-27  (unofficial)

In any case, the answer to your question would be one yocto second.

Good luck.


Dr. Ali Khounsary
Advanced Photon Source
Argonne National Laboratory
Argonne, IL 60439

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