Exa-

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This article is about the SI prefix. For other uses, see Exa (disambiguation).

Exa is a decimal unit prefix in the metric system denoting 1018 or 1000000000000000000. It was added as an SI prefix to the International System of Units (SI) in 1975,[1] and has the unit symbol E.

Exa comes from the Greek ἕξ, used as a prefix ἑξά-, meaning six (like hexa-), because it is equal to 10006.

Examples:

  • The total storage needed by Google Mail as of April 2012, ignoring backups and compression, is more than an exabyte (10240 megabytes of storage per user multiplied by an estimated 260 million users).
  • 1 EeV = 1018 electronvolts = 0.1602 joule
  • 1 exasecond is approximately 32 billion years
  • 1 exametre is approximately 110 light years
  • 0.43 Es ≈ the approximate age of the Universe
  • 1.6 Em—172 ± 12.5 light years—Diameter of Omega Centauri (one of the largest known globular clusters, perhaps containing over a million stars)[2][3]
Prefix 1000m 10n Decimal English word Since[nb 1]
Name Symbol Short scale Long scale
yotta Y  10008  1024 1000000000000000000000000  septillion  quadrillion 1991
zetta Z  10007  1021 1000000000000000000000  sextillion  thousand trillion 1991
exa E  10006  1018 1000000000000000000  quintillion  trillion 1975
peta P  10005  1015 1000000000000000  quadrillion  thousand billion 1975
tera T  10004  1012 1000000000000  trillion  billion 1960
giga G  10003  109 1000000000  billion  thousand million 1960
mega M  10002  106 1000000             million 1960 (1873)
kilo k  10001  103 1000             thousand 1960 (1795)
hecto h  10002/3  102 100             hundred 1960 (1795)
deca da  10001/3  101 10             ten 1960 (1795)
 10000  100 1             one
deci d  1000−1/3  10−1 0.1             tenth 1960 (1795)
centi c  1000−2/3   10−2 0.01             hundredth 1960 (1795)
milli m  1000−1  10−3 0.001             thousandth 1960 (1795)
micro μ  1000−2  10−6 0.000001             millionth 1960 (1873)
nano n  1000−3  10−9 0.000000001  billionth  thousand millionth 1960
pico p  1000−4  10−12 0.000000000001  trillionth  billionth 1960
femto f  1000−5  10−15 0.000000000000001  quadrillionth  thousand billionth 1964
atto a  1000−6  10−18 0.000000000000000001  quintillionth  trillionth 1964
zepto z  1000−7  10−21 0.000000000000000000001  sextillionth  thousand trillionth 1991
yocto y  1000−8  10−24  0.000000000000000000000001  septillionth  quadrillionth  1991
  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 (ma, 104) and myrio (mo, 10-4) 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[edit]

References[edit]

  1. ^ "Resolution 10 of the 15th meeting of the CGPM (1975)". International Bureau of Weights and Measures. Retrieved 2012-04-18. 
  2. ^ distance × sin( diameter_angle ), using distance of 5 kpc (15.8 ± 1.1 kly) and angle 36.3', = 172 ± 12.5 ly.
  3. ^ van de Ven, G.; van den Bosch, R. C. E.; Verolme, E. K.; de Zeeuw, P. T. (January II 2006). "The dynamical distance and intrinsic structure of the globular cluster ω Centauri". Astronomy and Astrophysics 445 (2): 513–543. arXiv:astro-ph/0509228. Bibcode:2006A&A...445..513V. doi:10.1051/0004-6361:20053061. best-fit dynamical distance D=4.8±0.3 kpc ... consistent with the canonical value 5.0±0.2 kpc obtained by photometric methods  Check date values in: |date= (help)

External links[edit]