This article is about the SI prefix. For the X Window System acceleration architecture, see EXA.
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exa (symbol E) is a prefix in the SI system of units denoting 1018 or 1 000 000 000 000 000 000.
Adopted in 1975, it comes from the Greek ἕξ, meaning six (like hexa), because it is equal to 10006.
Examples:
- 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)[1][2]
| 1000m | 10n | Prefix | Symbol | Since[1] | Short scale | Long scale | Decimal |
|---|---|---|---|---|---|---|---|
| 10008 | 1024 | yotta | Y | 1991 | Septillion | Quadrillion | 1000000000000000000000000 |
| 10007 | 1021 | zetta | Z | 1991 | Sextillion | Trilliard | 1000000000000000000000 |
| 10006 | 1018 | exa | E | 1975 | Quintillion | Trillion | 1000000000000000000 |
| 10005 | 1015 | peta | P | 1975 | Quadrillion | Billiard | 1000000000000000 |
| 10004 | 1012 | tera | T | 1960 | Trillion | Billion | 1000000000000 |
| 10003 | 109 | giga | G | 1960 | Billion | Milliard | 1000000000 |
| 10002 | 106 | mega | M | 1960 | Million | 1 000 000 | |
| 10001 | 103 | kilo | k | 1795 | Thousand | 1000 | |
| 10002⁄3 | 102 | hecto | h | 1795 | Hundred | 100 | |
| 10001⁄3 | 101 | deca | da | 1795 | Ten | 10 | |
| 10000 | 100 | (none) | (none) | NA | One | 1 | |
| 1000−1⁄3 | 10−1 | deci | d | 1795 | Tenth | 0.1 | |
| 1000−2⁄3 | 10−2 | centi | c | 1795 | Hundredth | 0.01 | |
| 1000−1 | 10−3 | milli | m | 1795 | Thousandth | 0.001 | |
| 1000−2 | 10−6 | micro | µ | 1960[2] | Millionth | 0.000001 | |
| 1000−3 | 10−9 | nano | n | 1960 | Billionth | Milliardth | 0.000000001 |
| 1000−4 | 10−12 | pico | p | 1960 | Trillionth | Billionth | 0.000000000001 |
| 1000−5 | 10−15 | femto | f | 1964 | Quadrillionth | Billiardth | 0.000000000000001 |
| 1000−6 | 10−18 | atto | a | 1964 | Quintillionth | Trillionth | 0.000000000000000001 |
| 1000−7 | 10−21 | zepto | z | 1991 | Sextillionth | Trilliardth | 0.000000000000000000001 |
| 1000−8 | 10−24 | yocto | y | 1991 | Septillionth | Quadrillionth | 0.000000000000000000000001 |
See also
References
- ^ distance × sin( diameter_angle ), using distance of 5kpc (15.8 ± 1.1 kly) and angle 36.3', = 172 ± 12.5 ly.
- ^ 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. doi:. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2006A%26A...445..513V. "best-fit dynamical distance D=4.8±0.3 kpc ... consistent with the canonical value 5.0±0.2 kpc obtained by photometric methods".
- International Bureau of Weights and Measures (2006), The International System of Units (SI) (8th ed.), ISBN 92-822-2213-6, http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf
External links
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