Exa-

This article is about the SI prefix. For the X Window System acceleration architecture, see EXA. For The CAE software developer, see Exa Corp..

Look up exa- in Wiktionary, the free dictionary.

Exa- (symbol E) is a prefix in the metric system denoting 10¹⁸ or 1000000000000000000.

Adopted in 1975, it comes from the Greek ἕξ, used as a prefix ἑξά-, meaning six (like hexa-), because it is equal to 1000⁶.

Examples:

Multiplying the 10240 megabytes of storage each Gmail user has (as of April 2012) with the estimated 260 Million Gmail users, the total storage needed for Gmail is more than an exabyte (not considering backups and how google might compress the stored data).
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)

References

^ "Resolution 10 of the 15th meeting of the CGPM (1975)". International Bureau of Weights and Measures. http://www.bipm.org/en/CGPM/db/15/10/. Retrieved 2012-04-18.
^ distance × sin( diameter_angle ), using distance of 5 kpc (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. 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"