{{short description|One millionth of a second}}
{{Infobox unit | name = microsecond | image = | caption = | symbol = μs | standard = SI | quantity = time | units1 = SI units | inunits1 = {{val|e=-6|ul=s}} }} A '''microsecond''' is a unit of time in the International System of Units (SI) equal to one millionth (0.000001 or 10<sup>−6</sup> or {{frac|1|1,000,000}}) of a second. Its symbol is '''μs''', sometimes simplified to '''us''' when Unicode is not available.
A microsecond is to one second, as one second is to approximately 11.57 days.
A microsecond is equal to 1000 nanoseconds or {{frac|1|1,000}} of a millisecond. Because the next SI prefix is 1000 times larger, measurements of 10<sup>−5</sup> and 10<sup>−4</sup> seconds are typically expressed as tens or hundreds of microseconds.
==Examples==
* 1 microsecond (1 μs) – cycle time for frequency {{val|1|e=6|ul=hertz}} (1 MHz), the inverse unit. This corresponds to radio wavelength 300 m (AM medium wave band), as can be calculated by multiplying 1 μs by the speed of light (approximately {{val|3.00|e=8|u=m/s}}). * 1 microsecond – the length of time of a high-speed, commercial strobe light flash (see air-gap flash). * 1 microsecond – protein folding takes place on the order of microseconds (thus this is the speed of carbon-based life). * 1.8 microseconds – the amount of time subtracted from the Earth's day as a result of the 2011 Japanese earthquake.<ref>{{cite news |last1=Gross |first1=R.S. |title=Japan quake may have shortened Earth days, moved axis |url=http://www.jpl.nasa.gov/news/news.php?release=2011-080 |access-date=23 August 2019 |agency=Jet Propulsion Laboratory |publisher=JPL News |date=14 March 2014}}</ref> * 2 microseconds – the lifetime of a muonium particle. * 2.68 microseconds – the amount of time subtracted from the Earth's day as a result of the 2004 Indian Ocean earthquake.<ref name="IndianOceanNASA">{{cite web | url=https://www.nasa.gov/home/hqnews/2005/jan/HQ_05011_earthquake.html | title=NASA Details Earthquake Effects on the Earth | publisher=NASA | date=January 10, 2005 | access-date=September 18, 2021 | last1=Cook-Anderson | first1=Gretchen | last2=Beasley | first2=Dolores}}</ref> * 3.33564095 microseconds – the time taken by light to travel one kilometre in a vacuum. * 5.4 microseconds – the time taken by light to travel one mile in a vacuum (or radio waves point-to-point in a near vacuum). * 8 microseconds – the time taken by light to travel one mile in typical single-mode fiber optic cable. * 10 microseconds (μs) – cycle time for frequency 100 kHz, radio wavelength 3 km. * 18 microseconds – net amount per year that the length of the day lengthens, largely due to tidal acceleration.<ref>{{Cite news|url=http://www.sciencealert.com/astronomers-find-a-day-on-earth-is-getting-longer-each-century|title=Earth's Days Are Getting 2 Milliseconds Longer Every 100 Years|last=MacDonald|first=Fiona|work=ScienceAlert|access-date=2017-03-08|language=en-gb}}</ref> * 20.8 microseconds – sampling interval for digital audio with 48,000 samples/s. * 22.7 microseconds – sampling interval for CD audio (44,100 samples/s). * 38 microseconds – discrepancy in GPS satellite time per day (compensated by clock speed) due to relativity{{hsp}}.<ref>{{cite web | url=http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html | title= GPS and Relativity | access-date=2011-10-01 | author= Richard Pogge }}</ref> * 50 microseconds – cycle time for highest human-audible tone (20 kHz). * 50 microseconds – to read the access latency for a modern solid state drive which holds non-volatile computer data.<ref>[http://www.intel.com/content/dam/www/public/us/en/documents/product-specifications/ssd-dc-s3500-spec.pdf Intel Solid State Drive Product Specification]</ref> * 100 microseconds (0.1 ms) – cycle time for frequency 10 kHz. * 125 microseconds – common sampling interval for telephone audio (8000 samples/s).<ref>{{Citation |last=Kumar |first=Anurag |title=Application Models and Performance Issues |date=2008 |url=https://linkinghub.elsevier.com/retrieve/pii/B9780123742544500041 |work=Wireless Networking |pages=53–79 |publisher=Elsevier |language=en |doi=10.1016/b978-012374254-4.50004-1 |isbn=978-0-12-374254-4 |access-date=2022-08-08 |last2=Manjunath |first2=D. |last3=Kuri |first3=Joy|url-access=subscription }}</ref> * 164 microseconds – half-life of polonium-214. * 240 microseconds – half-life of copernicium-277. * 260 to 480 microseconds - return trip ICMP ping time, including operating system kernel TCP/IP processing and answer time, between two Gigabit Ethernet devices connected to the same local area network switch fabric. * 277.8 microseconds – a fourth (a 60th of a 60th of a second), used in astronomical calculations by al-Biruni and Roger Bacon in 1000 and 1267 AD, respectively.<ref>{{cite book |author=al-Biruni |author-link=al-Biruni |translator=Sachau C Edward |year=1879 |title=The chronology of ancient nations: an English version of the Arabic text of the Athâr-ul-Bâkiya of Albîrûnî, or "Vestiges of the Past" |url=https://books.google.com/books?id=pFIEAAAAIAAJ&q=thirds&pg=PA148|pages=147–149 |publisher=W. H. Allen |oclc=9986841 }}</ref><ref> {{cite book |author=R Bacon | author-link= Roger Bacon |others=translator: BR Belle |year=2000 |orig-year=1928 |title= The Opus Majus of Roger Bacon |publisher=University of Pennsylvania Press |page=table facing page 231 |isbn=978-1-85506-856-8 |no-pp=true }}</ref> * 490 microseconds – time for light at a 1550 nm frequency to travel 100 km in a singlemode fiber optic cable (where speed of light is approximately 200 million metres per second due to its index of refraction). * The average human eye blink takes 350,000 microseconds (just over {{frac|1|3}} second). * The average human finger snap takes 150,000 microseconds (just over {{frac|1|7}} second). * A camera flash illuminates for 1,000 microseconds or 1 millisecond. * Standard camera shutter speed opens the shutter for 4,000 microseconds or 4 milliseconds. * 584554 years of microseconds fit in 64 bits: (2**64)/(1e6*60*60*24*365.2425).
==See also== * International System of Units * Jiffy (time) * Orders of magnitude (time) * Millisecond * Nanosecond * Picosecond
==References== {{Reflist}}
==External links== * [https://www.nist.gov/pml/time-and-frequency-division The National Institute of Standards and Technology (NIST)]
{{Orders of magnitude seconds}}
{{DEFAULTSORT:1 E-6 S}} Category:Orders of magnitude (time)