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{{Short description|Comparison of a wide range of timescales}}
{{Use dmy dates|date=September 2020}}
{{More citations needed|date=January 2020}}
An [[order of magnitude]] of [[time]] is usually a [[decimal]] prefix or decimal order-of-magnitude quantity together with a base [[unit of time]], like a [[microsecond]] or a [[million years]]. In some cases, the order of magnitude may be implied (usually 1), like a "second" or "year". In other cases, the quantity name implies the [[Base unit (measurement)|base unit]], like "century". In most cases, the base unit is seconds or years.
Prefixes are not usually used with a base unit of years. Therefore, it is said "a million years" instead of "a megayear". Clock time and calendar time have [[duodecimal]] or [[sexagesimal]] orders of magnitude rather than decimal, e.g., a year is 12 months, and a minute is 60 seconds.
The smallest meaningful increment of time is the [[Planck time]]―the time light takes to traverse the [[Planck distance]], many decimal orders of magnitude smaller than a second.<ref>{{Cite web|title=Planck Time {{!}} COSMOS|url=https://astronomy.swin.edu.au/cosmos/p/Planck+Time|access-date=2021-10-12|website=astronomy.swin.edu.au}}</ref>
The largest realized amount of time, based on known scientific data, is the [[age of the universe]], about 13.8 billion years—the time since the [[Big Bang]] as measured in the [[cosmic microwave background]] [[rest frame]].<ref>{{Cite web|title=WMAP- Age of the n Universe|url=https://wmap.gsfc.nasa.gov/universe/uni_age.html|access-date=2021-10-12|website=wmap.gsfc.nasa.gov}}</ref> Those amounts of time together span 60 decimal orders of magnitude. Metric prefixes are defined spanning {{10^|−30}} to {{10^|30}}, 60 decimal orders of magnitude which may be used in conjunction with the metric base unit of second.
Metric units of time larger than the second are most commonly seen only in a few scientific contexts such as observational astronomy and materials science, although this depends on the author. For everyday use and most other scientific contexts, the common units of minutes, hours (3 600 s or 3.6 ks), days (86 400 s), weeks, months, and years (of which there are a number of variations) are commonly used. Weeks, months, and years are significantly variable units whose lengths depend on the choice of calendar and are often not regular even with a calendar, e.g., leap years versus regular years in the [[Gregorian calendar]]. This makes them problematic for use against a linear and regular time scale such as that defined by the [[SI]], since it is not clear which version is being used.
Because of this, the table below does not include weeks, months, and years. Instead, the table uses the [[annum]] or [[Julian year (astronomy)|astronomical Julian year]] (365.25 days of 86 400 seconds), denoted with the symbol a. Its definition is based on the average length of a year according to the [[Julian calendar]], which has one [[leap year]] every four years. According to the geological science convention, this is used to form larger units of time by the application of [[SI prefix]]es to it; at least up to giga-annum or Ga, equal to 1 000 000 000 a ([[Long and short scales|short scale]]: one billion years, [[Long and short scales|long scale]]: one milliard years).
==Less than one second==
{| class="wikitable plainrowheaders"
|+Units of measure less than a second
!scope="col"| Multiple<br />of a<br />second
!scope="col" |Unit
!scope="col"|Symbol
!scope="col"|Definition
!scope="col"|Comparative examples & common units <!-- This is any multiple, within reason and which is commonly used, to express not only by comparative example the length of time but also, in other terms (common units) the interval of time. For example: 60 Seconds = 1 minute.-->
|-
| {{10^|-44}}
!scope="row"| [[Planck time]]
| style="text-align: center" |''t''{{sub|P}}
| Presumed to be the shortest theoretically measurable time interval<br />(but not necessarily the shortest ''increment'' of time—see [[quantum gravity]])
| '''{{val|e=-14|u=qs}}''': The length of one [[Planck time]] (''t''{{sub|P}} = <math>\sqrt{\hbar G/c^5}</math> ≈ {{val|5.39|e=-44|u=s}})<ref>{{cite web |url=https://physics.nist.gov/cgi-bin/cuu/Value?plkt |title=CODATA Value: Planck time |publisher= NIST | work = The NIST Reference on Constants, Units, and Uncertainty |access-date=1 October 2011 }}</ref> is the briefest physically meaningful span of time. It is the unit of time in the [[natural units]] system known as [[Planck units]].
|-
| {{10^|−30}}
!scope="row"| quectosecond{{anchor|Quectosecond}}
| style="text-align: center" | qs
| '''Quectosecond''', (''[[quecto-]]'' + ''second''), is one [[Names of large numbers|nonillionth]] of a second
|
|-
| {{10^|−27}}
!scope="row"| rontosecond{{anchor|Rontosecond}}
| style="text-align: center" | rs
| '''Rontosecond''', (''[[ronto-]]'' + ''second''), is one [[Names of large numbers|octillionth]] of a second
| '''300 rs''': The [[mean lifetime]] of [[W and Z bosons]]
|-
| {{10^|−24}}
!scope="row"| yoctosecond{{anchor|Yoctosecond}}
| style="text-align: center" | ys<ref>The American Heritage Dictionary of the English Language: Fourth Edition. 2000. Available at: http://www.bartleby.com/61/21/Y0022100.html {{Webarchive|url=https://web.archive.org/web/20080310072709/http://www.bartleby.com/61/21/Y0022100.html |date=10 March 2008 }}. Accessed 19 December 2007. '''note''': abbr. ys or ysec</ref>
| '''Yoctosecond''', (''[[yocto-]]'' + ''second''), is one [[Names of large numbers|septillionth]] of a second
| '''86 ys''': The estimated value on the [[half-life]] of [[Isotopes of hydrogen#Hydrogen-5|isotope 5 of hydrogen (hydrogen-5)]]<br />'''143 ys''': The [[half-life]] of the [[Isotopes of nitrogen|nitrogen-10]] isotope of nitrogen<br />'''156 ys''': The mean lifetime of a [[Higgs boson]]
|-
| {{10^|−21}}
!scope="row"| zeptosecond{{anchor|Zeptosecond}}
| style="text-align: center" | zs
| '''Zeptosecond''', (''[[zepto-]]'' + ''second''), is one [[Names of large numbers|sextillionth]] of one second
| '''1.3 zs''': Smallest experimentally controlled time delay in a photon field.<ref>{{cite journal |title=Coherent control of collective nuclear quantum states via transient magnons |journal=[[Science Advances]] |volume=7 |article-number=eabc3991 |doi=10.1126/sciadv.abc3991 |date=29 Jan 2021 |first1=Lars |last1=Bocklage |issue=5 |pmid=33514541 |display-authors=etal |pmc=7846183 |bibcode=2021SciA....7.3991B }}</ref><br/> '''2 zs''': The representative cycle time of [[gamma ray]] radiation released in the decay of a radioactive [[atomic nucleus]] (here as 2 [[electronvolt|MeV]] per emitted [[photon]])<br/>'''4 zs''': The cycle time of the [[zitterbewegung]] of an [[electron]] (<math>\omega=2m_e c^2/\hbar</math>) <br/>'''247 zs''': The experimentally measured travel time of a photon across a hydrogen molecule, "for the average bond length of molecular hydrogen"<ref>{{cite journal |url=https://www.science.org/doi/10.1126/science.abb9318 |title=Zeptosecond birth time delay in molecular photoionization |journal=[[Science (journal)|Science]] |volume=370 |issue=6514 |pages=339–341 |doi=10.1126/science.abb9318 |date=16 Oct 2020 |access-date=17 Oct 2020 |first1=Sven |last1=Grundmann |first2=Daniel |last2=Trabert|pmid=33060359 |display-authors=etal|arxiv=2010.08298 |bibcode=2020Sci...370..339G |s2cid=222412229 }}</ref>
|-
| {{10^|−18}}
!scope="row"| [[attosecond]]
| style="text-align: center" | as
| One quintillionth of one second
| '''12 as''': The best timing control of laser pulses.<ref>{{Cite web|url=https://phys.org/news/2010-05-attoseconds-world-shortest.html|title=12 attoseconds is the world record for shortest controllable time|website=phys.org}}</ref><br/>'''43 as''': The shortest X-ray laser pulse<ref>{{Cite journal|url=https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-25-22-27506&id=375881|title=Streaking of 43-attosecond soft-X-ray pulses generated by a passively CEP-stable mid-infrared driver|year=2017|doi=10.1364/OE.25.027506|last1=Gaumnitz|first1=Thomas|last2=Jain|first2=Arohi|last3=Pertot|first3=Yoann|last4=Huppert|first4=Martin|last5=Jordan|first5=Inga|last6=Ardana-Lamas|first6=Fernando|last7=Wörner|first7=Hans Jakob|journal=Optics Express|volume=25|issue=22|pages=27506–27518|pmid=29092222|bibcode=2017OExpr..2527506G|hdl=20.500.11850/211882|hdl-access=free}}</ref><br />'''53 as''': The shortest electron laser pulse<ref>{{Cite journal |last1=Kim |first1=H. Y. |last2=Garg |first2=M. |last3=Mandal |first3=S. |last4=Seiffert |first4=L. |last5=Fennel |first5=T. |last6=Goulielmakis |first6=E. |date=January 2023 |title=Attosecond field emission |journal=Nature |language=en |volume=613 |issue=7945 |pages=662–666 |doi=10.1038/s41586-022-05577-1 |pmid=36697865 |issn=1476-4687|pmc=9876796 |arxiv=2206.08895 |bibcode=2023Natur.613..662K }}</ref><ref>{{Cite web |date=2023-02-17 |title=Attosecond electron pulses are claimed as shortest ever |url=https://physicsworld.com/a/attosecond-electron-pulses-are-claimed-as-shortest-ever/ |access-date=2023-02-17 |website=Physics World |language=en-GB}}</ref>
|-
| {{10^|−15}}
!scope="row"| [[femtosecond]]
| style="text-align: center" | fs
| One quadrillionth of one second
| '''1 fs''': The cycle time for ultraviolet light with a wavelength of 300 [[nanometre|nanometres]]; the time it takes light to travel a distance of 0.3 micrometres (μm).<br/>'''7.58 fs''': The period of vibration of a hydrogen molecule.<br/>'''140 fs''': The time needed for electrons to have localized onto individual [[bromine]] atoms 6 [[Angstrom|Ångstrom]] apart after [[femtochemistry|laser dissociation]] of Br{{sub|2}}.<ref name="li-visualizing">{{cite journal|last1=Li|first1=Wen|title=Visualizing electron rearrangement in space and time during the transition from a molecule to atoms|journal=PNAS|date=23 November 2010|volume=107|issue=47|pages=20219–20222|doi=10.1073/pnas.1014723107|display-authors=etal|pmid=21059945|pmc=2996685|bibcode=2010PNAS..10720219L|doi-access=free}}</ref><br />'''290 fs''': The lifetime of a [[tauon]]
|-
| {{10^|−12}}
!scope="row"| [[picosecond]]
| style="text-align: center" | ps
| One trillionth of one second
| '''1 ps''': The mean lifetime of a [[bottom quark]]; the time needed for light to travel 0.3 millimetres (mm)<br />'''1 ps''': The typical lifetime of a [[Transition state theory|transition state]] one machine cycle by an IBM [[Silicon-germanium#SiGe transistors|silicon-germanium transistor]]<br />'''109 ps''': The period of the [[Photon energy|photon corresponding to]] the [[Hyperfine structure|hyperfine transition]] of the ground state of [[cesium-133]], and one 9,192,631,770th of one second [[Caesium standard|by definition]]<br />'''114.6 ps''': The time for the fastest overclocked processor {{as of|2014|lc=y}} to execute one machine cycle.<ref>{{cite web |first=Marco |last=Chiappetta |date=23 September 2011 |url=http://hothardware.com/News/AMD-Breaks-Frequency-Record-with-Upcoming-FX-Processor/ |title=AMD Breaks 8 GHz Overclock with Upcoming FX Processor, Sets World Record. The record has been surpassed with 8794 MHz of overclocking with AMD FX 8350 |publisher=HotHardware |access-date=28 April 2012 |archive-date=10 March 2015 |archive-url=https://web.archive.org/web/20150310020437/http://hothardware.com/News/AMD-Breaks-Frequency-Record-with-Upcoming-FX-Processor }}</ref><br />'''696 ps''': How much more a second lasts far away from Earth's gravity due to the effects of [[general relativity]]
|-
| {{10^|−9}}
!scope="row"| [[nanosecond]]
| style="text-align: center" | ns
| One billionth of one second
| '''1 ns''': The time needed to execute one machine cycle by a 1 GHz microprocessor<br />'''1 ns''': The time light takes to travel 30 cm (11.811 in)
|-
| {{10^|−6}}
!scope="row"| [[microsecond]]
| style="text-align: center" | μs
| One millionth of one second
| '''1 μs''': The time needed to execute one machine cycle by an Intel 80186 microprocessor<br />'''2.2 μs''': The lifetime of a [[muon]]<br />'''4–16 μs''': The time needed to execute one machine cycle by a 1960s [[minicomputer]]
|-
| {{10^|−3}}
!scope="row"| [[millisecond]]
| style="text-align: center" | ms
| One thousandth of one second
| '''1 ms''': The time for a neuron in the human brain to fire one impulse and return to rest<ref>{{Cite web|url=http://www.noteaccess.com/APPROACHES/ArtEd/ChildDev/1cNeurons.htm|title=Notebook|website=www.noteaccess.com}}</ref><br />'''4–8 ms''': The typical [[seek time]] for a computer hard disk<br />
|-
|{{10^|−2}}
!scope="row"| centisecond
| style="text-align: center" | cs
|One hundredth of one second
|'''1.6667 cs''': The period of a frame at a frame rate of 60 Hz.<br/>'''2 cs''': The cycle time for European 50 Hz AC electricity
'''10–20 cs''' (=0.1–0.2 s): The human [[reflex]] response to visual stimuli
|-
|{{10^|−1}}
!scope="row"| decisecond
| style="text-align: center" | ds
|One tenth of a second
|'''1–4 ds''' (=0.1–0.4 s): The length of a single blink of an eye<ref>{{cite web|url=https://faculty.washington.edu/chudler/facts.html|title=Brain Facts and Figures: Sensory Apparatus: Vision|author=Eric H. Chudler|access-date=10 October 2011}}</ref><br />
|}
== More than one second ==
In this table, large intervals of time surpassing one second are catalogued in order of the SI multiples of the second as well as their equivalent in common time units of minutes, hours, days, and Julian years.
{| class="wikitable plainrowheaders"
|+Units of measure greater than one second
|-
!scope="col"| Multiple of a second
!scope="col"| Unit
!scope="col"| Symbol
!scope="col"| Common units
!scope="col"| Comparative examples and common units <!-- This is any multiple, within reason and which is commonly used, to express not only by comparative example the length of time but also, in other terms (common units) the interval of time. For example: 60 Seconds = 1 minute.-->
|-
|{{10^|1}}
!scope="row"| decasecond
| style="text-align: center" | das
| single seconds
('''1 das''' = 10 s)
|'''6 das''': One minute (min), the time it takes a second hand to cycle around a clock face
|-
|{{10^|2}}
!scope="row"| hectosecond
| style="text-align: center" | hs
| minutes<br/>''('''1 hs''' = 1 min 40 s = 100 s)''
|'''2 hs''' (3 min 20 s): The average length of the most popular YouTube videos as of January 2017<ref>{{Cite web|url=https://www.minimatters.com/youtube-best-video-length/|title=YouTube Statistics and Your Best Video Length for Different Videos|date=11 March 2014|website=Video Production Washington DC - MiniMatters}}</ref><br/>'''5.55 hs''' (9 min 12 s): The longest videos in the above study
'''7.1 hs''' (11 m 50 s): The time for a human walking at average speed of 1.4 [[metre per second|m/s]] to walk 1 kilometre
|-
|{{10^|3}}
!scope="row"|kilosecond
| style="text-align: center" | ks
| minutes, hours, days<br/>
''('''1 ks''' = 16 min 40 s = 1,000 s)''
| '''1 ks''': The record confinement time for [[antimatter]], specifically [[antihydrogen]], in electrically neutral state as of 2011;<ref>{{cite journal|title=Confinement of antihydrogen for 1,000 seconds |date=5 June 2011 |doi=10.1038/nphys2025 |volume=7 |issue=7 |journal=Nature Physics |pages=558–564 |arxiv=1104.4982 |bibcode=2011NatPh...7..558A |author1=Alpha Collaboration |last2=Andresen |first2=G. B. |last3=Ashkezari |first3=M. D. |last4=Baquero-Ruiz |first4=M. |last5=Bertsche |first5=W. |last6=Bowe |first6=P. D. |last7=Butler |first7=E. |last8=Cesar |first8=C. L. |last9=Charlton |first9=M. |last10=Deller |first10=A. |last11=Eriksson |first11=S. |last12=Fajans |first12=J. |last13=Friesen |first13=T. |last14=Fujiwara |first14=M. C. |last15=Gill |first15=D. R. |last16=Gutierrez |first16=A. |last17=Hangst |first17=J. S. |last18=Hardy |first18=W. N. |last19=Hayano |first19=R. S. |last20=Hayden |first20=M. E. |last21=Humphries |first21=A. J. |last22=Hydomako |first22=R. |last23=Jonsell |first23=S. |last24=Kemp |first24=S. L. |last25=Kurchaninov |first25=L. |last26=Madsen |first26=N. |last27=Menary |first27=S. |last28=Nolan |first28=P. |last29=Olchanski |first29=K. |last30=Olin |first30=A. |s2cid=17151882 |display-authors=29 }}</ref>
'''1.477 ks''': The longest period in which a person has not taken a breath.
'''1.8 ks''': The time slot for the typical situation comedy on television with advertisements included
'''2.28 ks''': The duration of the [[Anglo-Zanzibar War]], the shortest war in recorded history.
'''3.6 ks''': The length of one hour (h), the time for the minute hand of a clock to cycle once around the face, approximately 1/24 of one [[mean solar day]]
'''7.2 ks''' (2 h): The typical length of feature films
'''35.73 ks''': the rotational period of planet Jupiter, fastest planet to rotate
'''38.0196 ks''': rotational period of Saturn, second shortest rotational period
'''57.996 ks''': one day on planet Neptune.
'''62.064 ks''': one day on Uranus.
'''86.399 ks''' (23 h 59 min 59 s): The length of one day with a removed [[leap second]] on [[UTC]] time scale. Such has not yet occurred.
'''86.4 ks''' (24 h): The length of one day of Earth by standard. More exactly, the [[mean solar day]] is 86.400 002 ks due to [[tidal braking]], and increasing at the rate of approximately 2 ms/century; to correct for this time standards like [[UTC]] use [[leap seconds]] with the interval described as "a day" on them being most often 86.4 ks exactly by definition but occasionally one second more or less so that every day contains a whole number of seconds while preserving alignment with astronomical time. The hour hand of an analogue clock will typically cycle twice around the dial in this period as most analogue clocks are [[12-hour clock|12-hour]], less common are analogue [[24-hour clock]]s in which it cycles around once.
'''86.401 ks''' (24 h 0 min 1 s): One day with an added [[leap second]] on [[UTC]] time scale. While this is strictly 24 hours and 1 second in conventional units, a [[digital clock]] of suitable capability level will most often display the leap second as 23:59:60 and not 24:00:00 before rolling over to 00:00:00 the next day, as though the last "minute" of the day was crammed with 61 seconds and not 60, and similarly the last "hour" was crammed with 3,601 seconds instead of 3,600.
'''88.775 ks''' (24 h 39 min 35 s): One [[Martian day|sol]] of Mars
'''604.8 ks''' (7 d): One week of the [[Gregorian calendar]]
|-
|{{10^|6}}
!scope="row"| megasecond
| style="text-align: center" | Ms
| weeks to years<br/>
''('''1 Ms''' = 11 d 13 h 46 min 40 s = 1,000,000 s)''
|'''1.6416 Ms''' (19 d): The length of a month of the [[Baháʼí calendar]]
'''2.36 Ms''' (27.32 d): The length of the true month, the [[orbital period]] of the [[Moon]]
'''2.4192 Ms''' (28 d): The length of February, the shortest month of the [[Gregorian calendar]], in common years
'''2.5056 Ms''' (29 d): The length of February in leap years
'''2.592 Ms''' (30 d): The length of April, June, September, and November in the [[Gregorian calendar]]; common interval used in legal agreements and contracts as a proxy for a month
'''2.6784 Ms''' (31 d): The length of the longest months of the [[Gregorian calendar]]
'''23 Ms''' (270 d): The approximate length of typical human [[gestational period]]
'''31.5576 Ms''' (365.25 d): The length of the [[Julian year (astronomy)|Julian year]], also called the ''[[annum]]'', symbol '''a'''.
'''5.06703168 Ms''': The rotational period of Mercury.
'''7.600544064 Ms''': One year on Mercury.
'''19.41414912 Ms''': One year on Venus.
'''20.9967552 Ms''': The rotational period of Venus.
'''31.55815 Ms''' (365 d 6 h 9 min 10 s): The length of the true year, the [[orbital period]] of the Earth
'''126.2326 Ms''' (1461 d 0 h 34 min 40 s): The elected term of the [[President of the United States]] or one [[Olympiad]]
|-
|{{10^|9}}
!scope="row"| gigasecond
| style="text-align: center" | Gs
| decades, centuries, millennia<br/>
''('''1 Gs''' = over 31 years and 287 days = 1,000,000,000 s)''
|
'''2.5 Gs''': (79 a): The typical human [[life expectancy]] in the [[developed world]]
'''3.16 Gs''': (100 a): One century
'''31.6 Gs''': (1,000 a, 1 ka): One [[millennium]], also called a [[kilo-annum]] (ka)
'''194.67 Gs''' (6.173 ka): The approximate lifespan of [[time capsule]] [[Crypt of Civilization]], 28 May 1940 – 28 May 8113
'''363 Gs''': (11.5 ka): The time since the beginning of the [[Holocene epoch]]
'''814 Gs''': (25.8 ka): The approximate time for the cycle of [[axial precession|precession of the Earth's axis]]
|-
|{{10^|12}}
!scope="row"| terasecond
| style="text-align: center" | Ts
| millennia to geological [[epoch (geology)|epoch]]s<br/>
''('''1 Ts''' = over 31,600 years = 1,000,000,000,000 s)''
|''' 3.1 Ts''' (100 ka): approximate length of a [[glacial period]] of the current [[Quaternary glaciation]] epoch
'''31.6 Ts''' (1000 ka, 1 Ma): One [[mega-annum]] (Ma), or one million years
'''79 Ts''' (2.5 Ma): The approximate time since earliest hominids of genus ''[[Australopithecus]]''
'''130 Ts''' (4 Ma): The typical lifetime of a [[Species|biological species]] on Earth
'''137 Ts''' (4.32 Ma): The length of the mythic unit of ''[[mahayuga]]'', the Great Age, in [[Hindu mythology]].
|-
|{{10^|15}}
!scope="row"| petasecond
| style="text-align: center" | Ps
| geological [[era (geology)|era]]s, history of Earth and the [[Universe]]
| '''2 Ps''': The approximate time since the [[Cretaceous-Paleogene extinction event]], believed to be caused by the impact of a large [[asteroid]] into [[Chicxulub crater|Chicxulub]] in modern-day Mexico. This extinction was one of the largest in Earth's history and marked the demise of most dinosaurs, with the only known exception being the ancestors of today's birds.
'''7.9 Ps''' (250 Ma): The approximate time since the [[Permian-Triassic extinction event]], the actually largest known mass extinction in Earth history which wiped out 95% of all extant species and believed to have been caused by the consequences of massive long-term [[volcanic eruptions]] in the area of the [[Siberian Traps]]. Also, the approximate time to the [[supercontinent]] of [[Pangaea]]. Also, the length of one [[galactic year]] or ''cosmic year'', the time required for the [[Sun]] to complete one orbit around the [[Milky Way Galaxy]].
'''16 Ps''' (510 Ma): The approximate time since the [[Cambrian explosion]], a massive evolutionary diversification of life which led to the appearance of most existing [[multicellular organisms]] and the replacement of the previous [[Ediacaran biota]].
'''22 Ps''' (704 Ma): The approximate [[half-life]] of the [[uranium]] isotope {{sup|235}}U.
'''31.6 Ps''' (1000 Ma, 1 Ga): One [[giga-annum]] (Ga), one billion years, the largest fixed time unit used in the standard [[geological time scale]], approximately the order of magnitude of an [[eon (geology)|eon]], the largest division of geological time.
'''+1 Ga''': The estimated remaining habitable lifetime of Earth, according to some models. At this point in time the [[stellar evolution]] of the Sun will have increased its [[luminosity]] to the point that enough energy will be reaching the Earth to cause the evaporation of the oceans and their loss into space (due to the UV flux from the Sun at the top of the atmosphere [[photodissociation|dissociating]] the molecules), making it impossible for any life to continue.
'''136 Ps''' (4.32 Ga): The length of the legendary unit [[Kalpa (time)|Kalpa]] in [[Hindu mythology]], or one day (but not including the following night) of the life of [[Brahma]].
'''143 Ps''' (4.5 Ga): The [[age of the Earth]] by our best estimates. Also the approximate half-life of the uranium isotope {{sup|238}}U.
'''315 Ps''' (10 Ga): The approximate lifetime of a [[main-sequence star]] similar to the [[Sun]].
'''434.8 Ps''' (13.787 Ga): The approximate [[age of the Universe]]
|-
| {{10^|18}}
!scope="row"| [[exa]]second
| style="text-align: center" | Es
| future cosmological time
| ''All times of this length and beyond are currently theoretical as they surpass the elapsed lifetime of the known universe''.<br/>
'''1.08 Es''' (+34 Ga): Time to the [[Big Rip]] according to some models, but this is not favored by existing data. This is one possible scenario for the [[ultimate fate of the Universe]]. Under this scenario, [[dark energy]] increases in strength and power in a feedback loop that eventually results in the tearing apart of all matter down to subatomic scale due to the rapidly increasing [[pressure#Negative pressures|negative pressure]] thereupon
'''300 – 600 Es''' (10 – 20 Ta): The estimated lifetime of low-mass stars ([[red dwarfs]])
|-
| {{10^|21}}
!scope="row"| [[zetta]]second
| style="text-align: center" | Zs
|
| '''3 Zs''' (+100 Ta): The remaining time until the end of [[Stelliferous Era]] of the universe, under the [[heat death of the universe|heat death]] scenario for the [[ultimate fate of the Universe]], which is the most commonly accepted model in the current scientific community. This is marked by the cooling-off of the last low-mass dwarf star to a [[black dwarf]]. After this time has elapsed, the [[Degenerate Era]] begins.
'''9.85 Zs''' (311 Ta): The entire lifetime of [[Brahma]] in [[Hindu mythology]].
|-
| {{10^|24}}
!scope="row"| [[yotta]]second
| style="text-align: center" | Ys
|
| '''600 Ys''' ({{val|2|e=19|u=a}}): The radioactive half-life of [[bismuth-209]] by [[alpha decay]], one of the slowest-observed radioactive decay processes.
|-
| {{10^|27}}
!scope="row"| [[Ronna-|ronna]]second
| style="text-align: center" | Rs
|
|'''3.16 Rs''' ({{Val|1|u=a|e=20}}): The estimated time until all stars are ejected from their galaxies or consumed by black holes.
'''32 Rs''' ({{Val|1|u=a|e=21}}): Highest estimate of the time until all stars are ejected from galaxies or consumed by black holes.
|-
| {{10^|30}} ''and onward''
!scope="row"| quettasecond ''and beyond''
| style="text-align: center" | Qs and on
|
|'''69 Qs''' ({{val|2.2|e=24|u=a}}): The radioactive half-life of [[tellurium-128]], the longest known half-life of any elemental [[isotope]].
'''1,340,009 Qs''' ({{val|4.134105|e=28|u=years}}): The time period equivalent to the value of 13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.13.0.0.0.0 in the [[Mesoamerican Long Count]], a date discovered on a stele at the [[Coba]] Maya site, believed by archaeologist [[Linda Schele]] to be the absolute value for the length of one cycle of the universe<ref name="Falk">{{cite book |last1=Falk |first1=Dan |title=In search of time the science of a curious dimension |date=2013 |publisher=St. Martin's Press |___location=New York |isbn=978-1-4299-8786-8}}</ref><ref>G. Jeffrey MacDonald [https://www.usatoday.com/tech/science/2007-03-27-maya-2012_n.htm "Does Maya calendar predict 2012 apocalypse?"] ''USA Today'' 27 March 2007.</ref>
'''{{val|2.6|e=11|u=Qs}}''' ({{val|8.2|e=33|u=years}}): The smallest possible value for [[proton decay|proton half-life]] consistent with experiment<ref>
{{cite journal |author=Nishino, H. ''et al.'' ([[Super-Kamiokande|Super-K Collaboration]]) |year=2009 |title=Search for Proton Decay via {{Subatomic particle|Proton+}} → {{Subatomic particle|Positron}}{{Subatomic particle|pion0}} and {{Subatomic particle|Proton+}} → {{Subatomic particle|Muon+}}{{Subatomic particle|pion0}} in a Large Water Cherenkov Detector |journal=[[Physical Review Letters]] |volume=102 |issue=14 |article-number=141801 |doi=10.1103/PhysRevLett.102.141801 |bibcode=2009PhRvL.102n1801N |pmid=19392425 |arxiv=0903.0676 |s2cid=32385768}}</ref>
'''{{val|e=23|u=Qs}}''' ({{val|3.2|e=45|u=years}}): The largest possible value for the [[proton decay|proton half-life]], assuming that the [[Big Bang]] was [[inflation (cosmology)|inflationary]] and that the same process that made [[baryon]]s predominate over [[antibaryon]]s in the early Universe also makes protons decay<ref name="dying">{{cite journal | last1=Adams | first1=Fred C. | last2=Laughlin | first2=Gregory | title=A dying universe: the long-term fate and evolution of astrophysical objects | journal=Reviews of Modern Physics | volume=69 | issue=2 | date=1997-04-01 | issn=0034-6861 | doi=10.1103/revmodphys.69.337 | pages=337–372|bibcode=1997RvMP...69..337A| arxiv=astro-ph/9701131 | s2cid=12173790 }}</ref>
'''{{val|6|e=43|u=Qs}}''' ({{val|2|e=66|u=years}}): The approximate [[Hawking process|lifespan]] of a black hole with the mass of the Sun<ref name="page">{{cite journal | last=Page | first=Don N. | title=Particle emission rates from a black hole: Massless particles from an uncharged, nonrotating hole | journal=Physical Review D | publisher=American Physical Society (APS) | volume=13 | issue=2 | date=1976-01-15 | issn=0556-2821 | doi=10.1103/physrevd.13.198 | pages=198–206| bibcode=1976PhRvD..13..198P }} See in particular equation (27).</ref>
'''{{val|4|e=63|u=Qs}}''' ({{val|1.3|e=86|u=years}}): The approximate lifespan of [[Sagittarius A*]], if uncharged and non-rotating<ref name="page">{{cite journal | last=Page | first=Don N. | title=Particle emission rates from a black hole: Massless particles from an uncharged, nonrotating hole | journal=Physical Review D | publisher=American Physical Society (APS) | volume=13 | issue=2 | date=1976-01-15 | issn=0556-2821 | doi=10.1103/physrevd.13.198 | pages=198–206| bibcode=1976PhRvD..13..198P }} See in particular equation (27).</ref>
'''{{val|5.4|e=83|u=Qs}}''' ({{val|1.7|e=106|u=years}}): The approximate lifespan of a [[supermassive black hole]] with a mass of 20 trillion [[solar mass]]es<ref name="page" />
<math>10^{10^{10^{76.66}}}</math> Qs: The scale of an estimated [[Poincaré recurrence theorem|Poincaré recurrence time]] for the quantum state of a hypothetical box containing an isolated black hole of stellar mass<ref name="page95">{{cite book | chapter = Information Loss in Black Holes and/or Conscious Beings? | last = Page | first = Don N. | title = Heat Kernel Techniques and Quantum Gravity | date = 25 November 1994 |editor=Fulling, S.A. | page = 461 | series = Discourses in Mathematics and its Applications | issue = 4 | publisher = Texas A&M University | arxiv = hep-th/9411193 | s2cid= 18633007 | isbn = 978-0-9630728-3-2
| bibcode = 1994hep.th...11193P }}</ref> This time assumes a statistical model subject to Poincaré recurrence. A much simplified way of thinking about this time is that in a model in which history [[Loschmidt's paradox|repeats itself]] arbitrarily many times due to [[Ergodic hypothesis|properties of statistical mechanics]], this is the time scale when it will first be somewhat similar (for a reasonable choice of "similar") to its current state again.
<math>10^{10^{10^{123}}}</math>Qs: The scale of an estimated Poincaré recurrence time for the quantum state of a hypothetical box containing a black hole with the mass of the observable Universe.<ref name="page95" />
<math>{10}^{{10}^{{10}^{{10}^{{10}^{1.1}}}}}</math> Qs (<math>{10}^{{10}^{{10}^{3,883,775,501,690}}}</math> years): The scale of an estimated Poincaré recurrence time for the quantum state of a hypothetical box containing a black hole with the estimated mass of the entire Universe, observable or not, assuming Linde's [[Eternal inflation|Chaotic Inflationary]] model with an [[inflaton]] whose mass is {{10^|−6}} [[Planck units|Planck mass]]es.<ref name="page95" />
|}
{| class="wikitable"
|+Other
!Multiples
!Unit
!Symbol
|-
|6×10<sup>1</sup> seconds
!1 minute
|min
|-
|6×10<sup>1</sup> minutes
!1 hour
|h ''(hr)''
|-
|2.4×10<sup>1</sup> hours
!1 day
|d
|}
== See also ==
{{cmn|colwidth=30em|
* [[Geologic time scale]]
* [[International System of Units]]
* [[Orders of magnitude (frequency)]]
* [[Planck units]]
* [[Scale (analytical tool)]]
* [[Temporal resolution]]
* [[Timeline of the far future]]
* [[Year]]
}}
==References==
{{reflist}}
==External links==
* [https://web.archive.org/web/20150317171205/http://exploringtime.org/?page=segments Exploring Time] from [[Planck time]] to the lifespan of the universe
{{Orders of magnitude}}
{{Time measurement and standards}}
{{Orders of magnitude seconds}}
{{Portal bar|Geology|Mathematics|Astronomy|Stars|Outer space|Science}}
[[Category:Orders of magnitude (time)| ]]
[[Category:Chronology]]
[[Category:Orders of magnitude|Time]]
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