Time (Orders of magnitude)
In the context of time, an order of magnitude is a description of the quantity of a time in respect to comparison between differing magnitudes. In common usage, the scale is usually the base10 or base−10 exponent being applied to an amount, making the order of magnitude 10 times greater or smaller. As the differences are measured in factors of 10, a logarithmic scale is applied. In terms of time, the relationship between the smallest limit of time, the Planck time, and the next order of magnitude larger is 10.
Low order of magnitude - measures by the unit second (s)
|Unit (s)||Multiple||Symbol||Definition||Comparative examples & common units||Orders of magnitude|
|10−44||1 Planck time||tP||The time required to travel one Planck length at the speed of light (c)||5.4 × 10-39 tP The time for a black hole the mass of the Earth to decay via Hawking radiation. 
×10−20 ys = 5.4×10−44 s: One 5.4Planck time tP = ≈ ×10−44 s5.4 is the briefest physically meaningful span of time. It is the unit of time in the natural units system known as Planck units.
|, 10−20 ys ( 10−19 ys10−44 s, 10−43 s)|
|10−24||1 yoctosecond||ys||Yoctosecond, (yocto- + second), is one septillionth of a second||0.3 ys: mean life of the W and Z bosons.[lower-alpha 1]
0.5 ys: time for top quark decay, according to the Standard Model.
1 ys: time taken for a quark to emit a gluon.
23 ys: half-life of 7H.
|1 ys and less, 10 ys, 100 ys|
|10−21||1 zeptosecond||zs||Zeptosecond, (zepto- + second), is one sextillionth of one second||7 zs: half-life of helium-9's outer neutron in the second nuclear halo.
17 zs: approximate period of electromagnetic radiation at the boundary between gamma rays and X-rays.
300 zs: approximate typical cycle time of X-rays, on the boundary between hard and soft X-rays.
500 zs: current resolution of tools used to measure speed of chemical bonding
|1 zs, 10 zs, 100 zs|
|10−18||1 attosecond||as||One quintillionth of one second||12 attoseconds: shortest measured period of time.||1 as, 10 as, 100 as|
|10−15||1 femtosecond||fs||One quadrillionth of one second||1 fs: Cycle time for 390 nanometre light; transition from visible light to ultraviolet; light travels 0.3 micrometers (µm).
140 fs: Electrons have localized onto individual bromine atoms 6Å apart after laser dissociation of Br2.
|1 fs, 10 fs, 100 fs|
|10−12||1 picosecond||ps||One trillionth of one second||1 ps: half-life of a bottom quark; light travels 0.3 millimeters (mm)
1 ps: lifetime of a transition state
4 ps: Time to execute one machine cycle by an IBM Silicon-Germanium transistor
|1 ps, 10 ps, 100 ps|
|10−9||1 nanosecond||ns||One billionth of one second||1 ns: Time to execute one machine cycle by a 1 GHz microprocessor
1 ns: Light travels 30 centimetres (12 in)
|1 ns, 10 ns, 100 ns|
|10−6||1 microsecond||µs||One millionth of one second||1 µs: Time to execute one machine cycle by an Intel 80186 microprocessor
4–16 µs: Time to execute one machine cycle by a 1960s minicomputer
|1 µs, 10 µs, 100 µs|
|10−3||1 millisecond||ms||One thousandth of one second||1 ms: time for a neuron in human brain to fire one impulse and return to rest
4–8 ms: typical seek time for a computer hard disk
100–400 ms (=0.1–0.4 s): Blink of an eye
18–300 ms (=0.02–0.3 s): Human reflex response to visual stimuli
|1 ms, 10 ms, 100 ms|
|100||1 second||s||The duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.||1 s: 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom.
60 s: 1 minute
|1 s, 10 s, 100 s|
|ks||One thousand seconds||3.6 ks: 3600 s or 1 hour
86.4 ks: 86 400 s or 1 day
604.8 ks: 1 week
|103 s, 104 s, 105 s|
|Ms||One million seconds||
2.6 Ms: approximately 1 month
|106 s, 107 s, 108 s|
|Gs||One billion seconds||109 s, 1010 s, 1011 s|
(32 000 years)
|Ts||One trillion seconds||
6 Ts: Time since the appearance of Homo sapiens (approximately)
|1012 s, 1013 s, 1014 s|
(32 million years)
|Ps||One quadrillion seconds||2.1 Ps: (66 million years) Time elapsed since the Cretaceous–Paleogene extinction event, during which all non-avian dinosaurs became extinct. 
7.1–7.9 Ps: 1 galactic year (225-250 million years)
|1015 s, 1016 s, 1017 s|
(32 billion years)
|Es||One quintillion seconds||312 Es: Estimated lifespan of a 0.1 solar mass red dwarf star.||1018 s, 1019 s, 1020 s|
(32 trillion years)
|Zs||One sextillion seconds||3 Zs: Estimated duration of Stelliferous Era.||1021 s, 1022 s, 1023 s|
(32 quadrillion years)
|Ys||One septillion seconds||1.6416 Ys: Estimated half-life of the meta-stable 20983Bi radioactive isotope.||1024 s, 1025 s, 1026 s and more|
High order of magnitude - measures by the unit year (a)
|Unit (a)||Multiple||Common units|
|10−50||Planck time, the shortest physically meaningful interval of time ≈ 1.71×10−50 a|
|10−9||1 nanoannum||1 second = 3.17 × 10−8 a ≈ 10−7.50 a|
|10−6||1 microannum||1 minute = 1.90 × 10−6 a
1 hour = 1.40 × 10−4 a
|10−3||1 milliannum||1 day = 2.73 × 10−3 a
1 week = 1.91 × 10−2 a
|100||1 annum||1 average year = 1 annum (= 365.24219 SI days)
1 decade = 10 a
1 century = 100 a
|103||1 kiloannum||millennium = 1000 a|
|106||1 megaannum||epoch = 1,000,000 a|
|109||1 gigaannum||aeon = 1,000,000,000 a
13.8 Ga = 1.38×1010 a ≈ 13.8 billion years, the approximate age of the Universe
|1018||1 exaannum||19 exaannum, the estimated half-life of the "stable" 20983Bi radioactive isotope|
The pages linked in the right-hand column contain lists of times that are of the same order of magnitude (power of ten). Rows in the table represent increasing powers of a thousand (3 orders of magnitude).
- Heat death of the Universe
- Second law of thermodynamics
- Big Rip
- Big Crunch
- Big Bounce
- Big Bang
- Cyclic model
- Dyson's eternal intelligence
- Final anthropic principle
- Ultimate fate of the Universe
- Timeline of the Big Bang
- Timeline of the far future
- Graphical timeline of the Big Bang
- Graphical timeline from Big Bang to Heat Death. This timeline uses the loglog scale for comparison with the graphical timeline included in this article.
- Graphical timeline of the universe. This timeline uses the more intuitive linear time, for comparison with this article.
- Graphical timeline of the Stelliferous Era
- The Last Question, a short story by Isaac Asimov which considers the inevitable outcome of heat death in the universe and how it may be reversed.
- PDG reports the resonance width (Γ). Here the conversion τ = ħ⁄Γ is given instead.
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- "Could the LHC make an Earth-killing black hole? — Starts With A Bang!". Medium. Retrieved 2015-10-21.
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- The American Heritage Dictionary of the English Language: Fourth Edition. 2000. Available at: http://www.bartleby.com/61/21/Y0022100.html. Accessed December 19, 2007. note: abbr. ys or ysec
- C. Amsler et al. (2009): Particle listings – W boson
- C. Amsler et al. (2009): Particle listings – Z boson
- esciencenews (2010)
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- Leong, Stacy (2002). "Period of the Sun's Orbit around the Galaxy (Cosmic Year)". The Physics Factbook.
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