Misplaced Pages

A cosmological decade (CÐ) is a division of the lifetime of the cosmos. The divisions are logarithmic in size, with base 10. Each successive cosmological decade represents a ten-fold increase in the total age of the universe.

As expressed in log (seconds per Ðecade)

When CÐ is measured in log( seconds/Р), CР1 begins at 10 seconds and lasts 90 seconds (until 100 seconds after Time Zero). CР100, the 100th cosmological decade, lasts from 10 to 10 seconds after Time Zero. CР${\displaystyle -\infty }$ is Time Zero.

The epoch CР−43.2683 was 10 seconds, which represents the Planck time since the Big Bang (Time Zero). There were an infinite number of cosmological decades between the Big Bang and the Planck epoch (or any other point in time). The current epoch, CР17.6389, is 10 seconds, or 13.799(21) billion years, since the Big Bang. There have been 60.9 cosmological decades between the Planck epoch, CР−43.2683, and the current epoch, CР17.6389.

As expressed in log (years per Ðecade)

The cosmological decade can be expressed in log years per decade. In this definition, the 100th cosmological decade lasts from 10 years to 10 years after Time Zero. To convert to this format, simply divide by seconds per year; or in logarithmic terms, subtract 7.4991116 from the values listed above. Thus when CÐ is expressed in log( years/Ð ), the Planck time could also be expressed as 10 years = 10 years.

In this definition, the current epoch is CÐ (17.6355 − 7.4991116), or CР10.1364. As before, there have been 60.9 cosmological decades between the Planck epoch and the current epoch.

In theories of physical cosmology, the history of the universe can be segmented into five eras:

References

1. Adams, Fred; Greg Laughlin (2000). The Five Ages of the Universe. Free Press. ISBN 978-0-684-86576-8.
2. Planck Collaboration (2016). "Planck 2015 results. XIII. Cosmological parameters (See Table 4 on page 31 of pfd)". Astronomy & Astrophysics. 594: A13. arXiv:1502.01589. Bibcode:2016A&A...594A..13P. doi:10.1051/0004-6361/201525830. S2CID 119262962.

v t e Time measurement and standards
Chronometry Orders of magnitude Metrology
International standards	Coordinated Universal Time offset UT ΔT DUT1 International Earth Rotation and Reference Systems Service ISO 31-1 ISO 8601 International Atomic Time 12-hour clock 24-hour clock Barycentric Coordinate Time Barycentric Dynamical Time Civil time Daylight saving time Geocentric Coordinate Time International Date Line IERS Reference Meridian Leap second Solar time Terrestrial Time Time zone 180th meridian
Obsolete standards	Ephemeris time Greenwich Mean Time Prime meridian
Time in physics	Absolute space and time Spacetime Chronon Continuous signal Coordinate time Cosmological decade Discrete time and continuous time Proper time Theory of relativity Time dilation Gravitational time dilation Time domain Time-translation symmetry T-symmetry
Horology	Clock Astrarium Atomic clock Complication History of timekeeping devices Hourglass Marine chronometer Marine sandglass Radio clock Watch stopwatch Water clock Sundial Dialing scales Equation of time History of sundials Sundial markup schema
Calendar	Gregorian Hebrew Hindu Holocene Islamic (lunar Hijri) Julian Solar Hijri Astronomical Dominical letter Epact Equinox Intercalation Julian day Leap year Lunar Lunisolar Solar Solstice Tropical year Weekday determination Weekday names
Archaeology and geology	Chronological dating Geologic time scale International Commission on Stratigraphy
Astronomical chronology	Galactic year Nuclear timescale Precession Sidereal time
Other units of time	Instant Flick Shake Jiffy Second Minute Moment Hour Day Week Fortnight Month Year Olympiad Lustrum Decade Century Saeculum Millennium
Related topics	Chronology Duration music Mental chronometry Decimal time Metric time System time Time metrology Time value of money Timekeeper

• Physics
• Space

• Physical cosmology
• Units of time