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
In physical cosmology, the age of the universe is the time elapsed since the Big Bang. Astronomers have derived two different measurements of the age of the universe:
a measurement based on direct observations of an early state of the universe, ...
.
As expressed in log (seconds per Ðecade)
When CÐ is measured in log( seconds/Ð ), ''CÐ'' 1 begins at 10
seconds and lasts 90 seconds (until 100 seconds after Time Zero). ''CÐ'' 100, the 100th cosmological decade, lasts from 10
100 to 10
101 seconds after Time Zero. CÐ
is Time Zero.
The
epoch
In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured.
The moment of epoch is usually decided by ...
''CÐ'' −43.2683 was 10
(−43.2683) seconds, which represents the
Planck time since the
Big Bang
The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models of the Big Bang explain the evolution of the observable universe from t ...
(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, ''CÐ'' 17.6389, is 10
(17.6389) seconds, or 13.799(21) billion years, since the Big Bang.
There have been 60.9 cosmological decades between the Planck epoch, CÐ −43.2683, and the current epoch, CÐ 17.6389.
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
100 years to 10
101 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
(−43.2683 − 7.4991116) years = 10
(−50.7674) years.
In this definition, the current epoch is CÐ (17.6355 − 7.4991116), or CÐ 10.1364. As before, there have been 60.9 cosmological decades between the Planck epoch and the current epoch.
In their view, the history of the universe can be segmented into
five eras:
References
{{Portal bar, Physics, Space
Decade
A decade () is a period of ten years. Decades may describe any ten-year period, such as those of a person's life, or refer to specific groupings of calendar years.
Usage
Any period of ten years is a "decade". For example, the statement that "d ...
Units of time