137.165.167.183: The explanation in simpler terms had the terms L_1 and L_2 reversed. Fixed.

2014-12-14T13:18:47Z

The explanation in simpler terms had the terms L_1 and L_2 reversed. Fixed.

en>Sadads: removing orphan tags, removed orphan tag using AWB

2010-11-30T23:22:27Z

removing orphan tags, removed orphan tag using AWB

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A '''cosmological decade ( CÐ )''' is a division of the [[Chronology of the universe|lifetime of the cosmos]]. The divisions are [[logarithmic scale|logarithmic in size]], with base 10. Each successive cosmological decade represents a ten-fold increase in the total [[age of the universe]].<ref>{{cite book
| last = Adams | first = Fred | authorlink =
| coauthors = Greg Laughlin
| title = The Five Ages of the Universe
| publisher = Free Press | date = 2000 | location =
| pages = | url = | doi = | id = | isbn = 0-684-86576-9 }}</ref>

==As expressed in log (seconds per Ðecade)==
When CÐ is measured in log( seconds/Ð ), ''CÐ'' 1 begins at 10 [[second]]s and lasts 90 seconds (until 100 seconds after Time Zero). ''CÐ'' 100, the 100th cosmological decade, lasts from 10100 to 10101 seconds after Time Zero. CÐ <math>-\infty</math> is Time Zero.

The [[epoch (astronomy)|epoch]] ''CÐ'' −43.2683 was 10(−43.2683) 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, ''CÐ'' 17.6389, is 10(17.6389) seconds, or 13.798(37) billion years, since the Big Bang.<ref name='planck_cosmological_parameters'>{{cite journal | arxiv=1303.5076 | title=Planck 2013 results. XVI. Cosmological parameters | author=Planck collaboration | journal=Submitted to Astronomy & Astrophysics | year=2013|bibcode = 2013arXiv1303.5076P }}</ref> 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 10100 years to 10101 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:
{| class="wikitable"
! Age !! Ðecades !! Process
|-
|Primordial || −50 to +5 || [[Timeline of the Big Bang|from the Planck time until universe becomes transparent to radiation]]
|-
|[[Timeline_of_cosmological_eras#Structure_formation|Stelliferous]] || 6 to 14 || stars shine brightly (our current epoch is +10.1364)
|-
|Degenerate || 15 to 37 || stars degenerate, get dimmer
|-
|Black Hole || 38 to 99 || stars evaporate, galactic black holes evaporate
|-
|Dark Era || 100 onward || [[Timeline of cosmological eras|lone protons and other particles get even farther and farther apart from each other]]
|}

==References==
<references/>

{{Time measurement and standards}}

[[Category:Physical cosmology]]
[[Category:Units of time]]

{{astronomy-stub}}
{{measurement-stub}}

Left quotient - Revision history

137.165.167.183: The explanation in simpler terms had the terms L_1 and L_2 reversed. Fixed.

en>Sadads: removing orphan tags, removed orphan tag using AWB