A Cosmic Calendar[^0]

<Chinese version>

 

(1) About Cosmic Calendar

(2) For Pre-December Dates

(3) For Month of December

(4) For December 31 (new year's eve)

(5) A Quick Reference: Geologic Time

 

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(1) About Cosmic Calendar (by Carl Sagan)

[...THE WORLD is very old, and human beings are very young. Significant events in our personal lives are measured in years or less; our lifetimes in decades; our family genealogies in centuries; and all of recorded history in millennia. But we have been preceded by an awesome vista of time, extending for prodigious periods into the past, about which we know little -- both because there are no written records and because we have real difficulty in grasping the immensity of the intervals involved.

Yet we are able to date events in the remote past. Geological stratification and radioactive dating provide information on archaeological, palenotological and geological events; and astrophysical theory provides data on the ages of planetary surfaces, stars, and the Milky Way Galaxy, as well as an estimate of the time that has elapsed since that extraordinary event called the Big Bang -- an explosion that involved all of the matter and energy in the present universe. The Big Bang may be the beginning of the universe, or it may be a discontinuity in which information about the earlier history of the universe was destroyed. But it is certainly the earliest event about which we have any record.

The most instructive way I know to express this cosmic chronology is to imagine the fifteen-billion-year [^1] lifetime of the universe (or at least its present incarnation since the Big Bang) compressed into the span of a single year. Then every billion years of Earth history would correspond to about twenty-four days of our cosmic year, and one second of that year to 475 real revolutions of the Earth about the sun... I present the cosmic chronology in three forms: a list of some representative pre-December dates; a calendar for the month of December; and a closer look at the late evening of New Year's Eve. On this scale, the events of our history books... are so compressed that it is necessary to give a second-by-second recounting of the last seconds of the cosmic year... In the history of life, an equally rich tapestry must have been woven in other periods -- for example, between 10:02 and 10:03 on the morning of April 6th or September 16th. But we have detailed records only for the very end of the cosmic year.

The chronology corresponds to the best evidence now available. But some of it is rather shaky. No one would be astounded if, for example, it turns out that plants colonised the land in the Ordovician rather than the Silurian Period; or that segmented worms appeared earlier in the Precambrian Period than indicated. Also in the chronology of the last ten seconds of the cosmic year, it was obviously impossible for me to include all significant events; I hope I may be excused for not having explicitly mentioned advances in art, music and literature or the historically significant American, French, Russian and Chinese revolutions.

The construction of such tables and calendars is inevitably humbling. It is disconcerting to find that in such a cosmic year the Earth does not condense out of interstellar matter until early September; dinosaurs emerge on Christmas Eve; flowers arise on December 28th; and men and women originate at 10:30 P.M. on New Year's Eve. All of recorded history occupies the last ten seconds of December 31st; and the time from the waning of the Middle Ages to the present occupies little more than one second. But because I have arranged it that way, the first cosmic year has just ended. And despite the insignificance of the instant we have so far occupied in cosmic time, it is clear that what happens on and near Earth at the beginning of the second cosmic year will depend very much on the scientific wisdom and the distinctly human sensitivity of mankind...]

------ Ref: <The Dragons of Eden> by Carl Sagan (1977)

 

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(2)

 

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(3)

 

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(4)

 

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(5)

A quick reference for various terms of geologic time mentioned in cosmic calendar.

 

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以下为本文的注解(Ref):

• [^0] 上网日期Posted: 02/Oct/2000(10月2号) --- 更新日期Updated: 08/Oct/2000(10月8号) --- 草稿Draft: (原稿dd/mm/yyyy) (发稿dd/mm/yyyy, [x]) (修稿dd/mm/yyyy) (Changed to HTML5 version, added two Ref, [^0] and [^1], 24-25/03/2021. On 01-02/04/2021, has expanded Ref [^1] to include two formula: N=[(366-T)/365]*15b, and T=366-(365*N)/15b, as well as their explanation, a table showing number of days in each month was also added.)
  
  
• [^1] In year 1977, when Carl Sagan published his book, The Dragons of Eden, the age of the universe estimated by scientist was 15 billion-year old. Now, in year 2021, a more accurate estimation is 13.8 billions@ years.
  
  The Cosmic Calendar use here will still base on 15 billion-year, i.e. 1 year has 365 days, => 1/Jan=(365/365)*15b=15b yr ago, 2/Jan=(364/365)*15b=N yr ago, 3/Jan=363/365)*15b=N yr ago, ......, 29/Dec=(3/365)*15b=N yr ago, 30/Dec=(2/365)*15b=N yr ago, 31/Dec=(1/365)*15b=N yr ago.
  
  From the above calculation, we can deduce a formula: N=[(365-(T-1))/365]*15b, and after simplify, it becomes: N=[(366-T)/365]*15b, and T=366-(365*N)/15b.
  
  N is the number of year, 15b is 15 billion => 15000000000, T is the total days counted from 1/Jan, eg: (1/Jan, T=1), (2/Jan, T=2), (3/Jan, T=3), ......, (29/Dec, T=363), (30/Dec, T=364), (31/Dec, T=365).
  
  The following table (with number of days in each month) shows the calculation method of T:
  
  

  月份(Month)	天数(Day)	总天数(TotalDay)=T	备注(Remark)
  1	31	31	1/Jan, T=1
  2	28	28+31=59	-
  3	31	31+59=90	21/Mar, T=21+59=80
  4	30	30+90=120	-
  5	31	31+120=151	1/May, T=1+120=121
  6	30	30+151=181	-
  7	31	31+181=212	-
  8	31	31+212=243	-
  9	30	30+243=273	14/Sep, T=14+243=257
  10	31	31+273=304	-
  11	30	30+304=334	-
  12	31	31+334=365	31/Dec, T=31+334=365

  
  例子(Example)
  
  Base on age of the universe = 15 billion-years
  
  (1) From date on the calendar to find out the corresponding T and N:
  
  Date on the calendar = 1/May
  => T=1+120=121
  => N=[(366-121)/365]*15b=10.068b, (about 10.1 billion-years ago)
  
  (2) From the known N (number of year) to find out the corresponding T and date on the calendar:
  
  Formation of the Earth is known to occur around 4.5 billion-years ago.
  => N=4.5b
  => T=366-[365*4.5b]/15b=256.5, => T=257
  => Date on the calendar = 14/Sep
  
  NB1:
  
  Per day = 15b/365 = 41.1 million years
  
  Per hour = 41.1m/24 = 1.71 million years
  
  Per minute = 1.71m/60 = 28,500 years
  
  Per second = 28500/60 = 475 years
  
  Base on age of the universe = 13.8 billion-years
  
  (3) From date on the calendar to find out the corresponding T and N:
  
  Date on the calendar = 1/May
  => T=1+120=121
  => N=[(366-121)/365]*13.8b=9.263b, (about 9.3 billion-years ago)
  
  (4) From the known N (number of year) to find out the corresponding T and date on the calendar:
  
  Formation of the Earth is known to occur around 4.5 billion-years ago.
  => N=4.5b
  => T=366-[365*4.5b]/13.8b=246.9, => T=247
  => Date on the calendar = 4/Sep
  
  NB2:
  
  Per day = 13.8b/365 = 37.8 million years
  
  Per hour = 37.8m/24 = 1.58 million years
  
  Per minute = 1.58m/60 = 26,300 years
  
  Per second = 26300/60 = 438 years
  
  To form a Cosmic Calendar base on 13.8 billion-year, one can use the above method, just replace 15b by 13.8b will do.