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Cosmic Calendar


By Jonathan - Posted on 05 April 2009

I'm a sucker for a good story, and modern science has a fascinating story to tell. Only recently have I begun to wholeheartedly listen to its story. And call me self-centered, but I love stories about me. I love to hear about my past and how I came into the world. Further, a childlike curiosity drives me to understand why the world is the way it is. Science has a barn burner of a story.

The effort to understand the universe is one of the very few things that lifts human life a little above the level of farce, and gives it some of the grace of tragedy.—Steven Weinberg

In recent centuries, we have teased out fragments of our origin story, a tale strange and vast. It is inextricably bound to the story of the origin of the universe, for the universe gave birth to us. If its story had been different, we would be different—if we existed at all. The story occurs on a timescale that is almost beyond human comprehension. We have become accustomed to think of history as a few thousand years after we learned to write, or perhaps a few million years beyond that. Perhaps the dinosaurs seem like deep history. This utterly pales in comparison to the real story. Human history is only the smallest part of the story. Even dinosaurs or callow newcomers on the universal stage. Words fail (as they often do) to convey understanding. I want to experience this story for myself, to get a small taste of the true proportions of history.

One way we have experienced our stories in the past is through rituals and festivals marked out on a calendar. Early calendars made sense of the yearly rhyme of season and flood. Within the yearly cycle, we placed holy days commemorating important events, important gods, rites of initiation, and the world's mythic creation. The yearly repetition increased our connection to our world and imparted a sense of continuity to our lives.

Someone's genius guided them to combine the great story of science with the calendar. The premise of the remix is simple: take the history of the universe from its beginning to the present day and condense it to the span of a single year. Mark milestones in the history of the universe on the calendar as they happen at that reduced scale.

I first saw Carl Sagan present the Cosmic Calendar as part of his wonderful Cosmos series.1 I loved flying with him as a child in his ship of the imagination. He introduced me to the beautiful and fascinating world around me as seen through the curious, playful, shrewd eyes of scientific inquiry. His Cosmic Calendar is an excellent example of how thought provoking he was as a educator. He is missed.

He presents the Cosmic Calendar masterfully and humanely, and it still inspires me. Scientific understanding has progressed since he recorded that program. For example, scientific consensus tells us that the universe is most likely to be about 13.7 billion years old rather than 15 billion, and the Milky Way is thought to have formed much earlier than Sagan stated.

I have decided to update and extend the original Cosmic Calendar and to to follow the Cosmic Calendar for a year. Rather than just reading about our history, I wanted to experience it in a modern ritual. It's one thing to read about something or see it illustrated in a diagram; it's another thing entirely to experience the long year and watch as milestones pass by. When something happens on the Cosmic Calendar, I'll post about it and give some background, maybe suggesting some places to investigate further or ways to observe the holiday.

At the time scale of a revised Cosmic Calendar:

1 year = 13.7 billion years
1 month ≈ 1.1 billion years
1 day = 37.5 million years
1 hour = 1.5 million years
1 minute = 26,000 years
1 second = 434 years
0.16 seconds ≈ 1 modern human lifetime

I can't get over the fact that my life is literally less than a blink of the eye on the Cosmic Calendar. How ephemeral am I! While I am saddened by the relatively short duration of my life, I am awestruck by the vastness of time.

If you would like to follow along, it may help to subscribe to my version of the Cosmic Calendar (XML or iCal).2

Caveat lector

I am not an expert on any of the materials included in the calendar, only an interested layman. It is highly likely that I will make mistakes in compiling the calendar. I will cite my sources—too many from Wikipedia I suspect—and endeavor to improve the calendar as time goes on.

Also note that science operates on consensus. The corollary to that is there will always be disagreement at the limits of science. I have tried to harmonize any conflicting information that I have found, but in the hands of a hobbyist, the nuances of the scientific debate is sure to get mangled.

I could have renamed this the Human Advent Calendar because this is the story of our coming into the world. It begins to answer the questions "Who am I?" and "Where did I come from?" from a human perspective. It may be self-centered, but as I said, I like stories about me. However, this shouldn't be taken as an endorsement of the idea that homo sapiens is the culmination of creation. It seems perfectly clear that we are just another wayfarer in the epic tale of this universe. The rest of the universe has just as much claim as we to the title of center of the universe.

As a last warning, science moves on. This calendar, even where it fairly represents current scientific understanding, should not be taken as dogma. If new data come in that conflict with the calendar, out with the old, in with the new; no regrets.

Further Study

Maps of Time: An Introduction to Big History by David Christian

The Structure of Big History: From the Big Bang until Today by Fred Spier

Big History: From the Big Bang to the Present by Cynthia Stokes Brown

Big History: The Big Bang, Life on Earth, and the Rise of Humanity (lectures) by David Christian


1. It was also published in his book The Dragons of Eden.

2. Anyone who wants to verify my dates can check the source code for the script I wrote just for this purpose. I sometimes used a calculator and a day-of-year table as a sanity check.