The Cosmic Calendar - How Old is the Universe?

Our universe is undeniably massive, but it's also incredibly old. 14 billion years old.

According to our best estimates, the universe is 13.8 billion years old. It goes without saying that that’s extremely old. But just how long of a time is 14 billion years? The human mind has a way of underestimating massive numbers. So, to truly understand the implications of a nearly 14-billion-year-old universe, we need a scale model. Famous astronomer and science communicator Carl Sagan introduced the concept of the cosmic calendar for exactly this reason.

The cosmic calendar is a scale model, not of size, but of the history of the universe in which we take its entire 14-billion-year history and compress it into a single calendar year. That means that the very first moment of the year, as the clock strikes midnight on January 1, is the Big Bang. Likewise, the very final moment before the clock strikes midnight on December 31 is the present. Everything else in between is the history of the universe. Every second on this scaled year is equal to 438 years in reality.

The Beginning of the Universe

Following the Big Bang and the formation of the universe, there was a period in which the entire universe was nothing but a big cloud of hot, dense plasma. This plasma was everywhere you looked, and therefore the universe was opaque. You could not see through this plasma. Since light takes time to travel to us, that means the farther away in the universe we look, the farther back in time we see. The farthest we can see in the universe is the remnant light of this time, and we see it in all directions. We call this light at the edge of the universe the Cosmic Microwave Background. This opaque era of the universe lasted about 380,000 years before everything had cooled down enough to see through it. And yet, on the cosmic calendar, the last light of the Cosmic Microwave Background came at 12:14 am on January 1st. Only 14 minutes from the start of the year.

Things started to slow down after that. It took nearly a billion years before the first galaxies began to form. This puts us at January 26 on the cosmic calendar. Our own galaxy, the Milky Way, would have formed about another 2 billion years after that, 11 billion years in the past, on March 1. As for our Sun and the Solar System? Those didn’t form until 4.5 billion years ago, which on the cosmic calendar brings us all the way up to September 9. If you want to see the Earth, you’ll have to wait a couple more days on the calendar, as it first shows up on September 14.

Life on Earth

It took nine and a half months on the cosmic calendar to go from the beginning of the universe to the formation of the Earth. We’ve already traveled through over three-fourths of our total year, and even at this point, the Earth would be nothing but a lifeless rock. To see the Earth we know and love, we’ve got to wait even longer. It turns out, once you get the Earth, it doesn’t take that long to get life. “Only” about half a billion years. The first signs of life on Earth appear a week after Earth’s formation on the cosmic calendar, on September 21.

But still, even with life on Earth, it wasn’t a familiar place. This was simple single-celled life. To really see the start of more familiar life, such as animals, you have to wait another two and a half months, December 7, to see the most simple and basic of animals. As for the dinosaurs, the most well-known extinct animals? They don’t pop up until 230 million years ago. That brings us all the way to December 25. Apparently the dinosaurs were Earth’s Christmas gift.

Human History

Let that sink in for a moment. We’ve made it up to December 25, only to see the earliest dinosaurs. There are only six days left out of our entire cosmic calendar, and we still haven’t seen any signs of humans. Surely they must pop up right away, right? Wrong. The dinosaurs don’t go extinct until December 30, and humans don’t appear until after the dinosaurs are gone. Now there’s only one day left for humans. If you want to see some humans on the cosmic calendar, you’re going to have to wait until December 31 at 8:00 pm. A measly four hours before midnight contains the entire 7 million years of human history.

But, in reality, that’s not really human history. That’s the history of our earliest ancestors that we could consider human. Our modern species, Homo sapiens, doesn’t appear until about 200,000 years ago, which equates to December 31 at 11:52 pm. That’s it. Eight minutes from midnight is all the modern human species gets. That is our entire history.

Except for one problem. History is usually considered to begin with the earliest forms of writing. It’s not history until someone can write it down so we can know exactly what happened. Some of the earliest civilizations, such as Mesopotamia and Egypt, only appeared 5,000 years ago. So, the entirety of recorded human history only lasts a measly 12 seconds on the cosmic calendar. What we consider to be modern history, the past 500 years or so, is only the final second before midnight.

The Cosmic Calendar. All 14 billion years of the history of the universe condensed into a single year. Image Credit: "Cosmic Calendar" by Efbrazil  (CC BY-SA 3.0)

Human timescales simply cannot compare to cosmic ones. In the grand scheme of things, humans are the newcomers in our universe. We’ve only been able to witness the smallest of fractions of the universe’s history for ourselves. The 200,000 year period our species has existed is only 0.0015% of the entire history of the universe.

But, if you look at things from a different perspective, even the entirety of the universe’s history so far, is nothing compared to the amount of time left in the universe. Even the theories placing the death of the universe at the earliest possible time, place it 33 billion years in the future. So on a revised cosmic calendar, where the end of the universe is the moment before midnight on December 31, that would put the modern day as being April 17. In some theories, the end of the universe is so far ahead of us that the modern day on the revised cosmic calendar would still take place early on January 1.