January 19th

Thinking About Time

On this day in dinosaurs, we examine the distance that separates us from the Mesozoic superstars. The know there is a great deal of time between our modern world and that of the dinosaurs, but it’s difficult to understand how much time has passed. For one, our brains aren’t hardwired to easily comprehend time at a millennial scale. This sort of reasoning does not improve our daily survival, but for our longtime survival, it’s becoming increasingly important that we understand our place in the narrative of life on earth–a narrative that we are shaping more with each passing year.


So how can we begin to fathom the enormity of time recorded in our planet’s geologic history? We can start on the scale of our universe. This was the tactic Carl Sagan, Ann Druyan, and Steve Soter used when creating the original series of Cosmos in 1980. They envisioned a cosmic calendar that compressed the history of our universe into a single year. Imagine that the big bang takes place in the very first instant of the year, 12 a.m. on January 1st. And the last second of the year is the moment you are reading these words.


With the entire year established in mind, you may find it interesting to learn that our star and its planetary system do not take shape until August. For most of the cosmic calendar, our home and the solar system don’t even exist.


Multi-cellular life doesn’t appear on earth until November. Almost the entire year has passed before life really gets going into anything we’d recognize today. So where do the dinosaurs arise? Christmas Eve, December 24th. The long, long reign of the non-avian dinosaurs is over on December 29th. The seemingly interminable dinosaur kingdom ends in less than a week on the scale of our universe. And modern humans, we appear at 11:54 on New Year’s Eve. Civilization is just a few seconds at the end of the year.


While cosmic thinking can be humbling and provides context for our world, it’s not always the most useful way to describe the history of life on our planet. Let’s re-calibrate and think on a different scale.

The Mesozoic Era–the age of reptiles or the age of the dinosaurs–began 252 million years ago. Paleontologists call this early portion of the Mesozoic the Triassic period. Dinosaurs, small and inconspicuous, arrived toward the end of Triassic. From a scientific standpoint, the Triassic lasts 51 million years (255 times the duration that anatomically modern humans have existed).

Beginning around 200 million years ago, the Jurassic period sees the dinosaurs rise to terrestrial dominance. Throughout the next 56 million years, giants like Brontosaurus, Apatosaurus, Stegosaurus, and Allosaurus take their place in the dinosaur pantheon. Dynasties rose and fell. Species adapted to their environment for a few million years and then gave way as continents changed, seas rose and fell, and mountain ranges were thrust up.

The third and final dinosaur epoch, the Cretaceous lasted from 145 million years ago to the mass extinction event 66 million years ago. Tyrannosaurus, Triceratops, the “duck-billed” hadrosaurs, and other favorites represent some of the very last dinosaurs to evolve during this time, a duration of 79 million years. The Cretaceous itself lasts longer than the time that separates our present day from the asteroid impact. It’s also worth remembering that there is more time between the famous Jurassic dinosaurs and T. rex than between the tyrant lizard king and us.

All this time is mind-boggling. But next time you’re outside and hear birds chirping, you’ll have a much better appreciation for their staying power. And I hope a better appreciation for your own tiny part in this epic and ongoing story.

Share your thoughts and pictures of your favorite lifeforms from earth’s history with us on Facebook and Twitter using the hashtag #TDIDinos.