Taking Time to Think About Time

Matt Lowry

Well folks, it's that time of year again... when the calendar has been ticking down to midnight on December 31st and will soon roll over to the New Year. It's been a time for reflection on the past year and a look to the future for what the next year holds. And so the cycle goes, year after year.

So, in this installment of my "Thoughts", I wanted to talk about time and our limited human perception of it. I often think that we don't truly appreciate just how awesome a thing time is, so here goes...

In our normal human experience, we often think of time on daily, weekly, or monthly cycles. This is usually due to our job or familial commitments, and with the hustle and bustle of our lives, it is often difficult to break our minds out of this shortsighted cycle of time. Sometimes we may look ahead, or behind, by a few years or even decades - one can imagine such thinking dominating in a history class, for instance. But, to be honest, most of us don't think that far ahead (or behind).

But let's try, for a moment, to break out of our mold. What about pondering time scales of thousands, hundreds of thousands, millions, or even billions of years? I mean the kind of time that literally staggers the mind of even the most scientifically educated among us. We astronomers often communicate to the public just how unbelievably large the universe is... but what about how incredibly old it is?

This is the concept that is commonly referred to as "deep time". In order to understand deep time more efficiently, I'd like to use the analogy developed by Carl Sagan in his Cosmos series - the "cosmic calendar". On this cosmic calendar, each month would represent a little bit over one billion years, with the end of the year, midnight on December 31st, representing the present moment.

Let us suppose that on January 1st at 12:00:01am the universe as we know it is created by the sudden expansion of space-time from a singularity in the event we call the Big Bang. In real time, that is about 14 billion years ago.

It isn't until the month of March, about 2-3 billion years later, that large galaxies like our own Milky Way begin to form into the structures we are familiar with today.

From April to August, a staggering 5-6 billion more years, the first generation of stars in the universe start to die out, spreading the newly formed heavy elements throughout the cosmos as they undergo their death throes. During this time, the later generations of stars begin to form.

In August, our own Sun forms along with the major planets that make up our solar system from a great cloud of gas and dust. The heavy elements that form so much the rocky inner worlds are the products of those old, dead stars, and the Earth is formed and begins to cool as the cosmic summer draws to a close.

During the month of September, as the cosmic autumn is beginning, just about 1 billion years after Earth's formation, the most primitive forms of life develop on our planet. From this point on, biological evolution takes over in our own little corner of the cosmos.

Throughout the month of October on into November, with the cosmic winter fast approaching, the evolution of life on Earth is slow, pain-staking and not greatly productive. But in November, the first multi-cellular organisms finally begin to appear.

In December, a lot of things start to happen, so I'll start breaking it down by the dates...

- On December 15th, there is the mysterious Cambrian explosion which, taking place over tens of millions of years, leads to a burst of newly evolved life forms unlike anything ever seen on Earth before. - On the 17th, the first vertebrates appear. - Early land plants come on the scene on the 18th. - The first four-limbed animals then show up on the 20th, with the insects beginning to flourish a bit later on the 21st. - On Christmas Eve, December 24th on the cosmic calendar, the dinosaurs finally appear, soon to be followed by our first mammalian ancestors on Christmas Day. - By the 27th, the first birds have evolved. - On the 28th, the dinosaurs, along with much of the life on Earth at that point, are wiped out by the freak impact of a large asteroid or comet with the Earth. Mammals become the dominant form of life on Earth.

And now, most of what we know as history or pre-history takes place on New Year's Eve on our cosmic calendar...

- By 10:15am on New Year's Eve, apes appear. - At 9:24pm, the first human ancestors begin to walk upright. - Homo erectus appears at 10:48pm. - Anatomically modern humans come on the scene at 11:54pm. - Writing is invented at 11:59:45pm. - The great Pyramids of Egypt are built at 11:59:50pm, a mere 10 seconds before the end of our year on the cosmic calendar. - And, at long last, one second before midnight, Christopher Columbus sails from Europe in search of the New World.

All of our recorded history, the rise and fall of empires, the great stories of the ages, the greatest works of humankind ever known all fit within the last few seconds of our cosmic calendar.

I like this view of deep time - it both humbles and exhilarates me to know the vastness not only of the size of our magnificent universe, but the age of it as well. After all, in the grand scheme of things, we humans are a very, very young species. The atoms that form our bodies are older than we can fathom, created in the violent birth and death of stars from many eons past. We are made of star stuff, the descendants of the Big Bang that started our cosmos those many billions of years ago, back in the mists of the cosmic spring so long ago.

One has to wonder: What will the next cosmic year hold?

Ad Astra! - Matt Lowry