The Earth is old. Very old. About 4.54 billion years old. That's 4,540,000,000. The number of years the Earth has been around is about an inch long on my screen. It can be hard to grasp just how very, very old the Earth is, so geologists developed what they call the Geologic Time Scale, or Deep Time, which is like a calendar with much bigger intervals.It measures time between major periods of the Earth's formative years. It starts off in the Precambrian Period, which is literally 86% of our planet's history, and we know little to nothing about it. The Earth went from a ball of molten rock to a life-sustaining planet with its very own moon in the roughly four billion years of the Precambrian.
It's subdivided, of course, and we do know some of the history. We know, for example, that the earliest evidence of primordial life crops up in the fossil record around 4 billion years ago, and the oldest definitive proof of said primordial life comes from about 3.6 billion years ago. We know that photosynthetic organisms started producing oxygen (you know, that stuff we breathe?) in large amounts about 3.5 billion years ago, which eventually caused an ecological catastrophe when it changed the composition of the Earth's atmosphere. More on that in a later post, because damn.
|Then this thing happened on our planet.|
The Precambrian Era ended, appropriately enough, with the Cambrian Explosion, in which animals suddenly evolved out of nowhere and started taking over the food chain. And inventing the food chain, because it really wasn't much of a thing yet. From there, stuff happened. A lot of stuff, but I'm not here to give you a rundown of everything that has ever happened on Earth. I'm here to give you a sense of perspective.
To that end, let's imagine that everything that has ever happened, happened within one year. The formation of the Earth happened at midnight on January 1. Today, at this moment, it is midnight on January 1 of the following year. On this scale:
- The earliest stages of life didn't come around until February 25th.
- Oxygen appeared in the atmosphere on June 13th, almost halfway through the year.
- Animals didn't come around until November 15th.
- Dinosaurs appeared on December 9th and were completely snuffed out by December 24th after only two weeks of existence, if you don't account for different species. Which is irresponsible.
As for humans? We just showed up four minutes ago as a species, and for most of that time we've been sitting around and scratching out heads. It wasn't until four seconds ago that anyone figured out we could write something. On the grand scale of geologic time, all of human history has been recorded in the last four seconds.