Translator: Luca Dinu Reviewer: David DeRuwe Hello. How old is this rock? What is the history of this rock?
Did you know that rocks have histories? Every rock has a beginning, a middle, and an end. So does this one.
I'm here, today, to talk to you about time. But it's not your usual, everyday time, with its ticking and tocking, where you wake up really early in the morning and go to bed really late. Nor am I going to talk about the average lifespan of a person, the 70 or 80 years when you grow up, fall in love, get married, and die.
I'm here to talk about geological time. There are many technologies that allow us to study these rocks. By looking at the mineralogical content of this rock, we can find out its history, the history of the region it was found in, the history of a country, a continent, and even extrapolate to outer space.
Rocks can also have fossils. Fossils tell us about history. As many of you know, every rock has an age that reflects the age of the Earth, which is 4.
6 billion years old. And this rock, this simple rock, which came from Rio Grande do Norte, 40 miles north of the city of Natal, is 3. 4 billion years old.
It can tell us a story. If we compare geologic time to a clock, with 4. 6 billion years being equivalent to 24 hours, then during the period between the beginning and 9:00 PM, life on Earth was microscopic and unicellular.
When did things start to change? During 80% of that 21-hour period, these small creatures were the main lifeform. Everything started to change at 2:00 AM of that same day.
But what was the Earth like back then? There was a series of meteor showers, comets, and all sorts of things hitting the Earth because it didn't have an atmosphere. The Earth was constantly being bombarded.
The Earth's temperature was extremely high. The crust, the hard part where we live, was very thin. Then, around 11:00 AM, free oxygen appeared.
Up until that point, meteors were hitting the Earth, and it didn't have any protection. It had no atmosphere or stratosphere to protect it. And life went on.
Or rather, the Earth went on. There was a moment, 600 million years ago, when life first appeared, and that early life is known as the Ediacaran biota. No one knows if it consisted of animals or plants.
It was preserved in 600-million-year-old rocks, more or less at 9:00 PM. Life continued, the Earth continued, and at 9:10 PM, 541 million years ago, the first differentiated lifeforms with exoskeletons appeared, represented here by this large predator, Anomalocaris. There's nothing like it today.
Anomalocaris was the top predator at 9:10 PM. And the history of the Earth went on. Researchers created a table showing geologic time that starts at precisely 541 million years ago because rocks that are 541 million years old or younger have fossils that show what life used to be like on Earth, what age the rocks were, etc.
That's why they created this table that goes back 4. 6 billion years, but starts at 541 and ends at 0 at the top. All the horizontal lines indicate times where there was environmental stress on Earth, stress that led to the extinction of many animals and plants.
But, scientists say five were the most impactful and catastrophic. You can see them here. In these five events, the Earth and life on Earth narrowly escaped total destruction.
The first one happened just before 11:00 PM, 251 million years ago. It happened at the Permian-Triassic boundary, between the Permian and Triassic periods. The land on the Earth was one big supercontinent: Pangaea.
Animals could go from one end of it to the other. At that moment, life on Earth was virtually extinguished, and 90 to 95% of all life went extinct due to drastic environmental changes. Time went on, and now we're at the end of the Triassic period, 201 million years ago.
The dinosaurs that appeared at the beginning of the Triassic, here in Rio Grande do Sul and in northern Argentina, were small and starting to get bigger. They were slightly bigger than chickens. So, 201 million years ago, the Pangaea supercontinent started to break apart, and gigantic volcanic events took place that changed the Earth's temperature, so much so that 80% of all species went extinct.
The Earth went on, and now we've arrived at 66 million years ago. The dinosaurs were enormous. No animal in the history of the Earth had ever been so big.
Time went on, and 66 million years ago, life on Earth was decimated again, mainly because of two factors: volcanism in India, which was colliding with the Himalayas, and a meteor strike in Yucatán, in Mexico, close to Cancún. The meteor strike that happened 66 million years ago was so powerful, it would be a 13 on the Richter scale, which would be incredibly devastating for us today. The most powerful earthquake we've known registered 9.
5 on the Richter scale. Very well. To give you an idea, the shock from the meteor strike may have been so powerful it was night around the world for three years.
If there's no night, there's no photosynthesis; if there's no photosynthesis, there are no plants. So the herbivores' food source disappeared, and then, so did the carnivores'. The food chain was completely disrupted.
But don't worry. Life survived. And after the extinction of the dinosaurs, came the rise of the mammals.
Mammals already existed, and they adapted to the disappearance of the large predators. The dinosaurs went extinct 66 million years ago, and as a result, mammals proliferated. But here I have another rock.
This rock was found about 3,000 km off the coast of Rio de Janeiro, 3000, at a depth of 3,000 meters, plus 2,000 meters of drilling. Scientists look at these rocks and find microfossils. The microfossils you see here, and in particular this one, survived the environmental stress.
Their shells are great recording devices and provide a record of what the chemistry of the water was like 66 million years ago, what the water temperature conditions were like 66 million years ago, what the currents were like, and allow us to reconstruct what the oceans were like. But the question is: "What about Homo sapiens? Where's Homo sapiens in all this?
" Now, I told you, the extinction of the dinosaurs was 66 million years ago, around 11:30 PM, and Homo sapiens still hasn't shown up. Homo sapiens appeared 300,000 years ago - here, represented by someone you'll recognize. On this clock, Homo sapiens appears at 11:59:54 PM.
That means we've only been around for six seconds. In the last five to ten years, scientists have been debating about the appearance of a new epoch, called the Anthropocene. We might be going through the sixth extinction event without people even noticing it.
As I said, rocks are millions of years old. Human beings have an average lifespan of seventy. Now, what could be the reasons for these changes?
One of them might be related to the population of the Earth. The global population is increasing considerably. At the time of Christ, the global population was 200 to 300 million people.
That's about the population of Brazil spread out across the entire world. In 1804, there were 1 billion people. Later, this number grew to 2 billion.
Then 3 billion. Four, five, six, seven . .
. And today, there are 7 billion 576 million of us, living and breeding like rabbits. Now, you see it took humans 300,000 years to get to a billion people, and now, the population is growing by a billion every ten years.
Scientists say the world population will reach a state of equilibrium at about 10 billion people. But the big debate is around when the Anthropocene started. What mark did it leave on the rocks I just showed you?
What is the main indicator? The main indicator is nuclear detonation radiation. The nuclear tests conducted in the '40s and '50s left their marks on rocks, which will bear signs of radiation forever, signs that can be detected with the right equipment and technology.
The big question is: how are we going to stop this? The question I would ask is: if we're so smart, and given that we've only been here for such a short while, why don't we do something about it? Thank you.
