This is a moment before time and space. It does not have a duration, nor a location. Our universe doesn't exist yet, we are suspended in some other dimension.
This existence is completely hypothetical, science still has no resources to investigate this scale of reality. But the time is about to begin. BANG This is the first instant of time.
This series will investigate the events from that point, until the present day, to understand how we left an infinitely dense and hot universe, until you, watching this video. We'll find out how Earth formed, when life emerged, and what challenges our ancestors faced in order for us to be alive today. This story is yours, it's every human being you've ever known, every organism that's ever lived.
By the end of this series, we will have advanced 13. 8 billion years into the future, to a special day called today. Let's go beyond the barriers of time and imagine the future and the last days of the world.
It will be an exciting journey from the birth to the death of our home: planet Earth. This first episode will cover the Hadean Eon, the first 600 million years of Earth. The most infernal, most violent, but also definitive period in our history.
Welcome to Hadean. The most common elements on Earth are: Iron (32. 1%), oxygen (30.
1%), silicon (15. 1%), magnesium (13. 9%), sulfur (2.
9%), nickel ( 1. 8%), calcium (1. 5%) and aluminum (1.
4%) None of these elements even existed when the universe began. They are elements much heavier than the hydrogen and helium that make up stars. All of these elements were formed in the cores of past generations of stars, and most can only be produced during a supernova.
Supernovae are the scandalous deaths of stars with immense masses, and in them, almost all the elements of the periodic table are formed from the fusion of lighter elements. This means that the Earth is made up almost entirely of the remains of star corpses! Or as Carl Sagan would say, we are made of stardust.
These elements are not evenly distributed on the planet. The lightest are on the surface and atmosphere, and the heaviest in the core. The Earth can be divided into 5 major layers: The atmosphere, the outermost part of the planet, is made up of gases, mainly nitrogen and oxygen.
Carbon plays a very small part in the composition of the atmosphere, despite its immense climatic importance. The crust is mostly made up of lots of oxygen and silicon, but also calcium, aluminum, and iron. Beneath the crust, which is broken into several tectonic plates, is the Earth's mantle, a convection zone for magma.
There, where what is below heats up and rises, and what is above, cools and descends, forming immense gyres that dynamize the surface. Beneath the mantle is an immense ocean of molten iron, also swirling. This is the outer core.
The motion of this layer is what likely forms the planet's electromagnetic field. It's amazing to think that such an inner layer of the planet is responsible for keeping the outermost layers protected, like Earth's atmosphere and hydrosphere. And the Earth's core is made of solid iron and nickel, rich in radioactive elements, the decay of which is a source of heat.
Earth-like planets made of iron and oxygen could not have existed in the universe's first generations of stars. Our universe is still very young, it is 13. 8 billion years old, which means that some types of stars have never died of old age* White dwarfs, for example, can live for hundreds of billions of years, and they are all in their infancy!
Which means that all the rocky planets that exist today in the entire universe are among the first of many that will still exist. They are likely to become increasingly common as the universe becomes older and more metallic. And Earth is a middle-aged planet.
But she is a very well preserved crown! Let's get to Earth's secret to becoming more and more lush, while her brothers rocky planets, Mercury, Venus and Mars fell into decay and became old and dead planets. But this can also be disconcerting for those who believe that the Earth was made to support human life!
For 4 billion years, Earth has not supported any plants, animals or fungi. In fact, during that eternity of time, it would be an inhospitable and unbearable place. Why complex life wasted so much time?
? That's what we're going to investigate. .
. . This is the Hadean eon, the first chapter of Earth time.
The name is in reference to Hades, the god of hell in Greek mythology. For its first few million years, our world was one of many balls of red-hot magma orbiting the Sun in formation. As it grew, the energy from the impacts was so great that it didn't even have a surface.
The world was globally covered by an ocean of molten rock, and a thick, mushy atmosphere of rock vapour. This is the accretion phase, 4. 6 billion years ago, the gestation of our world.
But we do not count this time in Earth's history, we are still a little before its true formation, in the same way that our birthday is celebrated on the day of our birth and not our fertilization. The solar system is in the middle of a nebula, and several other stars are also being born nearby, in an immense stellar nursery. It's a mess in here.
The gravity of protostars that rapidly accumulate mass moves the stellar gas in true cosmic storms. Our world is not yet born, but it is on the way. Not even the sun has matured.
It is still a protostar, immensely larger than any planet, but it has not yet sustained the nuclear fusion in its core that would make it a main-sequence star. Until it reaches critical mass, and an explosion reaction so powerful takes place that an immense shock wave propagates throughout the solar system. It blows away the gas that's preventing us from seeing what's going on here.
Now it is possible to see what our world will become. Let's call the fetus ProtoEarth. The formation of a planet is a cascade process.
Gravity slowly gathers dust grains into small pebbles. These pebbles become boulders. These boulders, in turn, come together and merge violently to form larger and larger objects.
Each of these shocks forms a more gravitationally influential body. The more mass, the more gravity, the more gravity, the more attraction, and consequently, the more mass. Over time, the largest objects end up cleaning up their orbits and establishing themselves as protoplanets.
ProtoEarth is one such object. Even after it was large, Proto-Earth was still hit constantly by meteors, during the intense bombardment phase. Huge impacts were not catastrophes, but the final phase of planet formation.
Shocks like the one that wiped out non-avian dinosaurs were part of everyday life. At first, the energy from the billions of impacts caused the planet to become very hot, a huge ball of molten rock. As the early proto-Earth was very viscous, heavier elements sank and lighter elements came to the surface.
That's how it ended up with an iron core and a gaseous atmosphere surrounding a solid crust. But that first crust and atmosphere didn't last long. Little is known about this early proto-earth protocrust, proto-atmosphere and proto-ocean because they were completely destroyed.
A catastrophe was about to happen to Proto-Earth, which would found Earth as we know it. Earth's childhood history is hard enough to study, because few rocks survive that long. But before the Earth-Moon system existed, there were two protoplanets, competing for a very similar orbit: ProtoTerra and Theia.
The proto-Earth was about 90% of Earth's mass, and Theia was the size of Mars. In the final phase of solidification of planetary crusts, these two bodies collided brutally, creating in the process, the Earth and the Moon, but making them return to the initial stage of formation. It is possible that a good part of the gases and water vapor in the proto-Earth's atmosphere was lost to space during this period.
It may be that without this event, the atmospheric pressure and the depth of the oceans would be much greater, preventing the formation of continental areas, on a fully aquatic planet. For the millions of years following the impact, Earth had a ring. This ring did not last long, it ended up, through the process of accretion, forming the Moon.
Its influence on the history of life is profound and definitive. We are 4. 5 billion years in the past, our solar system as a whole is about 70 million years old.
And it's not just Earth that's unrecognizable. The Sun is significantly smaller, cooler, dimmer. .
. younger. In its infancy, the Sun emitted almost 40% less light, which means that if the Earth did not have a lot of heat from its formation, and a greenhouse capacity much greater than the current one, it would have frozen in its first billion years.
. As it ages and starts to get richer in heavier elements, the Sun also expands and heats up. At this time, Venus and Mars were also close to maturing, oceans and atmospheres were defining, and the crust had begun to solidify.
These oceans lasted for billions of years before they were finally lost to space, but not completely in the case of Mars, as the planet's small ice caps of water show. Their geologies show, until today, scars of immense rivers and lakes that one day flooded these planets. But while Venus and Mars became habitable homes for living things, Earth recovered from its traumatic shock.
It was hell, the rocky planet with the worst prospects for living things at the time, by far. The newly formed Moon was somewhat macabre. If you could stand on the Earth's surface, waiting for the moon to rise 4 billion and 500 million years ago, it would be an apocalyptic vision, worthy of nightmares.
In the dark night, illuminated by lava, the first sign of the Moon's arrival would be strong earthquakes. They would only get stronger and stronger as an immense red and dark orange disk appeared and quickly rose above the horizon. It would look like a ghost, turning the night orange, but it could not be seen directly, because the atmosphere was not transparent, but very opaque, dense and steamy.
The Moon is still solidifying, and it glows with oceans of red-hot lava. But she is also much closer. Over billions of years of history, Earth's tides have slowly slowed and pushed the Moon away.
In the early years of this partnership, the day lasted less than 5 hours and the tides were catastrophic. The Moon also played some other important roles in establishing Earth as a habitable planet: It stabilized the planet's axis of rotation, preventing extreme seasonal climate variations And its gravity may have helped keep the planet's liquid iron core warm, which we believe be essential to generate the magnetic field that protects life from the sun's rays. Having a massive moon orbiting around it created permanent gravitational friction that at least in part delayed Earth's geological death.
The Moon, having a smaller mass, solidified its crust before the Earth. A few years ago, we thought that the Earth's solidification would have lasted at least 600 million years, but recent discoveries have greatly shortened the duration of our world's hellish phase. Today, we know that Hadean's final moments were much milder than we believed.
The oceans would already be permanent, although Earth is still greatly influenced by the strength and constancy of meteor impacts. The duration of the eon itself has not been modified, because in such ancient layers of geological time, datings are absolute ages. For the vast majority of Earth's ages, there are rocks to tell the story, however few.
But not for this, the deepest eon of geological time. No rock has survived the traumas of this hostile world. As rocks are vulnerable to erosion by rain, wind and friction, the older they are, the rarer they become.
But its most violent phase lasted less than we imagined. Apparently, the Earth solidified impressively quickly, as some new evidence suggests. But at its beginning, it didn't have a solid surface , it was covered by an immense ocean of magma with immense convection currents.
As much as there was hot magma everywhere, there were no flames, because fire was impossible, and would remain impossible for another 3 billion years. There was no free oxygen in the atmosphere, making the reaction impossible. And even if there was, there was no fuel like dry organic matter to burn.
This is the hottest phase in our history, although it has never known fire. The Earth was raw, its skin, or crust, had not yet formed, and the Earth's mantle reached down to the atmosphere. As the convection of this magma ocean slowed down, the Earth's first crust, the periodite, formed.
According to Robert Hazen, “Earth's first periodite crust was a critical but transient and juvenile phase born from the primordial magma sea. When it solidified and hardened, it was too heavy to stay on the surface, and it ended up sinking back into the mantle. Another less dense rock would be needed to found the crust, and that rock was basalt.
” Earth's first crust was thin, dense, and impermanent. As the Earth cooled, and water accumulated on the surface and mixed with the rocks that were melted by the mantle, a layer of less dense and more hydrated basalt grew. Basalt is an entirely black rock, which can be easily found around volcanoes or in basaltic flows that exist all over the world.
I'm lucky enough to live on top of one of them. This is the Black Earth phase, a world dominated by a dark, newly formed basaltic crust. But perhaps dry land was rare, because evidence shows that our world cooled very quickly.
Evidence that the oceans may have formed very early and in a very brutal way. Oldest rock on the planet comes from Australia and is 4. 43 ba.
The dating was done through zirconium crystals present in the rock. These crystals are extremely resistant, and nothing gets in or out of them easily, which makes them true time capsules. The original rock where these crystals formed was long ago destroyed, but they survived as sediment and were incorporated into new rock.
No rock from the Archean eon exists intact, and these crystals are our only window into that mysterious time. They formed when the world was “only” 160 million years old, and what is impressive is that they could not have formed in such a hellish condition. The immense amount of sulfur, nitrogen and carbon dioxide in the atmosphere made the sky opaque, with colors ranging from beige to green.
But you can imagine a greenish beige, or a beige green. At that point, the oceans already existed. This discovery means that just 160 million years after the formation of the solar system, Earth already had a solid crust and oceans.
Which makes the Hadean a lot briefer than we thought. This makes the history of ocean formation much more intense. .
. . The origin of water on the planet is also hotly debated, and today, two hypotheses dominate the scenario.
The first is that the region where Earth formed in the solar system was too hot to contain ice, which is how water collects in space rocks. If all the water near the Sun during initial formation was vapour, it may have been slowly transported to the outer reaches of the solar system. If that's the case, the water would have had to come back later, when the Earth was almost its final size, in the form of ice-rich meteors that bombarded the Earth's surface for millions of years.
This ice from the outer reaches of the solar system may have been thrown closer to the Sun by chaotic gravitational interactions at the Sun's periphery. According to another more current hypothesis, water was part of the composition of the planet from the beginning, and must have accumulated on the surface in the phase of “decantation” of the planet. If that was the case, the water could have come from within, as well as the atmosphere.
Imagine the Earth's crust as a thin film, the cream of porridge, floating in an immense ocean of magma. It is possible that bubbling regions were the escape of gases diluted in the magma, among them, water vapour. As the crust hardened and thickened, these gases would be forced out at high pressure, like permanent geysers that turned the earth into a huge sauna.
Volcanism on a global scale was bombarding the atmosphere with scalding nitrogen, carbon dioxide, sulfur and water in an increasingly dense atmosphere. Gases and water built up to the surface through this process. Over millions of years, the atmosphere was slowly forming and gaining density, both by gases escaping from the ground and capturing free gases left over from the formation of the solar system.
Water, like the gases in the atmosphere, has an importance very disproportionate to its mass. The atmosphere-ocean combination has a minimum mass, almost negligible, in relation to the mass of the entire planet, and the interior of the Earth is very poor in water. It means that almost all of it is on the surface.
That's because in the first tens of millions of years of our planet, water was an atmospheric gas. During the Earth's cooling process, temperatures slowly dropped, and for a while , the Earth's average temperature hovered around 100° Celsius, the boiling point of water. The atmosphere was dense and had a higher pressure, because temperatures above 100 degrees forced all the water in the oceans to remain in gaseous form.
The atmosphere wasn't transparent like it is today, but a thick boiling fog. Earth was a pressure cooker. That must have been an interesting moment in our world's history, because that's when liquid water finally became possible.
At this point, the day should be too hot to support liquid water, but at night, temperatures drop below the boiling point, causing the oceans to rain down in biblical proportions. In the morning, the boiling water oceans became unstable again. The oceans must have evaporated and rained countless times before gradually stabilizing.
At the end of that period, Earth was a planet with a warm global ocean, a chaotic climate, and no solid land. But much of what we know about ocean formation is still very speculative. The first pieces of dry land must have been islands formed by volcanoes.
These islands would have a completely black basalt floor, and may have been affected daily by tides, which at the time were colossal. At the bottom of this global ocean, there is no calm. Volcanic chimneys and geologically active zones may have been the cradle of all life.
And on the surface, super tides caused by the much closer Moon made tsunamis of hundreds of meters a routine event. And sometimes much larger rocks would also bombard the Earth, big enough to vaporize the oceans again for thousands of years. Each time an impact of this scale hit our planet, it was sterilized, and life would have to emerge once more.
But eventually, by the end of the Hadean, the intense bombardment would end. Prebiotic Earth doesn't last long, and life seems to happen as soon as possible. We used to think that life would have arisen once conditions on the planet calmed down, but now we know that chaos itself spawned life.
Recent research indicates that life already emerged in the Hadean, and that perhaps, without all the chemical and physical energy of that eon, life would never have arisen. As much as new evidence has shown that Earth's maturation was faster than previously thought, the official start of the next eon, the Archean, is 4 billion years ago, when the Earth was 560 million years old. And on the first day of the Archean, it was already inhabited.
The earliest forms of life were microscopic, which makes them very difficult to detect in the fossil record. But the earliest evidence of life is indirect, in the form of biogenic carbon. That is, rocks that contain isotopic proportions of carbon that indicate biological activity.
Carbon has 6 protons, but sometimes they have 6, 7 or even 8 neutrons in their nucleus. We call these carbons with different weights isotopes. Living beings assimilate much better the lighter carbon, called carbon 12.
When we count the carbons of things that are or were alive, we realize that the ratio of carbon 12:13 is very different from any rock. This is an indication of biogenic carbon, that is, accumulated by life. Therefore, finding rocks with a proportion of carbon isotopes typical of life is the safest way to infer the existence of the first microscopic beings.
The problem is that we know next to nothing about them. The first living beings were even simpler than bacteria and archaea, we call this hypothetical form a protobiont. Protobionts are a model of how life may have started, and basically, they are genetic material wrapped in proteins.
There are many hypotheses about the emergence of life, and to this day, this question remains highly debated and very enigmatic. Which sucks, because this is quite simply, the most important event in this entire story. The origin of life!
One of the biggest and most important questions in biology, science and existence. And we're still a long way from reaching a consensus, but we've already learned some interesting things. We know that when young, the oceans had much more rock debris and diluted metals.
A great soup of elements, in an ocean with monstrous tides and currents that defy imagination. Thunderstorms and lightning must be the most common weather by far. Like a newly set up aquarium, the waters were murky and dark.
In the absence of oxygen, chemical conditions were radically different. This element-rich water, when electrically stimulated, formed amino acids. This was demonstrated by Haldane, in the 50's.
This is important, because these are the fundamental elements for building proteins, indispensable for any living being and a structuring part of DNA. So the chemical conditions of the early ocean made common the most fundamental molecules for life. We're just racking our brains to figure out exactly how the pieces fit together.
Maybe we'll never know. Or maybe one day, we'll be able to reproduce these conditions in the lab, causing life to arise again for the first time. That would be an earthquake in science.
Life may have arisen on the walls of volcanic chimneys at the bottom of the ocean. In shallow and warm waters, full of organic molecules Or it could even have arisen on another planet, with another unimaginable chemical context, arriving here in the insistent meteors that bombarded the earth up to about 3. 8 ba.
This is the panspermia hypothesis, and as much as it sounds like science fiction, it is taken seriously as an academic discussion. One way or another, before Earth came out of the oven, life was already here. We know of biogenic carbon from rocks in the Jack Hills of Australia that are 4.
1 billion years old, which means it arose even earlier! How much earlier is impossible to know, as rocks older than that are very rare or even non-existent. This carbon is trapped in our well-known zirconium crystals.
But as far as we know, it was in the Hadean that life began, and from the very beginning, it shaped the planet and paved the way for the second great chapter of time: the Archean eon. But the question comes in: Did it appear only once? What if they had billions of firsts?
Perhaps, for a certain moment in history, life appeared all the time in its simplest form. But as the planet's climate, geology and chemistry changed, most of these forms were annihilated. On today's planet Earth, chemical conditions are so different that it would be impossible for life as we know it to arise again.
The Earth that started life was very exotic indeed. We know nothing about the incredible variety of molecules possible in these first steps of life. They test the limits of what we can call life.
As much as this seems like a basic question in biology, it is one of the most complex. Each biologist will give you a different answer, but most of them follow some definitions that compete in the field. But some of the consensuses are: Life metabolizes Life reproduces itself Life is complex and organized Life develops It evolves It is autonomous.
Many of the possible protobionts from that time may not meet all these principles, as well as viruses. The first life may have fed on the highly reactive sulfur that was exhaled from the ocean's many volcanic vents. She felt at home in the 100 degrees Celsius.
Oxygen was toxic to her. Which wasn't a problem, because there was no dilute O2 gas in the water or the atmosphere at that time. By the end of the Hadean, the oceans had stopped being vaporized all the time, and were more permanent.
Permanent and global. The world would be a huge ball of water, with dense weather and clouds everywhere. This primeval ocean is a hot soup of water filled with volcanic soot, which makes it dark and murky.
The tidal force was enormously greater, with the moon eerily close, and ocean currents moving chaotically like a pot of boiling water. As this primitive volcanism calmed down, the oceans became less and less energetic, which allowed the settling of most of the diluted particles in the water. The ocean, without any oxygen, was rich in iron molecules, which without oxidizing, gave a characteristic turquoise green color to the water, which combined with the depth, turned the oceans a dark green.
It is this huge green ocean, without any continents, with an extreme climate and a toxic atmosphere, that the next eon of Earth inherited. . .
. To survive on this alien planet, the first life was very different. Not even bacteria existed yet.
We do not know what kind of life this was, nor what exactly came first. And DNA, it was an innovation of the future, in larger and more complex organisms with metabolisms. All forms of life at that time were based on RNA.
The biggest difference between DNA and RNA is that DNA has two strands and RNA has only one. In our bodies, we have both, each one has a role. These nucleic acids were formed by molecules that formed naturally in the environment, as demonstrated by Haldane.
And the formation of life probably followed these steps: First, and most important of all, short RNA strands form spontaneously in early ocean chemistry. Then the RNA is isolated from the outside by a protein coat. So far we have something promising, but nothing alive.
They are still just molecules. The biggest of all steps takes place inside the capsule that surrounds the RNA: Replication! Life was now capable of replicating itself through the first cellular organelle, the ribosome, which gave biological evolution its START.
New experiments are getting closer and closer to being able to replicate the origin of life in the laboratory, and it may be that this is the decade when we will finally understand how life came to be. These experiments play with the chemistry of RNA, a molecule simpler than DNA but which also carries genetic information. The chemistry of the early oceans was radically different 4 billion years ago.
In this primordial soup, nucleotides linked together and spontaneously formed short strands of RNA. And RNA has an interesting trick: once formed, it becomes a catalyst, that is, it accelerates and induces chemical reactions. Hot water was another important source of energy for these first prebiotic reactions.
That's why volcanic vents on the ocean floor are the best candidates for the birthplace of life: They had a flow of hot water densely rich in chemical components, like sulfur, and the essential ingredients for the first nucleotides that form RNA chains. Some lipids, groups of molecules with properties similar to fats, accumulated in films on the walls of the chimneys, and eventually, they came off, forming bubbles, like soap! These bubbles enveloped everything that was diluted in the water: minerals, ions, and small RNA chains.
The first protocell. But it lacks a metabolism. This bubble is not yet alive, because it is very impermanent, but in a way, it reproduces itself!
These bubbles draw more fat and nucleotides inward, eventually breaking in two. The turning point that started the engine of evolution came when RNA strands stopped varying randomly and became permanent. With permanent, self-replicating chains comes heredity, an essential factor in natural selection.
This means that life did not arise just once, and the first steps of life's formation were actually common reactions and happened all the time. This is the era of the greatest diversity of life. From 3.
9 to 4 billion years ago, Earth's biology was reduced from thousands of types of life to just one. Today, there is little doubt that all life on Earth speaks the same genetic language and must share a common ancestor: we call it LUCA. English abbreviation for Last Universal Common Ancestor, or last universal common ancestor.
Let's meet him in the next episode! Let there be life. Hey little thing, how are you?
I have so much to tell you! What a humble beginning, and what achievements lie ahead of you. Know that the world that produced you will not be like this for a long time, and that you will radically transform it from now on.
You and Earth are one, and will shape each other forever. You will have a huge family! The greatest of all!
And it's going to be a rough and bumpy ride, but in four billion years, one of your descendants will become smart enough to imagine you, and its memory will recover. But until then, as important as you are, you will be forgotten. Time, like an endless stream, takes all its children.
That would be my message to the first form of life. In the next episode of the series, we'll understand what happened from that moment until the evolution of the first animals, and how oxygen transformed our world into the planet we know. We'll understand how and why the Earth froze completely over more than once, and why the first two hundred million years of animal evolution are so puzzling.
A special thanks to Bryan, who invited me to record here with him, and to Lucas Matheus, the artist who produced some of the most beautiful and crucial scenes in this video for me. If it weren't for Lucas' talent, many of the scenes you've just seen would be impossible, because his laptop doesn't help. To give Lucas a dignified working condition and bring more and more incredible art to the channel, we're doing a vakinha to buy him a TOP pc!
Thank you so much to everyone who is making us get closer and closer to this goal! <3 Also consider becoming a channel member Thank you so much and have a great life!
