Astrum Space - The Entire History of Earth In One Video

Episode Date: August 25, 2026

This supercut journeys through the history of our planet, from its violent birth, to its fiery death. We’ll explore Earth’s formation, how life began, the reign of the dinosaurs (and how it really ended), and find out what will become of our planet billions of years into the future, whether we’re here or not. To those returning and new to the channel: This supercut video combines Astrum’s best videos about Earth’s history, plus new and updated content. We’ve edited this into a new seamless video, remastered in 4K resolution, and re-recorded the older voiceover to match the quality of the recent episodes.▀▀▀▀▀▀Want to learn coding in a way that actually feels fun? Check out Coddy here: https://link.coddy.tech/bvMS/im?af_su... and start building your streak with bite-sized coding lessons, quizzes, and projects.▀▀▀▀▀▀Astrum's newsletter has launched! Want to know what's happening in space? Sign up here: ⁠https://astrumspace.kit.com⁠A huge thanks to our Patreons who help make these videos possible. Sign-up here: ⁠https://bit.ly/4aiJZNF

Earth is the place we call home. It's where we work, eat, sleep, and go about our daily lives. But how well do we really know it? For much of history, it would have been completely unrecognizable to us. Not the blue marble we know today, but molten, frozen, populated by towering, almost alien-like creatures that dominated, then died. has been through many phases. Let's imagine that alien scientists who have never seen Earth as it is today visited during these various stages in its development. Depending on when they arrived, they would have formed completely different ideas about the kind of planet Earth was.

What would they have seen 300 million years ago? Two billion years ago. 4.5 billion. And what will they see in the future. I'm Alex McCulligan and you're watching Astrum. Join me today in this supercut as we recreate Earth's complete history, from its glorious birth to its final moments with some of the greatest changes along the way. Now before we start, a little disclaimer. To answer these questions, we'll need to draw on some models that not all our scientists agree on. Traveling into the extremely distant past always carries some error bars. Some of the science we're pretty sure about. Other things are still being debated.

So, as we indulge our imagination, let's keep in mind that some of these claims are still being developed and rigorously questioned, as they should be. But to the best of our current knowledge, this is what our planet could have been like. It is a well-known idea that our solar system was formed from an accreting disk of intergalactic dust and matter 4.6 billion years ago, circling around a gravitational center that would, later, house the sun. Gravitational disturbances caused some of this dust to bunch together, and once that happened, each larger ball of matter found itself snowballing in size.

Larger clums had larger gravitational pull, which pulled in more mass. to grow the clumps. At this point in history, the vast spinning disk of matter from which our whole solar system was created had clumped together into planetesimals. These were further attracted to each other, crashing together to form the planets we know today. Within a mere 100 million years, this process of planetary accretion had gathered up almost all the material nearer to the sun to form what we call the terrestrial planets, Mercury, Venus, Mars, and our very own infant planet Earth. 100 million years later, the Earth is basically a hot, viscous ball of molten rock, and I doubt our alien visitors will want to hang around for very long.

Earth's thin atmosphere is made mostly of hydrogen and helium, most of which is stripped by the solar wind, since the Earth hasn't yet formed a magnetic field. As a result, the young planet has little protection from the sun's cosmic rays, and the planet is a hotbed of radiation. Earth is also constantly being bombarded with asteroids and comets, which add to its mass, a process called accretion. Just imagine a big ball of chewing gum that you keep adding to with fresh wads of gum, and you'll get the idea.

So not only is the young Earth hot and gooey, it's also growing. But these are not the only impacts the planet has to contend with. In the recent past, there was a cataclysmic event in which a protoplanet collided with the Earth, resulting in the formation of our Moon. Outside of that massive cataclysmic event, you might have thought that the bombardment of asteroids into the Earth and Moon was a fairly even process. that might not have been the case, at least not according to evidence discovered by NASA astronauts during their visit to the moon in the 1960s. When the Apollo astronauts came home from the moon,

the rocks they brought with them told a surprising story. The astronauts had brought home samples containing impact melt, rocks that had superheated intermagma due to being hit by a meteorite, which had, later, gradually cooled back into solid form. But while the Apollo team had collected these reconstituted rocks from different areas and craters on the near side of the moon, almost all of them were dated to around 4.1 to 3.8 billion years ago, with very few showing older impacts. The implication? For some reason, during this period of roughly half a billion years, there was an abnormal

spike in falling meteorites that crashed into our moon. This idea came to be known as the late heavy bombardment. This idea is controversial, and not everyone agrees that it happened that way. Such is the nature of scientific debate built on limited evidence. We don't get to go to the moon very often to collect more samples, so it's hard to tell if some process has been muddying the waters. But if the late heavy bombardment happened... what could have caused it.

And to answer that, we need to consider conditions back at the dawn of our solar system. Our aliens review the solar system 4 billion years ago, and although they find many asteroids have accreted into the terrestrial planets by this point, not all will have met that fate. There would still be some isolated leftovers between these planets. Some are still out there today, like the 1.5 million floating asteroids orbiting, the Sun between Mars and Jupiter, but this process had pretty much cleared out everything

in the inner solar system. Because of this, you might expect to have more impacts at the beginning, but fewer and fewer impacts as time went on, not a sudden spike. So why could there have been a surge in impacts 4.1 billion years ago that gave our Moon such a beating? That has created quite a puzzle for scientists. Although some now think they may have solved it. And to solve such a puzzle, scientists would need to bring their A-game, drawing on prior knowledge and data to figure out what answer fits the evidence best.

Too bad that there wasn't something that could provide instant feedback to let them know they got the answer right. But if you're looking for a guide to help you develop your coding skills, Coddy, the sponsor of today's video, can help. Coddy's platform teaches you vital coding skills by letting you try things out yourself. They provide puzzles, challenges, quizzes you can use to practice your coding skills on a daily basis. And if you get stuck, their tutor can provide instant feedback to help you figure out where you might be going wrong. Coddy's platform makes learning to code fun. They're easy to get started with, just answer a few initial questions and you're good to go. And there's no pressure to get things right first time.

In fact, one of the things I was impressed with is that their content is free. You can take up to five lessons a day with unlimited retries until you get it right. Or for $4.99, unlock unlimited code runs for the full experience. Get started on building your own coding knowledge with Kodi today. Scan my QR code or click the link in the description below to check it out. Now, back to solving the puzzle of that spike in impact. According to some scientists, the finger of suspicion points towards Jupiter, the largest planet in our solar system with more than two and a half times the mass of all the other planets

combined, and the first to form, along with Saturn, as our solar system took shape. If you would like to learn more about Jupiter and its influence on our solar system, check out this video. The suspected behavior of Jupiter is key to explaining the observations that have led to the proposal of the late heavy bombardment theory. Jupiter is not thought to have always orbited at a distance of 768 million kilometers from the Sun. Initially, Jupiter moved inward towards the Sun, reaching roughly where Mars orbits now, as Mars

and the other planets didn't exist there at that point, only to then change direction and pull away again. All of this possibly happened within just hundreds of thousands. to a few million years. What made Jupiter behave like this? The short answer is, its relationship with Saturn. When Jupiter formed, there was still a huge amount of gas swirling around our developing sun.

This gas dragged Jupiter along towards the center of the newly forming solar system. Once Saturn had formed, it also joined this death ride towards the sun. However, the two new planets bonded, as their gravities combined, and the sudden tug of Saturn behind it was enough to arrest Jupiter's grand procession towards the solar system's inner territory and to gently pull it back to the orbit we see it at today. But this procession was not without impact, quite literally. Our asteroid belt, with its one to two million asteroids, potentially only represents less than 1% of the matter that used to be there.

So when Jupiter came sweeping through with its massive, far-reaching gravitational pull, a lot of orbits became disrupted, and many of those objects started to fall inward. Let's hope our visiting aliens have decent maneuverability on their ship. Two types of asteroids were brought into this process, from both the inner and outer solar system. This fact becomes quite important later. Not all asteroids are the same, and you may be familiar with the terms S-type and C-type asteroids. S-type asteroids are the stony asteroids from the inner solar

system, mainly made up from silicate materials and nickel-iron. They are drier because they come from closer to the sun. C-type asteroids, the chondrite or carbonaceous asteroids, are the most common, and are among the most ancient objects in our solar system. They come from the outer asteroid belts, and they contain much larger amounts of something that would later prove crucial to our planet. Water. And all of these asteroids began to fall through the patch of space our planet was orbiting. The timing of this, as far as our planet is concerned, was crucial. By then, the surface of the Earth had cooled to form a more more stable crust, what we know as the lithosphere today.

This insulated anything above from the enormous heat of the magma below. The magma near the surface was much hotter than it is today, around 1,600 degrees Celsius, and it was much more liquid. Heavy elements, especially iron, had sunk towards the central core, leaving the lighter elements and minerals at the surface. As the asteroids rained down onto the surface, they brought with them a whole range of elements and minerals that would remain as part of this surface layer. It is now thought that many of the important deposits we find at the surface today, oars and metals such as lead, nickel, copper and gold, were brought here in this way.

More important than valuable metals, however, was the arrival of water. Vast amounts of water. Had all this water arrived earlier when the surface of our planet was hotter and less able to maintain an atmosphere, much or all of it would have escaped back into space, possibly leaving the planet an arid desert like Mars and the moon. A lucky break for Earth. Surrounding Earth during the bombarding chaos 4 billion years ago was a toxic atmosphere of methane and ammonia, covering an unstable but solidifying surface of basalt-type rock, dark, dark grey, almost black in colour, and with brightly glowing lava erupting through faults where it was shattered by the incoming hailstorm of asteroids. Steaming oceans of water

were forming, helping to further cool the developing surface, a true vision of hellfire and brimstone. It is partly because of this churning nature of the surface, floating on liquid magma, that today we see no trace of the craters left by these inferences. The forming lithosphere was fractured into many small tectonic plates that moved around and recycled themselves much faster than they do today, and no trace of these early rocks remains. The oldest surviving rock formations on our planet roughly mark the end of the Hadean period, and by this time this intense bombardment of our planet had likely come to an end. The end of the Hadean era also marks the beginning of a new devalued.

element in our planet's fascinating history, the story of life. It has long been debated how the very beginnings of life may have evolved on Earth. Key building blocks would have been needed, like hydrocarbons and other complex molecules. What conditions could have led to the origins of this organic molecular soup? Interestingly, while there is debate over the reality of the late heavy bombardment, this theory does help to answer this vital question. It is now known that all five of the essential building blocks of DNA and RNA exist in space and have been found on meteorites. But while the meteorites we see today burning up in the night sky as they enter our atmosphere

could never bring anything as delicate as these molecules to the surface of our planet, they would burn away to nothing before even reaching the stratosphere. But when much larger objects from space were raining water and ice, onto our newly formed surface, it is certainly possible that they ceded the earth with some of the right ingredients that made life viable. There is compelling evidence that life began at the very time when this bombardment was ending and new oceans had formed. Finding the answers to many of these questions is almost impossible on Earth, because

so little remains from this time. This is why scientists are so keen to study. clues that may still exist on the moon. The reason why this evidence is so well preserved on the moon is that, unlike on Earth, the surface of our moon was already quite stable, without the churning and recycling of the surface that occurred here on Earth at that time, so the craters remain intact. Also the surface of the moon is not being constantly eroded by weathering. There are no seas to grind it down, no wind and acid rain to wear a weather.

the rock. The dust that covers the surface is holverized rock that remains undisturbed following those dramatic impacts from billions of years ago. There are craters on our planet's surface, such as the Beringer Crater in Arizona, USA, but that dates only from 50,000 years ago. Of the late heavy bombardment era craters themselves, there is nothing visible at the present time. If such craters do survive somewhere on our planet that have not been completely eroded away, they could be buried under later sediments or lava flows, and we may never find them. We've been able to make progress in our understanding of this era thanks to the astonishing

382 kilograms of moon's surface rock brought back to Earth from the Apollo missions. Radiometric dating of these rock samples indicated that they were last molten during a narrow period of time around 3.9 billion years ago, consistent with when we believe that Earth and other inner planets were being bombarded by asteroids. Those large craters you see on the moon are where asteroids have impacted the surface, and when lava has flowed out, forming those characteristic smooth craters that we can see on clear nights. But did the visiting aliens witness this uptick in asteroid activity in the first place?

As I mentioned a minute ago, not everybody agrees in the theory of the late heavy bombardment, and as much more refined analytic techniques have been developed over time, questions have been raised about the time scale and duration of this period of asteroid activity. Some dating inconsistencies suggest that the craters may have formed over a much longer period of time, tailing off from the planetary accretion that form the terrestrial planets rather than a more concentrated period of activity. The sample materials that scientists have available from the Apollo missions are still limited as they stem from just a few carefully selected locations.

More samples from future missions will hopefully resolve some of those controversies, and the NASA- Artemis missions are currently aiming to do another landing on the surface of the moon in 2028. I can't wait to see what new discoveries this could bring. alien scientists are thrilled at the development of life that has just started down below right before their eyes. At the moment, that life is simple, the most basic of microbes, possessing very few features for sure beyond the ability to replicate and take in nutrients. This certainly warrants further observation though, so the aliens decide to let things cook for a bit, before they

later return to check how things are going. Let's imagine that the aliens return to Earth and one and a half billion years have passed, and instead of a molten planet, they find what our scientists call the pale orange dot. Earth has developed a solid crust and magnetic field, which has retained a methane-rich atmosphere with a distinct pale orange haze, very much like Saturn's Titan. Earth also has vast oceans of liquid water formed from rainfall. Looking upward, our alien scientist, See a terrifyingly huge moon overhead, far closer than it is today. Here's a fun fact. The moon has slowly been drifting away from Earth for the past 2.5 billion years, and is still

moving away from us at the rate of 3.8 cm per year. This drift will eventually stop, but not for another several billion years. But 2.5 billion years ago, the moon is much, much closer, and this proximity leads to far stronger tidal forces in the oceans. While this snapshot of Earth is probably more Earth-like than the previous snapshot, to me it almost feels more alien than before. Earth must have looked like a barren dream world, a lot closer to a surreal Salvador Dali painting than the teeming planet we know today.

Being experienced in the field of astrobiology, our alien scientists take some blue-green water samples and find the cause of this orange haze, photosynthesizing bacteria called cyanobacteria. The life they first witnessed has evolved. These primitive bacteria are living in communities in shallow water, which in turn have released oxygen into the atmosphere in an event called the Great Oxidation. As part of this transformation, the Earth now has a protective ozone layer, which shields lie from the most harmful effects of solar radiation.

The bacteria are also producing unusual rock structures called stromatolites, similar to these modern ones located in Western Australia Shark Bay. Cyanobacteria forms stromatolites by cementing grains of sediment together with biofilms, or, to put it in another way, microbial slime. Somatolites are one of the biosignatures that astrobiologists say we should be looking for on other planets, although they can have non-biological causes, so you have to look at them on a microscopic scale to be sure. Without any competitors, the cyanobacteria reigns supreme.

Using solar energy, they are converting carbon dioxide and water into nutrients, seeding the atmosphere with oxygen as a byproduct. are now the uncontested rulers of planet Earth, and they have permanently altered their atmosphere in ways that make our current way of life possible. Enthusiastic for Earth's future, our alien scientists decide to come back to Earth 650 million years ago. And boy, what a difference 1.9 billion years makes. The planet is now in its cryogenian period, at a time scientists call Snowball Earth. According to these models, Earth is completely frozen over. Think of the last Pleistocene Ice Age, only a lot colder. In fact, all of the Earth's surface and half of its

total ocean water are frozen solid. The Earth has become so cold that temperatures at the equator are similar to those in modern-day Antarctica. While the scientists aren't sure, sure what triggered this downshift in global temperatures, some theories include a major volcanic eruption that spewed ash into the atmosphere, a vast reduction in greenhouse gases due to photosynthesising life forms and Melanchovich cycles. There's already a video dedicated to Melanchovic cycles on our channel, but here's a really quick recap of what they are and what they mean. The first is the eccentricity of the Earth's orbit. When the pull of gravity from Saturn and Jupiter, is stronger, Earth is forced into a more elliptical orbit, which happens around every 100,000

years. During times of highly elliptical orbit, Earth sees the greatest variation in the length of each season, with summer lasting longer than winter. Any planetary orbit features abheelian, when the planet is furthest from the sun, and perihelian, where it is closest. However, a highly elliptical orbit means that the Earth's abheelian in July is at its first. this distance from the sun, so the amount of solar radiation that reaches Earth during this time is around 23% less than during perihelian in January. The result? Warmer, shorter winters for the northern hemisphere, and cooler, longer summers. The second Milankovic cycle concerns the obliquity, or tilt of the Earth on its axis. The more tilted the Earth, the more extreme the seasons.

and this varies on a roughly 41,000 year cycle. So when Earth is less tilted, the difference between seasons is mild enough that the summer can't melt the winter ice, which could allow it to accumulate and bring about an ice age. The third cycle is known as axial procession, or wobble. Like the name suggests, the Earth can wobble upon its rotational axis

as a result of the gravitational influences from the sun and moon, which caused the earth to bulge outward slightly at the equator, rather than maintain a perfect sphere. This movement varies on a 26,000-year cycle and makes the contrast between seasons more or less extreme depending on when perihelion occurs in each hemisphere. For example, modern-day perihelian occurs during the northern hemisphere's winter, meaning that their seasonal fluctuations are less extreme than for the southern hemisphere. Of course, it was quite likely a combination of factors that amplified this global cooling. Interestingly enough, underneath all this glacial ice is a single supercontinent called Panotia, centered on the South Pole. However, given the vast

glacial cover, our alien visitors are having trouble discerning land from ocean. As a side note, don't confuse this supercontinent with Pangea. Plate tectonics will eventually break apart Panotia and reform that later supercontinent in a few hundred million years. But let's not get ahead of ourselves. Our space visitors land and wander around the vast, endless glaciers, amazed that this frozen landscape was once covered in molten rock. At first, they think the harsh climate might have wiped out Earth's fledgling life,

but that life has proven remarkably resilient. Cyanobacteria remain in the ocean, perhaps clustered around hot hydrothermal vents, much like the black smokers that are currently at the mid-Atlantic ridge. There are also newly evolved microbial life forms, such as red algae. Complex, multicellular life remains elusive, but the fact that life has found a way to survive the planet's harshest freezing events so far is a testament to its staying power. At this point, I'd like to imagine our alien visitors having an argument among themselves. The youngest and most temperamental of the group is having a tantrum.

First a lava ball, then a barren bacterial playground, and now a ball of ice, it exclaims. Why do we keep coming back here? But the eldest of the group puts an arm, tentacle, or articulated limb of our preference, conference around its younger comrade. Patience, the wise alien tourist says to its impertinent partner, I have a feeling this planet is in for some major shake-ups. Let's come back in another few hundred million years. I think it will be worth the trip.

So, giving the planet time to change, our alien scientists decide to come back during the Devonian period 360 million years ago, and they are shocked by what they see. The planet has thawed completely. were temperatures generally warmer than those of the present day. Scientists estimate that the tropical sea surface temperatures range from 30 degrees Celsius to 21 degrees Celsius later in the Devonian, a temperature drop that coincides with diminishing CO2 levels due to increasing plant growth. The supercontinent has broken up and formed multiple continents,

the largest of which is Gondwana, covering the South Pole and much of the southern hemisphere. Gondwana incorporates much of what is modern-day Africa, South America, Antarctica, Australia, and India, so it's pretty big. But the most dramatic change our visitors notice is that life has already undergone the Cambrian explosion, a rapid expansion of biological diversity that filled the seas with all sorts of complex life. The oceans are now teeming with trilobites, clam-like brachio pods, and complex marine vertebrates, such as fish.

Among the more fearsome specimens are dungliosteus, a massive, armored fish 10 meters in length, and Titanichus, another giant with a taste for smaller prey, like krill-like zooplankton. Given the presence of these fish that look like great white sharks crossed with armored submarines, our alien scientists decide not to go for a swim, despite the invitingly warm waters.

Meanwhile, plants have completely transformed what was once barren continental crust. With no large herbivores in existence, vegetation grows unchecked into dense, sprawling forest, which have produced a layer of stable, nutrient-rich topsoil. But these trees would look very unusual to us. They are vascular plants. Related to today's ferns and some conifers, there is also an enormous tree-like fungus. called prototaxites, which stand some 8 meters tall. Very likely, these mysterious tree-like structures are fruiting bodies of far larger subterranean

organisms which haven't been preserved. A few marine species have even evolved limbs and are beginning to walk on land, such as Ichiostega, a rather charming, four-legged vertebrate that looks like a modern amphibian, whose stout limbs and lungs allow it to navigate swamp-like habit. As our alien visitors leave the Devonian period Earth, they finally have a sense of the ecological diversity and temperate climate that will follow. The once molten planet turned pale orange dot turned giant snowball now somewhat resembles the blue marble we know today.

The next time our time travelling aliens return to Earth, nearly 100 million years have passed. Death is now in its early Permian period, approximately 280 million years before the present day. The aliens are keen to see what new shifts have taken place in the Earth's geology and biospheres, so they look out across the planet. The biggest geographical change is that the continents of Euro-America and Gondwana have combined into a single landmass called Pangae. collision of these continents, called the Variscan Orogyny, unleashes powerful tectonic forces that create a mountain range called the Central Pangaean Mountains.

How tall are they? Well, Mount Everest is in the right ballpark, as this range is comparable in size to the modern Himalayas. In fact, they are so tall that they have a profound effect on the climate of Pangea. The central Pangaean mountains lie just beneath the equatorial rainy belt. And our scientists quickly discover the impact of these giant mountains on the entire continent. South of the range, it is a mega monsoon climate. However, there is a flip side to all this rain.

The mountain range in turn casts a rain shadow to the north, which creates a huge desert in Pangea's interior. Basically, when air travels over tall mountains, it moves upward and cools, causing precipitation, so that by the time it crosses the the mountains, the air is pretty arid. We see this effect today in the Gobi Desert, which is located in the rain shadow of the Himalayas. Pangaea's formation is a great example of how plate tectonics not only impact the world's landmasses and oceans, but its weather as well. Yet, there are also other factors shaking up the world's climate. During the early Permian, the earth is still

in the latter days of an ice age, dating back tens of millions of years. years, an event known as the late Paleozoic Ice House. Our leading theory for this cooling is that the explosion of plant life during the Carboniferous raised Earth's oxygen levels and diminished its CO2, leading to a reduction in the greenhouse effect, with Milankovic cycles also likely playing a role. During the late Paleozoic Ice House, vast glaciers built up but the poles and in the higher elevations. Yet, by the early Permian, the planet has begun entering a warming trend. The polar ice caps are retreating, but glaciers remain in most of the high elevation mountain ranges. So, between the climate disruptions caused by Pangea and the cooler

than normal but warming global temperatures, by forms on Earth have had a lot of adjustments to make. Since our aliens last visited, the formation of Pangea, has produced a vast super ocean called the Panthalassic, or Universal Sea, as well as a smaller ocean called the Paleotethys. The Panthalassic is so big, it occupies almost 70% of Earth's surface. To gather more information, and, if possible, see what's down there with their own eyes, our aliens enter a submersible and dive in. As it turns out, the safety provided by said vehicle is much needed.

Earth's oceans have had some terrifying new inhabitants. Among them is one of the strangest predators ever to patrol the watery depths, Pelicoprion, an 8-meter long shark-like fish with a wall of teeth in its lower jaw, resembling a buzz saw. I personally have always dreamed of a day when humans discover extraterrestrial life, But until that day comes, our best resource for understanding how life can evolve under various conditions is Earth's own fossil record. Earth was a different planet back then. In our own solar system, moons such as Europa, Ganymede, and Enceladus may have subsurface

oceans suitable for strange life forms. Meanwhile, on land, insects have begun to flex some serious muscle. There are all sorts of beetles, including Permocopede, and, and the insects. And Meganisotera, an extinct order of giant dragonflies. Just imagine a dragonfly with a wingspan about the size of common seagulls and you'll have the idea. Another frankly bizarre newcomer is Diplocalis, an early amphibian with a boomerang-shaped head. Look at how fascinating these Earth aliens are, I can hear our extraterrestrial zeno-zoologists say.

But by far, the most interesting quadrupede of the early Permian is the Dimetrodron. Although it is often mistaken for a dinosaur in the popular imagination, this 2 to 4-meter sail-backed predator is actually a synapsid, more closely related to modern mammals than reptiles. Vimetrodon's sail contains a network of blood vessels, which allows it to raise its temperature more quickly in sunlight, an early step towards temperature regulation. On the planet experiencing all kinds of climactic changes, this ability to regulate temperature would certainly be advantageous. It's a wonderful illustration of how much living organisms can and must change in order to survive.

Our planet's climate is like a complex system full of inputs with a biosphere as corresponding outputs. Planets like ours dictate what sort of life can exist on them. And interestingly, as a planet changes of the Earth. over time, the type of life it can support also changes. Impressed by Earth's development, our alien scientists decide to return in another 100 million years. Unbeknownst to them, they will miss the largest extinction event in Earth's history.

I'm not talking about the asteroid that eventually killed off the dinosaurs. A much more catastrophic extinction takes place around 252 million years ago called the Permian Terassic extinction event. Our leading theory is that volcanic eruptions release a huge amount of CO2 into the atmosphere, which raise global temperatures and make the oceans more acidic. This catastrophic event eradicates about 70% of terrestrial vertebrate species and 80% of all marine species, a mass die-off unmatched by any other in the history of the planet. Yet, as devastating as this is in the short term, it would eventually clear the

the field for a whole lot of evolutionary diversification during the Jurassic and Jurassic. Sensing that changes on the horizon, our aliens skip forward again, this time just 50 million years. Their sense of timing is excellent, as in the center of the arid and ancient supercontinent Pangaea, thousands of miles away from the sea, a key moment in Earth's history is about to start. A rain is beginning to fall. But not just any, rain. Just off Pangaea's West Coast, in what is now Canada, epoch-ending volcanic activity sent off a chain of events at all that made this world-altering downpour inevitable. It would never look the same, because this was the start of a rain that wouldn't abate for more than a million

years. This would truly push the butterfly effect to its limits. Imagine, If a butterfly flapping its wings can cause a tornado 1,000 kilometers away, what does an eruption 100 times larger than a supervolcano cause? Before the rain began, life in many parts of the world was adapted to the drier climate. The supercontinent, Pangea's huge size meant that the center was far removed from coastal climates and therefore received very little rain, favoring the evolution of species that required less water to survive. During this dry period around 300 million years ago, in the Carboniferous period, several species emerged that are still important today, including dragonflies, millipedes and spiders.

Throughout this period, the diapsids also exploded, a group containing lizards and snakes as well as archosaurs. Now, you may not know that name, but you certainly know what this group contains. crocodiles, birds, and yes, eventually dinosaurs. But we'll come back to those later. For now, let's remember that the earth back then was a tumultuous and unforgiving place, with impending threats left, right and centre, and above and below for that matter. While asteroids smashing into the crust better grab the attention of Hollywood, it's under the crust where the real danger has always been,

and it's here that we will find answers to what caused a million-year storm. We live on a vanishingly thin crust that is so shallow that if the earth was represented by the entire Lord of the Rings book trilogy, the layer harboring all the known life in the entire universe would be confined to just one single page. Beneath hot plumes rise up from the core, mushrooming as they rise and pushing molten magma up against the thin crust. These huge plumes punch through the crust wherever they meet it, completely ignoring continental

fault lines where Earth's modern volcanic activity is concentrated, like the Pacific Ring of Fire. These plumes can release magma at the surface for over 1 million years, in what are known as flood basalt eruptions. It is these eruptions that are linked to the most incredible extinction events during Earth's history and are probably the cause of the most destructive extinction event in history, the Great Dying, where ocean temperatures rose to 40 degrees Celsius. Despite life's ability to evolve, it is estimated that over 99% of every species that ever lived on Earth have gone extinct.

Of course, you can't exactly evolve out of the Earth. the way of a Mount Everest-sized asteroid travelling at 20 kilometres per second, but these volcanic processes, though slower and far less dramatic, can cause far greater devastation over a longer period. Evidence of flood volcanism is scattered across the world today. The eruptions of these flood basalts result in the creation of huge, unmistakable swaths of land, like the Siberian traps in northern Russia, the Deccan traps in western India, and The Rangelian large igneous province across Canada and Alaska.

They are all cooled flows of basalt rock, kilometers deep, making them over 100 times larger than supervolcanoes. When we date these flood basalts, we see that many of these eruptions align with mass extinction events. There is one though that doesn't. That is our rainmaker event that triggered the so-called Karnian pluvial episode or the time that it rained for over one million years. It's believed that volcanic activity in the Ranglian province is responsible for this remarkable

transformation of an arid desert into an oasis that jump-started the dinosaur's explosion. So what separated Rangelia's eruption from the rest? What made it different? Well, I've got news for you, size does matter. Although this was an extinction event, with around 30% of the ocean species wiped out during the CPE, Rangelia's eruption was just the right size to give life an overall boost on Earth. So the reason that the overall biodiversity was unchanged is because the level of extinction was matched by the emergence of new, exciting species more suited to this wetter world.

What our aliens witnessed was less an extinction event and more a reinvention period. So, how can slow eruption affect such an incredible change to Earth's climate? To understand how this transformational event shuffled the deck of life on Earth is to understand something that we are living through right now, climate change. Specifically, the release and production of carbon dioxide and the release of stored methane. Like these directly released carbon dioxide already contained within the mantle, but they can trigger its release from other stores too.

From a source of carbon I thought only humans had used. Huge reservoirs of fossil fuels. Now whether you remember the fire triangle from school or not, fuel, heat and oxygen, I think we can all appreciate that introducing 1,600 degrees Celsius magma to the base of untapped virgin coal beds is going to get spicy. Burning these crude coal beds would have released incredible amounts of particulates and greenhouse gases, both important for driving cloud formation and rainfall. Just as we are seeing today, the increasing levels of those greenhouse gases trap more of the sun's energy, and that energy has to go somewhere. So where does it go?

Earth's systems work to distribute their energy, and the one best place to absorb this extra energy is the water cycle, which becomes supercharged. The sun's energy is absorbed by the land and sea, evaporating water from the surface. Once in the atmosphere, the water can be carried great distances before precipitating onto land and returning to the sea along a meandering route. The more energy that is trapped by greenhouse gases, the faster the water cycle turns over. In these flood basalt eruptions, we see an extreme example of the complex interplay of the three major cycles, the geological carbon and water cycle. The formation of the Rangelian large igneous province would have released huge amounts of CO2. Our alien ship detected atmospheric levels exceeding 1,000 parts per million. two and a half times what they are today, increasing temperatures by three to four degrees

Celsius. This supercharged the water cycle, greatly increasing evaporation and cloud formation, and these clouds were increasingly able to deliver rain further and further into the center of Pangea. Throughout this period, the earth became warmer and more humid, a dramatic change in the climate. Species that had adapted to a particular, dry climate, environment or niche, before the rain, were put under stress from multiple fronts. During this turnover period in Earth's history, our aliens watched as old niches were seemingly destroyed as quickly as the new ones were created. The status quo was changing.

Not only that, but species had to cope with a pH shift too. Carbon oxide wasn't the only gas released by the Wranglion eruption. Hydrogen sulfide erupted into the atmosphere along with it. This egg-smelling gas reacted with oxygen and water to form sulfuric acid, which in this form is more well known as acid rain. As the rain fell, the soils and oceans became inundated with acidified water, which only further contributed to the environmental stress some species were facing. Interestingly, a large amount of amber can be found in the geological record from the Karnian. Amber is a protective mechanism for trees that they release when in peril, suggesting that plant life came under significant stress during this

period too. The incredible volume of rain across the supercontinent resulted in deluges of surface runoff. Accelerating across and through the arid terrain, these slightly acidic flows eroded the land as it went. Some of this acidic water seeped into and eroded small, fishers in limestone and dolomite rocks. Our aliens watched as rocks were literally dissolved in front of their eyes. Over time, elaborate new cave systems were formed, like Britain's Jurassic caves carved from Carboniferous limestone, which provided yet more unique habitats for life to exploit. Eventually, the flow reached the sea, carrying the eroded rocks and minerals into the ocean, further nudging the coastal ecosystems into new territory.

The ocean species were particularly hard hit, and large areas became anoxic, meaning they lacked oxygen, and highly acidified, which was not suitable for the existing ecosystems that inhabit those areas. Species like conodonts, ammonoids, crynoids, and green algae suffered particularly high extinction rates during the CPE, as did reef builders, while dynoflagellates, a constituent of today's ocean planktons, thrived. On their ship, the aliens moan in disbelief every time the ship's computer forecasts ongoing miserable weather. But back on land, one of the oldest known dinosaurs, hererosaurus was braving the elements and roaming the earth. Some six meters in length and weighing more than 300 kilograms, it was an outlier prior to the Carnian pluvial episode, when smaller

reptiles and mammals were far more numerous. Its home was the Ishigualasto formation, a volcanic floodplain defined by its dense jungle in what is South America today, a warm and humid environment, which the hererosaurus was well adapted to. So when the rains began to fall, it won the geological lottery as its habitats spread across Pangea. Advancing deeper into the continent, hererosaurus was greeted with literal oasis. Untouched habitat, that with the extinction of herbivores and other competition meant it was to be a boom time for the hererosaurus and similar dinosaurs. We can only imagine the variety

and richness of habitat available for all these wandering species to find and exploit and co-evolve with over time. Further away in the Dolomites, the alien sea herds of large dinosaur creatures roaming the plains, and their wandering footsteps have been recorded deep in the rock. Across a three to four million year period spanning the Carnian Pluvial episode, dinosaurs went from not featuring at all in the fossilized footprints to ecological dominance, making up over 90% of fossilized imprints. a remarkable takeover that agrees with other records in other parts of Pangea during this time period,

notably the Central European Formation and the Ischicolasto Basin in Argentina. The two million year periods spanning the Khanian pluvial event left its mark in indelible ways, forever changing the trajectory of life on Earth as well as the passage of water across and through its surface. The mega monsoonal climate featured four distinct downpours, each carving a trace through the landscape. Making the biblical storm that remade the Earth in 40 days and nights look more like a typical British summer in comparison. But the fifth period of rain never came.

Once the Ranglian eruption finally slowed, the emission of greenhouse and acid forming gases slowed, and it is likely that levels of carbon dioxide fell as it was consumed by the rich flora that covered Pangea, some of which would again become buried and form coal fossil fuel deposits for us to use today, continuing the carbon cycle. Now the storm has passed, we can answer our question. If a butterfly flapping its wings can cause a tornado 1,000 miles away, what does an eruption 100 times larger than a supervolcano cause? Well, a complete terraforming of land, sea and air,

And with such vast alterations to the Earth, vastly new species would rise to dominate it. Chief among the beneficiaries is a group of reptiles that would one day rule the planet, dinosaurs. Our alien scientists next return to Earth during the late Jurassic period 150 million years ago. Although Pangaea managed to hang around until the early Jurassic, by now it is starting to drift apart due to tectonic movements in the planet's lithosphere. The Earth is made up of about 15 to 20 tectonic plates, which are always moving toward or away from each other at a rate of around 1.5 centimeters a year, which, interestingly enough, is pretty much the same rate as our toenails grow.

As plates move away from each other, they open a rift marked by outpouring basaltic lava. So beginning around 200 million years ago, Lorasia breaks away from Godwana, and then, and Gondwana, creating two smaller supercontinants. In the north, Laresia contains modern-day North America and Eurasia. To the south, Gondwana includes modern-day South America, Africa, Australia, India, and Antarctica. A narrow body of water called the Tettis Sea is also opening up. It will one day grow into the North Atlantic Ocean, as outpouring basaltic lavas at the mid-Atlantic ridge continued to push the landmasses farther apart.

part. Meanwhile, in the south, Antarctica and Madagascar have begun to separate from Africa, opening up the Proto-Indian Ocean. While the continental landmasses still look quite different from how they look today, our alien visitors already have an inkling of where Earth's continental configuration is heading. The climate of the period is scorching hot. Global temperatures are 5 to 10 degrees warmer than they are today, with atmospheric CO2 levels approximately four times greater. What contributed to all this CO2? Very likely, the mass extinction of plants during both the Permian Chiracic extinction

event and the subsequent die-off called the End Choracic Extinction played hefty roles. Global temperatures are so warm that ice sheets are unable to form at the poles. Instead, the poles are covered in forests, which likely experience. warm summers and cool snowy winters. With so little water locked up in glacial ice, sea levels are significantly higher than they are today, with the peak happening right around this time, about 140 meters higher. In terms of flora, gymnosperms such as conifers have become one of the most successful plant types. Some trees, like the extinct Arrocaria Mirabilis, represented by this extraordinarily well-preserved

cone look eerily similar to what you might find today. This is also a golden age for cycads, palm-like vegetation with woody cylindrical trunks and stiff pinnate leaves. These plants grow heartily in the late Jurassic's expansive tropical and subtropical climate zones. As our alien scientists step out of their ship, they hear an ominous rumbling. Looking over, they spot a pack of towering sauropods. Not Not just any sauropods either, Super Soros, one of the most massive terrestrial animals in Earth's history, measuring up to 35 metres long and weighing 40 metric tons. Getting over their initial fright, our alien visitors realised that these Goliaths are in fact

herbivorous grazers, well adapted for reaching high vegetation. But their relief is short-lived. Stalking some of the smaller sauropods is a rangy allosaurus. a formidable species of carnivore nearly 10 metres long, with dozens of needle-sharp, serrated teeth. Luckily, our alien visitors escape their brush with the hungry carnosaur, and decide to finish the rest of their tour from the safety of their ship. Once they're in the air, they encounter a feathered Archaeopteryx, an avian dinosaur considered to be one of the first birds. Archaeopteryx is also sharing the skies with large flocks of non-avian terrorsors,

such as dimorphodon and the crested pterodacty. These winged predators are well adapted for catching smaller animals and invertebrates in their toothy, beak-like jaws. But as our alien scientists stopped their expedition for lunch in one of the more sheltered forest glades, something small and unassuming emerging from a burrow that catches the xenozoologist's interest again. A small furry creature called Tenoelabis. Tenoabis are some of of the earliest mammals. And while they may look unassuming, the great, great, great descendants of these humble, scurrying creatures will one day outlive the dinosaurs and dominate the earth.

But there is a deadly hurdle they will have to overcome first, one that 75% of the planet's other species will not make it past. Our aliens need to leave, but they return once again roughly 84 million years later. Let's imagine our alien explorers decide to descend and collect samples on a certain day 66 million years ago. But first, they need to make a pit stop. They are running low on Helium 3 and swing by Jupiter to fuel up. Without this source of power, their ship won't be able to take off again once they land

on Earth. Tomorrow they agree, they'll come back. When they return the next day, they double-check their GPS, or galactic positioning system. They must have made a mistake. There is no way the fireball covered in soot there looking at is the same thriving planet they flew over yesterday. Our alien friends are flabbergasted. What could have happened to cause such utter devastation? The earth they came back to is covered in raging wildfires, tsunamis up to one kilometer high, and immense inescapable death. A new reality has set in, one that is a very that is a

that would consume the planet for the next couple of decades. To find out what happened, let's jump forward in time to see what our human scientists have to say on the matter. In the 1980s, two human scientists made a huge discovery. They detected the presence of a chemical element called iridium in the geological record. Exactly at the point in time, dinosaurs disappeared from the fossil record, also known as the Cretaceous, paleogen, or K-P-G bound. Not only that, but this specific iridium ring has consistently been found at the K-PG boundary

in samples taken from around the world. It seemed like something deposited an immense amount of iridium all over the Earth's crust at the same time that dinosaurs went extinct. The curious thing is that iridium is usually pretty hard to come by on Earth, and these rock layers at the K-P-G boundary contained two hundred. hundred times the amount of iridium we would normally expect to find. Can you guess where iridium is abundant? Asteroids.

But if such a catastrophically large asteroid did crash down to Earth, it would leave behind a crater that would be pretty hard to miss. Well, just a few years later, the human scientist found that too. Known today as the Chixilub crater, it lies off the coast of the Yucalympia. Okutan Peninsula in Mexico, and spans a whopping 200 kilometers. After some testing, researchers confirm the age of the crater as being about 66 million years old, lining it up exactly with the iridium in the K-PG boundary and the disappearance of dinosaurs from the fossil record.

Another core piece of evidence that supports the asteroid theory is something called Tectites. They've been found in abundance in several places, with one of the most astounding discoveries coming from North Dakota, USA. The leading theory is that they are actually pieces of molten earth crust that were shot up into the sky on impact. High in the atmosphere, they cooled into natural glass, and then rained back down onto the earth in a glass shower at speeds of 160 to 300 kilometers per hour.

And remember, North Dakota is 3,000 kilometers away from the impact. So let's gather this evidence together and paint a picture for our alien travelers of what could have happened to Earth while they were filling up on gas. As our extraterrestrial explorers turned their back to Earth, they might have noticed an asteroid accelerating towards the planet, getting brighter and bigger against the blackness of space. About 10 to 15 kilometers wide and traveling at 7. 72,000 kilometers per hour, it makes contact just off the shore with the Yucatan Peninsula

of modern-day Mexico. This releases an insane amount of energy, all at one go, the equivalent of detonating billions of nuclear weapons at the same time. This was an earthquake felt around the globe. There's no way it went unnoticed, even by animals on the other side of the planet in modern-day Indonesia. At the impact site, the thermal radiation burns everything within a 1,500 km radius. The force of the impact from the asteroid makes the Earth's crust go molten and splash up like

water after a pebble has been dropped in, leaving behind a monstrous crater 25 kilometers deep and 100 kilometers wide. This causes a chain reaction of enormous tidal waves, hundreds of meters high, as the ocean pushed back from the immense force. Meanwhile, trillions of metric tons of debris, about 60 times the mass of the asteroid, explodes up into the atmosphere. Some of this debris are chunks of molten Earth crust, which, high in the atmosphere, coalesce into tectites.

And inevitably, what goes up must come down. For about 15 minutes following the initial impact, Earth is covered in a torrential storm of fire rain. Falling debris heats up to hundreds of degrees Celsius as it passes through Earth's atmosphere. This sets the world on fire, burning down 70% of its forests. Vaporized material that doesn't rain down as debris, such as silica dust from rocks, stays suspended in the atmosphere, along with unbelievable amounts of soot and carbon dioxide rising from the wildfires. If you're breathing a sigh of relief for our Indonesian dinosaur friends on the other side of

the planet, don't. Like with most things, it's never the actual impact that leads to the most devastation. It's the aftermath. The buildup of gases and particle debris in the atmosphere blocks out the sun, plunging the planet into an impact winter that will last at least 15 years. With no sun, plants are unable to photosynthesize, and both terrestrial and marine food chains collapse. Earth is a totally apocalyptic version of its former glory.

No wonder our alien travelers had to check their GPS. The impact this would have had on animals would have been devastating. 75% of all species are wiped out forever, making this one of the largest mass extinction events in Earth's history, second only to the Permian extinction we covered earlier in this video. All the animals that exist on Earth today are descendants of the survivors of this apocalypse. Others were not so lucky. Being large is a disadvantage in an apocalypse. You need lots of food, lots of space, and lots of resources. All terrestrial and marine dinosaurs suffered greatly and eventually died out as a result.

A small slither of avian dinosaurs had better luck and managed to slink through the evolutionary bottleneck into the Paleogene period. They still roam the Earth today through their direct descendants, birds. When we think of birds, we think beaks. But back in the Cretaceous days, birds came in all kinds of different, wonderful variations that we've never seen with our own eyes. Some had beaks, some didn't. Some had teeth, some didn't.

While it would be foolish to credit a single trait for the survival of an entire family line, it sure seems that if you were a bird 66 million years ago, having a beak stacked the odds in your favor. We think that beaked birds had an advantage, as they could dig out seeds from the ground when no other food source was available. Toward the end of the Cretaceous, Beaked birds were already eating a more varied diet than their non-beak cousins. This would have been a huge advantage when rations were scarce.

After all, being a picky eater in an apocalypse isn't really a good idea. Having enough force in the gizzard to crush tough fruits and seeds, and enough light stamina to gather food over large distances also helped with survival. Some species of mammal also managed to push through. He's thought that only mammals smaller than 10 cm survived, as they could hide underground where they were somewhat insulated from the lower global temperatures. Being small also meant they needed less food to survive. The platypus is an example of a mammal that coexisted with dinosaurs, survived their

K-PG extinction, and is still around to this day. Turtles also fared surprisingly well, although it isn't understood why. About 80% of the known turtle species made it through the K-PG extinction, as did crocodiles. While we can't be 100% sure why, some ideas are that crocodiles, like beaked-beak birds, have highly diverse diets, and they can survive without food for more than a year, thanks to their excellent energy conservation abilities. Following the catastrophe, repopulation seems to have happened very fast. If our alien scientists were to fly over Earth just 30,000 years later, they'd already

see flourishing new ecosystems rising from the ashes in some parts of the planet. Maybe it was for the best that our alien crew was low on Helium 3 and didn't have to witness the apocalypse first-hand. Revising our version of events, our alien friends are not convinced this is the false story. They are good scientists and better skeptics. Because the evidence paints one picture doesn't mean it can't also paint another. Indeed, that is the exact conundrum we Homo sapiens find ourselves in now. While many human scientists hold firmly to the asteroid theory, others think differently.

Let's rewind the tape and re-examine the evidence. The initial clue that started all this asteroid business is that pesky element eridium. While it is present in asteroids, it is also present in another key place, the Earth's core. This gives weight to another popular theory that crazy, strong volcanic eruptions could be the culprit behind the mass extinction instead. In this scenario, the world would still be covered by a blanket of smoke, soot and debris, tectites would rain down, and the sun would be blocked out for years, causing a super long winter and total ecosystem collapse, and our eridium would still make it into the geological record.

The effects are largely the same. The only difference is the root cause, so is an asteroid or volcanoes to blame? There is evidence showing massive volcanic activity during the late Cretaceous, before the supposed asteroid hit. Researchers say that the presence of flood basalt corresponds with three out of the five mass extinctions, including the one that killed the dinosaurs. Flood basalts are left behind when massive areas of land are rapidly flooded with lava. They leave behind the steppe-shaped igneous rock formations called traps. The great Permian extinction our alien friends witnessed was triggered

by volcanic eruptions that would later form the Siberian trap. Some scientists think the same thing happened to the dinosaurs and left its fingerprints in the deck and traps in modern-day West India. Data shows this region was highly active at the time of the dinosaur extinction. A violent eruption would have had far-reaching global effects, filling the atmosphere with dust, toxic sulfur and carbon dioxide gases, causing a wipeout in a similar way to the asteroid theory. Indeed, supercomputer simulations have shown that there is an incredibly strong correlation between flood basalt events and mass extinction events. much higher than pure chance.

However, some scientists don't think it is an either-or situation. A growing body of research is trying to reconcile a both-and version of events, suggesting that the impact of the asteroid and the subsequent earthquakes potentiated the ongoing volcanic activity, taking it over the lethal threshold and into mass extinction territory. But the extent to which each event played a role is still up for debauching. I hope this exploration of possible theories is enough to satisfy our alien scientists. By now, they've seen Earth in enough of its forms to know that if there is one thing they can rely on, it's transience. Earth won't be a ball of fiery rain and eternal winter

forever. It's just a matter of time before life springs up again. So they jump forward through time. And over 60 million years after their previous visit, our time-traveling aliens have returned to witness a truly magnificent and defining period in Earth's history, one which will shape the future of life on this planet and leave behind some of the most exciting paleontological relics ever discovered. The last Ice Age. Of course, these aliens are no strangers to Earth's dynamic changes throughout history. They've already witnessed great extinction events, extreme weather lasting for millennia, and

the evolution of increasingly complex life forms. But this visit is about to give our aliens a lesson in the extremes that life on Earth can endure. Over 100,000 years ago, many of our planet's ecosystems were reshaped by colossal ice sheets, piercing polar winds and barren landscapes, a glacial age where frigid temperatures lasted for millennia. And with the end of this period, period will cover the mysterious disappearance of many of its most iconic species. For reasons, we are still struggling to comprehend to this day. If they were being thorough, this Ice Age would not be the first our aliens have witnessed throughout Earth's history.

We've actually had five major ones in total. So what do they have in common? An Ice Age occurs when the Earth experiences cold temperatures for an extended period of time. millions to tens of millions of years, that is. This causes the Earth's surface to be taken over by large ice sheets and glaciers. The Ice Age we are talking about started around 2.6 million years ago with the dawn of the Pleistocene. And you may be surprised to learn that we are still in it.

Any ice age can feature both frozen glacial periods and warmer interglacial periods, and it is, in fact, the latest interglacial period that we've been experiencing for the past 11,000 years. So when people refer to the last ice age in popular culture, they often mean the last glacial period, which came right before and lasted from 115,000 to 11,700 years ago. It may also be surprising that the average temperature during the last glacial period was only about six degrees colder than today's global average. However, a global change in temperature can have profound effects, even when the difference is in the single digits. When we think about a six degree global drop in temperature, we mean six degrees worth of thermal energy being lost

from all our oceans, land masses, and the atmosphere combined. During our last glacial period, much of Europe and North America was dominated by two major expanses of ice, the Laurentide ice sheet and the Phenoscandian ice sheet. Because so much of Earth's limited water supply was locked away in these ice sheets, the average sea level was much lower, and the land mostly consisted of tundra-like vegetation spread across dry, grassy plains. There is no single factor that explains why the Earth was plunged into these frigid conditions. But a lot can be resolved by looking at its orbit at the time. Last century, the Serbian scientist Milutin Milankovic hypothesized that

long-term collective changes in the Earth's position relative to the Sun are a strong driver of Earth's long-term climate and could be used to explain how glaciation periods or ice ages are triggered. Melanchovich studied these three types of Earth orbital movements and how variations in these movements can change the amount of solar radiation that reaches Earth's surface. We mentioned those earlier in the video. They are the eccentric nature of Earth's orbit, or how close or far the planet is from the sun, which cycles every 100,000 years,

the planet's axis varying degree of tilt, which rocks back and forth over a 41,000-year period, and the Earth's axial procession, how much that axis wobbles, a 26,000-year cyclical shift. The combination of all three cycles works to influence the Earth's long-term climate, and they have been pretty reliable factors in predicting the major ice ages so far. However, shorter-term cycles are also important and can enhance or weaken these large-scale effects. Two major ones that occurred throughout the last Ice Age were the Dansgard-Ushka events associated with

sudden warming and Heinrich events causing rapid cooling. So here comes the big question, and it is indeed big, as you'll see in a moment, how did the creatures roaming on our planet adapt to these changes? What did they look like? How did they live? We mentioned that much of the last Ice Age occurred during the Pleistocene epoch, which spanned from 2.6 million to around 11,700 years ago. The Ice Age was a time when mega fauna walked the earth. And the word mega is no overstatement. Some of the largest of these creatures weighed 4,500 kilograms.

There are a few theories as to why everything tended towards the gigantic during the Ice Age, which involved different animal strategies for conserving energy. For example, Bergman's rule describes how. how for animals that produce their own body heat, like mammals, the colder the environment, the larger their body size. This is because larger-bodied mammals have a lower surface area to volume ratio, which prevents them from losing heat easily to the surroundings. So this might partly explain why so many large and imposing species evolved during the ice age, colder temperatures meant more pressure on animals to minimize heat loss if they wanted to survive.

Although the general strategy was to be big during the Ice Age, the diversity of species at the time proves that there were lots of different ways to do it. Let's start with the most famous one. Woolly mammoths are a picture of the Ice Age itself for most of us, a towering, dominating presence, marching through great snowdrifts, seemingly impervious to the cold. But the reality was perhaps slightly different from what we imagine. Woolly mammoths weren't actually much bigger than modern-day elephants.

Measurements made from their skeletons tell us that their shoulder height was 3.5 meters, whereas some of the larger male African elephants today can reach heights of 4 meters. Although they may have been a similar height to the elephants we know, they did have some key physical differences. Woolly mammoths aptly had warm, double-coated fur, separated into a thick underwall, and a layer of longer outer hairs. They also differed in their proportions

with longer bodies and shorter legs than modern elephants. Paleontologists think this was so they didn't have to stoop so much to graze on tundra-like vegetation, which is typically shorter than the trees and bushes of the savannah or rainforest. Further aiding their insulation was a layer of fat up to nine centimeters thick and small hair-covered ears to prevent heat loss. Finally, they had a raised bump on the top of their heads, which contained

large sinuses. This may have helped them to humidify and warm the air as they were breathing, a useful skill for Arctic conditions. Despite our best efforts to resurrect them, Wally mammoths are sadly extinct, though watch this space as a Texas biotech company colossal biosciences, is attempting to create a live woolly mammoth, or more specifically, a cold resistant elephant with the traits of the woolly mammoth, perhaps as soon as 2028. But woolly mammoths didn't all go extinct at once. In fact, it's now accepted that a population of 500 to 1,000 molly mammoths survived on Rangel Island until around 4,000 years ago. That's 1,000 years after

the great pyramids of Giza were built. Scientists think that the mammoths made it to the island across the land bridge of Beringia, which used to connect Alaska and Siberia before it was submerged under the Arctic Ocean. Now, onto some of the more obscure creatures of that glacial period. The Glyptodont. Their name means carved tooth in Greek, owing to the wide, grooved structure of their teeth, which was adapted for them to grind on the tough vegetation of the land they grazed. They were large, cumbersome creatures, weighing up to two tons, and walking on elephant-sized legs across the Americas. Their bodies were protected by a huge turtle-like shell or carapace, giving them a similar look to an armadillo, although they couldn't roll up into a ball.

So you can think of them as a distant relative of the armadillos that behaved more like a land tortoise or a hippopotamus. Quite the wacky combination evolution-wise. Our aliens would be forgiven for thinking that these creatures don't get around much, but recent studies testing the strength indicators of the Glyptodon's forearms have revealed that they bore most of their weight on their back legs, and they may have even been able to stand on them bipedally. This conjures up some even crazier images, a glyptodont standing to deliver a blow with their armate tail, or to reach a high food source, and proves that these creatures were

not to be messed with. The next creature might surprise you, as it still has relatives alive today, although we get to meet a mere fraction of the diversity that our alien travelers would have The late Pleistocene sloth included 27 genera in four families and an unknown number of species. These were great dispersers and roamed across the Americas, even reaching the Caribbean islands in the middle, Neogene, before the Isthmus of Panama formed. This is probably part of the reason why they were able to diversify into so many species, since they were exposed. to many different habitats. Through time, the sloths tended towards larger sizes, and by the late Pleistocene, nature had given birth to a group called giant ground sloths. Within this group, Eramotherium combined the height of a giraffe with the bulk of an elephant, and the first described

sloth fossil Megatherium Americanaum had an estimated body mass of 3,0008. 800 kilograms. Our modern-day sloths are puny in comparison. Their Pleistocene ancestors were around 950 times heavier, far more widespread, and if the relics they've left behind are anything to go by, they got up to a lot more. In a study from 2020, paleontologists reported finding the remains of at least 22 erymytherium sloths of various ages in the sediments of the sediments of the of Tanke Loma on the southwest coast of Ecuador.

It's likely that the sloths got caught in a shrinking watering hole during a drought and died from disease or starvation as the drought killed off their food sources. But weirdly enough, this autopsy report tells us a lot about how these animals lived, and that's where scientists get excited. Think about it. We know that they congregated at watering holes, suggesting that they were sociable animals, and that they were wallowing in the water to escape the sun and insects. Though the last glacial period was dominated by ice sheets,

they didn't cover the entire globe. Tropical regions like Ecuador see warmer seasons when animals would have needed a cool refuge. The sloth's wallowing behavior is shared with many large African mammals alive today, like hippos or rhinos. So it turns out that the Pleistocene watering holes were still the bustling ecological hubs they are today. So we know where they hung out,

but what else were the giant ground sloths getting up to? Mar del Plata in Argentina is home to several paleo burrows, which have been discovered intermittently over the past century. 42 of the largest burrows were dated back to the pliocene, or late Pleistocene, and reached 5 to 6 meters below the surface. At their largest, they are 1.8 meters wide and 40 meters long. Several mammal candidates were considered as the possible builders for these structures, but scientists now think that the culprits were the glossotherium and solidotherium ground sloths,

and there are several reasons why. The first clues were the arm bones of these sloths, which were designed to form a shovel-like structure with unusually long second and third fingers, making them well adapted for digging. The bones were strong too, designed to withstand intense bending forces similar to those experienced by modern galloping mammals. From further detective work on their skeletons, paleontologists estimated that these groundslost center of gravity was found above their hind feet, which suggests they too could achieve

a bipedal posture. This is a major requirement for digging, as your arms have to be able to exert pressure on the soil you're trying to dig, rather than support your body weight all the time. And the final clue? Well, this one quite literally caught the sloths red-handed. See, there were several claw marks on the sides and roofs of the burrow that had been perfectly fossilized with the tunnels themselves. So, paleontologists just had to match up these marks to the hand skeletons of the sloths, and just like that, it was a perfect fit. So, we can be pretty confident that we found the burrowers.

But considering these ground sloths weighed between 800 and 1,200 kilograms, this behavior is incredible and gives us real insight into the kinds of pressures they must have been facing. Scientists have proposed that the sloths may have relocated underground as a way to insulate themselves against the cold or shield themselves from the heat, depending on the climate at the time. It's also been suggested that the sloths were trying to escape predators, which really makes you wonder what kind of animal would want to take them on. Most likely, a saber-toothed cat or giant short-faced bear? As our aliens watch these big, tough creatures, brave weather extremes, megacized predators and shifting populations, they are excited to see them

emerge into the next epoch with their innate knack for survival. Except that's not what happens. Almost without warning, they vanish at the end of the Pleistocene. Between 72 and 88% of these large body creatures are lost from Australia and North and South America alone. But how? Why? Well, this topic has been intensely debated among human paleontologists for nearly a century. Some suggest that natural climate change was to blame, as the dawn of the interglacial period meant that sea levels started to rise, cutting off the land bridges and melting the ice sheets that species needed to reach more thermally suitable habitats. However, we've seen this explanation isn't a perfect fit, as some groups like the Wrangel Island mammoths survived far beyond this transition.

The other major theory was first proposed in the 1960, and brings us to the next point on our Ice Age journey. Humans. For the first time ever during their visits to Earth, our time-traveling aliens are gazing down on our very own ancestors. Homo sapiens evolved around 300,000 years ago, migrating out of Africa to colonize regions around the globe. This means they've lived through a fair chunk of the Pleistocene.

and shared the land with other ice-age creatures of the time. So much so, the paleontologists and our aliens are wondering whether we were responsible for the mega fauna extinctions at the end of the Pleistocene. Could this be true? Could we have taken on great woolly mammoths and giant ground sloths and won? To answer these questions,

the aliens are taking a close. a look at our ancestors of old. They may have evolved 300,000 years ago, but it wasn't until the late Paleolithic, or between 50,000 and 10,000 years ago, that Homo sapiens started to experience real cultural development. Hunter-gatherer culture was at its peak, and human burial practices started to spread between multiple human populations, so the paleoontological relics from this time period, are unusually good. We started to use more diverse tools, made personal decorations like pendants, and invested more energy in activities that went beyond just surviving. For example,

cave art was used as an outlet for humans to interpret the world around them, and many of the images they created can still be seen today. One of the most impressive, described as the Sistine Chapel of pre-history was discovered in Lesko Cave in Montignac, France. In just a small cave, over 500 painted and 1,500 engraved images have been found that were created up to 22,500 thousand years ago. From these images, you can see that aspiring human artists, mostly focused on animal subjects, perhaps as a testament to their hunter culture, or their close relationship with wildlife. Either way, we know our ancestors were aware of the Ice Age megafauna around them,

but were they capable of driving them extinct? We've talked about the rapid improvements to tools during the late Paleolithic, and this would have massively improved our ability to hunt. One brave Homo sapiens versus a woolly mammoth is unlikely to end well, but a whole group of them, armed with sharpness, spears that can throw them up to 40 metres, that creates a more even playing field. One particularly skilled group of hunters were the Clovis, the ancient ancestors of Native Americans, who had distinctively shaped spearheads or Clovis points. The fine craftsmanship of these

weapons suggested that these people were expert hunters, capable of taking on the local megafauna of North America where they lived. Another point of contention was the fact that, within a few thousand years of the Clovis people arriving in North America and spreading across the region, the megafauna had gone extinct. So we have to wonder whether it was the intense Clovis predation that led the last populations of these animals to collapse. Either that, or the timing is a pretty big coincidence. A 2024 study sought to investigate this by analyzing the only known Clovis individual, the 18-month-old Anzic child, which was first discovered in 1968 in western Montana.

The bones of the child are thought to be 12,700 years old, and a stable isotope analysis was used to create the protein diet of its mother. Researchers found that mammoth contributed around 40% to the maternal protein diet, and were similar to the diet of a mammoth specialist predator, the scimitar cat. This lends support to the theory that the Clovis people, with their effective longer-distance weapons and hunting strategies, were at least partially responsible for the rapid megafauna extinctions in North America. However, we're still lacking in paleontological remains for these people,

so we can't say that the conclusions drawn from the Ancic Child would be the same for all Clovis hunters. But if this evidence is anything to go by, our aliens would be right to want to keep an eye on the suspicious activities of Homo sapiens. And what about other regions? Megafauna suffered heavy extinctions in Australia too. Like North America, Australia lost 85% of its large mammal species right around the time that humans became established there.

Seems like, whenever humans arrive, things are. start to collapse. Paleontologists have some nifty tricks to piece together the timeline for this collapse, like measuring the levels of fungal spores, which are commonly produced in the dung of herbivores, as a proxy for megafauna populations. So, the more spores, the more mega-sized herbivores there were at the time. From this data, they found that megafaunal populations collapsed within 4,000 years of humans arriving. Although there were environmental changes in the tens of thousands of years before the

collapse, including wildfires and a transition from woodland to shrubland, humans were probably the straw that broke the mega camels back, and their hunting pressure was too intense for these animals to recover. Large mammals, like the megafauna, typically have slow population growth and don't reproduce often, so even low-intensity hunting would have a big impact. All in all, we're probably not giving the friendliest first impression to our time-traveling aliens. We seem to be at least partly responsible for the loss of lots of other Ice Age species, and it's not only the megafauna that were affected. Another mysterious disappearance in the late Pleistocene were the Neanderthals,

who vanished around 40,000 years ago. Neanderthals were the first humans to survive a cold, glacial ecosystem, with clever adaptations to do so. They were short and stocky, reaching maximum heights of around 160 centimetres. They had large noses with a high bridge, creating a larger nasal chamber which humidified the air as they breathed, a similar adaptation to the mammoths. Contrary to popular belief, the Neanderthals had quite a sophisticated culture.

They were also partial to cave art, ornamental objects and burial rituals just like Homo sapiens. So with all these abilities to help them survive the extreme climate, how did they come to meet their end? You guessed it, we might be to blame for this one too. Paleontologists think that we either out-competed them, or they didn't. were absorbed into our populations, which happened to be larger at the time. In fact, most people of European or Asian descent share between 1% and 2% of their DNA with Neanderthals, which would support the second theory. As for competition, the latest data suggests that Neanderthals and modern humans coexisted happily for up to several thousand

years in Europe, but it's possible that in some regions where resources were scarce, The pressure was greater, and we did compete more with our evolutionary cousins. Whilst their stocky bodies may have helped them produce and retain heat, this also made them worse at conserving energy. With bodies that were costlier to run, it was probably easier for the more energy-efficient Homo sapiens to move in and take over. Like many debates emerging from this time period, there's no simple answer for the Neanderthals' disappearance.

and the situation varies from place to place. Though we may have been the better competitor, then Neanderthals get a bad rep, and every new discovery adds to our appreciation of the complex culture, language and tools they left behind. There's no doubt that the last Ice Age brought about huge developments that would change the course of Earth's history forever, changes that our time-travelling aliens had come to witness.

Despite the unpredictable nature of this era, plenty of species were able to thrive during both glacial and interglacial periods, diversifying, evolving huge body sizes, and developing innovative ways to combat climate extremes. Though not everyone made it out alive, it's amazing to think that Homo sapiens once shared the land with these weird and wonderful species, human and animal alike. But perhaps the more concerning question is whether this will happen again.

We've already touched on the fact that the Earth has seen five major ice ages throughout its history, and this most recent one is still ongoing, is another glaciation event looming in our planet's future. We've mentioned Heinrich events, which occur on more short-term scale to the Milankovic cycles, and can cause periods of cooling around every 10,000 years. They happen when large amounts of ice are discharged into the ocean, which produces a global footprint that has historically made regions of North America and Eurasia become colder and drier. Data on the subsurface ocean temperatures has revealed that warming usually happens in the hundreds to thousands of years before these ice loss events,

as this is what destabilizes the ice sheet and promotes its breakup. This warming contributes to a weakening of the AMRQ, and both these factors act as triggers for Heinrich events. We've made a video on the AMARC over on Astrum Earth, which you can check out for more information. But the point is that we are seeing both of these signs happening now, so they could be warning signs a Heinrich event is coming. If it does, then it could cause enough cooling to trigger another glaciation period. Though, it's hard to say for sure.

It would probably have to coincide with another Milankovic cycle to cause Pleistocene levels of ice. But either way, things could get frosty. If we did experience another glaciation period, I wonder which species would survive. Would they have time to adapt? Or would temperatures plummet before they had the chance? Can Homo sapiens survive yet another age dominated by ice? Or are we in danger of being wiped out by something better adapted than us? As our aliens pack their notes away and leave the Ice Age behind, I'm sure they're left impressed

by the diversity of life that lived through this epoch of Earth's history. Though many of these creatures are now just remnants of the past, they still capture our curiosity with their skeletons, burrows, and even burial sites. Hinting at a world where, at least for a while, mankind lived alongside towering beasts and human kin, navigating the same raw, unforgiving wilderness together. With this, our aliens have witnessed almost the entirety of Earth's history up until the present day. But why stop there? These are time-travelling aliens, after all.

What might they witness in our planet's future? What is the Earth's ultimate destination? It turns out the outlook is bleak. When they arrive 500 million years from now, Earth is in danger, facing an extinction event unlike anything seen before. More devastating than the asteroid that wiped out the dinosaurs. More deadly than the volcanic eruptions that killed off 96% of marine species and 70% of land creatures 252 million years ago.

Instead, this great demise of life on Earth will be orchestrated by something we need, something we rely on, in fact. What will be the culprit? None other than our own life-giving sun. As our star gets brighter over the next billion years, the finely tuned balance that has kept our planet thriving for eons will begin to shatter. Our oceans, atmosphere and tectonics will shift so drastically that Earth becomes completely unrecognizable. The question is, will anything survive? Let's find out. This is the story of the future of our planet.

And although I mentioned it's our sun that has the potential to wipe out life, there's a lot of other stuff going on too. I'll take you through it all. But before we get started, a few disclaimers. Firstly, we'll be assuming that there is no human influence in any of this. We are covering how we think natural processes will play out on our planet, without humanity's intervention. Though, we'll come back to humans at the end. Secondly, it's useful to point out that Earth's future is not very well defined. We can project a general idea of what might happen based on our knowledge of planetary science,

geology and biochemistry, but a billion years is a really, really long time. I mean, one billion years ago, there were no such things as plants, almost no oxygen in Earth's atmosphere, and the continents were clustered together into a single landmass. Our home was literally a different world. Earth a billion years in the future will be just as foreign. Nevertheless, all the predictions I'm about to share are based in science, even if they feel a little vague. So, without further ado, let's see what's in store for Earth. Run the tape forward. One of Earth's most unique features is its plate tectonics.

And the first thing we notice is how fast plate tectonics shift. What we know is the Earth's plates have been moving for more than 3 billion years, and they're showing no signs of stopping. As per geologist Dr. Christopher Scottis's Pangea Proxima theory in 100 million years, based on the current trajectory of the continents, the map of the world looks something like this. Africa, which split into two continents a few million years earlier, collides with Europe and Arabia, closing the Mediterranean Red Sea and the Persian Gulf.

A massive Mediterranean mountain range, possibly higher than Everest, will run from Spain to Asia. Australia joined Southeast Asia, compressing Indonesia and the Philippines into new mountains. North America and Eurasia move apart, widening the Atlantic Ocean. Southern and Baja, California, joined Alaska, forming a new American mountain range, while the rocky mountains erode down into lowlands. In the hands of tectonics and subduction, the earth's surface is incredibly malleable. Eventually, in 250 million years, the land masses of the world converge into a new supercontinent called Pangea Proxima. The Atlantic and Indian oceans close, bringing the Americas together with Eurasia and Africa. South America curls around the southern

tip of Africa and Antarctica, creating an inland sea. The movement of these continents disrupts the global conveyor system of ocean currents. A lack of circulation, causes the water deeper than a few hundred meters to lose its oxygen, becoming unable to support most life, leading to another great extinction event. The land doesn't fare much better than the water either. Inland, the continent will experience semi-arid or desert climates, with extreme temperatures reaching up to 55 degrees Celsius. The only areas likely to be habitable for land mammals are those closest to the poles. But this configuration won't last forever.

Eventually, Earth's land masses will fan out again in an almost cyclical fashion. Whilst on the surface, they look drastic, these shifting continents are nowhere near the biggest changes life on Earth faces. We all know that atmospheric carbon dioxide levels influence the planet's climate. Luckily, the Earth has a built-in feedback loop

that naturally regulates these levels over millions of years. It's known as the carbonate silicate cycle, and it works in four main steps. When a volcano erupts, it emits carbon dioxide into the atmosphere. There, it interacts with water vapor to form carbonic acid. This slightly acidic water condenses into rain and cascades onto the earth's crust below. The carbonic acid in the rain reacts with the silicate materials in the rocks to form dissolved ions like calcium and bicarbonate. which gets swept up by streams and rivers. Once in the ocean, these ions are used by marine organisms to build their shells and skeletons,

which are made of calcium carbonate. You'll notice carbon dioxide reappears here as a byproduct. This process of chemical weathering has essentially pulled carbon dioxide out of the atmosphere and stored it in the ocean. When marine organisms die, their shells are eventually buried in the sea floor, forming carbonate rocks. Over millions of years, the oceanic crust, carrying these carbonate rocks, is subducted into the mantle, ready to be released via volcanic outgassing, and the cycle starts again. It's a delicate balance that keeps the planet's temperature, climate and atmosphere

in check when humans aren't getting in the way. But when the alien scientists return in 500 million years, something will have a much bigger impact on our climate than us. us or this cycle. The Sun. Small, subtle changes our star has been going through all this time finally become apparent, and its effects are felt on Earth like never before. As a main sequence star, our Sun is constantly fusing hydrogen into helium in its core. Since helium is heavier than hydrogen, over millions of years the Sun's core is becoming denser

and more contracted. Because of this, the outer layers of the Sun move close. hosted to the center too, and in the process, gravitational potential energy is released as heat and light. This increases the pressure and temperature of the core, which in turn accelerates the rate of fusion. The result is that the sun increases its energy output, and in turn its brightness as it ages. This has consequences.

As the sun gets hotter and brighter, it's also getting wider because of the extra energy being produced in the core. The Sun is stuck in the middle of a game of tug-of-war between two forces, this outward pushing force generated by nuclear fusion and the inward pull of the stars' own gravity. On the whole, this system looks stable, but zoom out to a timescale of billions of years, and you can see that it isn't. As more and more hydrogen is used up, the Sun's core slowly starts collapsing, while the outer layers grow larger.

Right now, the sun is getting over 1% brighter every 100 million years. So, in 500 million years, the sun will be about 5% brighter than today. This extra energy warms Earth, speeds up reaction rates and causes oceans to evaporate, which we'll come back to. This increase in reaction rates accelerates chemical weathering, pulling carbon dioxide out of the atmosphere faster than volcanic outgassing can replace it. Atmospheric carbon dioxide plummets. This is the start of the plant apocalypse that our aliens will have to witness.

Think of plants like tiny factories. Using photosynthesis, they turn carbon dioxide into sugar, which they use to grow and build new things, but they also need to burn some of that sugar for energy to keep everything running smoothly, a process known as respiration. When the amount of carbon dioxide gained from photosynthes, is equal to the carbon dioxide lost from respiration, the plant is at its compensation point.

It is breaking even energetically. To grow big and healthy, the plant must make more sugar than it burns. If it doesn't, the plant eventually dies. Photosynthesis comes in two main forms, C3 and C4. Most plants, including trees, grasses, root vegetables, cotton, and stable grains like wheat, rice, and oats are C3 plants. They need relatively high levels of carbon dioxide because their system isn't very efficient. According to a 2019 study from the International Journal of Astrobiology, within about 500 million years, the concentration of carbon dioxide will fall below 150 parts per million, lower than the critical threshold needed to sustain C3 photosynthesis. But this extinction

event is a slow burn. Plant groups die off one by one, well before the 150 parts per million level is reached. However, it won't kill them all. There's still the C4 plants, which make up just 5% of Earth's plant biomass today. They can survive on much less atmospheric carbon dioxide, just 10 parts per million, because they have evolved a different enzyme system and therefore have a higher carbon dioxide resistance. It's thought to be a more carbon dioxide resistance. It's C4 plants could survive anywhere from 800 million to 1.2 billion years into the future. But even with this brilliant ruse up their leaves, they can't outlive the brightening sun. Our aliens jump forward in time. In 1 billion years, the sun is just over halfway through

its main sequence lifetime. As its core gets even denser, the rate of fusion increases too. Today, the sun turns 600 million tons of hydrogen into helium and every second, in the process converting about 4 million tons of matter into energy. The more energy it releases, the more luminous the star appears. And if they travel forward in time another billion years, the sun becomes 10% brighter than it is today. The effects on Earth are disastrous. Models vary wildly, but some believe the surface temperature could skyrocket to a sweltering

50 degrees Celsius or more. more than triple the 20th century average. This transforms the planet into a near, uninhabitable world. Oceans evaporate faster than rainfall can replace them. Vast regions turn into deserts reaching over 70 degrees Celsius in the daytime. Without photosynthesis, oxygen levels in the atmosphere fall to about 1% of what they are today. This would be devastating for complex life that relies on it to breathe. But it's more likely they'd starve to death before this became an issue for them. With no plans to eat, herbivores die out, and carnivores quickly follow. It must be tempting in all of this for the aliens to interfere, to save some species

from their inevitable tragic end. But like with every extinction that has gone on before, our aliens must observe only whatever their desires. The Earth must tread its course. So far we've covered how rising temperatures affect the carbonate silicate cycle, cause atmospheric CO2 levels to drop and spell the end of complex, spell the animal life on Earth. But there's one more key piece to the puzzle, oceans. A billion years from now, 27% of our modern oceans have already been subducted into the

Earth's mantle. The rest won't stay put for long. As the sun grows hotter, the oceans start to evaporate, turning the sky into a thick, steamy greenhouse. Water vapor fills the lower atmosphere, warming the planet steadily. The water cycle persists, rain still falls and river still flow, things remain pretty stable for a while. As that water vapor accumulates in the atmosphere, it creates an insulating blanket around the planet. Temperatures continue to rise, eventually triggering a runaway greenhouse effect. Increasing the Earth's temperature uncontrollably, the only other planet

where we've seen anything like this is Venus. Today it's completely uninhabitable at around 460 degrees Celsius with pressures similar to being 900 meters under the ocean. When we gaze over at the goddess of love, are we seeing our own future? Depending on the pace of this evaporation, Earth is doomed to lose its oceans within 1 to 1.5 billion years. Yet Earth won't be entirely dry, at least not right away. Deep down, below the crust, huge amounts of water. Perhaps several times the amount in Earth's modern-day oceans are still locked away. Over time, some of that water seeps back to the surface through geological activity,

but it won't be enough to bring back the seas. The last place surface water persists are the poles, but with no rivers to feed them and no life to decompose, these polar lakes are no more than sterile nutrient-poor puddles. Eventually, even these evaporate too. Earth transforms into a barren desert world. Massive dune fields stretch across the equator, and salt flats mark the old ocean floors,

similar to the Atacama Desert in Chile. Without surface water, the earth's crust dries out. Without lubrication, then, seduction can no longer take place. Tectonic activity grinds to a halt, freezing earth's plates in place. In the absence of that geological action, our planet slowly begins accumulating impact craters and shield volcanoes over mantle hotspots. Over millions of years, these volcanoes release trapped carbon dioxide from the mantle

into the atmosphere. The planet gets even hotter. A dry, suffocating world wrapped in a thick blanket of carbon oxide and water vapor. The only remaining hideouts are tucked away in underground ice caves or in high elevation mountains where the final smatterings of water could remain. Here, protected from the searing surface, we find Earth's last living creatures. Salt-loving microbes capable of enduring brutal heat and dehydration. Some might even drift high into the atmosphere, surviving in cooler layers above the scorch ground,

much like what scientists speculate could be possible on Venus, which potentially has a habitable zone 51 to 62 kilometers above its surface. 150 million kilometers away, the sun continues to brighten and intensify. 2.8 billion years from now, it is 28% brighter than today. pushing surface temperatures to around 190 degrees Celsius, even at the poles on Earth. They put up a good fight, but then the last of the microbes perish, and with them, all signs of life disappear. If our team of advanced alien scientists flew past Earth three billion years from now, they wouldn't detect a single biosignature.

They'd have no idea that our world once teamed with the buzz of lush rainforests, rushing rivers and waterfalls and a chattering human civilization, they'd see a barren world, a stagnant rock, waiting for the inevitable. In roughly six billion years, we approach the end of not just the Earth, but our entire solar system as our sun begins dying too. As it uses up the last of its hydrogen stores, fusion in the core stops. That outward pressure generated by the reaction, So there's nothing to counter the core's gravity and it starts collapsing.

As the sun's core contracts and heats, hydrogen fusion ignites in a shell around it, driving rapid expansion and a surge in brightness. Within another billion years, the sun's luminosity exceeds a thousand times what it is today as it swells from a sub-giant into a red giant. Red giants cool and shed vast amounts of mass through dense, stellar winds, material that could one day see new stars and planets. As the Sun loses about half its mass, its weakened gravity lets the outer planets drift outward, roughly doubling their orbits. Earth's orbit expands to about 1.5 astronomical units, but tidal forces eventually

pulled it inward again. At the Red Giant's peak in about 7.6 billion years, the Sun's radius reaches 1.19 astronomical units, 256 times what it is now, and engulfs the Earth, consuming our planet entirely. Until recently, scientists differed on how likely it was that Earth would be swallowed up by the sun, with some suggesting our orbit could expand as the Sun grows, moving us out of the danger zone and saving us from this grisly fate. But a new study using data from NASA's transiting Exoplanet survey satellite shows planets are being destroyed all over the galaxy, and it doesn't look good for Earth. They found more than 130 potential planets, but there were very few around red giants,

implying they had vanished. It seems stars swallow their inner planets far more often than we had previously thought. author, Dr. Edward Bryant, stated that we expected to see this effect, but we were still surprised by just how efficient these stars seem to be at engulfing their close planets. So with Earth and the other inner rocky worlds of our solar system gone, the sun sheds its outer layers, leaving behind its hot, dense core. Over trillions of years, this white dwarf will gradually cool and fade, taking with it any memory of the solar system it once ruled.

And as its last light dwindles into darkness, our visiting aliens finally turn off their scanning devices, pack away their things, and leave for the last time. Their billions of years-long mission to see the life of planet Earth and this solar system is finally complete. But is that really it? Even though this is written in the stars, it doesn't mean it's will spell the end for us. I mentioned at the beginning that this is what would happen assuming no human intervention, but humans have a compulsive habit of rewriting nature's story. We've done

it so many times already, just imagine what we may be capable of in a few million years, if we make it that far. We could intervene to find ways of adapting to or even preventing some of these events from occurring by terraforming parts of Earth for survival, or perhaps even colonizing other planets. The Earth's story may end, but ours doesn't have to. And even if it does, that's okay. After all, we are made of star dust, so it's only fitting that we're reunited with the stars. I want to give a quick shout out to a special supermassive black hole tier member on Patreon,

Brian Kaye. Thank you for going above and beyond to support the channel. There's a reason these educational mini-documentaries are free for everyone. It's not just the ads or sponsors, but it's thanks to our hundreds of Patreon members who make it possible for everyone to get the best possible content. If you'd like to be part of that group, the people who keep space education open to everyone, join us on Patreon through the link below. We would love to have you.