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, 1
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. Something my good friend James
Stewart from Astram Earth knows all
about.
>> Yeah, thanks Alex. 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 Scotiz's pangia proxima
theory in a 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 Persian
Gulf. A vast Mediterranean mountain
range, possibly higher than Everest,
will run from Spain to Asia. Australia
joins Southeast Asia, compressing
Indonesia and the Philippines into new
mountains. North America and Eurasia
move apart, widening the Atlantic Ocean.
Southern and Baja California join
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 superc continent called Pangia
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 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 semiarid or desert
climates with extreme temperatures
reaching up to 55° C. The only areas
likely to be habitable for lamb mammals
are those closest to the poles. But this
configuration won't last forever.
Eventually, Earth's lamb masses will fan
out again in an almost cyclical fashion.
please click the link if you want to find out more. But for now, it's Back to
the Future with Alex.
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
silicut 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 silicut materials in the rocks to
form dissolved ions like calcium and
bicarbonate which get 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 seafloor,
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 in 500 million years, something
will have a much bigger impact on our
climate than 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 closer 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
tugofwar 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 time scale 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. It seems
atmosphere cause plants to start dying out? 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 photosynthesis 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 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.
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 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 we 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° C 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° C 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 plants to eat,
herbivores die out and carnivores
quickly follow.
So far, we've covered how rising
temperatures affect the carbonet silicut
cycle, cause atmospheric CO2 levels to
drop and spell the end of complex plant
and 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 rivers 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°
C with pressures similar to being 900 m
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 nutriump
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 Atakama desert in Chile. Without
surface water, the Earth's crust dries
out. Without lubrication, subduction 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 dioxide 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.
Saltloving microbes capable of enduring
brutal heat and dehydration. Some might
even drift high into the atmosphere,
surviving in cooler layers above the
scorched ground. Much like what
scientists speculate could be possible
on Venus, which potentially has a
habitable zone 51 to 62 km above its
surface.
150 million km away, the sun continues
to brighten and intensify.
2.8 8 billion years from now, it is 28%
brighter than today, pushing surface
temperatures to around 190° C, 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 a team of advanced alien scientists
flew past Earth 3 billion years from
now, they wouldn't detect a single bio
signature. 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 6 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 disappears. 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 subgiant 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 pull it inward again. At the
red giant's peak in about 7.6 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 grizzly
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. Lead 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.
Even though this is written in the
stars, it doesn't mean it 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 stardust, so it's only
fitting that we're reunited with the
stars.