As a species, we're always thinking of ways to fix problems here on Earth, but how about
ways in which all life here on Earth is wiped out.
So today, we’re going to be discussing plausible ways in which Earth could be destroyed.
Now, before we begin, there’s a few notes you should keep in mind.
First, it’s important to note that destroying Earth is not an easy job.
Asteroids as big as the one that killed the dinosaurs don’t hit the planet often.
The chances of an asteroid of that size hitting earth is so improbable, that it only happens
perhaps once every 50 to 100 million years.
And yet, when asteroids that big do hit, they don’t wipe all life out on the planet.
The asteroid that wiped out the dinosaurs 65 million years ago, wiped out 75% of all
species on Earth at that time.
And second, as we’ll find out today, most of the ways in which all life on Earth could
be killed tend to be astrophysical events and not Human-made disasters, such as climate
change, nuclear warfare and so on.
The most popular one is a big asteroid hitting Earth.
Asteroids big enough to wipe all life out on Earth don’t hit Earth very frequently.
It takes a very large asteroid, one bigger than the one that ended the dinosaurs, to
kill all life on Earth.
The Mars sized body that theoretically created the Moon would most likely be large enough
to kill all life on Earth.
If a Mars sized object hit Earth today, it would probably kill all life on Earth and
create a new moon within a few million years, due to all the debris it sends out to space.
It’s always difficult to say if all life is dead on a planet since microbes like tardigrades
are able to withstand extreme conditions for long periods of time, including the vacuum
of space.
Asteroids of a big enough size do exist, but it’s exceptionally unlikely that one would
hit Earth.
It doesn’t necessarily have to be big asteroids though.
A medium sized asteroid could do the same amount of destruction as a massive one if
it impacted Earth at a higher speed.
Fortunately, the bigger they are the less frequently they come, and there’s a roughly
inverse relationship between size and frequency of asteroids.
However, that doesn’t necessarily mean that your civilization is always safe from asteroid
impacts.
A xenophobic civilization may decide to end your civilization by sending a seemingly innocent
asteroid in the direction of your planet.
We discussed this in a few Fermi paradox episodes, in the von Neumann probes episode and briefly
in the intelligent civilizations episode.
More so in the von Neumann probes episode, but we discussed how a hostile civilization
may use von Neumann probes to kill all life off in their galaxy and not using an asteroid.
There’s two ways a xenophobic civilization could do this, either find a sufficiently
sized asteroid and set it on course for the planet or construct an artificial asteroid
and set it on course for the planet.
If you were using a natural asteroid then, depending on how advanced the civilization
is, you need to find one that’s not in their solar system, since they’d notice all the
heat given off by the rockets.
However, if the civilization is primitive then you can redirect an asteroid from inside
their solar system and they wouldn’t have a clue, as they have no way of telling.
If an asteroid was on course to impact Earth, we would most likely know about it a few centuries
beforehand, giving us more than enough time to setup and colonize a base, either on the
Moon or Mars.
If we knew for certain that Earth would become uninhabitable then I’m sure the idea would
be to evacuate as many people as possible, instead of only a select few.
A black hole coming close enough to Earth and devouring it would be another way Earth
could be destroyed.
The odds of a black hole wandering into our solar system are even more improbable than
a large enough asteroid colliding with Earth.
It’s fairly easy to predict asteroid collisions centuries in advance.
We know that no major asteroids are going hit Earth for centuries and there are organisations
setup for the sole purpose of predicting asteroid collisions.
However, with a black hole, it’s a lot harder to see them coming if there’s nothing beside
it.
We see objects in space, either because they emit or reflect radiation.
But black holes do neither because they just take in the light, due to their exceptionally
strong gravitational pull that does not let anything escape, not even light the fastest
thing in the universe.
So with no matter in their immediate surroundings, black holes are invisible to us, except from
seeing a gravitational lensing effect on background stars.
But we can also black holes due to their effect on matter or celestial bodies.
A black hole consuming a star, stars orbiting a black hole, and so on are all ways we can
indirectly “see" black holes.
With that being said, a black hole couldn’t float into the solar system undetected.
As soon as it comes near enough to the outer regions of the solar system, the Oort cloud,
we would see the gravitational effect and know straight away.
If the black hole didn’t already have an accretion disk, it would most likely have
one now after it’s gathered matter from the Oort cloud.
It would begin to send asteroids and comets into Earth, increasing the chances of a very
large asteroid hitting Earth.
If an asteroid flung by the black hole didn’t end all life on Earth, then the gravitational
force of the black hole would, as it comes closer.
Another popular one is that a black hole gets made in a lab and starts eating the planet.
Hypothetically, a very advanced civilization could create a black hole in a lab.
If they were able to make a black hole, it would be very small.
A Mount Everest black hole, that would have a mass of 10^15 grams, would only be as big
as an atomic nuclei and would therefore fly straight though the planet, if it was fired
at Earth.
But before it could do that, it would emit Hawking radiation at an immense rate, because
black holes emit Hawking radiation at a rate inversely proportional to their mass.
So a black hole as small as one with a mass of Mount Everest would have an associated
temperature that is very high and would immediately evaporate into nothing, whereas a more massive
black hole evaporates a lot slower and has an associated temperature that is very low.
If the black hole hit you it would kill you because of the immense gravity involved.
But it would take a rather massive one to have any effect on Earth and I don’t think
we have to worry about scientists accidentally compressing an entire planet into a black
hole here on Earth.
As a general rule, planets don’t fit in a laboratory.
Another way Earth could be destroyed is from a nearby supernova.
If the supernova is close enough, the energy from it can be enough to remove Earth’s
ozone layer.
With no ozone layer, all life forms would be a lot more vulnerable to ultraviolet radiation
from the Sun, greatly increasing everyone’s chance of cancer.
A supernova as close as 100 light years or less, would have a profound impact on the
planet.
Fortunately, there are currently no supernova candidates close enough to do any damage.
However, it’s possible that that may change as Earth continues its orbit around the Milky
Way.
The solar system is just entering the Milky Way’s Orion Arm, where star formation is
more frequent meaning that it’s more likely that the solar system will come within range
of a supernova.
Supernovae are a lot more common that you’d expect.
The biggest stars, such as the hypergiants and supergiants, only have lifetimes of a
few million years compared to the Sun’s ten billion.
We can somewhat predict when a supernova is about to happen, but the radiation travels
at light speed so if you’re civilization is unaware then it would be doomed within
seconds.
Gamma ray bursts are a lot more dangerous as they’re completely unpredictable.
Most gamma ray bursts observed have been billions of light years away and harmless, but if one
was only 10,000 light years away all life on Earth would be destroyed.
A more realistic one is the Sun gradually getting hotter.
Every day the Sun gets a tiny bit warmer.
Every 110 million years, the Sun’s energy production increases by about 1%.
When Earth first formed, 4.5 billion years ago, the Sun only generated 70% of the energy
it produces now.
As the Sun produces more energy, the habitable zone moves further out.
Within a few billion years, way before the Sun explodes as a red giant, we will have
to colonize another planet unless we do something here on Earth.
But even if we prevented the increasing levels of solar luminosity, eventually Earth will
become so hot that all the oceans will evaporate.
We could colonize Mars.
Problem is, a few billion years after that the Sun will expand as a red giant and Mars
will become too hot as well.
That’s another one, the death of our Sun, where Earth will be engulfed by the Sun.
Another one is when the Milky Way will collide and merge with the Andromeda galaxy.
It’s thought that the Milky Way galaxy and Andromeda galaxy will collide in about 4 billion
years and take a few billion years to actually coalesce.
By then the Sun won’t have begun its helium burning process, so it won’t be a red giant
yet however Earth will become uninhabitable by then as the Sun will increase in enough
luminosity to wipe all life out on Earth.
Although the two supermassive black holes will merge, it’s very unlikely that there
will be any star collisions because of the large distances between each star system.
There is a small possibility that Earth could be ejected from the solar system and an even
smaller possibility of Earth being captured by another star after being ejected.
The supermassive black hole in the centre of our galaxy, Sagittarius A*, and the supermassive
black hole in the centre of Andromeda will begin to radiate very strong gravitational
waves once they’re only a light year apart and eventually marge.
It’s estimated that in about 150 billion years from now every other galaxy in the Local
Group will have merged into this galaxy.
All the possibilities we have discussed so far, an asteroid hitting Earth, a black hole
hitting Earth, a supernova and gamma rays, the death of the Sun and colliding galaxies
are all astrophysical events.
However, there is the possibility that Earth could be destroyed by Humans.
Earth could be destroyed by the outbreak of a deadly disease, global warming, nuclear
warfare, artificial intelligence or even the grey goo scenario.
Grey goo is an end of the world scenario by which tiny self replicating machines get out
of hand and uncontrollably consume all of Earth’s mass by using it to create more
of its self.
See the von Neumann probes episode for a more detailed discussion on self replicating machines.
Comment down below your thoughts on destroying Earth.
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Thank you so much for watching, have a nice day.