In anticipation of spooky october on this channel, we’re starting early because I
came up with more spooky scripts than I can fit in a single month.
One of the more spooky aspects of this universe are extinction events you don’t know about
beforehand.
The dinosaurs, for example, were blissfully unaware of what was coming their way 66 million
years ago.
One day they were going through their daily humdrum lives of eating plants and each other,
the next their world changed, and the earth turned bleak and dark almost instantly.
These changed conditions meant their doom as they desperately must have wandered the
hellscape that earth had become watching the extinction of their food.
This has happened a number of times in the history of life on earth, great dyings that
came about by means that the subjects of it had no understanding of.
A dinosaur did not know what an asteroid was.
As a technological civilization doing science, we like to think we do have a handle on this,
and indeed we are at the very beginnings of being able to detect and even deflect asteroids
that would have otherwise surely caused more dinosaur level extinction events here on earth.
But there have also been ideas advanced on how other natural phenomena could cause an
extinction event such as a gamma ray burst or supernova nearby that could sterilize the
surface of the earth.
There we do not yet have the technology to know exactly when it would happen, but we
also would need technology far in advance of what we have now in order to mitigate it.
Thankfully, this does not appear to be on our plate for the foreseeable future.
Earth’s current neighborhood is quiescent.
A backwater in a spiral arm in the suburbs of the galaxy.
There are currently no supernova prone stars close enough to Earth to be a threat, nor
does there appear to be any sources of gamma ray bursts, though it has been floated that
at least one extinction event in Earth’s history might have been caused by one.
The future however remains uncertain, the galaxy’s stars are dynamic and always on
the move and in the far future we may well face this kind of threat should we get too
close to a dangerous star.
But we can also mitigate that and shield earth from things like gamma ray bursts with solar
orbital shields, so long as we gain a sufficient command of astrophysics to know when such
an event is going to happen, there is no guarantee of that, but it’s an understanding we are
actively gaining even today this early in the game.
But another question can be asked, what of the cataclysmic events possible in the universe,
if any, that we don’t know about or aren’t currently thinking about in terms of extinction.
Within this, there is one that not only could cause the extinction of not just some of the
life on earth, but a sustained extinction event lasting millions of years that could
cause the extinction of most of the life present in the milky way.
It, in itself, may even be a solution to the Fermi Paradox.
It’s the idea that galaxies could get cataclysmically sterilized by their very centers.
Now this one may again be avoidable with high technology.
But it would be a technology that would need to be implemented not just on scales of decades
such as to mitigate an asteroid threat, nor millenia, but a shield being maintained for
at least a hundred million to over a billion years as the quasar rages.
You either maintain the shield or go extinct, or you go extinct and no longer maintain the
shield.
Any living worlds with surface life in such a galaxy that don’t have technology could
be rapidly wiped from existence and only their subsurface microbes might be able to hang
on.
For earth, it would be the reduction of life back to its earliest form, the anaerobic microbes.
The culprit in all of this, is one of the most cataclysmic events possible in the universe,
a quasar.
And they also happen to be one of the most mysterious astronomical events we know of
because we don’t entirely understand the mechanism for which they come about, or if
they could happen again.
A quasar is a type of Active Galactic Nucleus, but it’s not the only type.
So all quasars are active cores of galaxies, but not all active cores of galaxies are quasars.
Scientists think the mechanism for these objects are the supermassive black holes lying at
the centers of most galaxies.
Massive amounts of dust and gas falling into the black hole causes it’s accretion disk
and environs to go into radiation output overload, resulting in an extremely luminous galactic
core radiating strongly at most frequencies of the electromagnetic spectrum, due to the
extreme gravity and friction going on as the material falls in.
This material however goes silent once it passes the event horizon of the black hole.
Natures cataclysms often do this, the eye of a hurricane can be quite calm despite it
being the center of a dangerous storm.
Here the black hole is something like the eye of the storm of a quasar.
Even though one of the most intense environments possible is happening just outside it, inside
it is a mystery, but ultimately the black hole does not care.
It merely accretes matter at any rate in which it falls in.
This environment however requires very dense amounts of material for the black hole to
feed on, which galaxies early on tend to deplete, so most quasars we see are not just distant
in space, but distant in past.
They happened long ago, with the youngest one we know of coming in at about 600 million
years old as the light traveling the interstellar medium took that long to get here.
We do not see close quasars in our local group of galaxies.
The fact that we see no close quasars tends to suggest that they are a phenomenon more
of the early universe, than something that can happen today.
But that may not be the case.
The amount of dust and gas needed is already gone in most galaxies for a quasar, but plenty
still remains.
But we don’t actually know that quasars become impossible, because nothing stops the
conditions that create a quasar from happening again, to the point that in principle you
could create an artificial quasar if you gathered and moved enough material around, allowing
for a burst of energy almost unparalleled if a Kardashev type III civilization really
needed that for some reason, maybe to create a splinter universe of our own.
But with that comes the question of whether a quasar can turn back on.
The milky way may or may not have once been a quasar, it’s an unknown.
One possibility though is that this galaxy is semi-rare in that it never hosted one,
and unusually never went through that phase.
This is good, because if it had, any life forming up in the galaxy might have been sterilized
by the massive amount of broadband radiation emanating from the galactic core.
At the same time however, it could simply be that this galaxy has simply not reached
a quasar phase, yet.
To make a quasar, just add gas and dust, and that’s exactly what’s going to happen
when the Milky Way and Andromeda collide.
It pays to remember here that both the Milky Way and Andromeda have supermassive black
holes at their centers that will collide and merge when the two galaxies hit.
This process has already started, the haloes of the two galaxies are already interacting,
but the main action is due to happen in about 4.5 billion years.
Coming with that will be the merging of the two galaxy’s remaining gas and dust setting
up the possibility for a quasar igniting much later than the conditions presented by the
early universe.
Quasars near and far are spooky.
For the amount of energy produced, they are more or less the most powerful events that
happen in the universe, they are quite small.
All of that energy is compacted into an area not that much larger than the solar system.
The power of a trillion suns, concentrated in one small area.
There are even quasar ghosts, where the cataclysm happened, but shut off, yet left an echo reverberating
through the host galaxy visible as an eerie green emission from excited atoms, betraying
the violent recent history of that galaxy.
Recent observations however have expanded on this.
Observing 48 quasar galaxies, researchers found that in comparison to a group of 100
non-quasar galaxies, it could be established that galactic collisions do indeed cause some
quasars.
The quasars feature distorted structures indicating a galactic collision, and when that happens
huge amounts of gas and dust gravitate towards the central supermassive black holes.
This can cause a burst of star formation, but can also drive out remaining gas and dust
causing a galaxy to become extinct, as it were, with a subsequent fall off of star formation.
It turns out that the distant quasars we see are three times more likely to be interacting
with other galaxies than not.
Since quasars tend to happen earlier in the universe’s history, they probably weren’t
a problem for life because they eventually shut down before the galaxy is populated enough
with heavier elements from supernovae, though how that plays out is uncertain.
A late quasar however is extremely dangerous.
If a galaxy has life, but not civilizations that could mitigate the radiation with a billion
year shield, the quasar would basically sterilize that galaxy.
Earth won’t see this with the Andromeda collision, by that point the sun will be a
red giant and have swallowed earth entirely, or alternatively it will be baking it as a
cinder world.
But life anywhere else that can’t build a giant shade is in trouble.
This is made worse if we are truly early in the game in this galaxy, and life on average
takes far longer to get going than it did on earth.
By the time of the quasar, the galaxy could be burgeoning with life on countless worlds,
whereas right now, it may not be.
But there is hope, the quasar may not affect ice shell worlds harboring subsurface oceans
or microbial life existing beneath exoplanet crusts benefiting from natural shielding,
but surface life is not likely to survive the sustained, long term effects of a quasar.
You can however envision an odd scenario here.
Galactic collisions are predictable and take billions of years to unfold.
Once you have astronomy, you learn if it’s going to happen or not.
If you had a civilization in a galaxy, a motive to colonize the whole thing might be that
you simply don’t want all life in your galaxy to go extinct.
So you head out, looking for other life-bearing worlds in which to save them, setting up a
minimal presence there, and building a shield to protect that world from the rage of the
galactic core to keep life in the Milky Way going.
We can call this a shepherd civilization that’s merely looking to archive and preserve biology
in a galaxy because they value life.
They might prevent any species they find from meeting its armageddon.
This however likely would not make for a good technosignature because it would be difficult
to detect on intergalactic scales, this type of civilization would be on the order of a
Kardashev type III civilization, but at the same time wouldn’t behave like one despite
spanning an entire galaxy, because transits from active galactic nucleus shades wouldn’t
likely be detectable at intergalactic distances.
The irony being that such a civilization would not be trying to use the most powerful energy
source available to them, but rather they would be trying to hide from it, as a kind
of great terror of energy.
Imagine a scenario, 4.5 billion years from now.
In the skies of an exoplanet we’ve moved to because Earth is no more, we see the great
andromeda milky way collision unfolding before us in the night sky.
By that time, we will be a truly ancient species and barring resets and extinction events,
including those at our own hands, we might choose to head out and search the clement
worlds of the milky way and for that matter Andromeda for signs of life.
And then we might build star shades and save them to keep the chorus of life going in both
galaxies.
Or, if we are gone, or become something else, perhaps someone else might build a starshade
for us, the former life of the planet that once existed, known as earth that all the
universe forgot once existed.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently having just lost
a staring match with a possum.
I was winning until all of a sudden his eyes turned red.
That’ll make you blink.
Never underestimate a quantum mechanical possum, and spooky season is almost upon us and do
check out my books at your favorite online book retailer and subscribe to my channels
for regular, in-depth explorations into the interesting, weird and unknown aspects of
this amazing universe in which we live.