The Fermi Paradox — Where Are All The Aliens?

Are we the only living things
in the entire universe?

The observable universe is about
90 billion light years in diameter.

There are at least 100 billion galaxies,
each with 100 to 1000 billion stars.

Recently, we’ve learned that planets
are very common, too,

and there are probably
trillions and trillions

of habitable planets in the universe,

which means there should
be lots of opportunity

for life to develop and exist, right?

But where is it?

Shouldn’t the universe be
teeming with spaceships?

Let’s take a step back.

Even if there are alien civilizations
in other galaxies,

there’s no way we’ll ever know about them.

Basically, everything outside of our
direct galactic neighborhood—

the so-called Local Group—is pretty much
out of our reach forever,

because of the expansion of the universe.

Even if we had really fast spaceships,

it would literally take billions of years
to reach these places,

traveling through the emptiest areas
in the universe.

So, let’s focus on the Milky Way.

The Milky Way is our home galaxy.

It consists of up to 400 billion stars.

That’s a lot of stars—roughly 10,000 for
every grain of sand on Earth.

There are about 20 billion Sun-like stars
in the Milky Way

and estimates suggest that a fifth of them

have an Earth-sized planet in
its habitable zone—

the area with conditions that
enable life to exist.

If only 0.1% of those planets
harbored life,

there would be 1,000,000 planets
with life in the Milky Way.

But wait, there’s more!

The Milky Way is about
13 billion years old.

In the beginning, it would not have
been a good place for life,

because things exploded a lot.

But after one to two billion years,
the first habitable planets were born.

Earth is only 4 billion years old,

so there have probably
been trillions of chances

for life to develop on
other planets in the past.

If only a single one of them had developed
into a space-traveling super-civilization,

we would’ve noticed by now.

What would such a civilization look like?

There are three categories.

A Type I civilization would
be able to access

the whole energy available on its planet.

In case you’re wondering, we’re currently
around 0.73 on the scale

and we should reach Type I sometime in the
next couple of hundred years.

Type II would be a civilization
capable of harnessing

all of the energy of its home star.

This would require some serious science
fiction, but it is doable in principle—

concepts like the Dyson sphere, a giant
complex surrounding the Sun,

would be conceivable.

Type III is a civilization that
basically controls

its whole galaxy and its energy.

An alien race this advanced would
probably be god-like to us.

But why should we be able to see such
an alien civilization in the first place?

If we were to build generation spaceships
that could sustain a population

for around 1,000 years, we could colonize
the whole galaxy in 2 million years.

Sounds like a long time, but remember,
the Milky Way is huge,

so if it takes a couple of million years
to colonize the entire galaxy,

and there are possibly millions,
if not billions, of planets

that sustain life in the Milky Way,

and these other lifeforms
have had considerably

more time than we’ve had,

then… where are all the aliens?

This is the Fermi paradox,
and nobody has an answer to it.

But we do have some ideas.

Let’s talk about filters.

A filter, in this context,
represents a barrier

that is really hard for life to overcome.

They come in various degrees of scary.

One: there are Great Filters,
and we have passed them.

Maybe it is way harder for complex life
to develop than we think.

The process allowing life to begin hasn’t
yet been completely figured out,

and the conditions required
may be really complicated.

Maybe in the past the universe
was way more hostile

and only recently have things cooled down
to make complex life possible.

This would also mean that we may be
unique, or at least

one the first, if not
the first, civilization

in the entire universe.

Two: there are Great Filters,
and they are ahead of us.

This one would be really, really bad.

Maybe life on our level exists
everywhere in the universe,

but it gets destroyed when it
reaches a certain point,

a point that lies ahead of us.

For example, awesome
future technology exists,

but when activated,
it destroys the planet.

The last words of every advanced
civilization would be,

“This new device will solve all of our
problems once I push this button!”

If this is true, then we are closer to the
end than the beginning of human existence.

Or, maybe there is an ancient Type III
civilization that monitors the universe

and, once a civilization is advanced
enough, it gets eliminated

in an instant.

Maybe there is something out there
that it would be better not to discover.

There is no way for us to know.

One final thought: maybe we’re alone.

Right now, we have no evidence
that there’s any life besides us.

Nothing.

The universe appears to be empty and dead.

No-one sending us messages,
no-one answering our calls.

We may be completely alone,

trapped on a tiny moist mudball
in an eternal universe.

Does that thought scare you?

If it does, you’re having the
correct emotional reaction.

If we let life on this planet die,

perhaps there will be
no life left in the universe.

Life will be gone, maybe, forever.

If this is the case, we just have
to venture to the stars

and become the first Type III civilization

to keep the delicate
flame of life existing

and to spread it until the universe
breathes its final breath

and vanishes into oblivion.

The universe is too beautiful not
to be experienced by someone!

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