What will cause the end of Humanity ?

The one that says that at some point in the future, something is going to kill us all.
We don’t know how it will happen. We don’t know when it will happen. We don’t know why it will happen.
The worst part? We don’t even know if it will happen, which is a scary part by itself.

The theory? The “Great Filter” of civilizations.

Chapter 1: “If the Universe is so huge, then where is everybody?”

On a clear night in the countryside, look up to the sky and you may be lucky enough to see something like this:

It’s beautiful no doubt. Every single one of those bright dots represents a star much like “Sol”-our own Sun- and like our Sun, these stars all have their own set of planets like our Solar System:

But that’s insane, if you look up at the sky there must be a gazillion stars up there right?

Well yeah, it is insane and according to Minute Physics :
There are only about 5,000 stars visible to the naked, average, human eye… and because the Earth itself gets in the way, you can only see about a half of those from where you stand.
On a favourable night, you could see up to 2,500 stars in the night sky, all the visible stars we can see are the most luminous and largest stars within a 60 lightyear radius from Earth.

As Colin Stekkinger has corrected (reminded) me, in fact there are some stars that are visible further than the stated 60 lightyear radius:

“For example, Rigel is visible on almost any night, even with significant background noise. It's also 864 light years from Earth. Polaris, The North Star, is 433 light years from Earth. The Pleiades are an average of 444 light years from Earth, and a good eye can easily pick out the individual stars.”
But that’s hardly scratching the surface as our Galaxy has 100 billion stars, that tiny amount you’re looking at is just this:

Photo source: Google Images, exact site unknown (as of yet)- coincidentally (ps: it’s not actually a coincidence, it’s to do with the speed of light) the furthest extent of Human Radio signals just so happens to have the same sized area as the observable sky:

As Colin Stekkinger has cleverly continued to correct me, the closest galaxy to ours, “Andromeda” due to its large magnitude is still visible to the naked human eye despite being 2.5 million light years away.
So the question is this:

Given that even our Milky Way Galaxy alone has 100 billion stars and trillions of planets, where is everyone?
I mean let’s think about it for a second, here are the facts:

According to NASA (US Space Agency), at least 17% of all stars have planets similar to Earth (not too far or close to their Sun) to hold life so roughly 1/5 of all the stars in the universe have an Earth like planet.
There are 1 * 10^24 stars in the universe. This is 1 million billion billion stars (24 zeros) in the universe.
Thus, there should be 200,000 billion billion stars with an Earth like planet in the universe.
Let’s play it safe and say that only 1% of these planets ever develop life. In other words, 2,000 billion billion stars in the universe have developed life up until today (13.77 billion years after the universe begun).
And out of those stars above, playing it safe again let’s say only 0.01% of those planets have ever developed intelligent Human level life since the universe begun 13.77 billion years ago. This is still 200 million billion stars
Hell, using that logic, in our own Milky Way Galaxy the number of Star Systems with Intelligent Human level life since the universe begun should still be 20,000 Stars with Human level life in the surrounding planets.
Yet, in the 60 years since mankind entered the Space Age since the launching of Sputnik I in 1957, we’ve never found any traces of alien life, nor have we received one back so far.

Sputnik I (Soviet Union) was the first man-made satellite to be sent into space:

It’s annoying. There is no one calling out to us when yet there surely should be.

According to the Atlas of the Universe, within a 50 lightyear space there are 2,000 stars.

Author’s comments: So this seems to suggest then that we’ve hardly “scratched the surface”, perhaps for example the aliens have only just heard mankind’s first signal today and are sending a signal back as we speak, but we would not receive it for another 60 years if that were the case.
Yet, all of this is the wrong way of thinking about it.

Remember how I said the universe is 13.77 billion years old? Think about this for a moment. Theoretically, there could be millions of extraterrestrial races in existence already right? So they should be really advanced then right?

Why?

Below is a graph of Mankind’s technological progress in the last 4,400 years:

Because technological progress is logarithmic (speed of progress is increasing faster over the same amount of time), this allowed us to go from zero to hero real quick. In the span of 4,400 years, Humanity went from the Pre-Industrial “Hunter-Gatherer” Age into the Industrial, Nuclear and Space Ages. From being hunted by various wild animals, today we are in the Digital Revolution and on the edge of the “Fourth Industrial Revolution”.

Theoretically, if I were to be sent back in time to Ancient Rome with a Military Helicopter, this would be enough to convince the Romans that I was a god, for this is how far mankind has come even in the last 2,000 years. Our technology is so advanced that the Romans couldn’t possibly begin to understand what the hell was going on.

So then, imagine for example that there were an alien civilization out there which had a, say, 2-million-year headstart. Their technology to us would also make them seem like gods in our eyes, right?

So, how fast is Humanity advancing then?

In 1965, Gordon Moore (co-founder of Intel) came up with Moore’s Law (taught in universities today for undergraduate IT students), the observation that:

“… the number of transistors per square inch on integrated circuits had doubled every year since their invention. Moore's law predicts that this trend will continue into the foreseeable future.”

As Tim Whikrm has corrected me, Moore’s Law states that: “… the computational/processing speed of the chip will double every two years post 1975, not every year. (It's accepted as 18 months).”

Source: Moore's Law

Using Moore’s Law we can predict how advanced Humanity will become in the future:

Photo source (for both pictures): Estimating the Speed of Exponential Technological Advancement, The emerging Future

How crazy is that am I right? That’s why a hypothetical alien civilization that is even 2,000,000 years older than us for example would be viewed as gods.
The below image illustrates the possible existence of a significantly more advanced species than our own, let’s say that an alien civilization evolved on a planet 8 billion years older than Earth, theoretically we would expect any intelligent life there to be millions of years more advanced than us:

Photo source: The_Great_Filter_Commonly

In fact, in the image above it even shows that Planet X has a 3.46 billion year time advantage over Earth so if the Aliens evolved even 3 billion years after their planet formed, they should be extremely advanced right? Yet where are they?

Luckily for you, certain people throughout history have already accounted for the existence of super advanced civilizations.

One such example is the Soviet Astronomer Dr. Nikolai Kardashev. In 1964, Dr. Kardashev asserted that there were 3 types of civilizations in the universe:

So remember how I said earlier that there should be 20,000 Earthlike planets holding human level intelligent life?

If even 1% of that number were old and advanced enough to reach Type III Civilization- a technological point so impossibly powerful that we could never not detect it- then in the galaxy there should be 200 Type III alien species right?

So then where are they all? Why can we not find them? And if they exist, why haven’t they found us if they’re so advanced?

This is a phenomenon called Fermi’s Paradox (where is everyone given that the universe is huge and old?) and though he was neither the first one to invent it or formalise it, the Italian Physicist Dr. Enrico Fermi first mentioned it whilst talking to his colleagues in 1950.

As an aside, Drake’s Equation which is associated with Fermi’s Paradox is used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy. This is for all you curious people out there:

Chapter 2: “The Great Filter- the scariest theory known to man”

So we’ve already established that space is huge, space is old so given this there should be a lot of intelligent life out there right? In our own galaxy there should be 20,000 intelligent species from the start of the universe until today which is a span of 13.77 billion years.

Over time there should have been around 200 Type III civilization- species which were advanced enough to colonize the entire galaxy.

In fact we don’t even need them to be Type III to detect them, even a Type II civilization would be quite easy to spot, a race strong enough to harness all the power of its star could build a “Dyson Sphere”. It’s a supermassive piece of Stellar Engineering which involves covering the Sun with a massive metal structure which then harnesses its power output directly for use.

Below is an artist’s impression of a Dyson Sphere:

Any such civilization advanced enough to build these should be even more numerous than the 200 Type III civilizations in the Galaxy. Yet we’ve never heard from them either, nor have we ever detected them.
There is no way we could not have detected these civilizations, it would be like putting an elephant in your bedroom and then saying you can’t see it which is improbable right?

Even worse, if they are that advanced then they should have found us by now (or maybe they don’t care?). Yet we’ve never heard from them.

So where are they all then?

Enter the theory of the “Great Filter of Civilizations”:

Photo source: Does A Great Filter Solve the Fermi Paradox?:

The Theory of the Great Filter states: that at some point (we don’t know when) of an intelligent species’ life on their journey from cavemen to type III civilization, there will be a point along this journey that is extremely hard or even impossible to get through successfully.

Like I said before the scariest part is not knowing when the Great Filter occurs. Maybe it starts tomorrow? Maybe even in a million years? Maybe we’ve already passed it? Or maybe because it’s a theory it doesn’t even exist.

There are however 2 scenarios to estimate where Humanity is on the path to the Great Filter:

We’re the first civilization to get past the Great Filter-that’s why there’s no one else out there (yet). Perhaps life for example is a lot harder to form than we thought. For example, it took 2 billion years for life on Earth to evolve from the simple Prokaryotic cell into a complex Eukaryotic cell (a nucleus). - Great Filter - Wikipedia
We’re screwed because the Great Filter is coming soon. This would imply that most intelligent species get to where we are today and then some freak event stops them from going any further (a very terrifying thought)
And the scariest thing about the Great Filter?

According to Nick Bostrom, Oxford University Academic Source: http://www.nickbostrom.com/extra...:

“The discovery of even simple life on Mars would be devastating, because it would cut out a number of potential Great Filters behind us. And if we were to find fossilized complex life on Mars, it would be by far the worst news ever printed on a newspaper cover, because it would mean The Great Filter is almost definitely ahead of us.”
Chapter 3: “Identifying the Great Filter of Civilizations”

So, the Great Filter is likely ahead of us… that’s the scariest thing I’ve heard all day, it means Humanity might in fact have an expiration date.

But what is it? That’s the issue because no one knows.

Although we don’t know the exact time it will occur, at least we know that we should be expecting it to arrive sometime in the future.

We don’t know why it will occur either, but we can safely assume that it’s a very common event if there are an apparent lack of alien civilizations out there.

I have a few ideas as to what the Great Filter for us might be:

The Great Filter is worldwide Thermonuclear War (very possible)

Pretty self-explanatory actually.

Who can advance Science and Technology if there are no people left alive to do so? Though Humanity is an intelligent animal, at our base we are still just that: animals, animals subjected to the same failures and weaknesses as our ancestors.

Thus, we can only assume that other intelligent species at our level of development would not be wise enough yet to see long term consequences of such rash decisions as that of using Nuclear weapons in war. Or worse, they do but like us do it anyway for whatever reason.

It’s very likely that many of these civilizations bombed themselves out of existence. This is unfortunately a very very likely possibility.

The Great Filter is overpopulation without any solutions (not likely)

If the world becomes overpopulated before we are able to find a viable solution, then Humanity will starve itself to death.

In the past, the English scholar Thomas Malthus had insisted in 1798 that:

“while technological advances could increase a society's supply of resources, such as food, and thereby improve the standard of living, the resource abundance would enable population growth, which would eventually bring the per capita supply of resources back to its original level.”

-Malthusian trap - Wikipedia
It’s called the “Malthusian Trap”, and this is demonstrated as seen below:

This is still a very distant possibility although extremely unlikely since Human technology as I stated in Chapter I is increasing exponentially, allowing us to outpace the danger of starving to death.

The Great Filter is Climate Change without any solutions (not likely)
Here, climate change has melted much of the ice in the North and South Poles, raising sea levels which have affected Earth’s geography significantly:

This effect of Climate Change cannot be understated. From before, I had said that overpopulation is not a likely issue as our exponential technological advancements keep us from dying. So theoretically we could use our technology, to increase Agricultural Productivity right?

Of course, if sea levels rise this will be substantially harder. A lot of the arable land that used to be there is now gone. So how much food could we possibly produce before the Malthusian trap become a reality?

But like overpopulation, our exponential technology advances will allow us to probably shift some people to the Moon or something or find a way to grow food in space. So I wouldn’t worry about this too much.

The Great Filter is the impossibility of “Faster Than Light” (FTL) travel (very likely)
We could prolong Humanity’s existence by colonizing the entire Solar System and all the planets and natural satellites in it. But what then? What if once again after thousands of years we were lacking in resources or there had been a solar system wide nuclear war?

Nothing in the universe travels faster than light in a vacuum.

Light travels at 300,000 km per second in space (a vacuum).

The nearest Star System to us is the Alpha-Centauri Star System which is 4.37 light years away, that means if we were to head in that direction at 300,000 km/second, it would take us 4.37 years to get there. For us right now that’s impossible.

America’s “New Horizons” spacecraft would take 78,000 years to get to Alpha-Centauri, and of course it’s not even big enough to hold massive amounts of people.

Until we do manage to find a way around this, our inability to leave the Solar System is most likely to be the Great Filter of Civilizations (most probably after Nuclear War).

In popular Science Fiction, a proposed (but impossible with current understanding of Physics) solution would be to invent a “Slipspace Drive” to travel faster than light from Christopher Nolan’s Interstellar (2014).

There is only 1 super advanced civilization out there, and it kills any species that gets too advanced.
Ever seen Roland Emmerich’s Independence Day (1996)?

There’s a scene in it which illustrates my point (warning: obvious spoilers impending):

President: “I know there is much to learn from each other if we can negotiate a truce. We can find a way to co-exist. Can there be a peace between us?”

Alien: “Peace? NO PEACE!”

President: “What is it you want us to do?”

Alien: “Die…die…”
“But really? Is this even possible?” - I hear you say.

Of course. Why wouldn’t it be?

Certain people like to think that a civilization that advanced couldn’t possibly be malevolent. They also think that surely as a civilization gets more advanced, it gets more altruistic and wise. Though I suppose I can understand their point of view…

…it’s plain wrong.

I seriously doubt that any Alien visitor to Earth would be the “good kind”, instead I’d be expecting something like the “Engineer” from Ridley Scott’s Prometheus (2012):

Firstly, there is absolutely no evidence to suggest that technological advancement is related to increased benevolence and wisdom.

Seriously, just take a look at the Human Race. 1 million years ago humans were killing each other. Today we still are and nothing has changed. In fact we’ve gotten even better at killing each other haven’t we? That’s why the threat of Nuclear War is a very real possibility.

Just because we’ve gotten more advanced does not mean we’ve gotten wiser. I mean, this is the Age of the Internet where despite there being unprecedented amounts of knowledge never before so available in history than today, there is still a huge amount of ignorance in the average person. Lack of intelligence in this age of information? What was that about wisdom and technology being related again?

Secondly, there is also absolutely no evidence to suggest that an advanced civilization that found Earth would be altruistic rather than evil.

Looking back on Human history, it in fact suggests the exact opposite.

A painting of the evil British East India Company on the sub-continent:

In our own history, the civilizations that were “good” (not really) like China and India, didn’t colonize other countries.

They had all they needed. Both India and China were stuck in something Economists call the “High-Level Equilibrium Trap”, a term used to describe the historic economic situation of both China and India:

“… pre-industrial economy had reached an equilibrium point where supply and demand were well balanced. Late imperial production methods and trade networks were so efficient and labor was so cheap that investment in capital to improve efficiency would not be profitable.”

-High-level equilibrium trap
Basically, China and India were so rich that they didn’t even need to send their ships over the oceans to look for new resources.

Meanwhile, this is a map of 15th century Europe:

At this time, the countries of Europe were so evenly matched and enjoyed such similar advantages in geography and technology, and were so well balanced in fact that no country could really be defeated by another entirely.

The only way for say Spain to beat France would be to expand their borders in order to acquire more resources to fund their military and economy.

And that’s exactly what happened fast forward to 1898 (Source: Atlas of colonialism):

In India alone, 85 million people died as a result of British Colonialism :

So yeah, I doubt that any Type III Alien civilization that finds Earth would be “the good guys”. It has a higher chance of being the Decepticons from Transformers honestly:

The “good aliens”/ the ones who won’t be visiting Earth (because they’ve all the resources they could ever need) wouldn’t even want to explore the vast emptiness of space. It’s only the malevolent aliens that would be paying Earth an unexpected visit. They do this for our resources or in the case of this answer to enact the Great Filter onto us, to ensure that we don’t become as advanced as them to challenge their supremacy.

Final Summary:

Yeah so the Universe is so old and large that we should have found life by now. But we haven’t and that’s a huge problem because one thing it implies is that there is a “Great Filter of Civilizations” that destroys entire species before any of them can become advanced Type III civilizations (advanced enough to harness the power of its entire galaxy).

This is very worrying because there’s a huge chance that we could be facing this Great Filter soon, we don’t know when it will come or how or why or even if it will come at all.

But if we’re lucky, we could be that one civilization to make it through- that single Green line at the very far right:

Photo source: Does A Great Filter Solve the Fermi Paradox?

We can prepare against it, but co-operation will be difficult when fighting an “unseen” enemy.

And that could possibly be the scariest thing ever.