What if there are thousands of alien empires in the Milky Way, each spanning a few to maybe tens of star systems, chatting, trading, sometimes shooting or ignoring each other politely? And if so, why is nobody visiting us? While the Milky Way is ancient and gigantic, even travelling at 10% the speed of light, any civilization could take over the whole galaxy within a million years.
But we haven’t seen anybody yet. So it seems we are alone in the Milky Way. But this idea is built on a lot of assumptions.
Usually when scientists speculate where all the alien civilizations are, they assume technology will progress to a point where colonising all of space becomes kind of easy. But what if we are thinking about this the wrong way? What if the universe is full of life, but no matter how technologically advanced you are, space is never easy?
What if aliens slowly crawl through space, expanding like humans did over the ocean? Let's look at the only data point we have: ourselves. The Available Real Estate in the Galaxy Oceania is a region with tens of thousands of islands scattered across millions of square kilometers, separated by an unforgiving, deadly sea.
Kind of like a galaxy. Some 5000 years ago the first people set out to colonise Oceania. Especially the Polynesians achieved mind blowing feats.
Without any modern technology they set out into the vast nothingness hoping to find a new island to claim or like die far from home. But most of the pacific islands are merely a few wet rocks or corrals, maybe some palm trees and if you are lucky, birds making a pit stop. Others with more vegetation are often hostile, lacking the resources to really sustain a lot of people and remain uninhabited even today.
And then there are the good islands. The Polyneisians colonised them, spreading their culture and society to dozens of remote islands of all sizes. Some united in kingdoms spanning many islands, others were independent, many home to competing and belligerent tribes.
And although thousands of kilometers apart, even the most remote islands were connected with at least some trade and exchange. A microcosm of humanity. But it didn’t always work out.
The extremely isolated Pitcairn islands were settled for hundreds of years and relied on trade with each other and bigger islands hundreds of kilometers away. And then the local population vanished. We don’t know why – maybe because the islanders did the human thing and ravaged the natural resources until they became unsustainable.
Maybe the decline on distant bigger islands severed important connections. We only know their culture declined and they left or died out. What if space is an ocean to us?
A hostile place that’s hard to conquer? Would alien civilizations spread like the Polynesians? The Universe is kind of a horrible place The Milky Way has around 200 billion star systems and it seems that almost all of them have planets.
Estimates vary, but there may be some 300 million to tens of billions of rocky, earth-like planets, in the habitable zone around a star, where water can be liquid. Amazing! Except that most of them are terrible.
Hells of lava, dead frozen worlds, bare rocks sterile from radiation, blanked by toxic atmospheres. It's easy to forget, but Venus and Mars are “earth-like”, too. Mars is the next human frontier and fairly exciting – but Mars dust is poison and deadly radiation and low gravity will make you sick.
Mars is the worst. Except Venus is even worse, crushing you to death, burning and dissolving you in acid. If humanity was really motivated and had the resources and energy, both could be terraformed within maybe a thousand years – we showed how in other videos.
But the thing is, we already have a planet that's pretty great, so currently humanity's motivation is not very strong. Now let's think about this in terms of galactic expansion. If the milky way is like a vast ocean full of islands, most are planets like Mars and Venus.
, Barren rocks or corals, where nothing grows and the elements kill you. Imagine boarding a generation ship to travel for 100 years or more, only to arrive at a new star and then you get a… Mars. Or worse, a Venus.
What a let down. Terraforming them is such an intense investment in terms of resources to make it worth spending the time to travel to the stars for bad planets. Maybe the simple reason we don’t see galaxy spanning civilizations is that the economics just don’t add up for almost all of the star systems out there.
But wait, you might say: It's actually easy! A high tech race with unlimited resources could automate this process, sending thinking machines that report back every few thousand years with new planets ready for fresh settlers, or automated ships with embryos. But if it were that easy someone would have done it by now.
So either we are really alone – or it's not easy. Thinking about alien civilizations you need to make loads of assumptions – and for this video we are assuming that space is hard, even for high tech civilizations that have broken free from the limitations we have today. Now things are getting exciting.
So what if alien civilizations actually ignore the bad islands and just pick the very best? Stringing together island empires like the Polynesians? Thousands of Galactic Empires Every star moves in its own orbit through the galaxy and most stellar neighbourhoods are only temporary.
At any given time, in some regions there will be more good islands than in others. While simply because of bad luck, other regions will be pretty isolated. Earth might currently be in one of these backwaters, surrounded by really bad islands for dozens of light years in all directions.
We may be Pitcairn island, so isolated that nobody knows we are here, or cares to establish a colony so remote. But elsewhere in the Milky Way good islands may be more common! There it would be relatively easy for a high tech civilization to jump from one good star system to the next, creating connected empires.
Strings of worlds, with all the adventure and challenges of expansion even to really good planets. Do they need to animate dead worlds with oceans? How do they cope with alien microorganisms or strange ecosystems?
Do they need to burn it all down and create a mirror of their home world, or do they adapt? How many centuries do they need to make a planet truly their home? Empires expanding in regions full of good islands would probably meet each other.
Maybe they trade, maybe they fight. Maybe they have coffee and chat about the meaning of it all. And just like some of the Polynesian islands, it is likely that many of these planets would be abandoned or for the empires to break apart for a number of reasons: First of all, most great neighbourhoods would dissolve over time and connected islands would become remote.
Then it just may be the nature of civilization to become unsustainable or self destructive – humanity is extremely young and we’ve already flirted with extinction. There are numerous existential risks, cultural, technological and environmental that any civilization has to deal with. And smaller colonies on new planets would likely be less resilient than their homeworlds and in bigger danger of dying out.
Whenever this happens this would leave a good island free again for others to rediscover and colonise. Also space is just a different ballpark. The enormous distances between stars make it hard to maintain a consistent civilization – just think about how many cultures we have on Earth alone.
Imagine if sending a message between continents took decades to arrive. Would colonies care what the home world wants from them, if it can neither help nor really enforce its will on them? This also would make interstellar war, except the genocidal kind, completely uneconomic.
Would you go to war with someone because their great grandfather killed yours? At these distances, it's not like anyone could easily sneak up on each other anyway. And on a much more fundamental level, if island empires don’t exchange relevant amounts of genetic information – if there are no hook ups between worlds –, sooner or later these populations will develop in different directions and eventually become different species.
Making it less likely that they’ll want to be under common rule. So the idea of enormously big, connected empires may just not be feasible if the galaxy is an ocean where good islands are few and far between. But this also means that new civilizations may pop up constantly, spread and partially or completely die out, even if just by splitting into different factions.
Islands may be recolonized and abandoned over and over. What would this mean for us? We might think we are alone only because we are on an isolated island right now.
But there could be thousands of worlds full of diverse civilizations elsewhere, that we would eventually drift closer to - does this make the milky way more scary or less scary? Is it a good thing that we'd have time to get our act together before we face anyone else? Or is it a great tragedy that we might not have the chance to meet our neighbours beyond for a long, long time?
Well we don’t know, but it is something for you to ponder tonight when you look up at the sky again. Hopefully humanity is still at the beginning and we’re learning a tiny bit more about the universe every day – one day, we might spot a good island. And if we are lucky, many more close by.
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Let’s conduct a few stellar experiments! We’ll first add some more mass to this protostar. More.
. a bit more. .
Wow! We’ve just created a blue giant, a star with 10 times the mass of our sun. Let’s now add a couple of million years and see what happens.
A supernova! Breathtaking. And look!
It leaves behind a black hole. Fascinating stuff. Now we record our findings.
Be careful to preserve the sparkle! It’s now time for Duck’s final inspection. This one is always a nailbiter.
He has incredibly high standards. Luckily for us our work is scientifically accurate, offers an overview of important astrophysical processes and is a real stunner. Duck approves.
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