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  • An observable universe is a big place that's been around for more than 13 billion years.

  • Up to two trillion galaxies made up of something like 20,000 billion billion stars

  • surround our home galaxy.

  • In the Milky Way alone,

  • scientists assume there are some 40 billion earth-like planets

  • in the habitable zone of their stars.

  • When we look at these numbers, it's hard to imagine that there is nobody else out there.

  • It would change our perception of ourselves forever if we found others.

  • Just knowing that this vast place is not dead would shift our perspective outward,

  • and could help us get over our irrelevant quarrels.

  • But before looking for our new best friends, or worst enemies,

  • we have a problem to solve: What are we actually looking for?

  • [Kurzgesagt intro]

  • In a universe that big and old,

  • we have to assume that civilizations start millions of years apart from eachother,

  • and develop in different directions and speeds.

  • So not only are we looking over distances of dozens to hundreds of thousands of light years,

  • we're looking for a civilization ranging from cavemen to super advanced.

  • So, we need a conceptual framework to enable us to think better thoughts

  • that make us able to search better.

  • Are there universal rules that intelligent species follow?

  • Currently our civilization sample size is only one,

  • so we may make incorrect assumptions based solely on ourselves.

  • Still, better than nothing.

  • We know that humans started out with nothing but minds and hands that could build tools.

  • We know that humans are curious, competitive, greedy for resources, and expansionist.

  • The more of these qualities our ancestors had,

  • the more successful they were in the civilization building game.

  • Being one with nature is nice,

  • but it's not the path to irrigation systems, or gunpowder, or cities.

  • So it's reasonable to assume that aliens able to take over their home planet also have these qualities.

  • And, if aliens have to follow the same laws of physics,

  • then there is a measurable metric for progress: Energy use.

  • Human progress can be measured very precisely by how much energy we extracted from our environment,

  • and how we made it usable to do things.

  • We started with muscles, until we learned to control fire.

  • Then we made machines that used kinetic energy from water and wind.

  • As our machines got better and our knowledge of materials expanded,

  • we began to harness the concentrated energy from dead plants we dug up from the ground.

  • As our energy consumption grew exponentially, so did the abilities of our civilization.

  • Between 1800 and 2015, population size had increased sevenfold,

  • while humanity was consuming 25 times more energy.

  • It's likely that this process will continue into the far future.

  • Based on these facts, scientist Nikolai Kardashev developed a method of categorizing civilizations,

  • from cave dwellers to gods ruling over galaxies:

  • The Kardashev Scale; a method of ranking civilizations by their energy use.

  • The scale has been refined and expanded on over the decades,

  • but in general it puts civilizations into four different categories.

  • A Type 1 civilization is able to use the available energy of their home planet.

  • A Type 2 civilization is able to use the available energy of their star and planetary system.

  • A Type 3 civilization is able to use the available energy of their galaxy.

  • A Type 4 civilization is able to use the available energy of multiple galaxies.

  • These levels differ by orders of magnitude.

  • It's like comparing an ant colony to a human metropolitan area.

  • To, ants we are so complex and powerful, we might as well be gods.

  • So to make the scale more useful, we need subcategories.

  • On the lower end of the spectrum, there are Type 0 to Type 1 civilizations:

  • Anything from hunter-gatherers, to something we could achieve in the next few hundred years.

  • These might actually be abundant in the Milky Way.

  • But a civilization that is not actively transmitting radio signals into space

  • might be as close as our nearest stellar neighbor, the Alpha Centauri system,

  • and we would have no way of realizing they exist.

  • But even if they transmitted radio signals like we do, it might not be very helpful.

  • On an interstellar scale, humanity is practically invisible.

  • Our signals may extend over an impressive 200 light years,

  • but this is only a tiny fraction of the Milky Way.

  • And even if someone were listening,

  • after a few light years our signals decay into noise,

  • impossible to identify as the source of an intelligent species.

  • Today, humanity ranks at about level 0.75.

  • We have altered our planet:

  • we've created huge structures, mined and stripped mountains,

  • removed rainforests, and drained swamps.

  • We've created rivers and lakes,

  • and changed the composition and temperature of the atmosphere.

  • If progress continues, and we don't make Earth uninhabitable,

  • we will become a full Type 1 civilization in the next few hundred years.

  • Any civilization that becomes a Type 1 is bound to look outside,

  • because it's likely that it's still curious, competitive, greedy and expansionist.

  • The next reasonable step towards transitioning to Type 2 is trying to alter and mine other planets and bodies.

  • This might start with outposts in space, transition to infrastructure and industries near the home planet,

  • move on to colonies, and end with terraforming other planets,

  • by changing their atmosphere, their rotation, or position.

  • As a civilization expands and uses more and more stuff and space,

  • its energy consumption scales with them,

  • so at some point, they may embark on the largest project a lower Type 2 civilization can take on:

  • harnessing the energy of their star by building a Dyson Swarm.

  • Once this megastructure is finished,

  • energy has become practically unlimited for molding the home system however they see fit.

  • If they are still curious, competitive, greedy and expansionist,

  • and now have complete control over their home system,

  • stellar infrastructure in place, and the energy output of a star,

  • the next frontier moves to other stars light years away.

  • For a Type 2 civilization,

  • the distance to other stars might feel like the distance between Earth and Pluto does to us today:

  • Technically within reach,

  • but only with immense investments in terms of time, ingenuity, and resources.

  • This begins their transition towards Type 3.

  • This step is so far beyond us

  • that it becomes hard to imagine what exactly these challenges will look like,

  • and how they'll be solved.

  • Will they be able to find a solution to the vast distances

  • and travel times of hundreds or thousands of years?

  • Will they be able to communicate and keep a shared culture and biology between colonies light years apart?

  • Or will they split into separate Type 2 civilizations?

  • Maybe even different species?

  • Are there deadly challenges between the stars?

  • So the closer a species gets to Type 3,

  • the harder it becomes to fathom what it might actually look like.

  • They might discover new physics, may understand and control dark matter and energy,

  • or be able to travel faster than light.

  • We might be unable to grasp their motives, technology, and actions.

  • Humans are the ants, trying to understand the galactic metropolitan area.

  • A high Type 2 civilization might already consider humanity too primitive to even talk to.

  • A Type 3 civilization might feel about as like we feel about the bacteria living on the anthill.

  • Maybe they wouldn't even consider us conscious, or our survival relevant.

  • We could only pray that they're nice gods.

  • But the scale doesn't necessarily end here.

  • Some scientists suggest there might be Type 4 and Type 5 civilizations,

  • whose influence stretches over galaxy clusters or superclusters,

  • structures comprising thousands of galaxies and trillions of stars.

  • Ultimately, there might be a Type Omega civilization,

  • able to manipulate the entire universe, and possibly others.

  • Type omega civilizations might be the actual creators of our universe,

  • for reasons beyond our comprehension.

  • Maybe they were just bored.

  • As flawed as this classification may be,

  • this thought experiment is already telling us interesting things.

  • If our ideas about the nature of species that form interstellar civilizations is sort of correct,

  • then we can be pretty sure that there are no civilizations of Type 3 and beyond near the Milky Way.

  • Their influence would in all likelihood be so all-encompassing,

  • and their technology so far above our own, that we couldn't miss them.

  • The galaxy should flash with their activity in thousands of star systems.

  • We should be able to see or detect their artifacts or movements between different parts of their empire.

  • Even if a Type 3 civilization did exist in the past, and died a mysterious death,

  • we should be able to detect some of the remnants of their empire.

  • But when scientists looked, they didn't find remnants of harvested stars,

  • decaying megastructures or scars of great interstellar wars.

  • So they're very likely not out there and never were.

  • In a sense, this is very sad, but also very reassuring.

  • It leaves the galaxy to us and others similar to us.

  • So the most promising civilizations to look for may be somewhere in the spectrum from Type 1.5 to Type 2.5.

  • They wouldn't be too advanced to understand them and their motives.

  • They may have finished their first megastructures,

  • and they might be in the process of moving staff between stars,

  • transmitting enormous amounts of information into space,

  • by accident, or on purpose.

  • They would probably also look to the stars and look for others.

  • Then again, maybe we've got it all wrong.

  • Maybe progress to Type 2 does not mean expanding outwards,

  • and humanity is still too immature to imagine otherwise.

  • For now, all we really know is that we haven't seen anybody yet.

  • But, we've only just started looking.

  • Until we finally find friendly super aliens and can ask them to explain the rules of the universe to us,

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  • *duck noise*

  • Subtitles by: Bruno Andre Fernandes Ortega and others

An observable universe is a big place that's been around for more than 13 billion years.