Searching the Cosmos: What Are We Looking For?
So, imagine this: The universe we can see is ridiculously huge, and it’s been around for way over 13 billion years. Think about it – there are up to two trillion galaxies out there, and each one is packed with maybe something like 20,000 billion billion stars. Just in our own home galaxy, the Milky Way, scientists figure there could be around 40 billion planets that are like Earth and sitting in that cozy ‘habitable zone’ around their star.
When you look at numbers like that, it’s really tough to think we’re the only ones home. Finding others would totally flip how we see ourselves, forever. Just knowing this massive place isn’t empty would really make us look outward and maybe, just maybe, help us get over our own silly arguments here on Earth.
But hold on a sec. Before we start looking for potential best friends (or worst enemies!) out there, we have a big question to tackle: What exactly are we even looking for?
The Challenge of Time and Distance
This universe is so big and so old that we have to figure civilizations probably started millions of years apart from each other. They’d also develop in wildly different ways and at different speeds.
So, not only are we trying to peer across crazy distances – we’re talking dozens or even hundreds of thousands of light-years – but we’re also looking for life that could be anywhere from, well, basically cavemen all the way up to super, super advanced beings.
Finding a Framework: Universal Rules?
Because of this huge search space, we need a good way to think about it, a kind of roadmap, so we can search smarter. Are there certain rules that intelligent species might follow as they grow?
Right now, our sample size for ‘intelligent civilization’ is… just one: us. This means we might guess wrong based only on ourselves. Still, it’s better than having no ideas at all!
What We Know About Humanity (and Assume About Aliens)
- Humans started with nothing but our minds and hands that could build tools.
- Humans are naturally curious, competitive, greedy for resources, and driven to expand.
- The more our ancestors had these traits, the better they were at building civilizations.
- Being ‘one with nature’ sounds nice, but it’s not the path that leads to stuff like irrigation systems, gunpowder, or cities.
So, it makes sense to guess that aliens who managed to take control of their home planet probably have some of these same qualities too.
Progress and Energy: A Measurable Metric
If aliens have to play by the same rules of physics as we do, then there’s one thing we can actually measure to see how far along they are: Energy use.
You can track human progress really well by looking at how much energy we pulled from our surroundings and how we learned to use it to do things.
- We started relying on our own muscles.
- Then we figured out how to control fire.
- Next came machines that used kinetic energy from water and wind.
- As our machines got better and we learned more about materials, we started tapping into the concentrated energy from fossil fuels (dead plants we dug up).
As we used way more energy, our civilization’s abilities shot up. Look at this: Between 1800 and 2015, the human population grew seven times bigger, but humanity was using 25 times more energy! It seems likely this trend will keep going way into the future.
The Kardashev Scale: Ranking Civilizations by Energy
Based on these ideas, a scientist named Nikolai Kardashev came up with a way to sort civilizations, from simple cave dwellers all the way up to beings possibly controlling galaxies. He called it the Kardashev Scale. It’s basically a ranking system based on how much energy a civilization can use.
The scale has been updated and added to over the years, but generally, it splits civilizations into different categories:
- Type 1 civilization: Can use all the energy available on their home planet.
- Type 2 civilization: Can use all the energy available from their star and its planetary system.
- Type 3 civilization: Can use all the energy available in their galaxy.
- Type 4 civilization: Can use all the energy available from multiple galaxies.
These levels aren’t just a little bit different; they’re different by huge amounts, like comparing an ant colony to a giant human city. To ants, we’re so complex and powerful, we might as well be gods.
Adding Detail: Lower Types and Subcategories
To make the scale a bit more useful, especially at the lower end, people often talk about subcategories or even a Type 0. This covers everything from hunter-gatherers up to a civilization like ours, or what we might become in the next few hundred years.
These lower-level civilizations (Type 0 to maybe Type 1-ish) might actually be quite common in the Milky Way. But if a civilization isn’t actively sending out strong signals, even if they were on a nearby star system like Alpha Centauri, we might never know they exist.
Even if they did send radio signals like we do, it might not help much. On the scale of the stars, humanity is pretty much invisible right now. Our signals have only traveled about 200 light-years, which is just a tiny, tiny dot in the vast Milky Way. And even within that range, after a few light-years, our signals get so weak they turn into noise, making it impossible to tell they came from intelligent life.
Where Does Humanity Rank Today?
Right now, humanity is estimated to be somewhere around level 0.75 on the Kardashev Scale. We’ve definitely changed our planet:
- Built enormous structures.
- Mined mountains.
- Removed rainforests.
- Drained swamps.
- Created new rivers and lakes.
- Changed the mix and temperature of the atmosphere.
If we keep progressing and don’t wreck Earth completely, we’re expected to become a full Type 1 civilization in the next few hundred years.
The Journey Towards Higher Types
Any civilization that reaches Type 1 is probably going to start looking outwards. Why? Because they likely still have those traits: curiosity, competitiveness, greed, and a drive to expand.
Transitioning to Type 2: Mastering the Home System
The next logical step after Type 1 is trying to change and use other planets and space rocks in their home system. This might start small with space outposts, then grow into infrastructure and industries near the home planet, move on to building colonies, and eventually lead to terraforming other planets (changing their atmosphere, how they spin, or even their position).
As a civilization spreads out and uses more and more stuff and space, their energy needs go up right along with it. So, at some point, a lower Type 2 civilization might take on their biggest project: capturing the energy of their star. The classic idea for this is building a Dyson Swarm – a massive collection of structures orbiting the star.
Once something like a Dyson Swarm is done, energy becomes practically unlimited for them to shape their home system however they want.
Transitioning to Type 3: Reaching for the Stars
If they’re still curious, competitive, greedy, and expansionist, and they now have total control over their system, built star-spanning infrastructure, and can use all their star’s energy, their next big step is other stars, many light-years away.
For a Type 2 civilization, the distance to other stars might feel sort of like the distance between Earth and Pluto feels to us today: technically possible to reach, but it takes enormous effort in time, cleverness, and resources. This is when they start moving towards Type 3.
The Mystery of Type 3 and Beyond
This step is so far ahead of us that it gets really hard to even picture what the challenges will be like and how they’ll solve them.
- Will they figure out how to handle vast distances and travel times that could take hundreds or thousands of years?
- Will they manage to communicate and keep a shared culture and biology among colonies spread across light-years?
- Or will they split up into separate Type 2 civilizations? Maybe even turn into different species?
- Are there dangerous things lurking between the stars?
The closer a species gets to Type 3, the harder it is for us to guess what they’d actually look like or be doing. They might discover entirely new physics, learn to control things like dark matter and dark energy, or even find a way to travel faster than light. We might not be able to understand why they do things, what their tech is, or what their actions even mean.
Think of it this way: Humans trying to understand a Type 3 galactic civilization is like ants trying to understand everything happening in a giant human city.
A high Type 2 civilization might already see humanity as too basic to even bother talking to. A Type 3 civilization might view us sort of how we view the bacteria living on that anthill – maybe they wouldn’t even see us as conscious or care if we survived. We might just have to hope that they’re nice ‘gods’.
But the scale potentially keeps going! Some scientists suggest there could be Type 4 and Type 5 civilizations influencing huge structures like galaxy clusters or superclusters (which have thousands of galaxies!).
And way, way out there, maybe there’s even a Type Omega civilization, possibly able to mess with the entire universe, or even others. Type Omega civs might even be the ones who actually made our universe, for reasons we can’t even begin to understand. Maybe they were just bored! (See, some humor here!)
The Big Question: Are High-Level Civs Nearby?
Even though this scale system isn’t perfect, just thinking about it tells us some really interesting things.
If our ideas about how interstellar civilizations might behave are even somewhat correct, then we can be pretty sure there are no civilizations of Type 3 or higher anywhere near our part of the Milky Way.
Why? Because their influence would almost certainly be so massive, and their technology so far beyond ours, that we absolutely couldn’t miss them.
- Their activity should make thousands of star systems in the galaxy practically flash.
- We should be able to see or detect their artifacts or how they move things around their huge empire.
- Even if a Type 3 civilization existed a long time ago and vanished mysteriously, we should still be able to find some leftover pieces of their empire.
But scientists have looked, and they haven’t found signs of stars being harvested, huge decaying structures, or evidence of massive interstellar wars.
So, it’s very likely they aren’t here, and probably never were nearby.
In a way, this is kind of sad (no cosmic neighbors to visit!), but it’s also quite reassuring. It leaves the galaxy open, for us and for other civilizations that might be similar to us.
Who Should We Be Looking For?
Given all this, the best bet for finding other civilizations might be those somewhere in the Type 1.5 to Type 2.5 range.
- They wouldn’t be too advanced for us to maybe understand them or why they do things.
- They might have finished building their first really big structures (like maybe starting a Dyson Swarm).
- They might be moving stuff between stars, accidentally or on purpose sending out huge amounts of information into space.
- They would probably also be looking up at the stars themselves, searching for others just like we are!
Then again, maybe we’re totally wrong about all of this. Maybe getting to Type 2 doesn’t mean spreading outwards, and humanity is just too young and inexperienced to imagine other possibilities.
For now, all we really know for sure is that we haven’t spotted anyone else yet. But, let’s be honest, we’ve only just started looking.