How many alien races are there, anyway?
Welcome to the Science Asylum.
I am Nick Lucid.
We noticed something weird happening around KIC 8462852.
That’s a star, in case you’re wondering.
There a massive structure of small irregularly-shaped objects.
Aliens?
Probably not aliens.
It could be a whole bunch of comets, but they’re not moving like comets usually do.
Definitely aliens.
Alright, alright, let’s consider aliens for a few minutes.
It would help to know how many aliens there might be
and it shouldn’t be surprising that people have had this discussion before.
Arguably, the most famous estimates come from the Drake Equation.
It considers a bunch of factors we care about: The rate at which stars are born in our galaxy,
The fraction of stars that have planets, The average number of planets per star that
could support life, The fraction of those planets that actually
develop life, and the fraction of those planets that develop
intelligent life.
It also considers some other factors we don’t care about like:
The fraction of intelligent races that learn to communicate by radio wave,
and the length of time those races use those radio waves.
This equation is a great place to start because it’s just a bunch of multiplying.
Unfortunately, we don’t care if we can communicate with them... just if they exist.
I mean, they’re probably not screaming in all directions via radio waves, anyway,
so let’s tweak this a little.
First, we can get rid of all that radio stuff, but now the units are in civilizations per
year, which isn’t very helpful.
We could include how long the civilizations last before going extinct,
but that’s kind of depressing, so let’s just imagine they evolve beyond
the universe or something.
Multiplying by a time gives us units of civilizations, solving our problem.
It still doesn’t consider space travel and the colonization of other planets,
but that calculation is way more complicated.
We’ve got pretty good estimates for the first few numbers.
Both NASA and the European Space Agency say the rate of star formation is:
7 stars per year.
Thanks mostly to Kepler, we know what fraction of stars have planets:
Pretty much all of them, so the fraction is about 1 or 100%.
The average number of planets per star that could support life is a bit smaller.
For a planet or large moon to habitable, it has to be a certain distance from its star.
Not too hot, not too cold, but just right, which is why we call it
the “Goldilocks Zone.”
Also, thanks to Kepler, this turns out to be about 0.4 planets per star.
In other words, about 40% of stars have one planet in their Goldilocks zone.
The rest of the numbers we know almost nothing about,
which means we get to talk out of our butts.
Oh, oh, can I start?
Sure.
Yeah!
If life can develop, it will develop.
Life is awesome like that.
Intelligent life is the ultimate goal of life.
Because, duh.
And civilizations? They last forever.
You can’t use infinity.
Aww man!
OK, let’s go with a billion years.
OK, so if we take that really optimistic viewpoint seriously,
When we multiply everything out, we get about 2.8 billion civilizations in our galaxy.
Since there are about 100 billion stars in the galaxy
that’s 1 civilization for every 35 stars, which is pretty impressive.
Yeah, it is!
Ahhh!!!
Don’t be ridiculous!
Bad clone! Bad!
Sorry.
Whether or not life will develop depends on so many factors.
So many.
The ultimate goal of life is just to survive and reproduce.
There’s no reason to think intelligent life is anything special.
Also, we’re on the verge of destroying ourselves,
so I’m surprised we’ve lasted this long.
That's awfully pessimistic, but let's take a look anyway.
Multiplying that out, we get about 1 times 10 to the negative 11 civilizations
or 1 civilization for every 100 billion galaxies.
Since there are only about 100 billion galaxies in the universe,
that’s one intelligent civilization for the whole universe.
Us.
That’s way too pessimistic and we all know there's at least two.
[Alien Noises]
I’m personally a bit more moderate in my estimates.
I get a little over 400 civilizations in our galaxy, which means the civilizations are an average
of about 5,000 light years apart.
Considering KIC 8462852 is about 1500 light years from Earth
and that civilizations probably won’t be evenly spaced.
It’s not out of the question to think it could be an alien structure around that star.
So, are you an optimist, a pessimist, or a moderate?
Let us know in the comments.
Thanks for liking, sharing, and subscribing.
And until next time, remember, it’s OK to be a little crazy.