So the History Channel of all places has been running shows on how Aliens have been visiting earth for a long time, and have contributed to our societies since we were apes, and yadda yadda. The History Channel’s long slide into meaningless drivel aside, I wanted to just throw out some hard numbers about how feasible alien contact with earth might be.
So let’s just assume that there are other intelligent life forms in the galaxy that are capable of interstellar space travel and are interested in contacting other intelligent life forms for whatever reason. This isn’t a safe assumption for a whole lot of reasons, but let’s roll with it to set up a best case scenario.
So given that, lets look at some of the problems:
Space is incomprehensibly large.
I mean that quite literately. Our brains really haven’t evolved to conceptualize very big numbers, or very large distances. So we can’t help but feel like a trip to visit us would be a long journey, but something relatable to other long journeys we have taken. Maybe it’s like being on a train for a whole bunch of years.
Unfortunately space is so vast that it doesn’t really work out like that. Traveling even to star systems that are relatively astronomically close, even traveling at the speed of light would take many human lifetimes. Venture out much further and there’s a good chance that the species you’re planning on visiting will have died out, or been destroyed by a cosmic event by the time you arrive.
Say that we’re lucky enough to have an intelligent life form in the middle of our own galaxy. Great news! At the speed of light it will take them 50,000 years to get here. For a little perspective, modern humans have only been around for 200,00 years. We almost went extinct 70,000 years ago. We developed agriculture only 10,000 years ago. We’ve been using radio waves for only around 90 years.
If our friends don’t live in our galaxy, then perhaps they are in our nearest major galaxy of Andromeda, a mere 2.5 million light years away. If our friends had decided to visit us 2.5 million years ago, they would have made that decision based on information from 5 million years ago. That means they would be choosing to come to visit Australopithecus or basically, bipedal apes.
But 2.5 million years ago, the only information coming off the planet earth was in the form of radiant waves of energy, the most common of which is light. Visible and infrared. What an alien race could tell about a planet from 2.5 million light years distant is pretty limited due to attenuation.
We haven’t been around all that long
So lets go back to radio. We started using it around 90 years ago, sending out ordered information content out into the universe. This surely is something that would pique the interest of an alien species. The problem is, it’s only traveled 90 light years. Since we’re near the edge of our galaxy, our radio waves have only traveled 1/1000th of the total distance into our own galaxy.
The observable universe is 93 billion light years across, but has only been around 14 or so billion years. A life form could have been intelligent for 5 billion years already, but not have received any light from our galaxy, let alone our planet. At least not light from who we are now, or where we are now. When looking over long distances, you’re really looking very very far back in time. When things are far enough away, you’re not looking across to where they are, you’re actually looking back at the beginning of the universe.
Where would they start?
How would they know where to look? At a very conservative estimate there are ten million billion planets in the universe. Even a civilization with access to vast amounts of power and very advanced technology could only reach out to planets that were relatively close.
Using the extremely flawed drake equation, there are a whole lot of advanced civilizations out there. Unfortunately, the number of planets theoretically capable of supporting them is a much much greater number.
Why would they want to?
I won’t dive too much into far out futurism, but there are also very real problems with the set of underlying assumptions that drive speculation about alien contact or visitation. It’s not at all a safe assumption that a spacefaring race would be interested in contacting other sentient life or interacting with them in any way.
Stupid physical realities!
So you have two very fundamental problems with any theorizing about alien visitation to earth.
- The universe is very very large
- The speed of light is as fast as anything can travel.
The combination of these 2 facts screws up a whole lot of things for traveling large distances in space, but leaves us with some pretty hard constraints around alien visitation.
- They would have to be very close (astronomically speaking)
- They would have to exist in the same time as us (this is sort of part of #1)
- They would have to capable of speed of light travel
- They would have to have access to a tremendous amount of power
- They would have to have some reason to want to contact us
The bottom line
Given the number of stars, planets, and basic elements available in the universe, it’s statistically very very likely there are other advanced civilizations out there. And there are probably quite a few of them.
But given those 5 constraints, it’s very very unlikely they have visited us.
Now hold your horses
There are some caveats. If a civilization is capable of faster than light travel, that pretty much blows this whole thing out of the water. They may be able to bend space-time, or create wormholes. But the energy demands of these kinds of things are insanely large.
A one meter wormhole would take one years worth of energy from 10 billion stars to fuel. Bending space-time to create a warp drive to travel 10 times the speed of light would require energy equal to 10 billion times the mass of the observable universe.
So we don’t have much of an escape here.
It’s a magical world
Unfortunately there is exactly zero hard evidence of alien visitation. There are plenty of anecdotes, plenty of stories, but no real proof.
While it is possible that aliens could have visited, the odds of it having happened are vanishingly small, and it would have come at a tremendous cost, even for a very advanced race.
It’s unlikely they would borne this cost to probe the asses of hillbillies, or to fuck with our heads by zipping their spaceships around at night.