In 1975, astrophysicist Michael Hart released a paper suggesting that the most plausible reason we haven’t found life elsewhere — or been visited by life from somewhere else — is that it simply doesn’t exist.
This is one possible solution to what’s called the Fermi Paradox. Physicist Enrico Fermi gets the glory of his name attached to this paradox as a result of a casual conversation he had with a bunch of other scientists. Fermi and his friends looked at the scale of the universe and postulated that, even if intelligent life is extremely rare, there is a good chance there are millions or billions of advanced civilisations, so where is everybody?
More specifically, they estimated that, even if all we can do is travel as slowly as we can with Earth-based technology now, it should only take 5 to 50 million years to colonise our galaxy. So, again, where is everyone?
Scientists use something called the Drake Equation to estimate the probability of life elsewhere. The thing is, there are a number of variables to input into the Drake Equation and we don’t know what values they should take. We know more than Frank Drake did in 1961 when he proposed his equation, but we still don’t know enough.
I previously wrote an article about the Drake Equation and pointed out that, depending on the input variables you choose, there may be as few as 0.000000000091 intelligent civilisations in our galaxy (i.e. none, basically) or as many as 15,600,000. Furthermore, the Drake Equation has its critics and maybe it’s just completely wrong to begin with.
Back in March, Quanta Magazine wrote an article about how the movement of stars might help distribute civilisations across the galaxy. The Sun orbits the centre of our galaxy every 230 million years, which means we’ve been around the centre of the Milky Way at least 50 times. This rotation brings us closer to certain stars at certain times and similarly further away from others. So a civilisation wishing to ‘hop’ to another star might wait for the appropriate time in the galactic orbit to do so, thus reducing the distance it needs to travel. Of course such civilisations would have to exist for hundreds of millions of years to be this patient.
However, the upshot is that the galactic orbit makes it more likely that we’d have been visited by another civilisation, should one exist. That makes the question even more emphatic: where is everyone?
Scientists consider a number of possible reasons why we haven’t been visited by intelligent life.
It does not exist
This is a trap in my opinion. The ego of mankind has argued for an anthropocentric universe since the year dot, that we are somehow special and unique.
First the Earth was the centre of everything and then, when that was proved wrong, the Sun was the centre of everything. Then, when that was proved wrong, it was yes, but we’re the only galaxy in the universe. And of course that’s not true either.
We’re one planet orbiting a typical star amongst hundreds of billions in the galaxy and we’re in one galaxy amongst hundreds of billions in the universe. We’re not particularly special — live with it.
Intelligent life is rare
This is probably true. Only one species out of roughly 9 million on Earth has developed the intelligence to ask these questions and begin to travel away from the home planet.
But even the most pessimistic solutions to the Drake Equation would still have civilisations elsewhere in the universe. However, if intelligent life is that rare then it’s unlikely it exists in our galaxy and maybe intergalactic travel is just too much for even a super advanced race.
They’ve been already
Perhaps not in Roswell in 1947, but it’s quite possible alien species have visited or at least passed by at some point in the past. Our civilisation is extremely young — mere thousands of years and on cosmic time scales that’s not even the blink of an eye. They could well have called in when we were literally a drop in the ocean.
We just haven’t given it long enough
Let’s assume there’s other intelligent life in the galaxy. Things happen on the scale of millions of years in the universe and we’ve been ‘civilised’ for mere thousands and advanced enough to investigate the cosmos for mere hundreds.
Cosmic distances are vast and even with far better propulsion systems than our own it’ll take time to cross those distances.
There’s also the lifespans of species to consider. How long to you need to live to cross the vast distances? How many generations do you have to commit to man (or ‘green blob’ if aliens are such) a spacecraft’s journey?
Who’s to say aliens haven’t long since learnt that meddling with other species is a nightmare of diplomacy that always ends in disaster. Perhaps they shun contact with other planets because previous experience has made them paranoid.
Lack of interest
We tend to think it’s natural to be curious and to want to explore, but we have no idea what sort of motivations an alien species may have. We frame everything on the basis of our own human emotions and desires and I think that could be a mistake. Maybe they don’t have emotions as such or maybe whatever their equivalent to emotions is, it just doesn’t drive them to explore. Perhaps they are simply content.
We’re not worthy
Maybe we’ve been observed and maybe they think we’re not worth the bother. Sure, they might see a species that’s developing and producing some decent science, but they’ll also see a species that’s been at war for virtually its entire existence and still can’t get along now.
If I’m honest I’d give the Earth a miss, particularly if I’d seen what they watch on telly.
They can’t live here
Maybe they’ve looked at our atmosphere and determined they can’t breathe it (or do whatever the alien equivalent of breathing is). Maybe our planet is simply poisonous to them.
Maybe they’re here already
Maybe they’re so advanced that they exist here without us knowing it, in the same way an ant has no concept of the intelligent human that’s about to step on it.
Who’s to say they’re not like Douglas Adams’ Hooloovoo and exist as a super-intelligent shade of the colour blue?
I think this is unlikely but I’m wary of falling into a trap based on anthropocentric assumptions.
In reality, I think it’s a combination of many of those reasons. I think it’s incredibly egocentric of us to think we’re even worth visiting or contacting in the first place. I’m sure there are more interesting, less violent, less crazy species they could visit.
Intelligent life may be rare in the first place and then it has to survive long enough to develop reasonable interstellar travel, assuming it wants to do that in the first place. If they do want to travel and make contact with other civilisations, they’d have to select a planet with an atmosphere they can breathe, find a species they think is worth visiting, perhaps wait for the galaxy’s rotation to set things up conveniently and then be prepared to embark upon a colossal journey.
I don’t think we’ve been around long enough to expect a visit even if the aliens wanted to drop in. The assumption that there are no aliens anywhere because none have visited us is a huge exercise in egocentricity.
The truth is out there but I suspect we haven’t be around long enough to find it. If I’m honest, I suspect we won’t ever be around long enough to find it either.