A recently published paper suggests that according to our current understanding of science, the existence of humans is improbable.
The paper published by Cai et al builds upon previous work determining the likelihood of intelligent life emerging in our galaxy. Yet, it’s the first study to consider something previous papers have missed: the likelihood of intelligent life destroying itself. The study considered the following factors;
- The rate of star formation, i.e., how many stars are likely to form in a volume of space. Life forms on planets, planets form from the remains of stars, ergo, this number is crucial.
- The rate of sterilising events, i.e., the frequency of catastrophic events that would wipe out life on a planet. In this study the authors used supernovae (exploding star) as the apocalyptic event. Any planets within 23 lightyears of the blast would be in the ‘kill zone’ and thus their ‘life-counter’ would be reset back to zero.
- The probability that intelligent life would kill itself. A bit hard to consider, but quite realistic. We all know how good us humans are at making planet killing technology such as nuclear weapons. Additionally, we can prove from the existence of climate change that it is possible for life to destroy itself.
- The time taken for intelligent life to evolve. The longer this takes, the lower the chance of other intelligent life existing at present.
- The rate of abiogenesis, i.e., the process from which non-living matter becomes living matter from natural processes.
The authors varied some of the variables to produce a range of possible results. The focus of this work was to determine one number: the quantity of Extraterrestrial Intelligence (ETI) in our galaxy the Milky Way.
The result, depending on how you look at it is either exciting or scary.
The human race is weird, in galactic terms — we’ve emerged at at unlikely time in an unlikely place.
Let’s say the time taken for ETI to evolve is similar to that on earth: around 3 billion years. The study found even if there was a 99% chance of life wiping itself out, there would be around 40 ETI species in our galaxy alone, with most of it being a few billion years older than us.
How Did the Scientists Come to This Answer?
How can one can even make the claim that humanity is like a random mole on the backside of the galaxy? Well, two of the three variables I mentioned before are necessary for getting life started in the first place;
A) how many stars form in that region of space.
B) The rate of life-destroying events that occur.
We’re actually not in the most happening part of our galaxy:
You can see our Sun, around halfway between the centre and edge near the Perseus Arm.
Since most of the star formation occurs in the bright centre, it follows that most of the life should be there too. While life-destroying events are also more likely in this area, the high rate of star formation cancels this out.
The graphs below show the dispersion of life in time and space. The X-axis is the distance from the galactic centre and Y-axis depicts time since the Milky Way formed.
You can see three columns of graphs. Columns A, B and C have the time needed for life to evolve set to one, three and five billion years respectively. From top to bottom, the probability of intelligent life wiping itself out is increased using the values 0, 50 and 99%.
When there is no chance for life to wipe itself out, the graph looks like a flame with the red parts having the most life and blue having the least. When the chance is set to 99% at the bottom row, the graph looks like a messy patch of smoke.
While the results change with differing values for the various factors, you don’t have be a scientist to see that the general area of the graph where life exists is at the left side.
But here’s where things get interesting. If you look closely, there’s a star on each graph — thats us. We’re around 26,000 light years (8 kpc) from the centre of the Milky Way and around 13.6 billion years after it formed.
No matter the shape of the graph, each one says the same thing:
Humanity is an outlier, we exist further from the middle of the galaxy and later in its formation than science would predict.
So, What Does This Actually Mean?
The answer to this question depends on who you are. But one thing is for sure — scientifically speaking, we are weird.
Additionally, it can be inferred that the likelihood for ETI is pretty high and we just may have yet to make contact with them. However, this paper does not answer the Fermi Paradox, which asks:
If the universe is so large and contains billions of Earth like planets, there should be other intelligent life out there. If so, why haven’t we met them yet?
The study suggests that most life in the Milky Way is older than us, so would this mean other alien races are aware of us but refuse to engage? Or are we actually alone?
Either way, in my opinion the scientific community should engage in more research like this. It may not yield useful technology that fix problems on Earth, but it may give us perspective on who we are and our place in this universe.
‘The day science begins to study non-physical phenomena, it will make more progress in one decade than in all the previous centuries of its existence.’ — Nikola Tesla
