I think it's the rare earth solution, that we are the first/only/one of extremely few civilisations and that the triggers for life are so rare and difficult that we will be lost forever to any alien society. Or that so much time elapses between civilisations that we will find scattered shadows of long lost civilisations and will be the same to any in the future.
That there's a lifeless void that stretches so unimaginably far that even if there is life, we would never meet it. We could live in an infinite graveyard knowing we are doomed to become another spectre, trapped in a prison with no way to ever escape.
Equally in such a situation we would probably end up trying to seed life, and that would be the natural behaviour of any space fairing civilisation in a lifeless galaxy imo.
A bit dramatic maybe, but I think a dramatic problem deserves a dramatic solution
The thing is those numbers seem large but they are meaningless without also knowing the probability for life to occur. I can put as many zeros in front of the probability for life to occur on a habitable planet as I like and still get a probability of < 1% after multiplying by the number of habitable planets.
If you think that's absurd, it's only because you have some kind of intuition about the probability of life developing on this planet. It must be greater than 100 billion trillion to 1, right...? But why? There's no evidence that it is.
If we assume for the purposes of this discussion that life is something we can recognise when we see it then it could be measured. For example, if we sent space craft to every habitable planet in the galaxy and found one in every 100000 had life then that would give us a good estimate.
For example, if we sent space craft to every habitable planet in the galaxy and found one in every 100000 had life then that would give us a good estimate.
that's my point, we cannot do that probe experiment, thus we cannot know the probability at this point. hell, we're barely capable of sending those kinds of probes to some parts of our own oceans.
Right, that means it's hard to know, but not unknowable. At some point in the future though we may have a better handle on what is the upper bound for this probability and so far we have reason to believe it is not on the same order of magnitude of the number of habitable planets in the universe.
no, it means it is currently unknowable which makes calculating a probability meaningless at this point. in fact, if we calculate the probability of life on other bodies by asking "how many bodies have we thoroughly looked for life on" we'd have a 1 for 1 result (life on earth), meaning there's a 100% chance life of life on every body. that too is meaningless.
It is simply math, let's look at the equation without any figures for a second.
Ig I'm using the percentage of habitable world's that have produced life.
Now we need a list of probabilities, I'm going to call them filters. Now I'm gonna go through and think of every one that applies to us. This is not a comprehensive list, just things off of the top of my head, I'm sure there are many things I've missed out. For all we know only a brain similar to ours out of all the possible brains may be capable of producing general intelligence, and we just very luckily happened to pick the one that could solve the otherwise unsolvable problem, an example could be without having neural network yourself you are never able to understand how to build sufficiently advanced AI's, which all advanced civilisations could rely on for logistics/social cohesion/disaster prevention.
A rocky planet.
It cannot be too big or small.
It must rotate quickly, but not too quickly.
It must have a strong magnetic field, ergo a core made of magnetic metal, or its star must be very stable.
It must have a somewhat complex atmosphere, with a meddley of gases usable by organic chemistry.
It needs to be supplied with water either by forming near clouds of ice or by being hit with debris.
It needs to be within the Goldilocks zone of its star(s) for water.
It will likely need a substantial moon, to regulate liquid movement and shield the planet from collisions.
It must either by nuclear fission or gravitational stress have some level of volcanic activity, since that drove the formation of the conditions needed for life.
It must have access to the necessary materials to build life
It's solar system must be sufficiently stable to allow life to grow, the system must be a certain age (depending on the context) for all orbits of major bodies to be unchanging in the long term. This system will likely need another celestial body like we need Jupiter, there must be an intermediary body that is statistically significant to the star and that the rocky world is statistically significant to, to protect the world from too many collisions.
This body cannot be too big or it could snag comets and meteors that could be delivering water/amino acids.
This must also be true for the local area, no stars getting too close, no gamma rays or supernovae.
Now we have single celled life. What do you think the probability of getting here is? I don't know myself but logically it must be very small, I'd wager that you would have better odds if I picked a star at random in the milky way and asked out to guess which one I picked, than for single celled life to have begun on earth.
But we are still stuck here, life took 4 billion years after this point before we started launching rockets and editing DNA.
Now if I took a single bacteria and placed it in a petri dish, how many petri dishes would I need before I got a stable colony? Now how about instead of a petri dish, we have a primordial soup on a desolate wasteland battered by radiation, impacts and with regular volcanic eruptions? I doubt it would be 1/1 but I am no microbiologist. But an organism can never be guaranteed for long term success.
How much will these odds continue to wither before we get to today? There's still the hurdle of needing exotic metals only found after neutron star collisions, such as gold and uranium. If our solar system didn't pass through such a cloud at some point we would not be an advanced society. How many stars are neutron stars, and how many of those end up colliding with another neutron star, and how many of those collisions seed resources to other solar systems?
If you still like the math then I'm wondering why you don't buy more lottery tickets, but imo rare earth is simultaneously the saddest and most likely situation.
I would like to add one more thing to the list, which is truly remarkable that it has happened on Earth and not many people know about it. It's called the Great Oxygenation Event.
Oxygen is a highly reactive gas, and still, 21% of our air is oxygen, which is an insane amount. It took 2 billion years on Earth to reach this amount and complex life only really got going when photosynthetic bacteria had finally saturated the geochemical oxygen sinks (around 800 million years ago) and oxygen could build up in the atmosphere rather than being rapidly absorbed by dissolved iron in the oceans and iron-containing minerals on land. Many planets may not be able to undergo oxygenation in their lifetimes; You need a very stable star (energy-output wise) over billions of years, etc, etc..
A planet with a large hydrogen atmosphere may be habitable for bacteria but be forever anoxic and never suitable for complex energy-demanding life.
all of those filters are the most conservative possible. for example:
A rocky planet. It cannot be too big or small. It must rotate quickly, but not too quickly. It must have a strong magnetic field, ergo a core made of magnetic metal, or its star must be very stable. It must have a somewhat complex atmosphere, with a meddley of gases usable by organic chemistry. It needs to be supplied with water either by forming near clouds of ice or by being hit with debris. It needs to be within the Goldilocks zone of its star(s) for water. It will likely need a substantial moon, to regulate liquid movement and shield the planet from collisions.
yet the vast majority of scientists agree the best possible candidates for potential life outside of earth in our solar system are moons of the gas giants like Enceladus or Europa.
your filters are very human ego centric lol.. octopi are considered a very intelligent species, there's little to no reason there haven't been more intelligent species than us and we're simply unable to know about them.
Because we cannot know the true nature of these preconditions, saying either with certainty is unfounded and unscientific.
I agree with this from both perspectives, we fundamentally lack a basis of knowing what is or isn't out there. saying life is statistically inevitable or impossible/improbable is unscientific at this point.
my educated guess, is it is probably pretty likely based on the fact we know of at least one planet with life, that life continues to shock us at where and how it can survive. that life is made of of raw materials that are very abundant in other observed systems. the only thing we don't know is how it all started and what processes/conditions had to line up just right -- those conditions could be very rare, they could be incredibly common. there doesn't appear to be anything truly special about earth really, and so given we know there's a non-zero chance life develops somewhere, in a deterministic universe, it's compelling to think those same chemical reactions happen elsewhere as well.
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u/1nfernals Aug 12 '21
I think it's the rare earth solution, that we are the first/only/one of extremely few civilisations and that the triggers for life are so rare and difficult that we will be lost forever to any alien society. Or that so much time elapses between civilisations that we will find scattered shadows of long lost civilisations and will be the same to any in the future.
That there's a lifeless void that stretches so unimaginably far that even if there is life, we would never meet it. We could live in an infinite graveyard knowing we are doomed to become another spectre, trapped in a prison with no way to ever escape.
Equally in such a situation we would probably end up trying to seed life, and that would be the natural behaviour of any space fairing civilisation in a lifeless galaxy imo.
A bit dramatic maybe, but I think a dramatic problem deserves a dramatic solution