Right, Every time the chance of intelligent alien life somewhere out there it devolves into UFOs or us spotting such. We have now found lots of planets in the habitable zone or Goldilocks zone , lots more that many thought. Of course there is life on some of them. Mostly on the level of pre-Cambrian life, I would guess. There could be some life as advanced as us- or more- but 1000 light years away, and they aint gonna come here.
There could even be some life (but not as we know it ) here in our solar system.
I was wondering if they had a realistic speed they were working on that had not fully developed yet, I wasn’t thinking anything even close to the speed of light. More like an unmanned spacecraft that could travel for decades.
If you can’t get ‘anything even close to the speed of light’, then an unmanned spacecraft that can travel for ‘decades’ won’t get you very far. The fastest spacecraft yet built, the Parker Solar Probe travells at 690,000 km/h (430,000 mph). This is incredibly fast.
To get to the nearset star would take more than 6000 years at that speed.
Oh, I wouldn’t give up yet. Unmanned probes might reach a much faster velocity, and be capable of functioning for much longer than is currently possible; so maybe the ‘decades or centuries between stars’ goal is not impossible. If we can make intelligent and reliable AI which can last that long, smart and curious probes might even spread out across the galaxy in due course. But this exploration process wouldn’t be anything like Star Trek,
Well, within our galaxy “the number of possibilities goes way down” to an estimated 200 to 400 billion stars. That’s not a small number. Very conservatively, that means around 200 million habitable planets similar to Earth.
And this is the problem I have with the idea of a Great Filter being in our past, so that some stage of the evolution of life, or even its abiotic formation, is alleged to be incredibly improbable. It’s true that all we have as a sample of one, but consider it in the following way.
You have a gigantic bag of 200 million marbles. You pull one out at random and examine its detail. You only have this sample of one, but it seems completely absurd to believe that by some incredible stroke of luck, you picked the one marble that was completely unique and that there was no other similar to it among the remaining 199,999,999.
I don’t know how you can be so certain that no other civilizations exist similar to our level of technological advancement and beyond. The numbers and distances involved are so huge, and our scientific knowledge still so limited, that there’s no basis for such a belief. Our detection capabilities, and even knowing what to look for, are still very primitive. All we’ve been able to determine recently is that planetary systems like our solar system are very common.
How much time do you spend pulling marbles out of that bag hoping to find a match before you give up and do something else? One year? Five years? Ten years? Twenty years? Fifty years? One hundred years?
Forever?
We only have one marble so far. The other planets and moons in our own solar system are not habitable and don’t count, and all the others are much too far away for us to know much about them, or even detect them.
Sure, many planets would have life. Even life “as we know it”. Maybe even intelligent life. Space faring? Maybe if they have other planets in their system. But I cant accept star faring, unless they have another habitable planet within a light year.
Altho Proxima Centauri b has a planet in the right zone, it is tidally locked and likely has way too much UV, due to that star being volatile. The best chance is Ross 128 b- 11 LY away. We aint going there in person, nor are they coming here.
And remember our Galaxy is about 100000 LY across. So, 50000 LY to travel from many?
Mind you, if we took some lichens, etc- and tardigrades- they might live nicely in a few spots on Mars. So i expect life on many planets.
So, we can’t know about them, or even detect them for the most part? This one is easy, then: The answer to the question as to how many inhabitable planets are available for us to use is 23. When you come up with a way to check that figure, get back to me.
Your metaphor assumes someone reached into the bag and picked us. But no one picked anything. We’re just one marble that happened to become self‑aware. Every intelligent species would say the same thing from inside its own marble.
So our existence doesn’t tell us how many other marbles like us are in the bag — only that at least one exists. And from a statistical standpoint, you can’t infer anything meaningful about the rest of the bag from a sample size of one.
So you’re asserting that, with extensive evidence now that most stars have planetary systems, that out of 200 to 400 billion planetary systems, there are only 23 planets in the habitable zone. When you come up with a way to make that seem plausible, get back to me.
No, I’m assuming it was completely random.
Sure, there’s the anthropic principle, but that only tells us that if life had not developed and evolved here, then we wouldn’t be here to observe it. It tells us nothing about the probability of alien life.
With no other information, that’s true. But the supporting information we have is the number of stars in the galaxy and the prevalence of planetary systems. That’s the point of the analogy – that there’s such a huge number of marbles with the potential to be just like ours that believing we’re completely unique begins to sound like a kind of religious hubris.
But it wasn’t. It wasn’t an absurd stroke of luck. The first marble pulled is guaranteed to be one that supports intelligent life.
Or, if you prefer, marble after marble is pulled at random and the first one that gets examined is one that has intelligent life on it, because the intelligent life on it is the thing that does examining.
As you said about the anthropic principle, it tells us nothing about the probability of alien life.
The anthropic principle is basically philosophical navel-gazing that doesn’t tell us anything about alien life. But scientific observations do tell us useful things:
The immense number of stars in our own galaxy alone, as already discussed
The fact that most of them have planetary systems
The conclusion that many millions of them must be in the habitable zone for life as we know it, even if we exclude those not favourable to life for other reasons, such as being tidally locked or subject to unstable stellar flares
The fact that elements and compounds are the same everywhere in the universe, potentially leading to similar abiotic processes when conditions are favourable
The fact that the JWST has already discovered the presence of compounds like methane, carbon dioxide, water, and dimethyl sulfide (DMS) in the atmospheres of exoplanets, which are consistent with life. DMS is gas that, on Earth, is primarily produced by marine phytoplankton and microbial life.
Your analogy doesn’t actually tell us anything about the probability of intelligent life. All it really establishes is that there are a shit‑ton (a real scientific uber accurate number) of marbles in the bag — which is a fun fact, but not evidence.
The anthropic principle means we can only ever observe from the inside of the one marble where observers happened to arise. That gives us zero information about how common or rare intelligence is on the other marbles.
Without knowing the underlying probability distribution — the base rate — a single observed instance can’t update anything. It’s the classic sample‑size‑of‑one problem, and treating it as meaningful is just GIGO.
Of course the question can never really be answered until we really do find life on other planets. But in the previous post I’ve offered reasons to lean towards the belief that alien life exists, and is likely to be abundant in numbers though sparse in density (life-bearing planets are very far apart, but the galaxy is big enough to contain millions of them).
Because to believe otherwise one is obliged to explain how abiogenesis happened on Earth but failed to happen on very large numbers of planets with essentially identical conditions. It shouldn’t be controversial that, statistically, large numbers of such planets must exist just as the result of billions of different planetary systems. So what happened? What was different on Earth?
This is part of what the “Great Filter” hypothesis seeks to explain. But all it can really come up with is “maybe, for unknown reasons, abiogenesis is extremely unlikely” which I find unpersuasive.
I suppose it’s possible that the process is so delicate that the Earth had just the right mix of necessary compounds and just the right temperature at the time to start things off, precise conditions that other similar planets lacked, but I’m doubtful. The Miller-Urey experiment which created amino acids from inorganic compounds was later criticized on the grounds that the simulated atmosphere they used was quite different from a later understanding of the composition of the Earth’s primordial atmosphere. To me this just shows that the precursors to life can arise under a variety of different conditions.
But this question won’t be resolved until we find that elusive second marble.
What exoplanet studies have revealed is that our solar system is far from a typical one, even allowing for bias in what we can detect. I could easily believe that only one stellar system in a thousand possesses a planet that would even be a candidate for abiogenesis. It may be one in ten thousand, or a hundred thousand. And a critical assumption for decades has been that liquid water plus organic molecules plus an energy source will after at most a half-billion years produce cells. We can presume that the development of life is inevitable because somehow it happened here, how we don’t know exactly know, so we can default to saying “just add ingredients and stir: voila!, life!”. For all we know abiogenesis requires a fantastically, ridiculously unlikely combination of rare occurances. If there are reservoirs of liquid water elsewhere in our solar system, subsurface aquifers inside Mars, the outer moons and larger asteroids, and if those reservoirs turn out to be absolutely and completely sterile, it would be a devastating blow to the inevitability of abiogenesis.
) here in our solar system.