Have we reached the point when it is kooky to not believe in massive amounts of intelligent life having evolved throughout the universe?

[wolfpup]

@Lumpy

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.

First of all, cite that our solar system is somehow atypical? What does that even mean?

Second, if just one in a thousand planetary systems have a planet in the habitable zone, that gives you around 200 million candidate planets. Quite a respectable number.

ETA: Depending on the criteria you apply, we currently know of either 37 or at least 12 exoplanets in the habitable zone that are suitable for life as we know it. And that’s within the very, very limited range of our instruments.

@Lumpy

For all we know abiogenesis requires a fantastically, ridiculously unlikely combination of rare occurances.

That’s possible but extremely unlikely, and I’ve already addressed that. It’s just one of the far-out premises of the Great Filter hypothesis.

[Mijin]

@wolfpup

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).

The problem with this, is that the Fermi paradox does not only concern why we haven’t had aliens land on our doorstep, but also why we cannot see any evidence of life anywhere.
Humans are already quite close to technology that would be detectable on interstellar scales. Remember that centuries, even millennia, are a blink of an eye in this context.

Now, it could be that the millions of life-bearing worlds that you allude to, includes few to zero technological civilizations. In which case, that’s still the primary filters being behind us. Anything up to human levels of progress that gets us down to a handful or less civilizations is a great filter we’ve passed.

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?

There’s a vast number of required events between the organic materials required for a protocell (which is the limit of what we can see forms spontaneously) and even a modern cell, let alone a technological civilization.
We have no idea of the probability of the majority of these events, let alone their probability in total. We don’t need to suggest that there’s anything different about all the other billions of planets in our galaxy. We simply have no basis yet to assume that there should be some minimum number of worlds that reached our level or above. The only data we have for sure is: we don’t see any yet.

[wolfpup]

@Mijin

@wolfpup

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).

The problem with this, is that the Fermi paradox does not only concern why we haven’t had aliens land on our doorstep, but also why we cannot see any evidence of life anywhere.
Humans are already quite close to technology that would be detectable on interstellar scales.

You raise some good points but I take issue with this part. The term “interstellar scale” spans quite a large range in a galaxy that’s between 100,000 to about 150,000 light-years in diameter.

Suppose that the nearest alien civilization with approximately our level of technological capability was – very optimistically – 100 light-years away. What would you expect to see in order to detect them? What could they see if they happened to be looking in precisely our direction?

I would suggest that the answer is “absolutely nothing” to both questions, and this would still be true 100 years from now when they observed today’s radio emissions from Earth. Such signals would all just be lost in galactic noise, the CMB, and intrinsic quantum mechanical limits, even assuming the aliens knew what to look for and exactly where to look for it. We have the same problem, and the farther away such technological civilizations might be, the more intractable the problem of detecting them.

I think the old adage that “absence of evidence is not evidence of absence” is especially applicable here.

[Mijin]

@wolfpup

You raise some good points but I take issue with this part. The term “interstellar scale” spans quite a large range in a galaxy that’s between 100,000 to about 150,000 light-years in diameter.

I was thinking of scales up to a few thousand light years. On first draft I considered saying “galactic scales” but that might have implied being able to see across the zone of avoidance, or even into other galaxies.

@wolfpup

Suppose that the nearest alien civilization with approximately our level of technological capability was – very optimistically – 100 light-years away. What would you expect to see in order to detect them? What could they see if they happened to be looking in precisely our direction?

A couple of things on that.

Firstly, it’s not so much expectation, as what could potentially be visible. I think an (incorrect) assumption sometimes made in this context, is that the Fermi paradox only concerns technology that we can envision aliens having. But of course it’s possible, indeed I would think likely, that we wouldn’t understand many of their grand projects.

Anyway, in answer to the question; anything that blocks, emits or refracts large amounts of EM radiation (as, for example, a Dyson swarm would).

In terms of what aliens looking towards earth would see, it’s unlikely that any of our 1926 technology would be detectable, so they wouldn’t know there was intelligent life here. But our atmosphere, if they could detect it, has various indicators of biological life.

@wolfpup

I would suggest that the answer is “absolutely nothing” to both questions, and this would still be true 100 years from now when they observed today’s radio emissions from Earth. Such signals would all just be lost in galactic noise, the CMB, and intrinsic quantum mechanical limits, even assuming the aliens knew what to look for and exactly where to look for it. We have the same problem, and the farther away such technological civilizations might be, the more intractable the problem of detecting them.

Even if it is true that modern signals would be undetectable at that range, why are we talking about human levels of technological progress?
In the context of the Fermi paradox, and if we’re not positing any prior great filters, it’s necessary to explain why the signs of species millions, perhaps billions, of years of technological progress ahead of us cannot be seen. This is why the apparent lack of Dyson swarms is a meaningful observation.