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Comment by chicob | Hacker News Reader

Isn't it intuitive that there is a strong chance we are alone, or is it just me?

I've always found the Fermi paradox quite unconvincing. And the Drake equation makes it even more obvious.

There's not enough evidence to base your intuition on. We don't even know if life exists elsewhere in our own solar system. SETI has only looked closely at a few then thousands of stars. We have no idea whether the evolution of life on Earth is typical or not (relatively early start, development of multicellular life, brains, eyes, etc).

We also have no idea what alien civilizations might do. Do they stick around their home star, or spread out? Do they last a long time or go extinct? Become god-like or go totally VR? Would they bother to make themselves known over a long enough period of time that other civilizations would detect them? We simply don't know.

I wish we were more careful distinguishing between "life" and "alien civilization." Alien civilizations may not be alive: they may be robots, etc.

This is important, because if we look specifically for life, it limits the scope of our imagination and search. It's SETI, not SETIL.

I think it's a shame vbuwivbiu's answer was killed, because though it was brief I find it's quite insightful. Intuition may be a good guide in contexts which matter strongly for broad well-being under the conditions we evolved for or situations where faculties we gained like that apply well by analogy or side effect. In the cosmic perspective the vast majority of matters are not like that.

My own first take would be that with such a vast number of opportunities for life to arise, it would be incredibly strange if it happens only once, and to me that seems to be the most common view, at least among those who accept a physical theory for the origins of life.

Gets slightly hairier for "intelligent" life, "civilizations",advanced technology" and so on, but the same basic reasoning seems to hold.

The Fermi paradox isn't trying to convince you of anything.

It raises a question, that is basically "how do we need to adjust this model to explain the fact that we've not yet met anyone?"

I mean, it is called a paradox, so it implies an expectation of a different reality.

Yes, but the expectation is "if this model is right, there should lots of aliens". It's not trying to convince you the model is right, but raising the question of what is wrong given that the model appears to be contradicted by observation.

> Isn't it intuitive that there is a strong chance we are alone, or is it just me?

I went to a pretty conservative high school. I had no trouble convincing conservative (evolution is a lie) christians that we are probably not alone in the universe, because it is intuitive that we aren't alone. It went like this:

* There is probably at least one planetoid per star that could support (microbial) life as we know it.

* 100 billion stars per galaxy.

* A trillion galaxies.

* In these trillions of places that could support life, there is not a single microbe? So much for God's infinite power. He must really hate life.

The sheer hubris that there isn't any life in any of the other trillion galaxies usually makes people reconsider.

Now I followed this up with the fact that we are probably never going to see any of these alien lifeforms, particularly if they are just bacteria in another galaxy. The distances are too vast.

An argument could be made that god put life exactly once in each galaxy, and that we have a manifest destiny to colonize it. (You see this argument gleefully applied to resource extraction on earth.) But I never convinced anyone to give all their money to Nasa as part of god's plan.

But it is known that people have a bias towards tangible figures, like meaningful probabilities and round numbers. This heavily distorts the range of imaginable possibilities.

Probabilities are real numbers between 0 and 1. For example, 1.E-301 is one of them. But if one is to take that probability out of a hat people just blatantly ignore it.

>The sheer hubris that there isn't any life in any of the other trillion galaxies usually makes people reconsider.

Hubris is on both sides of this, isn't it? On the face of little to no evidence, how can we estimate such probabilities?

nothing in this universe is intuitive except for a handful of parochial human matters

Exactly. And our expectations are in tune with our own parochial condition. Who is to tell what the rest of the entire Universe should look like?

There are many things we don't know, so the default answer is, most of the time, "we don't know".

Why is it intuitive?

To me, it's more intuitive that we cannot expect to be alone in this galaxy. Perhaps we're the first advanced civilization, but in that case we will not be the last. The vastness of the universe make the chance of us being one-of-a-kind thing really low. If we accept that laws of physics created us, then they can happen else where. And the Drake equation gives an estimate, albeit we have no idea if the variables are reasonable.

> The vastness of the universe make the chance of us being one-of-a-kind thing really low. If we accept that laws of physics created us, then they can happen else where.

You would probably agree that no other alien civilizations speak English. Why not, in the vastness of the universe? Because while the universe is big, the possibility space of languages is so much bigger that no language will ever be repeated.

If history were such that the entire world spoke one language, we might seriously think that aliens had to speak it too.

A key question is whether life is like a language in an infinite possibility space, or is something special.

> The vastness of the universe make the chance of us being one-of-a-kind thing really low.

But it also means the chance of ever communicating with a different life form is really low.

All it takes is some egotistical civilization that builds von Neumann replicators to build KILROY WAS HERE monuments made of diamond on every moon in the galaxy (it's a big galaxy, but there's millions of years to play with). It's at least mildly surprising that there's no evidence of any extrasolar visitors in our solar system's past.

I don't find it mildly surprising the space-fairing aliens practice leave-no-trace.

This assumes von Neumann replicators are acheivable, and if they are, that any species capable of creating them would want to.

We should be able to detect structures signals from past civilisation, if any such exists. If not, we would probably make it easier to future civilisations to detect us.

Detection is different than recognition. The signs of microscopic life were known and even exploited for thousands of years before anyone realized that what was leavening our bread and making us sick was life.

It was implied that I was talking about advanced civilisations. Without some significant kind of structured radiation we cannot detect them with our current technology.

Probably depends on whether we can expect to find them within something like two thousand light years, or two hundred million plus.

It's intuitive to me because I try not to fall for the human-scale numbers.

The Drake equation does not give an estimate. It gives us a train of multiplying factors to which arbitrary values can be assigned, and with it a false sense of a sound estimate.

It's like the lab coat archetype in ads: it looks sciency, but it really isn't.

I have the suspicion we have a very big survival bias.

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