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Comment by mewpmewp2 | Hacker News Reader

I don't understand Fermi Paradox. Why couldn't the chance of life be extremely miniscule, e.g. given all billions of stars and planets, why couldn't there have been even 10% or 0.0001% odds of it happening at all one any given stars or planets? E.g. maybe even it happening on one was such a lucky occurrence?

Maybe given even 1,000,000 of observable universes the odds were just 1 out of 1,000,000.

How can people confidently claim that there must be some other civilizations, we wouldn't know the odds in the first place unless we know the exact mechanisms involved.

To me it seems like the probability could have been anything. It could have required any amount of certain chemical reactions to happen in certain order where the probability can vary wildly depending on the amount and likelihood of those reactions. E.g. it could be 0.01 to the power of 1,000,000 or as well as to the power of 10e64 and so on.

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> To me it seems like the probability could have been anything.

The point is that we do know some things about the universe and, given what we do know, we think the probability is high. So we're obviously missing something but we don't know what.

The thing that makes the Fermi Paradox so interesting is that every resolution is either interesting or implies something interesting.

> So we're obviously missing something but we don't know what.

Isnt the answer dead simple though? Space is mostly empty. Everything is very far away and getting even further as the universe expands. If there were bits of life scattered around the universe I wouldnt expect contact between them.

The paradox seems to rely on the assumption that if aliens existed they would have colonized the entire universe by now but that seems like a huge leap when we look at ourselves.

Universe is almost 14B years old. Life on earth is almost 4b years old. There have been several mass extinction events which almost completely whiped out life. There are planets in our system that may have had life but would have died off a very long time ago. Its kind of remarkable that we are here and how much progress we’ve made. We are certainly fitter than average (survivorship bias proves that). Yet we are nowhere even remotely close of expanding out into the solar system and beyond. And how could we, if virtually all of that space is void of resources we need to survive? Why is it inevitable that some alien would have solved that?

Exactly. One of the base assumptions of the Fermi paradox is that travel between solar systems is practical, which is far from proven at this point. If we are bound by the rocket equation, that is to say if Newton's First Law holds, then the answer to the Fermi paradox is simple. Travel between solar systems is less practical than just colonizing your own solar system, even through extreme measures like swarms of orbital colonies.

When you think about it, an interstellar starship that must expend mass to change velocity is going to have to make a severe tradeoff between mass and travel time. In practical terms you have to first build a colony that can sustain itself indefinitely in your own solar system before you build one that can also accelerate/decelerate to a million kph and doesn't have the advantage of being near a free source of energy or any sources of new materials.

How do we know the probability of chained events required to start life in any given planet with potentially suitable environment?

How do we know that the probability isn't something like 0.01 to the power of some very large number, far higher than amount of total planets etc?

If we don't know the exact mechanism for all we know the odds could be infinitely low, even so low that even after billions of big bangs only 1 would have had life occurring anywhere at all and lower than that. Because maybe the first life form literally had to appear spontaneously from bruteforce chemical reactions with such low odds of ocurring.

What you're describing is one possible resolution and part of what's interesting. A very big open question is "which, if any, of the known factors are wildly rarer than we think?". Another possible resolution is that most of our estimates are actually ok and there's some other variable that's going to whack us on the head at some point.

I just don't get how anyone can go past the idea that maybe it required freak N amount of specific chemical reactions to happen in a row for the first lifeform and without knowing N the odds could just simply be anything. It seems as if people seem to assume that odds of first life form occuring are high and basically just a matter of time, which doesn't make sense to me.

People go past that idea by noticing that it happened on Earth almost as soon as it possibly could have happened. If we just got incredibly lucky, you'd think the planet would have sat around a while before the big stroke of luck, but it didn't. This is fairly suggestive that abiogenesis is not that unlikely.

You can't make any such conclusion from a single event.

If life is so rare, then having two planets in the same system with life, even at different epochs, seems absurd. That’s why I said it’s scary. It means that life can easily get a kickstart but for some reason it doesn’t make it all the way to interstellar civilizations. And that reason could very well be ahead of us and could eliminate humanity. That’s the hypothesis of “The Great Filter”.

https://en.wikipedia.org/wiki/Great_Filter

Life started on Earth really fast after it was physically possible for it to exist on the surface. So either Earth was astronomically lucky, or forming life was easy (on the scale of a couple hundred million anyway), or Earth got seeded really quickly by the next passing rock. The first is unlikely, almost by definition, and the other two both imply life is common.

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