Interstellar travel?

[Thorgalaeg]

IMO it's a bit crazy to assume we are the only living things in this universe. What makes you think we are so special?

We used to think we're the centre of the universe.. we used to think our sun was the only star in the universe.. then we used to think our solar system was the only one in existence.. then we used to think our galaxy was the only one in existence..

We really don't know if we are special or ordinary. However we know that life appeared in Earth very very early, quickly (in geological time at least) after liquid water. So from there we can infer that life is not an special and weird occurence but the normal process once the conditions minimally allows for it. Of course it could be that life is indeed very rare and Earth won the lottery but that seems more improbable.

 

[Manfred Belheim]

That's the best way to work out reliable estimates of probability isn't it. Gut instinct and what feels right...

 

[Thorgalaeg]

That is totally unrelated to that i posted.

 

[Lexicus]

That's the best way to work out reliable estimates of probability isn't it. Gut instinct and what feels right...

TIL the Copernican Principle is "gut instinct"

 

[Manfred Belheim]

That is totally unrelated to that i posted.

Well the last sentence of your post.

If you google "abiogenesis probability" you unfortunately get a load of stuff related to debates with Creationists, which is not what I'm looking for at all. But as far as I can tell (and please correct me if I'm wrong) there just doesn't exist any reliable estimate of what this probability is. We have a lower limit on what it can be (or upper limit, depending on how you're writing your probabilities) based on the probability of a random chance formation of the most basic form of "living" molecules, which seems so improbable as to have been unlikely to have happened anywhere ever, but other than that (again, as far as I can tell) we just don't know.

And we can't work out how likely life is to evolve based on the statistics, because we have no statistics, other than "it definitely happened at least once".

So yeah... to work out how often something has happened in the universe, you don't just need to know how big the universe is and how long it's been around, but also at least some basic estimate of the probability of the thing happening. Which we don't know at all. So this whole discussion is based around nothing more than "probability deduced by gut instinct".

As I've tried to point out, this is not me saying "we're definitely alone in the universe" because such a statement is equally as unfounded as "we're definitely not alone in the universe".

 

[Manfred Belheim]

TIL the Copernican Principle is "gut instinct"

Well if you did you didn't learn it from what I said because the Copernican Principle isn't concerned with abiogenesis. It certainly doesn't say anything about the validity of inferring statistical trends from single data points either.

 

[elmurcis]

If alliens are smart enough they won't get close to Earth even if would knew about our existence like centuries on milleniums ago (maybe they did... as Gods?)- civilization still is trying to finish kindergarden and we dream about university already.. but there are many great talents who are capable of doing bigger stuff than running around globe with fighters and missiles.

 

[El_Machinae]

We definitely made up spacefaring alien civilisations. Which doesn't mean they don't actually exist of course, we've "made up" plenty of things which have later actually been discovered, but it does mean that there's no real requirement to explain why we haven't seen them yet.

Not sure I agree. How else would we iteratively improve our methodology for those who want to look? It leads to efficiencies, which brings forwards in time the answers to the questions we ask.

 

[warpus]

"it definitely happened at least once"

That's a LOT different of a statement than "It probably happened ONLY once"

 

[Lexicus]

Well if you did you didn't learn it from what I said because the Copernican Principle isn't concerned with abiogenesis. It certainly doesn't say anything about the validity of inferring statistical trends from single data points either.

The Copernican principle is the idea that there is nothing special about the Earth or its immediate region of the universe. This is a reason other than "gut instinct" to suppose that life is common throughout the universe. There is also the mediocrity principle - it is a lot likelier that Earth is one of many planets hosting life than that it is the only one. That is also something more than gut instinct.

 

[Timsup2nothin]

The best argument I've seen is the time interval issue. Our own "spacefaring era" is a tiny fraction of a tiny fraction of the history of the universe. Even if we go with the "the universe is so big that multiple incidents of intelligent life reaching spacefaring is an odds on certainty" we are left with a very small chance that more than one of them will hit that tiny sliver in history even close to simultaneously. So if we go with "the next step is expansion" we come to the reality that expansion expands at an exponential rate. The first to reach their "age of interstellar expansion" would have. Their rate of expansion would then increase exponentially as they started to expand, and they would be everywhere. Since they apparently aren't here no one else has reached that point.

 

[Manfred Belheim]

Not sure I agree. How else would we iteratively improve our methodology for those who want to look? It leads to efficiencies, which brings forwards in time the answers to the questions we ask.

I didn't say it wasn't interesting or wouldn't help with future searches for such evidence. Just that the lack of evidence isn't something that needs to be explained. We don't operate with a model of the universe that requires there to be loads of aliens flying around, so it isn't a gap in our understanding of the universe.

That's a LOT different of a statement than "It probably happened ONLY once"

Well I've already told you that "it probably happened ONLY once" isn't an accurate representation of what I think or anything that I've said, so it really shouldn't come as much surprise that it's a lot different to something I actually said

The Copernican principle is the idea that there is nothing special about the Earth or its immediate region of the universe. This is a reason other than "gut instinct" to suppose that life is common throughout the universe. There is also the mediocrity principle - it is a lot likelier that Earth is one of many planets hosting life than that it is the only one. That is also something more than gut instinct.

The Copernican principle isn't the same as the mediocrity principle though, and doesn't really have much to say about the origins of life. There's also the (weak) anthropic principle which would seem more applicable here. When you're discussing life itself, you have to accept the fact that we are in a "special" position since it's only the fact that we are alive that we can even ask the question.

 

[warpus]

Well I've already told you that "it probably happened ONLY once" isn't an accurate representation of what I think or anything that I've said

Logically speaking your position then has to be "It probably happened more than once", which is exactly what my position is, so there is no disagreement here.

 

[Timsup2nothin]

You guys do recognize that there are all sorts of things that happen only once, right? Unique is pretty normal, it's two that is the absurdity.

 

[Lexicus]

The best argument I've seen is the time interval issue. Our own "spacefaring era" is a tiny fraction of a tiny fraction of the history of the universe. Even if we go with the "the universe is so big that multiple incidents of intelligent life reaching spacefaring is an odds on certainty" we are left with a very small chance that more than one of them will hit that tiny sliver in history even close to simultaneously. So if we go with "the next step is expansion" we come to the reality that expansion expands at an exponential rate. The first to reach their "age of interstellar expansion" would have. Their rate of expansion would then increase exponentially as they started to expand, and they would be everywhere. Since they apparently aren't here no one else has reached that point.

Judging from Earth's history, there may be hundreds or thousands of planets hosting nothing more complex than single-cell organisms for every planet that hosts multicellular life (let alone "intelligent" life). To me one of the most exciting potentials for astrobiology/xenobiology is finding analogues of the precursor life (or "proto-life"?) forms that I think must have existed before the current DNA/RNA paradigm became dominant on Earth.

It is also possible that the technological/energy requirements for spaceflight, radio communication etc inevitably destroy the ability of the host planet to sustain the civilization creating it.

I have also offered the explanation that the difficulty of interstellar travel means that technological civilizations achieve the ability to simulate entire universes in computers long before achieving the ability to travel to other star systems within reasonable time periods, thus meaning any incentive to actually travel to other stars is gone long before it can be done.

The Copernican principle isn't the same as the mediocrity principle though, and doesn't really have much to say about the origins of life. There's also the (weak) anthropic principle which would seem more applicable here. When you're discussing life itself, you have to accept the fact that we are in a "special" position since it's only the fact that we are alive that we can even ask the question.

They're not the same, but they are related. The Copernican principle might even be considered a special case of the mediocrity principle.

The anthropic principle is not some kind of refutation of the Copernican principle, by the way.

 

[Thorgalaeg]

Well the last sentence of your post.

If you google "abiogenesis probability" you unfortunately get a load of stuff related to debates with Creationists, which is not what I'm looking for at all. But as far as I can tell (and please correct me if I'm wrong) there just doesn't exist any reliable estimate of what this probability is. We have a lower limit on what it can be (or upper limit, depending on how you're writing your probabilities) based on the probability of a random chance formation of the most basic form of "living" molecules, which seems so improbable as to have been unlikely to have happened anywhere ever, but other than that (again, as far as I can tell) we just don't know.

And we can't work out how likely life is to evolve based on the statistics, because we have no statistics, other than "it definitely happened at least once".

So yeah... to work out how often something has happened in the universe, you don't just need to know how big the universe is and how long it's been around, but also at least some basic estimate of the probability of the thing happening. Which we don't know at all. So this whole discussion is based around nothing more than "probability deduced by gut instinct".

As I've tried to point out, this is not me saying "we're definitely alone in the universe" because such a statement is equally as unfounded as "we're definitely not alone in the universe".

It is not just "it happened once" but "it happened once quickly", maybe not statistically representative but it is supports more the "life is a common occurrence" side than the "life is a exceptional thing" side.

 

[warpus]

You guys do recognize that there are all sorts of things that happen only once, right? Unique is pretty normal, it's two that is the absurdity.

In the entire universe? Name one.

 

[El_Machinae]

Logically speaking your position then has to be "It probably happened more than once", which is exactly what my position, so there is no disagreement here.

No. He's not putting a value on the probability. You seem to

 

[warpus]

No. He's not putting a value on the probability. You seem to

Neither am I though.

Our position seems to be exactly the same, if I'm reading that last post right.

 

[El_Machinae]

Neither am I though.

Our position seems to be exactly the same, if I'm reading that last post right.

Your two statements don't match. Either you think that it probably happened more than once, or you don't put a value on the probability. Which is it?