Interstellar travel?

[Manfred Belheim]

We have two hypotheses:
1) Earth is the only planet with life.
2) There are other habitable planets in our Universe.

We cannot prove either of them so far (first one is unlikely possible to prove in any foreseeable future). It doesn't mean we cannot research this problem and look for hints and clues which eventually may lead us to the solution. Useful information is anything which makes either hypothesis more likely and gives us ideas where to search.

I'll assume you meant "inhabited" in point 2, otherwise the two things aren't mutually exclusive.

I'm not sure what part of "we have no information that is relevant to determining how widespread life is" you interpreted as me saying we cannot do any research towards finding any, but this isn't what I said. Information that "gives us ideas where to search" is not useful in answering that question. The things you listed are not useful information for answering that question. So... that's that I guess.

 

[red_elk]

I'm not sure what part of "we have no information that is relevant to determining how widespread life is" you interpreted as me saying we cannot do any research towards finding any, but this isn't what I said.

So, what information would you consider relevant to determining how widespread life is, short of discovery of life itself?
I'd say everything we find during research, even failed attempts, is useful and relevant to determining this.

All Life was created, by his noodly goodness.

Ramen to that.

 

[Manfred Belheim]

So, what information would you consider relevant to determining how widespread life is, short of discovery of life itself?
I'd say everything we find during research, even failed attempts, is useful and relevant to determining this.

Can I just remind you that you argued with me saying, specifically, that astronomy had so far not provided us with any useful information for determining how widespread life is in the universe. Now you seem to be asking me what potential useful discoveries in any field I would say would be useful. That's widening the scope somewhat.

 

[red_elk]

Can I just remind you that you argued with me saying, specifically, that astronomy had so far not provided us with any useful information for determining how widespread life is in the universe. Now you seem to be asking me what potential useful discoveries in any field I would say would be useful. That's widening the scope somewhat.

I'm trying to understand your position. You seem to argue that things like discovery of exoplanets or findings of Mars rovers is useless and irrelevant information to the possibility of finding extraterrestrial life.
In my opinion, even researching place A on Mars and finding there is no life there, is both useful and relevant for that purpose.

Imagine the chain of events something like this:
- Discovery of potentially habitable planet
- Discovery of liquid water there
- Discovery traces of simple organic matter, such as aminoacids
- Finding complex organics, proteins, DNA...
- Finding traces of bacteria or viruses
- Observing alive lifeform
- Catching, dissecting it and confirming it has extraterrestrial origin

At what point the information becomes useful? In my opinion, it is relevant from the very beginning, because it may eventually lead us to the discovery.

 

[Akka]

If it makes it better replace "exact copy of your house" with "something very much like a modern human dwelling".

It's quite better (it gets out of "specific copy" to "general concept") but it's still not adequate (it's still confusing instances with processes).

Also, it adds the idea of "intent" - something artificial, by definition, doesn't build itself. Unless life has been a creation (of gods, aliens or whatever, which is still a possibility to keep in mind but not one I consider as a serious option), then it's a spontaneous mechanism.

However, applying them to a question that they do not directly apply to

You're going to have to explain to me how the physical mechanisms of life don't directly apply to the general understanding of how life came to be. That's like saying gravity doesn't apply to star birth.

For example, existence of exoplanets in habitable zone makes 2-nd hypothesis more likely. Discovery of water oceans in Europa and Enceladus, organic matter on Mars, gives us directions for further search.
All this is useful information.

I would agree, but I was teached recently that in fact it's just penis length measuring.

 

[Manfred Belheim]

I'm trying to understand your position. You seem to argue that things like discovery of exoplanets or findings of Mars rovers is useless and irrelevant information to the possibility of finding extraterrestrial life.

Okay well first, "irrelevant information to the possibility of finding extraterrestrial life" isn't the same "irrelevant information as regards determining how probably extraterrestrial life is". I'm talking about the latter. Second, Mars rovers don't really fall under the category of "astronomy". Even with the recent results of the Mars rover, there's still no evidence of life itself. And even if there was, we know there's the possibility of "cross-contamination" with Mars and Earth anyway.

So all that aside... yes the discovery of exoplanets is I suppose relevant, as was the "discovery" of other stars in general. It tells us that other locations exist in the universe, which is obviously a prerequisite for life existing in other locations. But also it's kind of what prompts the question in the first place, rather than evidence for it. Although exoplanets have only been proven to exist at all in the last 25 years or so, I think it's always been reasonable to assume they did exist to some degree. I get that the same "statistical sample of 1" argument applied before we discovered them, but at the same time they are basically just large lumps of basic elements and compounds, nothing anywhere near as complex as life. Plus we had at least some sort of reasonable models for how planetary systems could and probably did form. So really the discovery of exoplanets doesn't really add much to the debate as of yet. And really that's the only relevant thing that astronomy has given us as regards this question.

...
At what point the information becomes useful? In my opinion, it is relevant from the very beginning, because it may eventually lead us to the discovery.

Yes but the point wasn't about what could lead us to a discovery, it was about what we currently know that helps us determine how likely life is. You seem to be misconstruing what I'm saying.

 

[Manfred Belheim]

It's quite better (it gets out of "specific copy" to "general concept") but it's still not adequate (it's still confusing instances with processes).

Also, it adds the idea of "intent" - something artificial, by definition, doesn't build itself. Unless life has been a creation (of gods, aliens or whatever, which is still a possibility to keep in mind but not one I consider as a serious option), then it's a spontaneous mechanism.

I mean... honestly I wonder why people ever bother making analogies. The point is never to claim that it's an exact 1-to-1 analogue, and yet analogies always end up being picked apart to that degree.

All I was saying was that the fact that building blocks of a thing exist in abundance, doesn't imply that the thing itself therefore exists in abundance. So any arguments about how abundant stars, planets, water, carbon, organic compounds, or even amino acids are, don't directly apply to how adundant life is.

 

[red_elk]

So all that aside... yes the discovery of exoplanets is I suppose relevant, as was the "discovery" of other stars in general. It tells us that other locations exist in the universe, which is obviously a prerequisite for life existing in other locations. But also it's kind of what prompts the question in the first place, rather than evidence for it. Although exoplanets have only been proven to exist at all in the last 25 years or so, I think it's always been reasonable to assume they did exist to some degree. I get that the same "statistical sample of 1" argument applied before we discovered them, but at the same time they are basically just large lumps of basic elements and compounds, nothing anywhere near as complex as life. Plus we had at least some sort of reasonable models for how planetary systems could and probably did form. So really the discovery of exoplanets doesn't really add much to the debate as of yet. And really that's the only relevant thing that astronomy has given us as regards this question.

The reason why I mentioned discovery of exoplanets and astronomy in general, is because I remember reading a book in early 90-s, where author tried to estimate the range of probabilities that extraterrestrial life exists. One thing he mentioned, is that we didn't even know how widespread planetary systems are and this added large degree of uncertainty to the final result. At that time, there were only weak evidences of gas giants in star systems nearby. There were different theories about formation of star systems and some of them were concluding that Earth-like planets might be extremely rare. Now, 30 years later we ruled out those theories and decreased the level of uncertainty.

 

[hobbsyoyo]

Yeah we're actively trying to put a boundary box on the variables in the Drake equation.

 

[warpus]

But today is you lucky day. This was established that at the moment you pulled the white marble out of the bag.

It can't be my lucky day since I don't know how likely it is that white marbles end up in the bag. It would only have been my lucky day if I pulled out the only white marble out of a bag containing a lot more black marbles.

But the bag could easily contain ALL white marbles. Or 7 white marbles. Or 50,000. or 50%. You have no idea. That is not an assumption you can make.

Remember, the premise is that we have no idea what the probability is that a white marble ends up in the bag. You can't just assume that there is only 1 white marble in there, you have no idea how many white marbles are in there

 

[Akka]

I mean... honestly I wonder why people ever bother making analogies. The point is never to claim that it's an exact 1-to-1 analogue, and yet analogies always end up being picked apart to that degree.

Analogies are good, but they need to be RELEVANT. Their goal is to illustrate a concept, a relationship. If the analogy used is fundamentally different in its concept, then it's not working.
Trying to claim that a spontaneous process can be extremely rare to the point of uniqueness by making a parallel with a finished product is just nonsensical and unrelated.

All I was saying was that the fact that building blocks of a thing exist in abundance, doesn't imply that the thing itself therefore exists in abundance. So any arguments about how abundant stars, planets, water, carbon, organic compounds, or even amino acids are, don't directly apply to how adundant life is.

And you're wrong, it DOES directly apply. That's not an opinion, that's a logical fact. The more restricted the conditions, the rarer the event. If life uses very basic matter, it means there is a much larger pool of places from which it can arises.

Life isn't created (unless you're going into religious stuff, at which point we're back to "then what created the creator"). So it means it's a spontaneous events happening in specific circumstances.
The question is : which are these circumstances, and how rare are they ?
The rarity of the elements needed for life seems pretty much critical to answering this question.

Because in the end : what CAN be the incredibly rare requirement that would make life's chances of appearance so low that it's unique in the universe ? Just what are the possible requirements for a spontaneous chemical process which aren't about matter used and environmental variables ? Because none of them seems to be this kind of rare in the universe.

 

[Manfred Belheim]

The reason why I mentioned discovery of exoplanets and astronomy in general, is because I remember reading a book in early 90-s, where author tried to estimate the range of probabilities that extraterrestrial life exists. One thing he mentioned, is that we didn't even know how widespread planetary systems are and this added large degree of uncertainty to the final result. At that time, there were only weak evidences of gas giants in star systems nearby. There were different theories about formation of star systems and some of them were concluding that Earth-like planets might be extremely rare. Now, 30 years later we ruled out those theories and decreased the level of uncertainty.

Yeah it helps. And as you say it's a step on the road. But the other uncertainties are just as uncertain so it doesn't help with any current estimates. If I tell you that X = ? * ?, and then later on I give you more information and tell you that X = 17 * ?, are you any closer to calculating X?

 

[Manfred Belheim]

It can't be my lucky day since I don't know how likely it is that white marbles end up in the bag. It would only have been my lucky day if I pulled out the only white marble out of a bag containing a lot more black marbles.

But the bag could easily contain ALL white marbles. Or 7 white marbles. Or 50,000. or 50%. You have no idea. That is not an assumption you can make.

Remember, the premise is that we have no idea what the probability is that a white marble ends up in the bag. You can't just assume that there is only 1 white marble in there, you have no idea how many white marbles are in there

I think you've inadvertantly ended up championing the other side of the argument...

 

[Manfred Belheim]

Analogies are good, but they need to be RELEVANT. Their goal is to illustrate a concept, a relationship. If the analogy used is fundamentally different in its concept, then it's not working.
Trying to claim that a spontaneous process can be extremely rare to the point of uniqueness by making a parallel with a finished product is just nonsensical and unrelated.

Oh whatever. I've already clarified the point of the analogy. Seems pretty clear to me. Forget I ever typed it if you like, it's not really important.

And you're wrong, it DOES directly apply. That's not an opinion, that's a logical fact. The more restricted the conditions, the rarer the event. If life uses very basic matter, it means there is a much larger pool of places from which it can arises.

Yes but without that knowledge of how abiogenesis did or can occur, that still leaves you knowing absolutely nothing about how likely it is. If we suddenly discovered that the universe is 100x larger than we knew before, and therefore contains 100x as many habitable planets as we thought, we could say with some reasonable certainty that the odds of there being more life out there are 100x greater than they were before. But all that tells us is that instead of being a completely unknown number, it's now a completely unknown number multiplied by 100. Also known as a completely unknown number.

Life isn't created (unless you're going into religious stuff, at which point we're back to "then what created the creator"). So it means it's a spontaneous events happening in specific circumstances.
The question is : which are these circumstances, and how rare are they ?
The rarity of the elements needed for life seems pretty much critical to answering this question.

Yes but without knowing (or at least having an estimate of) the probability of every step in the chain, you're no closer to an answer than if you know the probability of none of them at all. They're all critical yes, but without the complete set there's still no answer.

Because in the end : what CAN be the incredibly rare requirement that would make life's chances of appearance so low that it's unique in the universe ?

Abiogenesis. We don't know how it happened or could happen. And no I'm not being a creationist, I'm just saying we can't say how likely or unlikely that was because we don't know the mechanism.

 

[timtofly]

We have to accept a definition for life first though. Life may have way more to it than known biological parameters. We may be the only biological equivalent to life as we know it in the universe. I am not even saying the earth, solar system, or universe is some conscious life form. That is the point that we do not know what is in the bag, and probability is well nigh useless. Probability only works if there is eventually discovered biological forms of life that is even close to us.

 

[uppi]

It can't be my lucky day since I don't know how likely it is that white marbles end up in the bag. It would only have been my lucky day if I pulled out the only white marble out of a bag containing a lot more black marbles.

But the bag could easily contain ALL white marbles. Or 7 white marbles. Or 50,000. or 50%. You have no idea. That is not an assumption you can make.

I didn't mean that your lucky day involves pulling the only white marble from the bag. You need to to draw a marble from the bag at all.

Except for the case in which the bag contains all white marbles, the probability of drawing one is always less than 1. Even if 50% percent of the marbles are white, you still need luck to get a white one if you only have one trial. So when you hold a white one in your hand, you were lucky, you just don't know by how much.

Remember, the premise is that we have no idea what the probability is that a white marble ends up in the bag. You can't just assume that there is only 1 white marble in there, you have no idea how many white marbles are in there

Exactly. And statistics tells you, that having drawn a white marble does not change this lack of information at all, when your situation is preconditioned on that fact.

 

[red_elk]

If I tell you that X = ? * ?, and then later on I give you more information and tell you that X = 17 * ?, are you any closer to calculating X?

Yes.. We know approximate boundaries for every question mark in this equation. If we figure out one term, it narrows down the possible range of final results.

It's already known that if life on Earth is unique in the Universe, the probability of developing life anywhere must be extremely low, near zero. And while this is a valid hypothesis, so far there are no evidences which support it. All what we see suggests that similar Earth-like conditions likely arose in millions or billions other places.

 

[Broken_Erika]

...... All what we see suggests that similar Earth-like conditions likely arose in millions or billions other places.

Across Billions of years.......Some are likely long extinct while others are likely just starting. I guess the real question is how many are around a similar level as us.

 

[Timsup2nothin]

It's already known that if life on Earth is unique in the Universe, the probability of developing life anywhere must be extremely low, near zero. And while this is a valid hypothesis, so far there are no evidences which support it. All what we see suggests that similar Earth-like conditions likely arose in millions or billions other places.

Thing is that "Earth-like conditions are all it takes for life to begin" is also a valid hypothesis, and there is also no evidence to support it either. And there is evidence against it.

Without knowing how the process started on Earth we can't put a limit on how exact an "earth-like" is required. We can observe that Earth is certainly "earth-like" right now, and yet no spontaneous life processes are beginning. So we know that whatever the limit is, at least this earth-like planet is now outside of it. All we know about current Earth is that it can sustain life. Did the Earth pass through an incredibly narrow time window where it was capable of originating life, not merely sustaining life? In the four billion plus lifespan of Earth as a not life originating mudball it's possible that the conditions for originating life lasted one year, or one month, or one day. There is no way to tell from here.

So it is just as easy to think that, yeah, probability of developing life anywhere might well be vanishingly close to zero, and we just happen to be on the bizarrely fortunate mudball.

 

[Berzerker]

one theory credits the moon with life, the immense tides being the driver... And life appears to have begun during or shortly after the late heavy bombardment. These occurrences combined with the Earth's location in the solar system - with liquid water - certainly limit the conditions under which life began. Or maybe life was brought here by an impactor. But that begs the question: how did life get started on an impactor?