Has anyone else used Drake Equation calculators?

[Red Iron Crown]

What is the basis for that, in light of the cosmological principle? If that principle is accepted, does your scepticism not require a reason to think that our spot in the universe is very special - whereas everthing we know points to that not being the case?

The cosmological principle is a supposition, not necessarily a correct one, and we may never be able to gather enough data to verify it. I don't think Earth is very special aside from the fact it has life, which we haven't observed elsewhere. I'm not saying it's impossible or even unlikely that there is other life out there, just that we have nowhere near enough data to make any kind of accurate estimate. If the universe is finite, and the probability of life arising is sufficiently low, then it is entirely possible that there is no other life. We just don't know enough to say it is a given.

[Albert VDS]

Are you sure you grasp how immense the unniverse is.

In our galaxy alone there are 100 billion stars which have atleast 1 planet orbiting it. Even a very small precentages is a large number.

Also life on Earth can live in the most hostile places.

[Red Iron Crown]

"Sufficiently low." If, say, there are 10^100 habitable planets in the universe and the odds of life arising are 1 in 10^200, it is unlikely that there is life elsewhere. We just don't know how likely life arising is in relation to the other numbers.

Life being able to survive in difficult conditions is pretty much irrelevant, it's the difficulty of life arising from non-life in the first place that is important.

[Albert VDS]

Odds don't rule out that there no more than one. Take a dice, you have 1/6 chance of throwing a 6. That doesn't mean you can only throw 1 6 in 6 throws.

Of course we don't know exactly how life arrose, but hardyness does give it a bigger chance.

[Red Iron Crown]

Odds don't rule out that there no more than one. Take a dice, you have 1/6 chance of throwing a 6. That doesn't mean you can only throw 1 6 in 6 throws.

Of course. My point was that if the odds are slimmer than the number of cases by enough of a margin, the probability of a particular result approaches zero. Or using your dice analogy, if you have a thousand-sided die and can roll it ten times, what are the odds of rolling at least one 1?

Of course we don't know exactly how life arrose, but hardyness does give it a bigger chance.

I don't see how. Life, once established, expands vigorously into every niche into which it can fit, given enough time; I don't think that's arguable. It's that "once established" part that we're talking about here, and we have literally no idea how difficult that is, we can't even reproduce it in the lab as far as I know.

[phoenix_ca]

I don't see how. Life, once established, expands vigorously into every niche into which it can fit, given enough time; I don't think that's arguable. It's that "once established" part that we're talking about here, and we have literally no idea how difficult that is, we can't even reproduce it in the lab as far as I know.

I believe the original run of Cosmos covered that somewhat. It's possible to generate organic matter from inorganic matter under the right conditions (conditions similar to what we think the Earth was like some few billion years ago). How that ever got around to actual cellular life might've been dumb luck. All you really need to get that started is some lipids, and some other parts to hang-out and operate inside those lipids.

[SargeRho]

It's that "once established" part that we're talking about here, and we have literally no idea how difficult that is, we can't even reproduce it in the lab as far as I know.

We have a pretty good idea of how it happened actually. A good portion of it has been reproduced in the lab, too.

[Red Iron Crown]

I believe the original run of Cosmos covered that somewhat. It's possible to generate organic matter from inorganic matter under the right conditions (conditions similar to what we think the Earth was like some few billion years ago). How that ever got around to actual cellular life might've been dumb luck. All you really need to get that started is some lipids, and some other parts to hang-out and operate inside those lipids.

It's a big, big step from organic matter to life. As far as I know, we've never created life where none was before, even in ideal lab conditions. All we have is a theory of how it could happen.

Don't take me for a creationist or anything, I'm just saying the process of life from not-life involves some extremely improbable events, and we're not sure how that probability compares to the number of possible places where life can arise in the universe.

[phoenix_ca]

Don't take me for a creationist or anything, I'm just saying the process of life from not-life involves some extremely improbable events, and we're not sure how that probability compares to the number of possible places where life can arise in the universe.

Fair enough. Maybe Europa could shed more light on that. I really wish we were sending even more probes out that way.

[Red Iron Crown]

Agreed, if we discovered life arising independently somewhere else in the solar system, that would imply that it's not as improbable as we might have suspected. Or that there is some condition in the solar system that makes it easier to arise.

[sndrtj]

Biologist here! . I'd like to point out that the chance of life parameter is measurable. At least a low estimate is possible. The crux here is measuring atmospheric oxygen on exoplanets. Sure, there are physical processes that can produce atmospheric oxygen, but they are few. Oxygen is a very reactive chemical, of which the vast majority of oxygen in an atmosphere will react to form minerals in geologically short time spans. Unless it is replenished continuously. By life. This is what is happens on Earth. If all life on the planet were to wiped out today, there would be very little oxygen left a few million years from now.

Measuring the chemical makeup of exoplanets' atmospheres is possible by way of spectroscopy. An exoplanet with an oxygen-rich atmosphere is very likely to harbour life. Measuring the rate of oxygen-rich exoplanets can thus be a measure of the chance of life appearing on planets.

However, estimates by this measure would be on low side of things. Life on Earth has evolved to produce oxygen, but this doesn't have be true for alien life. Already on Earth we find the most bizarre chemical processes that life can utilize.

What is, I think the most difficult parameter in the drake equation is the chance of evolving intelligent life. There is not really a known way to measure this. And even here on Earth, we don't even have a decent description of what 'intelligent' even means! Cetaceans are super smart animals, but would we consider them "intelligent"? Or does the definition of intelligence include heavy tool use? A cetacean might be very smart, but it can make less use of its capacity as it simply doesn't have the dexterity to handle tools. And so on. I would be inclined to say that the emergence of intelligence is somewhat of an evolutionary outcome on very long time scales. Humans are not the only smart species on the planet. Our deceased cousins, the Neanderthals, for instance, made heavy tool use and had art. One can teach a gorilla or bonobo to understand and respond to human language. Cetaceans have highly developed brains, and show features of having distinct cultures. It was very recently discovered that the framework of it all - neural systems - has likely already evolved independently at least twice on Earth alone (see: http://www.nature.com/news/jelly-genome-mystery-1.15264 ). Who knows what a few tens of million years of extra evolution would have accomplished. A world ruled by dolphins?

[Red Iron Crown]

Have we detected any oxygen-rich exoplanets? I didn't know that was such a strong indicator.

[sndrtj]

Not yet. Current spectroscopes are not sensitive enough to detect the faint light from an Earth-like exoplanet (most exoplanets are discovered by the gravitational or obscuring effect they have on their parent star, not by direct measurement) required for such experiments. However, performing spectrography on an exoplanet has been done, and oxygen has been detected (just not in vast quantities indicative of life) on planet HD209458b (https://en.wikipedia.org/wiki/HD_209458_b). This planet is both large (bigger than Jupiter) and VERY close to its star, which means that much star light falls through its atmosphere, facilitating atmospheric analyses.

But we will get there soon enough for Earth-like planets. If I could place my bet on it, I suspect we will find an oxygen-rich Earth-like exoplanet in the next 10 years. With any luck, a planet in the Kepler dataset might already fit the bill. It would be a huge discovery thing for exobiology.

[rkman]

I don't think Earth is very special aside from the fact it has life, which we haven't observed elsewhere.

We haven't observed life elsewhere because when it comes to that we are almost completely blind. We know that much. We are using the equivalent of Huygens' first microscope, we see things we haven't seen before but we know there is much more to be seen.

I'm not saying it's impossible or even unlikely that there is other life out there, just that we have nowhere near enough data to make any kind of accurate estimate.

How much life is out there is a matter of estimates and accuracy, and i agree that we do not have enough data to make an accurate estimate about that.

But I think the issue of there being any other life at all is fundamental, not a matter of estimates nor accuracy. There is no accuracy in "yes" or "no", it's either 100% correct or 100% wrong.

We just don't know enough to say it is a given.

I think it would be much harder to explain why in the entire universe we are the only ones, than it is to explain abundance of life in the universe. We already have explained the latter (known physics), it's just that we have not observed it.

The reason why we have not observed life elsewhere is our very limited observational technology, which is insufficient to observe life in 99.99999...% of the universe.

We know enough to say it is "pretty much a given" that there is life elsewhere, and extremely unlikely that it is not. At least you seem to agree it is not unlikely, which is not all that different than thinking that it is likely.

Basically you are saying it is not 100% certain, i'm saying it is 99.9999% certain. If you think it is likely, does that not mean you think the chance is better than 50%?

the process of life from not-life involves some extremely improbable events

It is more a matter of favorable conditions than one of probability. Generally it is actually very probable for something to happen if the conditions are being met, even if the conditions are a rare occurrence.

Edited June 12, 2014 by rkman

[Red Iron Crown]

Basically you are saying it is not 100% certain, i'm saying it is 99.9999% certain. If you think it is likely, does that not mean you think the chance is better than 50%?

I think it likely, but that's a personal opinion not supported by evidence. I cannot give a number because we don't have the data.

Basically, we just don't know how astronomical the odds are for life and intelligence arising. Since we don't know those odds, we can't make a meaningful estimate of the likelihood of life and intelligence existing elsewhere in the universe. Your "99.9999% certain" is just a from-the-hip estimate, not based on any real numbers.

[rkman]

I think it likely, but that's a personal opinion not supported by evidence. I cannot give a number because we don't have the data.

You keep saying that, but i think you know we have plenty data that shows physics works the same everywhere in the universe, and that life is a physics process.

Your "99.9999% certain" is just a from-the-hip estimate,

True, but so is your "it is not unlikely".

not based on any real numbers.

Again: we have plenty of real numbers on physics - the same physics that underpins life.

How likely do you think it is that Earth is the only planet with any form of life in the entire universe? I can't think of any way to explain how that could be, can you?

[Red Iron Crown]

You keep saying that, but i think you know we have plenty data that shows physics works the same everywhere in the universe, and that life is a physics process.

Please share the data that is relevant to the likelihood of life and intelligence arising.

True, but so is your "it is not unlikely".

The difference being that I admit it's from the hip and not supported by numbers or observations.

Again: we have plenty of real numbers on physics - the same physics that underpins life.

Again, please share the data that gives a quantitative estimate of the likelihood of life elsewhere.

How likely do you think it is that Earth is the only planet with any form of life in the entire universe? I can't think of any way to explain how that could be, can you?

I can't speak to the likelihood, because we don't have enough data. It could be anywhere from very likely to very unlikely, depending on the relative odds of life arising and the number of potential cases.

[Mr Shifty]

My gut suspicion is that life is relatively plentiful, but technological civilizations are pretty much non-existent (aside from ours of course.) It's quite clear, looking at the sample of living species we have on Earth, that high-technology is not a prerequisite for survival. There's no compelling reason to think that humanity will have a larger than average species-lifetime (species persist for about a million years on average); it seems likely to me that the entire hominid family will be extinct within a million years (and perhaps all but humans within a couple hundred.) There's absolutely no indication that, in the absence of humans, there would arise another tool wielding, social animal with as vastly complex a language ability as we have. (There is no other animal now that comes even remotely close to our ability to convey information through speech.) And even if one did, there's no reason they'd develop civilization; humans did not for hundreds of thousands of years. And we ourselves barely made it. Humans are all remarkably genetically similar, suggesting we passed through a genetic bottleneck of perhaps a couple thousand individuals at some point in our (genetically) recent past. There was no 'intelligent species' niche waiting for us for the 500 million years macro-scale life existed before our arrival. Life doesn't need intelligence, and intelligence (not to mention technological civilization) isn't anything close to inevitable, given life.

[phoenix_ca]

(species persist for about a million years on average)

If homo sapiens around for that long, it's pretty safe to say that by that time our use of technology will have changed us into something completely unrecognizable to us. Hell, it's safe to say that if technology continues its current progression, that'll be true in even a thousand years, though probably not to the point of whatever we do to ourselves being considered speciation.

[rkman]

Please share the data that is relevant to the likelihood of life and intelligence arising.

Again, please share the data that gives a quantitative estimate of the likelihood of life elsewhere.

Same argument as before: life is a physics process, and we have plenty data that shows physics is the same everywhere in the universe.

Given that, i think the burden of proof is on you as to how it could be that in spite of the same physics, Earth is unique in the entire universe wrt to harboring life.

The difference being that I admit it's from the hip and not supported by numbers or observations.

That's not different, i also admitted my estimate is from the hip.

Otoh i do say there are observations that support my 'from the hip' estimate: data shows physics is the same everywhere in the universe, and life is a physics process. What is the basis for your 'from the hip' estimate?

I can't speak to the likelihood, because we don't have enough data.

But you did speak to the likelihood. You said you think it is not unlikely. In other words, you think it is likely. Not all that much different than my position on this.

[Red Iron Crown]

Same argument as before: life is a physics process, and we have plenty data that shows physics is the same everywhere in the universe.

Given that, i think the burden of proof is on you as to how it could be that in spite of the same physics, Earth is unique in the entire universe wrt to harboring life.

I agree that it's very likely that physics are the same throughout the universe, and that life is a physical process (some would get into mysticism about that, but not me). There is a ton of evidence to support that, and not much if any to refute it. My point isn't that physics are different elsewhere. I haven't suggested this, nor do I think it is true.

My point is that the likelihood of life arising elsewhere in the universe is based on the relative magnitudes of the number of planets which could sustain life versus the probability of life arising on one of those planets. If the inverse of the probability is much, much greater than the number of planets, then it could be a high probability that Earth is the only place life has arisen. This doesn't require different physics. There is nothing about Earth being the only life-supporting planet that violates physics as we know it.

For example, say a lottery ticket has a 1:10,000,000 chance of winning. If you have 1,000 tickets, it is unlikely that you'll win even though a winning ticket is possible given the rules of the game. Similarly, if the magnitude of the odds of life arising is significantly greater than the number of planets, then the likelihood of life arising elsewhere is low, even though the rules of physics permit it.

Since we have no good estimate of the probability of life arising on a planet, and only the roughest of estimates for the number of potentially life-supporting planets, we can't say with any kind of confidence whether it is likely or not that there is other life out there.

My personal feeling is that there is other life out there, but that's just a personal feeling not supported by science (indeed, I don't think any kind of conclusion based on science is possible in this matter, knowing what we know now). The post that sparked this whole thing was a statement that it's a "given" that there's other life out there, when we just don't know that to be true nor do we have an accurate estimate of the likelihood.

Edited June 13, 2014 by Red Iron Crown

[rkman]

Similarly, if the magnitude of the odds of life arising is significantly greater than the number of planets, then the likelihood of life arising elsewhere is low, even though the rules of physics permit it.

I understand that, but in think you greatly underestimate the number of planets in the universe. Best observations so far have it the universe is at least several orders of magnitude larger than the observable universe, and much larger (possibly infite) is not excluded. Kepler and other planet hunters have shown planets are more abundant than previously thought.

For Earth to have unique physics conditions, the chance of such conditions arizing at all must be 1 in trillions upon trillions upon trillions. I'm not sure how many more trillions to add, but the number is well beyond any Earthly standard of "large".

We have as of yet not seen any such uniqueness in the observable universe, there is no evidence to support the idea that Earth is unique, but there is a lot of evidence to the contrary. So given what we know, based on evidence/observations, it is rather implausible that Earth is the only planet in the Universe with life.

[Red Iron Crown]

I understand that, but in think you greatly underestimate the number of planets in the universe. Best observations so far have it the universe is at least several orders of magnitude larger than the observable universe, and much larger (possibly infite) is not excluded. Kepler and other planet hunters have shown planets are more abundant than previously thought.

The very large estimates for the number of planets is why I suspect there is other life out there, but without knowing the odds of life developing I can't put any kind of real estimate on the likelihood that is mathematically valid.

For Earth to have unique physics conditions, the chance of such conditions arizing at all must be 1 in trillions upon trillions upon trillions. I'm not sure how many more trillions to add, but the number is well beyond any Earthly standard of "large".

We have as of yet not seen any such uniqueness in the observable universe, there is no evidence to support the idea that Earth is unique, but there is a lot of evidence to the contrary. So given what we know, based on evidence/observations, it is rather implausible that Earth is the only planet in the Universe with life.

I'm not suggesting physics is different on Earth, or that Earth is unique or special aside from the fact that the low probability event of life arising has happened here. Please stop arguing against something I'm not suggesting, I agree that the physics here on Earth are very likely the same everywhere in the universe.

Until we can put some sort of real estimate on the odds of life arising, it is not at all implausible that life exists on Earth only. All it takes is sufficiently long odds for life arising to make it possible, or even likely.

[No one]

That calculator didn't go as low as 10^-15, even when being optimistic I couldn't put in the values I wanted.

I don't know about the odds of life arising on any given planet, but intelligence seems incredibly unlikely.

[rkman]

...aside from the fact that the low probability event of life arising has happened here. Please stop arguing against something I'm not suggesting,

I am arguing against the latter suggestion. It would mean Earth is unique, but there is no evidence to suggest that it is unique.

I agree that the physics here on Earth are very likely the same everywhere in the universe.

And you think it is plausible that physics conditions on Earth (that gave rise to life on Earth) are unique in the universe.

I can't put any kind of real estimate on the likelihood that is mathematically valid.

Same way that i can't put a mathematically valid estimate on the chance of me being hit by lightning. Yet i can be pretty sure i don't need to worry about it.