Chance of Life Elsewhere

[HP]

Okay, some one tell me if this makes sense:

The chance a random planet (that's not Earth) has life in it is p

p is non-zero

The number of planets in the Universe is say N

So the chance of life elsewhere is 1-(1-p)^N

Okay so how many planets are there? Well, in the observable Universe, we've detected like a 100 (I'm out of date though, this was like 4 years ago). What about the rest of the Universe? There is no limit to the number of planets there could exist.

The only thing we can say is there is at least 100 planets.

Therefor we can only say the chance of life elsewhere is at least 1-(1-p)^100

So anyone claiming there is probably not life elsewhere is bit.... wrong, no?

This will work for any definition of life, as long as p is non-zero

[MrMon]

It's not exactly the same thing, but try:

Drake Equation (http://en.wikipedia.org/wiki/Drake_equation)

[PairTheBoard]

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So anyone claiming there is probably not life elsewhere is bit.... wrong, no?


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Just because you figure there is some chance does not mean you can't conclude there is "probably not".

PairTheBoard

[HP]

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Just because you figure there is some chance does not mean you can't conclude there is "probably not".

PairTheBoard

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why not?

[HP]

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It's not exactly the same thing, but try:

Drake Equation (http://en.wikipedia.org/wiki/Drake_equation)

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The Drake equation states that:

N = R* × fp × ne × fl × fi × fc × L

where:

N is the number of civilizations in our galaxy, with which we might hope to be able to communicate;

and

R* is the rate of star formation in our galaxy
fp is the fraction of those stars that have planets
ne is the average number of planets that can potentially support life per star that has planets
fl is the fraction of the above that actually go on to develop life at some point
fi is the fraction of the above that actually go on to develop intelligent life
fc is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L is the length of time such civilizations release detectable signals into space.

Yeah, so in the way he's done things, I would say that for R* one can only find a minimum. R* could be a googolplex or whatever

edit: woops nevermind, he was only looking at our galaxy, not the universe

[PairTheBoard]

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Just because you figure there is some chance does not mean you can't conclude there is "probably not".

PairTheBoard

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why not?

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Suppose the "some chance" you figure is 1 in a googolplex. Even though there is then "some chance" you would still say it's "probably not" the case.

PairTheBoard

[HP]

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Suppose the "some chance" you figure is 1 in a googolplex. Even though there is then "some chance" you would still say it's "probably not" the case.

PairTheBoard

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why? This would imply you are confident the Universe contains less than ~1 googolplex planets. I don't see how you could say that

[mjkidd]

There ~ 10^11 galaxies in the universe, and about 10^11 stars/galaxy. Say 10 planets/star, and you get 10^23 planets. We are not off by a google orders of magnitude. Both a "google" and, particularly, a "googleplex" are absurdly large numbers that should never be mentioned. There aren't a google of anything in the universe, let alone a googleplex.

[FortunaMaximus]

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Suppose the "some chance" you figure is 1 in a googolplex. Even though there is then "some chance" you would still say it's "probably not" the case.

PairTheBoard

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why? This would imply you are confident the Universe contains less than ~1 googolplex planets. I don't see how you could say that

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It's a reasonable assumption to make based on known information.

If you plug different values into the Drake equation, you're going to get a wide range of answers. The last 4 elements in the equation are mere guesswork. But you'll get a range. Best ya can do, really, and unless you introduce an element of improbability by giving a value of 0 to an element, you're gonna get the obvious result.

So the answer's non-zero. That and the Fermi Paradox (wtf, they ain't here yet? Where are they? in short) makes it an interesting puzzle. All you can do is define the problem and make better guesses.

[HP]

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There ~ 10^11 galaxies in the universe

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source please

[HP]

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It's a reasonable assumption to make based on known information.

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I think it's not a reasonable assumption :/

[PairTheBoard]

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Suppose the "some chance" you figure is 1 in a googolplex. Even though there is then "some chance" you would still say it's "probably not" the case.

PairTheBoard

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why? This would imply you are confident the Universe contains less than ~1 googolplex planets. I don't see how you could say that

[/ QUOTE ]

Estimates are that there are fewer than a googolplex atoms in the Universe.

Besides that, you are engaging in a fallacy if you insist on no upper bound for the unknown number of planets but declare a lower bound for the unknown probability that a random one contains life. Until you decide on some actual numbers your argument goes nowhere.

PairTheBoard

[HP]

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Estimates are that there are fewer than a googolplex atoms in the Universe.

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I would really like to see a source. The is the heart of the issue, I don't think anyone can come up with any kind of meaningful estimate

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Besides that, you are engaging in a fallacy if you insist on no upper bound for the unknown number of planets but declare a lower bound for the unknown probability that a random one contains life. Until you decide on some actual numbers your argument goes nowhere.

PairTheBoard

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If you say so. But put it this way, if I wanted to bet there is life eslewhere, and you gave me 1 to 1-(1-p)^100 odds, I would gladly take this bet

(if I had a linear utility function)

[FortunaMaximus]

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It's a reasonable assumption to make based on known information.

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I think it's not a reasonable assumption :/

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Fair enough. The number of possible interactions between elements do give you the gigantic numbers you want tho. /images/graemlins/tongue.gif

[mjkidd]

Carl Sagan said ~100 billion galaxies. He might be an order of magnitude low, but probably not too much more than that.

[HP]

linky (http://www.atheistfoundation.org.au/carlsagan.htm)

We have found from modern astronomy that we live on a tiny hunk of rock and metal, third from the sun, that circles a humdrum star in the obscure outskirts of an ordinary galaxy which contains some 400 billion other stars, which is one of about a 100 billion other galaxies that make up the universe

ok this makes no sense to me at all /images/graemlins/frown.gif

The only way I could make sense of the number '100 billion' is if he was just talking about the observable Universe

Anyone in SMP care to chime in about how one could possibly estimate the number of stars in the Universe?

[PairTheBoard]

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linky (http://www.atheistfoundation.org.au/carlsagan.htm)

We have found from modern astronomy that we live on a tiny hunk of rock and metal, third from the sun, that circles a humdrum star in the obscure outskirts of an ordinary galaxy which contains some 400 billion other stars, which is one of about a 100 billion other galaxies that make up the universe

ok this makes no sense to me at all /images/graemlins/frown.gif

The only way I could make sense of the number '100 billion' is if he was just talking about the observable Universe

Anyone in SMP care to chime in about how one could possibly estimate the number of stars in the Universe?

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Unless you contend it's infinitely many, then However many it is could be far less than the odds against any one having life, whatever That is. Until you determine both figures you can't conclude anything.

PairTheBoard

[mjkidd]

Of course he's talking about the observable universe.

[HP]

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Unless you contend it's infinitely many, then However many it is could be far less than the odds against any one having life, whatever That is. Until you determine both figures you can't conclude anything.

PairTheBoard

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sure let's assume it's not infinitely many for now

And I agree however many it is could be far less than the odds against any one having life, whatever That is. But we don't know if that's the case. Even if we knew what p was, whatever p is, we wouldn't know if it was the case, or what the chances of it being the case is.

I sort of agree with this statement:

"Until you determine both figures you can't conclude anything."

I would rather say more generally:

"Until you determine p, and the probability distribution of N you can't conclude anything"

However I will still conclude the chances of life elsewhere is greater than p. We've detected many planets...

[HP]

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Of course he's talking about the observable universe.

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Right, ok. Maybe I should have clarified in my title "in the Entire Universe"

[mjkidd]

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Of course he's talking about the observable universe.

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Right, ok. Maybe I should have clarified in my title "in the Entire Universe"

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Why bother? We can have no concept of how big the unobservable universe is. Any result of the Drake equation will be either 0 or "Who the [censored] knows, but it's really really big"

[PairTheBoard]

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However I will still conclude the chances of life elsewhere is greater than p. We've detected many planets...



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Then I think what your observation amounts to is the statement, "the more planets there are in the universe with a chance for life, the greater the chance for life in the universe".

I don't think anybody would argue with that. I'm afraid it doesn't say much though.

PairTheBoard

[BluffTHIS!]

Check out Stephen Hawking's site: link. (http://www.hawking.org.uk/lectures/lindex.html)

then "public lectures">"life in the universe"

[HP]

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Of course he's talking about the observable universe.

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Right, ok. Maybe I should have clarified in my title "in the Entire Universe"

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Why bother? We can have no concept of how big the unobservable universe is. Any result of the Drake equation will be either 0 or "Who the [censored] knows, but it's really really big"

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agreed (except for that 0 part. How could it be lower than p?)

which brings us to:

anyone claiming there is probably not life elsewhere is bit.... wrong (given a non-zero p)

[HP]

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I'm afraid it doesn't say much though.

PairTheBoard

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agreed

[HP]

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Check out Stephen Hawking's site: link. (http://www.hawking.org.uk/lectures/lindex.html)

then "public lectures">"life in the universe"

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sweet link, ty

[kerowo]

There is a difference between saying there is life in the universe and that it will be calling us up or landing at the White House any time soon.

The last I heard on various Discovery channel shows is they are fairly confident they could find life on at least on of Jupiture's moons, similar to what is found at heat vents at the bottom of the ocean. So if you mean intelligent life, say so. The universe is too big for us to be the only intelligent life out there, but at the same time the size means we'll most likely never run into one.

[HP]

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There is a difference between saying there is life in the universe and that it will be calling us up or landing at the White House any time soon.

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Good point, but I am guessing it's a small difference as we are pretty sure a signal cannot travel much faster than the speed of light. For now let me provide this cop out so this thread doesn't go on a tangent:

I'm assuming it's impossible to send a signal faster than 2 times the speed of light (just to make sure /images/graemlins/grin.gif)

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So if you mean intelligent life, say so.

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I mean whatever kind of life people are talking about when they say "There is probably not life elsewhere in the Universe". My argument works for any definition of life, as long as the 'p' for that definition of life is greater than 0

[PairTheBoard]

Let N denote the number of planets with a chance for life, and let p denote that non-zero chance for each such planet.

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anyone claiming there is probably not life elsewhere is bit.... wrong (given a non-zero p)


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You could say they are a "bit....wrong" because nobody knows what N and p are. But what makes them right or wrong depends on the product N*ln(1-p), not the fact that p is nonzero.

PairTheBoard

[HP]

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You could say they are a "bit....wrong" because nobody knows what N and p are.

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Yeah that's what I was getting at, it seems we are in agreement. In hindsight I should have worded it better

[Piers]

Admittedly making probabilistic estimates from a data sample of one is very tricky.

Clearly p > 0 but what else?

I think it is very suggestive that life appears to have developed around 4 billion years ago, about as soon as it was able to.

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Suppose the "some chance" you figure is 1 in a googolplex. Even though there is then "some chance" you would still say it's "probably not" the case.

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If the mechanism whereby life developed on earth was very unlikely around 1 in a googolplex and consequently Earth is the only planet with life, then the chance that it would develop within the first few million years on the one planet it did develop on would have DS frothing at the mouth crying miracle.

The Anthropic principle gets us around being on the one place in the universe that life evolved, but does not expliam why it evolved so quickly.

My instinct says p is quite high, probably extremely close to one for earth like planets.

The only out is to show that N, the number of earth like planets is extremely small. So what’s so special about our Sun, and what’s this crap about Gliese 581 c.

[CallMeIshmael]

Once you assume that there are a non infinite number of planets in the universe (a good assumption), then there are values of p such that the statement "there is probably no other life in the universe than ours" is correct

so, no, your conclusion does not follow from the premise

[Piers]

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Once you assume that there are a non infinite number of planets in the universe (a good assumption), then there are values of p such that the statement "there is probably no other life in the universe than ours" is correct

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obviously.

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so, no, your conclusion does not follow from the premise

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/images/graemlins/confused.gif /images/graemlins/confused.gif
What has that got to do with my estimation of p?

[HP]

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Once you assume that there are a non infinite number of planets in the universe (a good assumption), then there are values of p such that the statement "there is probably no other life in the universe than ours" is correct

so, no, your conclusion does not follow from the premise

[/ QUOTE ]

i assume you are talking to me. Let me clarify what I was trying to say:

It is illogical for anyone to say the statement "there is probably no other life in the universe than ours"

sure they can get lucky and be right, but i'd still call them 'wrong' for thinking that

[CallMeIshmael]

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i assume you are talking to me. Let me clarify what I was trying to say:

It is illogical for anyone to say the statement "there is probably no other life in the universe than ours"

sure they can get lucky and be right, but i'd still call them 'wrong' for thinking that

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If you are claiming they were wrong because they are making a statement without knowledge of N and p, then, you have an argument.


But, if I were to say "there is probably life on other planets", do you make the same statement?

[CallMeIshmael]

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Once you assume that there are a non infinite number of planets in the universe (a good assumption), then there are values of p such that the statement "there is probably no other life in the universe than ours" is correct

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obviously.

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so, no, your conclusion does not follow from the premise

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/images/graemlins/confused.gif /images/graemlins/confused.gif
What has that got to do with my estimation of p?

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sorry, wasnt directed at you. I just used quick reply

[T50_Omaha8]

"What is the probability a randomly selected planet is earth-like" is a question I'd like to have addressed.

We've got oxygen, hydrogen, and carbon in sufficient amounts (and bonded in a manner that's apparently conducive to life) and we're the appropriate distance from a star such that water can exist in liquid form.

How probable is each of these requirements? I imagine that there is some acceptable range of atmospheric composition/density, rotational/orbital variation (to cause energy to absorb differently over different places, creating climatic stability), and total solar insulation recieved that a planet can have in order to cause water to be in liquid form. That is to say, planets of various sizes and with different energy input rates could feasibly be 'earth-like'. It doesn't seem unlikely at all to me that planets like earth aren't extremely uncommon.

(Much of my post addresses the largely theistic idea that life on any random planet is extremely unprobable. One argument I specifically had in mind can be found right here (http://www.reasons.org/resources/apologetics/design_evidences/2001_probabilities_for_life_on_earth.shtml). I think many of their parameters are irrelevant, or could be variable in relation to other parameters.)

[T50_Omaha8]

In fact, I just did a quick scroll through the link I provided for a quick laugh. I suggest you do the same.

[HP]

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If you are claiming they were wrong because they are making a statement without knowledge of N and p, then, you have an argument.

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That's all I'm saying.

plus a little more: no one has knowledge of N (besides maybe a lower bound)

[HP]

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But, if I were to say "there is probably life on other planets", do you make the same statement?

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You could possibly be making this statement in a logical way

[HP]

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In fact, I just did a quick scroll through the link I provided for a quick laugh. I suggest you do the same.

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from that page:

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Maximum possible number of planets in universe 10^22

Thus, less than 1 chance in 10182 (hundred trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion) exists that even one such planet would occur anywhere in the universe.

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so yeah, there's not a maximum possible number of planets in the universe. I'll give them the benefit of the doubt and assume they are talking about the observable universe.

and even then their calculation seems wacked. I guess that's what you meant by good for a laugh /images/graemlins/smile.gif

[CallMeIshmael]

HP,

can you define "probably".. because, from several posts in this thread, it seems your definition might be off

[HP]

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HP,

can you define "probably".. because, from several posts in this thread, it seems your definition might be off

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60% confidence say

[CallMeIshmael]

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HP,

can you define "probably".. because, from several posts in this thread, it seems your definition might be off

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60% confidence say

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ok, then how can you get to > 60% chance of life on some non-earth planet without knowledge of p

(unless you mean that the statement can be logical after we find life on another planet)

[HP]

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ok, then how can you get to > 60% chance of life on some non-earth planet without knowledge of p

(unless you mean that the statement can be logical after we find life on another planet)

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I was implying some one could possibly find p in a logical way

However some one could not find N in a logical way (only a lower bound)

[CallMeIshmael]

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I was implying some one could possibly find p in a logical way

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how can you estimate the probability of an event occuring without ever observing it happening?

[HP]

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I was implying some one could possibly find p in a logical way

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how can you estimate the probability of an event occuring without ever observing it happening?

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Regardless of whether this can be done or not, the following is still true:

one cannot logically say there is probably no life elsewhere in the Universe

agreed?

Now to answer your question. I haven't thought about it much to be honest (none at all until you came into this thread). Well, if we became extremely knowledgeable exactly as to how life arose on Earth, and our astronomical techniques became so good we were able to figure out the chances of a random planet having a particular make up, then maybe from there we could run some simulations?

I could easily be wrong, it was my best guess

[Piers]

Don’t forget coevolution between life and the planet. Earth is ideal for us to live in partly because we made it so.

Life in general is very adaptable; there are many extreme conditions on earth where life survives. A world could be very different from earth but have some selected earth life forms survive on it. Europa? Of course being hospitable to life is not necessarily equivalent to having the conditions to generate life from scratch.

So even if Earth like planets are rare, it is not necessarily true that earth like life is similarly rare.

[PairTheBoard]

I saw an interesting show about a theory for how Earth's moon formed. The theory has an astroid-planetoid type body colliding with the Earth. But it has to collide in just the right way or else similations don't show the moon forming. I think it had to be a kind of glancing blow type collision. So the chances of it happening just right look pretty small.

In addition, I learned that the Moon is a profound stabalizing force on the Earth's axis of rotation. The Moon makes the Earth's axis sort of wobble back and forth, keeping it relatively stable. Without the Moon the axis would gyrate all over the place. The implications are that the Earth's weather patterns would be relatively chaotic. While you might see primitive life forms evolve on the planet, more advanced forms would never get a chance. Environmental conditions would change too rapidly causing too frequent mass extinctions.

PairTheBoard

[HP]

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In addition, I learned that the Moon is a profound stabalizing force on the Earth's axis of rotation. The Moon makes the Earth's axis sort of wobble back and forth, keeping it relatively stable. Without the Moon the axis would gyrate all over the place. The implications are that the Earth's weather patterns would be relatively chaotic.

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I've heard a physics professor say the same thing. My money says there's a lot of Earth-like planets out there that never got hit by an asteroid just the right way, and those planets don't have complex life on them

[HP]

btw I would say there probably isn't complex life elsewhere in the Universe /images/graemlins/grin.gif

and I'm more or less an atheist. I will make a new post some time maybe about why I think so

[Piers]

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The implications are that the Earth's weather patterns would be relatively chaotic. While you might see primitive life forms evolve on the planet, more advanced forms would never get a chance. Environmental conditions would change too rapidly causing too frequent mass extinctions.

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The thing about intelligence is that it makes the organism much more adaptive, and able to survive extreme changes in environmental conditions. A steady environment gives little evolutionary advantage to intelligence.

Maybe the reason intelligent life took so long to evolve on Earth is that the climate was too steady and there was not enough mass extinction.

[HP]

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The thing about intelligence is that it makes the organism much more adaptive, and able to survive extreme changes in environmental conditions. A steady environment gives little evolutionary advantage to intelligence.

Maybe the reason intelligent life took so long to evolve on Earth is that the climate was too steady and there was not enough mass extinction.

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So you think we were just really lucky to get a moon?

[Piers]

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So you think we were just really lucky to get a moon?

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Something different would have happened if there was not a moon. Its possible to make guesses as to what that might be. However I know that I would not exist without a moon, so I am glad there is one.

[MidGe]

If there can be life here, it is very likely that there is life elsewhere. Don't fall for the "life is sooo special" paradigm. It is merely theist trying to advance their agenda's view of characterizing life as somehow special or unique. Ego! /images/graemlins/smile.gif

[kerowo]

We are just recently able to find planets in other systems so we don't have a lot of practical data on how common moons are, so thinking that the only way to get a moon is the way the Earth did doesn't make any sense.

The universe is too big for there to be a lot of things that happen only one time. In the end I think there is too much hand waving in the equations for where you stand on this not to come down to your belief system. At this point in time there isn't enough data for someone to make an argument that is going to change my mind on this. Still fun to argue about though...

[T50_Omaha8]

Umm, for some reason I don't buy that planetary moons are exceptionally rare. There are around 150 of them in our own solar system, with around a dozen being 'moonlike' in terms of a comparable size to our own.

[PairTheBoard]

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Umm, for some reason I don't buy that planetary moons are exceptionally rare. There are around 150 of them in our own solar system, with around a dozen being 'moonlike' in terms of a comparable size to our own.

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I think our Moon is unique in our solar system as far as it's relative size to the planet it orbits. I believe that's what gives it its stabalizing power on our axis of rotation. I believe the process of gravity acting on Saturn-like Rings formed around a planet during its phase of formation accounts for the other moons in our system, according to simulations. But the large Moon/Earth size ratio cannot be accounted for by that theory. That's my understanding of the current thinking anyway. I don't think it should be discounted because it is inconvenient for prior notions of how common a phenonmenon we might have thought it was.

PairTheBoard

[FortunaMaximus]

Giant impact hypothesis.

Hartmann and Davis, '75. Abstract / PDF can be found here:

Link to abstract on ScienceDirect. (http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-4731494-16J&_user=10&_coverDate=04%2F30%2F1975&_rdoc=18&_f mt=summary&_orig=browse&_srch=doc-info(%23toc%236821%231975%23999759995%23353127%23F LP%23display%23Volume)&_cdi=6821&_sort=d&_docancho r=&view=c&_ct=21&_acct=C000050221&_version=1&_urlV ersion=0&_userid=10&md5=8a60b66b6fdd8e3462cec383b9 a1ae86)

Bang two rocks together, life arises. Man bangs two rocks together, grilled mammoth for dinner.