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Do you believe in life elsewhere?

#261
It is mathematically and statistically MORE inprobable that we are the only life in the universe.

Smart betting money is on life elsewhere.

The universe is incomprehensibly large. With telescopes we can see 14,000,000,000+ light years away.

Alpha Centauri is only 4 light years away. On the space shuttle travelling 20,000mph - it'd take 150,000 years to get only as far as Alpha Centauri!

There's probably life elsewhere.
 
#263
Relic said:
I mean, yes, you're doing more than just saying "we don't know", you and 12bass for instance are totally stepping outside of the question of "is there life out there" and explaining why the question itself is pointless at this stage of human culture. At least that's how I'm reading you guys.
I'm looking at it rather as an interesting question that's so open as to invite varying opinions - ie "what is reality?" etc etc where since no one can TRULY answer this, all we have are opinions and perspectives.
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Actually, I'd suggest that the matter of whether or not extraterrestrial life exists is something which is likely to have a profound impact on humanity. However, at present, the fact is that all we can do is speculate about an answer. It isn't that I think that the question is pointless. There are simply too many unknown variables to allow any degree of certainty about an answer. And without a high degree of certainty, there exists no reasonable grounds for belief. What often seems to happen is that people want an answer so much that they make a "leap" in spite of the absence of supporting evidence. Some of us refuse to make such a leap, and instead withhold judgment until such time that the necessary evidence becomes available.
 
#264
Probability is purely mathematical rather than an intuitive thing. Very crudely (to simplify the essence of the Drake equation):

L=N*p

where L is number of planets with life, N is number of planetary candidates for life, and p is probability of life occurring on a planet.

Trouble is we have no idea of the value of p. It could be almost any value greater than zero and less than 1. If p is very, very, very small - and it may be, we have no idea at all of its actual value - then it doesn't matter how big N is, L is also going to be small. L might be 1, or it might be more - no way of knowing or even guessing what is "most likely" as we don't know p's value.

That's basically it. I don't think the idea is that hard, really, if one understands that we have no data with which to sensibly estimate p. There is no "smart betting" - only speculative guesses, any of which could be right or wrong and with no way to distinguish between the two, currently.

And Dave, for the record, I lecture in physical sciences, science education and philosophy of science at one of the biggest universities here in England for a living (when I'm not playing bass, that is). Not that there's any such thing as an argument from authority, of course. Just pointing out that I know what a hypothesis is, and how it differs from an estimate. ;)
 
#265
bassybill said:
Probability is purely mathematical rather than an intuitive thing. Very crudely (to simplify the essence of the Drake equation):

L=N*p

where L is number of planets with life, N is number of planetary candidates for life, and p is probability of life occurring on a planet.

Trouble is we have no idea of the value of p. It could be almost any value greater than zero and less than 1. If p is very, very, very small - and it may be, we have no idea at all of its actual value - then it doesn't matter how big N is, L is also going to be small. L might be 1, or it might be more - no way of knowing or even guessing what is "most likely" as we don't know p's value
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Lineweaver, C. H. & Davis, T. M. (2002). "Does the rapid appearance of life on Earth suggest that life is common in the universe?". Astrobiology 2 (3): 293–304.

Is the only real treatment of an estimate I know of.
 
#266
bassybill said:
....And Dave, for the record, I lecture in physical sciences, science education and philosophy of science at one of the biggest universities here in England for a living (when I'm not playing bass, that is). Not that there's any such thing as an argument from authority, of course. Just pointing out that I know what a hypothesis is, and how it differs from an estimate. ;)
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no problem, buddy. i respect your opinion. it's just that I disagree with some of your conclusions.

and i know that YOU are not belittling me. i stand by my assertion that there is nothing invalid about my hypothesis... and we very much agree that there is no evidence either way.

if my hypothesis is proved wrong (very difficult, as I have already said that science can not prove a negative & i know you agree with that), I won't lose any sleep.

i merely pointed out that the jury is still very much out, and if your point is that not only is it out, but likely to remain so into the foreseeable future, we very much agree there.

davesignatureII.gif
 
#267
aborgman said:
Lineweaver, C. H. & Davis, T. M. (2002). "Does the rapid appearance of life on Earth suggest that life is common in the universe?". Astrobiology 2 (3): 293–304.

Is the only real treatment of an estimate I know of.
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Yes, that's an interesting paper and represents a genuine attempt to get some hard maths into the probability estimates. But in the end, it still reaches the inevitable conclusion that we can't just say at present whether life is common in the universe or not. We don't have enough data and so the jury is still out.

Link to the original paper for those interested in the mathematics:

Invalid Link Removed

To sum up, it's saying that even the rapid start life got here on the Earth is not enough to say with confidence that life is widespread. We could have just got very lucky, very early - a bit like winning the lottery the first time you buy a ticket. Until we know more about other lottery winners, we're stumped.
 
#269
bassybill said:
To sum up, it's saying that even the rapid start life got here on the Earth is not enough to say with confidence that life is widespread. We could have just got very lucky, very early - a bit like winning the lottery the first time you buy a ticket. Until we know more about other lottery winners, we're stumped.
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absolutely... could not agree more! or even the nature of the lottery...

and when i say "my hypothesis is not invalid (or whatever it was I said), i mean my hypothesis may provide a useful starting point for inquiry... i am NOT meaning to imply that it gives us any useful info on the existence or non existence of ET life.

davesignatureII.gif
 
#271
bassybill said:
We have no way of knowing what the odds are. There's no reliable way for us to mathematically estimate the probability or improbability of the origin of life. Intuitive opinions like this might be correct, or they could be way, way, way out and underestimate the improbability of life by orders of magnitude. There's no way to tell.
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Of course you're right, and I came into this thread too late to just spout an unfounded and fun opinion amid serious discussion of things like astronomy and epistemology :bawl: Just keeping it light because the idea is so much fun to me.

Imagination!
 
#272
bassybill said:
Probability is purely mathematical rather than an intuitive thing. Very crudely (to simplify the essence of the Drake equation):

L=N*p

where L is number of planets with life, N is number of planetary candidates for life, and p is probability of life occurring on a planet.
Click to expand...


If it's all well & good to reduce the Drake Equation (and I'm all for making it a bit clearer!) down to L+N*p, then why not reduce it even further down to L≅N?

Because regardless of how large or small p is, if a scientifically rigorous estimate of the number of planetary candidates for life yields an astronomically large value for N, than if and only if p=0 are the "believers" (sic) SOL. All other values for p yield a potential for life.

Or maybe that's the semantic difference you alluded to earlier: Lots of folks in this thread seem to be insisting we can predict the potential for life, whereas you're insisting we can't predict the absolute Yes/No answer.
If so, yes, you're right. But predicting the possibility makes for a far more entertaining conversation! :)
 
#273
Roscoe East said:
If it's all well & good to reduce the Drake Equation (and I'm all for making it a bit clearer!) down to L+N*p, then why not reduce it even further down to L≅N?

Because regardless of how large or small p is, if a scientifically rigorous estimate of the number of planetary candidates for life yields an astronomically large value for N, than if and only if p=0 are the "believers" (sic) SOL. All other values for p yield a potential for life.

Or maybe that's the semantic difference you alluded to earlier: Lots of folks in this thread seem to be insisting we can predict the potential for life, whereas you're insisting we can't predict the absolute Yes/No answer.
If so, yes, you're right. But predicting the possibility makes for a far more entertaining conversation! :)
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Saying L approximates to N is effectively assigning a value of p close to 1.

I'm sure you understand that in reality, N will be (large but) finite and 0<p<1. That could give almost any logically allowable true value for L. We know that the actual true value for L=>1. That's all we know and that's all I've been saying.

I like to think that life is going on elsewhere, just as several other people have said in this thread. I find the idea fascinating, imaginative, entertaining - all the things others have mentioned. I've been a sci fi fan since I was a young child for that very reason. I just know that we can't say that we're unlikely to be alone in the universe simply by assuming that because there's so many planets there has to be a lot of them with lifeforms. I guess I'm really just pointing out that such an observation is an over-simplification.
 
#274
Completely off topic (of the thread, but not off topic in the forum sense, as this is music related) - as I type, I'm listening to the soundtrack of Jerry Goldsmith's wonderful score for the film "Alien". Magnificent music, reminds me of Holst in many ways. But sometimes, I'm glad we haven't got that proof of extra-terrestrial life after all... :D
 
#275
bassybill said:
10E23 stars - but what if the probability of life is say, 1 in every 10E85? It could be, for all we know. Then it would be even more amazing that we exist at all, and extremely improbable that such a thing has ever happened elsewhere. The reverse argument could be equally true. That's the whole point. We don't know.
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Thinking about this I don't know that they are equally true.

The fact is that nature shows a marked preference for high levels of organization. If you assume that mathematics and physical law apply consistently throughout the universe, which means that evolution also holds, and take the view that life is really a highly organized set of chemical reactions then I think you have to conclude the same set of chemical reactions has occurred elsewhere and that what grew out of those reactions would eventually find a way to adapt to it's environment.

In short if the universe gave to rise to life once it necessarily means that should almost inevitably give rise to again.

Unless you want to invalidate the base assumptions.

Of course that doesn't prove anything but I think it does justify preferring life in the universe over us being unique.
 
#280
MakiSupaStar said:
Based upon how easily things like mold and bacteria grow here on earth, I can't imagine it being that unlikely for stuff to grow in other parts of the universe. I bet that there's even simple life on planets within our own solar system.
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Well, stuff grows because life reproduces. It's how it gets started that we've been talking about here.

I do agree that there are some fascinating places to speculate about in our own solar system, though - especially Mars and, even more so perhaps, Europa. If there were any signs of life discovered there, it would completely blow out of the water most of the comments I've made in this thread. But it's a big "if" and we don't know how big it really is yet (which is the point I've been making all along).
 

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