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  #41  
Old 30th May 2012, 02:03 PM
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Default Re: Estimate the number of robot civilizations

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Originally Posted by DanDare View Post
I think we are still talking at cross purposes here. The Drake equation and speculating about robot civilizations are not science projects. They are political projects. The Drake equation came out at a time when nobody thought it was even worthwhile looking for life elsewhere. Drake's aim was to show that the search was reasonable, not to prove anything. Speculating about robot civilisations is fun and inspiring.

If you are of the mind set that there is no point looking for ETI then the Drake equation demonstrates that there are ranges of values for the elements that result in positive outcomes and those values are not known to be incorrect. Given how hostile scientific organisations have been toward even trying to look for life elsewhere I think the equation served its purpose.
But the question we're being asked here is to estimate the number of robot civilisations out there - we're not being asked whether the search should be funded. I am certainly in favour of SETI projects, but at the same time, I look at what they've found so far, and have to give an answer in response to that when answering the question of "does extraterrestrial life exist".

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Originally Posted by the_gelf
All science was once "conjured from thin air"

All maths (especially inductive and imaginary) is conjured from "thin air".

Do you have the same disagreements with gravity waves and imaginary numbers? They are in the same boat, and neither have been observed.

When a scientist observes that amino acids are known to form into RNA molecules, and those amino acids are observed elsewhere in the universe, galaxy, local cluster, solar system, do you disagree with him?

In the same light, do you disagree with the application of cepheid variables, or the Hubble constant replacing parallax, or the validity of using Christoffer notation on a physics problem? Each of these concepts have a degree of certainty, and a degree of uncertainty - the questions to ask yourself is why you trust some, but not others.

You trust that g=9.8, but have you measured it yourself?, you trust a car will start, but have you designed a closed circuit magnetic induction coil to test this actually works? What is it about certain scientific facts that qualify to you as trustable and not trustable, or is it entirely subjective?
I completely disagree that all science was once "conjured from thin air". What actually usually happens is people notice things about the world, and then they study it. Darwin didn't "conjure" natural selection "from thin air", he travelled around the world seeing different forms of life from around the world, and slowly reached a series of conclusions based on that evidence. Most science is an attempt to explain things that we can observe, not explanations of things that we can't observe. I use the word "observe" very loosely - not to mean things we can see with our own eyes, but things we can measure. For example the evidence for invisible forces and things like the existence of electrons comes from very precise experiments, and is the explanation for those "observations."

I don't disagree that amino acids are found through out the universe, but I don't find that meaningful evidence for the existence of extraterrestrial life. Amino acids are just simple molecules made up of some of the most common elements in the universe. It's a long way to go from molecule of carbon, oxygen, hydrogen and nitrogen to life. Perhaps it's happened multiple times, perhaps it's only happened once. Until I see evidence, I won't believe that it's happened more than once.

I don't agree or disagree about the application of cepheid variables, Hubble constants or the validity of using Christoffer notation on a physics problem, because I don't know enough about them. I accept things to be true when I have seen good evidence for them, and don't accept things to be true when I haven't seen good evidence. In the case of those things, it seems probable that they are true I guess, but being in the position of ignorance that I am on those questions, I can't say, except I'd tell somebody to look up the evidence for themselves if they wanted to know.

I have tested gravity in year 11 or 12 physics (I don't remember which) and we calculated that it was around 9.8m/s^2, although I don't really remember how accurate we were. We dropped a series of balls of different weights off the top of the school and timed them with stop watches, and then used Newtonian physics to calculate g, knowing time and distance (and mass, because we were also testing whether heavier objects fell faster). Perhaps not rigorous enough to publish in a scientific journal, but I'm yet to hear a better explanation for our observations then that gravity is indeed 9.8ms^-2. (edit - this may have even been in earlier high school. I don't remember).

Last edited by owheelj; 30th May 2012 at 02:05 PM.
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  #42  
Old 30th May 2012, 11:40 PM
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Default Re: Estimate the number of robot civilizations

Something interesting to connect to
What-If and What-Is: The Role of Speculation in Science

Not quite what I am trying to get to, which is talking about political effects outside of science, but still relevant.
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  #43  
Old 31st May 2012, 01:06 AM
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Default Re: Estimate the number of robot civilizations

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Originally Posted by DanDare View Post
Something interesting to connect to
What-If and What-Is: The Role of Speculation in Science

Not quite what I am trying to get to, which is talking about political effects outside of science, but still relevant.
Good link, the preamble is certainly relevant on the merits of speculation's role in science, and the distinction between the probable and the possible.
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  #44  
Old 31st May 2012, 10:26 AM
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Default Re: Estimate the number of robot civilizations

Speculation is a natural part of science, we do it all the time. It opens debate, pushes thought in new directions, and often will lead to new discoveries.

owheelj - claiming
Quote:
Until I see evidence, I won't believe that it's happened more than once.
Is akin to saying 'absence of evidence is evidence of absence', also known as the logical fallacy of argumentum ad ignorantiam in the old tongue.

For example, until i see evidence that there are cockroaches in my house, i wont believe there are any. Or a field a little closer to my area, until i see evidence that there are novel invasive organisms in Australia, i wont believe there are any.


In science we work with likelihoods, is it more likely that X is the case or not, within a framework of deductive and inductive logic.


Here is a great video, Feynman on how science works

http://www.dailymotion.com/video/xp2...nce-works_tech

Also a video interview i did with Lineweaver on this topic.
http://www.youtube.com/watch?v=4K09GeJeSmM
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  #45  
Old 31st May 2012, 10:36 AM
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Default Re: Estimate the number of robot civilizations

You misunderstand the "argument from ignorance" logical fallacy, probably because the Carl Sagan quote is so often misused. An argument from ignorance is when you say that because there isn't evidence for something, therefore the opposite conclusion is true. It's only a fallacy if you're following that logical pathway. ie. "You can't prove that God exists, therefore he doesn't exist" is a logical fallacy, while what I said was along the lines of "you can't prove that god exists, therefore I won't believe in Him until you can." The difference may appear subtle, but it's not. I'm saying that until there is evidence, the best estimate of the question is 0 - I'm not saying that because there is no evidence, this proves that the answer is 0.

I'm happy to accept that it's theoretically possible that life, robotic, intelligent, or otherwise exists beyond Earth, but unless serious evidence can be presented, I'm not going to believe that there actually is.
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  #46  
Old 31st May 2012, 11:25 AM
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Default Re: Estimate the number of robot civilizations

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Originally Posted by owheelj View Post
You misunderstand the "argument from ignorance" logical fallacy, probably because the Carl Sagan quote is so often misused. An argument from ignorance is when you say that because there isn't evidence for something, therefore the opposite conclusion is true. It's only a fallacy if you're following that logical pathway. ie. "You can't prove that God exists, therefore he doesn't exist" is a logical fallacy, while what I said was along the lines of "you can't prove that god exists, therefore I won't believe in Him until you can." The difference may appear subtle, but it's not. I'm saying that until there is evidence, the best estimate of the question is 0 - I'm not saying that because there is no evidence, this proves that the answer is 0.

I'm happy to accept that it's theoretically possible that life, robotic, intelligent, or otherwise exists beyond Earth, but unless serious evidence can be presented, I'm not going to believe that there actually is.
Actually, no, i dont misunderstand it at all. Not even sure how/ why you have dragged in Sagan. Actually bringing god into this makes no sense, we are talking about biological systems, not supernatural forces.

The fallacy is quite straight forward:
X must be true, because it has not been disproved AND
X must be false, because it has not been proven true.

Thats it, nothing else to it.

You are saying, that the best estimate of aliens is 0, becuase it has not been proven 1.

As said, it is argument from ignorance, you have set up a false dichotomy.

I grant that you have noted you will change your answer on future evidence, but then the answer should simply follow, that because aliens has not been proven as 1, then more evidence is needed, and not that the best guess is 0.

We have got evidence for 'alien' life, we are it. Life got going once, thus, in order to make a judgement in one direction or the other, that the best guess is 1 or 0, then we need to understand what gets life going to start with.

If it is the case that life is extremely improbable to get going, then this pushes our expectation that there are aliens toward the 0 end, if it appears that life gets going with not so much as a warm bath and a fart, then this pushes it towards 1.

Then the question becomes about intelligence and so we need to answer those questions also.

So no, i understand it perfectly well thanks
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Last edited by Slothhead; 31st May 2012 at 11:38 AM. Reason: Spolling err
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  #47  
Old 31st May 2012, 11:43 AM
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Default Re: Estimate the number of robot civilizations

Carl Sagan is the person often quoted as saying; "absence of evidence is not evidence of absence" (from the Demon-haunted World).

Let me put it like this though. Imagine we live in a universe where life on Earth really is the only life in the universe, and everything else is the same as our universe. What would it take for us to be able to realise the truth? What evidence could possibly exist that would lead us to that conclusion? Clearly all we could have would be an absence of evidence, and so while we have an absence of evidence we have to say that based on what we do know, the best conclusion is that there is no life outside of Earth. If new evidence appears we need to re-evaluate the question.

Your argument is identical to the "purist" agnostic argument, that we can't say whether we think God exists or not, because you can't prove it one way or the other. The reality is that there is no evidence for things that don't exist, and we can draw tentative conclusions based on the lack of evidence, until real evidence appears.
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  #48  
Old 31st May 2012, 11:56 AM
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Default Re: Estimate the number of robot civilizations

I also note that there is a difference between not having evidence, and having null evidence. ie. If I say that there is a can of dog food on my computer desk and you look but can't see it, and conclude that there isn't, this isn't an argument from ignorance, even if parts of the desk are obscured and it's possibly hidden somewhere on the desk. On the other hand, if I make that claim, and you argue that because you haven't seen the evidence, since you can't see my desk, therefore it's false, that would be an argument from ignorance.

We actually have looked for life outside of the Earth, and so far those results have been negative. This is not an absence of evidence, but evidence of absence. It's far from conclusive, because the universe is very big, and so far we've only looked in a small region, but if the answer is indeed negative we'll never have a conclusive answer.
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  #49  
Old 31st May 2012, 12:04 PM
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Default Re: Estimate the number of robot civilizations

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Originally Posted by owheelj View Post
Carl Sagan is the person often quoted as saying; "absence of evidence is not evidence of absence" (from the Demon-haunted World).

Let me put it like this though. Imagine we live in a universe where life on Earth really is the only life in the universe, and everything else is the same as our universe. What would it take for us to be able to realise the truth? What evidence could possibly exist that would lead us to that conclusion? Clearly all we could have would be an absence of evidence, and so while we have an absence of evidence we have to say that based on what we do know, the best conclusion is that there is no life outside of Earth. If new evidence appears we need to re-evaluate the question.

Your argument is identical to the "purist" agnostic argument, that we can't say whether we think God exists or not, because you can't prove it one way or the other. The reality is that there is no evidence for things that don't exist, and we can draw tentative conclusions based on the lack of evidence, until real evidence appears.
Absence of evidence is evidence of absence, it is just not conclusive. Evidence is not proof, merely support. How much evidence, and of what quality, is what matters. If I can't see god, then that does not mean that god does not exist-he may be below my visual radar. if I could see god, then that would be some support for his existence. But even if we could all see god, it does not prove that god exists, it could merely prove we all suffer from the same delusion. Likewise, if nobody believed in god, it does not prove that he does not exist. He could exist.

However, are we being rational when we believe in something that has no evidence? It does not appear so. Certainly, a god that demands our belief in him without evidence would be evidence of an irrational god.
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  #50  
Old 31st May 2012, 12:12 PM
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Default Re: Estimate the number of robot civilizations

I think it's important to note the difference between an absence of evidence and null evidence. For example - does the cup on my desk have water in it? From your perspective, you have an absence of evidence. You can't see the cup. On the other hand, I can see the cup, and can't see water in it, so I have null evidence. Argument from Ignorance, to which the "absence of evidence" phrase refers to is talking about not having any evidence - positive or negative. It's not saying; "we looked and couldn't find it." It's saying "we haven't looked and couldn't find it."
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