Estimate the number of robot civilizations

[Slothhead]

Originally Posted by owheelj

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.

Yeah i know where the line comes from, the book is sitting nearby in this pile of crap i call a desk.

No my argument isnt a purist agnostic argument either because there is "evidence of absence".

The line "absence of evidence is not evidence of absence" is a conditional statement and depends on whether the evidence should exist, because absence of evidence can be evidence of absence.

For example, the absence of any evidence that there are elephants in my office, is evidence that there is an absence of elephants in the office. PROVIDED the conditions are met that we are talking about real elephants given the fundamental information we understand about them. They are big, they eat lots, and like to stamp around. If there were elephants in the office, the evidence would be obvious and steaming.

Thus, the lack of evidence for extra terrestrials as surveyed by SETI in that quadrant is evidence that there are no extra terrestrial radio emitters in that area. It doesnt necessarily mean that there are no super advanced civilisations, just that there are no aliens emitting radio waves that we can detect.

Maybe its the case that they dont use radio waves, or maybe its the case that we cannot detect said radio waves, maybe it is the case there are no aliens and so on. But that is all we can say. If we extend our conclusions too far, we simply miss things.

I think including the god part in this is a crimson sardine, because we are talking about very different things. The absence of evidence for the god that people claim is evidence for its absence as they have defined it.

I think we are likely talking about the same thing, but using the words slightly different or not full establishing a position, nothing unusual there for the internet.

[loubert]

my estimate. using complex numbers is .... i.

[Loki]

The Drake equation is not equivalent to "do alien civilisations exist or not?". It can provide no actual data on extant alien civilisations. It is a speculation on the number of alien civilisations which might exist. Unfortunately the terms used in the Drake equation are speculative themselves, rendering any inference obtained from use of the equation a nonsense.

That someone does not see the Drake equation as valid says nothing about their speculative feelings on whether alien civilisations may or may not exist or on whether they think searching for evidence of such is warranted.

and once again, as it seems regularly necessary;

Originally Posted by Carl Sagan-The Demon Haunted World

appeal to ignorance - the claim that whatever has not been proved false must be true, and vice versa (e.g., There is no compelling evidence that UFOs are not visiting the Earth; therefore UFOs exist - and there is intelligent life elsewhere in the Universe. Or: There may be seventy kazillion other worlds, but not one is known to have the moral advancement of the Earth, so we're still central to the Universe.) This impatience with ambiguity can be criticized in the phrase: absence of evidence is not evidence of absence.

Use of the Drake equation to support the existence of alien civilisations is an appeal to ignorance of sorts.

[the_gelf]

Originally Posted by Loki

Use of the Drake equation to support the existence of alien civilisations is an appeal to ignorance of sorts.

Taking a Carl Sagan quote out of context to imply we should cease imagination leaves a sick empty space where my apathy used to be.

[Loki]

Oh FFS

No-one claims the Drake equation is accurate, including Drake himself. The equation can be manipulated to give any answer you like with reasonable sounding data points. It is a product of the 60's and that is where it should stay.

What's wrong with saying "there is no reason alien civilisations don't exist, it is quite possible that life will begin wherever there is liquid water for long enough. It would be a wonderful thing to find, let's go looking".

Why try to add certainty to the search with bogus math? That would be just like saying "gawd is real coz my book says so".

Here's Drakes original numbers;

• R* = 10/year (10 stars formed per year, on the average over the life of the galaxy)
• fp = 0.5 (half of all stars formed will have planets)
• ne = 2 (stars with planets will have 2 planets capable of developing life)
• fl = 1 (100% of these planets will develop life)
• fi = 0.01 (1% of which will be intelligent life)
• fc = 0.01 (1% of which will be able to communicate)
• L = 10,000 years (which will last 10,000 years)

Drake's values give N = 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 10,000 = 10.


Current estimates vary from 0 (obviously false as we actually know of 1, ourselves) to 182 000 000 (see wiki).


Which value do you think is correct?






from xkcd

[Slothhead]

Originally Posted by Loki

Which value do you think is correct?

42 because Douglas said so.

[Loki]

Maybe they were robot mice? Now there's a thought.

[owheelj]

Originally Posted by the_gelf

Taking a Carl Sagan quote out of context to imply we should cease imagination leaves a sick empty space where my apathy used to be.

Can you explain how the quote is out of context, and how it implies that we should cease imagination? I fail to understand how you came up with either of these conclusions.

[the_gelf]

Originally Posted by owheelj

Can you explain how the quote is out of context, and how it implies that we should cease imagination? I fail to understand how you came up with either of these conclusions.

Well the quote is a defense against human-centric religion's accusation that science has not found alien life yet, (therefore their propounded conclusion is that humans must be the centre of the universe yada yada).

I don't see why getting caught up on the exactitude of the Drake equation have become an issue, it's just easier for some people to think that way (the numbers become conceivable by nonmathematicians). The whole point was that no matter how small the numbers were, there must be life elsewhere in the galaxy - that was all it implied!, i.e it reacehd the conclusion that life other than earth must be >1, therefore the SETI program is justified (the documentation of how SETI does it's search is interesting in itself). You might be surprised at how difficult it is to measure weak signals like those emitted by theoretical other civilizations.

So, yes, I think there is 'impatience with ambiguity' in this thread, where the ambiguity comes down to creative conflicts(which was entirely the point, last time I checked the thread title and preamble).

I respect that 'hardcore facts' are what people want, but it was intended to be an exercise in assessing the veracity of speculation, not verification of the speculative.

Seeing a lot of this lately

[owheelj]

Actually, if you read the book, the quote is part of a section describing logical fallacies. The section begins;

In addition to teaching us what to do when evaluating a claim to knowledge; any good baloney detection kit must also teach us what not to do. It helps us recognise the most common an perilous fallacies of logic and rhetoric. Many good examples can be found in religion and politics, because their practitioners are so often obliged to justify two contradictory propositions. Among these fallacies are...

- Demon-haunted World, page 212.

He then lists with a short description; Ad hominem (when you say a person's argument is wrong because of a personal trait, not when you merely insult a person), Argument from authority, argument from adverse consequences, appeal to ignorance (the bit quoted earlier), special pleading, begging the question, observational selection, statistics of small numbers, misunderstanding the nature of statistics, inconsistency, non sequitur, post hoc, ergo propter hoc, meaningless question, excluded middle, short-term vs long-term, slippery slope, confusion of correlation and causation, straw-man (arguing against a similar but distorted position to the one the person holds - not merely arguing against a position somebody doesn't hold, asking them if the hold a position that they don't, or misunderstanding their position), suppressed evidence, and weasel words.

Each fallacy contains a description and an example. As you can see, the quote is not a "defence against human-centric religion's accusation that science has not found alien life yet" - it's a description of what an "appeal to ignorance" is ("the claim that whatever has not been proved false must be true, and vice versa"), followed by a series of examples.

Perhaps you should actually look at the context, before claiming something is being used out of context.