The meaning of the term "consistent with" in general seems very clear,
and I haven't noticed it being misused in this thread. The surprising thing
is that its use here has been criticized.
While the title of the thread could have been better worded, its meaning
is clear, too, and the reason for the second clause is perfectly clear.
I agree with the title, as I said back in post # one-hundred-something.
There is more and more evidence, perhaps not mounting literally every
day, but frequently, which supports the idea that ETs can be out there.
That is evidence *for* ETs. On the other hand, as far as I know,
we don't yet have any evidence *of* ETs, which is what the second
clause states, as a warning not to misinterpret the first clause.
-- Jeff, in Minneapolis
Last edited by Jeff Root; 2011-Oct-07 at 09:58 PM. Reason: added missing word
"I find astronomy very interesting, but I wouldn't if I thought we
were just going to sit here and look." -- "Van Rijn"
"The other planets? Well, they just happen to be there, but the
point of rockets is to explore them!" -- Kai Yeves
What Jeff said.
I don't see what the big deal is here anyway. If the current evidence is not conclusive, then that means that we cannot yet conclude that we have evidence of ET.
In any case, if such conclusive evidence is eventually found, does the process by which we arrived at that evidence really matter? I think not. It doesn't matter whether we take a random guess, theorize, speculate (unfounded or founded) or flip a coin in order to discover conclusive evidence of ET. So what is needed in order to discover ET is a powerful heuristic, and this does not necessarily include having a correct theory of ET beforehand.
Possible locations for abiogenesis include Mars, Venus, Ceres, Europa, Titan, Enceladus... the list goes on, with decreasing amounts of probability in each case.
As I've said elsewhere on this forum, ballistic panspermia is unlikely (some might say very unlikely, and I wouldn't disagree), but it is not against the mainstream. Something can be both unlikely and mainstream.
Order of Kilopi
As Jeff pointed out, the real eyebrow-raiser is the criticism of the expression "consistent with". (No, Jeff didn't refer to it as an eyebrow-raiser, but my phrasing is consistent with what he said.)
There seems to be a "skepticaller than thou" attitude in certain quarters. Evidence doesn't have to be conclusive to serve as a lead. If police find fingerprints on a murder weapon, they interview the suspect. They do not have to present alternative explanations for how come the fingerprints came to be there, any more than they have to present non-life explanations for methane on Mars. The fingerprints don't necessarily mean the suspect is the murderer, but they don't ignore it just because there might be another reason for them being there.
I think that you think that the process matters as far as conclusive evidence is concerned. You think that, working on a certain unproven assumption somehow biases the result, but I don't see how that can possibly happen with conclusive evidence of the existence of something. We don't create evidence, we discover it. I see nothing wrong in saying what if there is life under such and such conditions and then carrying on with that assumption as if true with the eventual aim of checking whether in fact it is true. The whole point of making unproven assumption is not to believe it, but in fact, to test whether or not it is true.
I hope this makes things clearer.
We have a cor um of agreement here.
That as no such trace has yet been confirmed as real no such conclusion is possible..
That is not based on a belief structure but real and active science.
any other point is less than science. So for me is less than true. Awaiting confirmation.
Thanks for the explanation, Isaac.
And thanks for the thumbs up, Wayne, even if it was just a big C on my machine!
There have been numerous environments in Earth where we thought life was impossible, but it has turned out to exist in all of the ones with liquid water conditions anyway. Since life on Earth seems to exist everywhere that liquid water conditions exist, it would be very interesting to finally explore somewhere outside of Earth with liquid water conditions. That first exploration may be some sort of digger that explores deep into Mars, or Europa, or some other planet/moon. Or it might be careful study of rocks or ice which displayed firm evidence of having recently been in liquid water conditions (a short enough time so we could reasonably find the remains of soft creatures).
Until that first data, we are in a situation where it's presumptive to have a default condition. We simply have too little data.
We observe and see no evidence of life on Mars, that is the reasonable default condition.
The default might be incorrect and that is a situation which would demand correction if there is evidence to indicate otherwise.
I have sealed containers of deionized water that contain no apparent or detectable life sitting on my desk, your proposal that everywhere we find liquid water, we find life, would seem to require some adjusting.
Right now, based on what we know, it's an even balance of lack of information.
Certainly it's possible to kill natural life to create an artificial "environment", but we do not expect by default that someone has sterilized Mars.I have sealed containers of deionized water that contain no apparent or detectable life sitting on my desk, your proposal that everywhere we find liquid water, we find life, would seem to require some adjusting.
Suppose I tell you that I have a glass of water on my desk. Do you think there is life in that glass of water? You have not detected any life in this glass of water. Should your default assumption be that there is no life in it?
Suppose I give you more data--suppose I tell you that I have looked at this glass of water very closely, and I don't see any signs of life. Okay, maybe my eyesight isn't good enough to see microscopic life forms (if microscopic life forms exist), but surely this is strong evidence that there is no life in that glass of water! Right?
And I think you misunderstand the concept of verifiability . As far as logical positivism goes, the concept of verifiability applies to propositions (theoretical statements). "There is life on the Moon" is a verifiable proposition, because we can go and verify empirically whether in fact it is true. "There is a reality beyond what we can measure" is not a verifiable proposition, according to logical positivism. If something is verifiable then it is merely potentially verified, so "verifiable evidences" reads "potentially verified evidences". All evidences are verified, if it's not verified then it's not yet evidence.
Microscopic life is another question.
The possibility that a planet might lack macroscopic life, but nonetheless have micro-organisms, is not science fiction but mainstream science. The Earth itself seems to have been like that for several billion years -- most of its history.
Detecting microscopic organisms presents a challenge, not because they are hidden, or invisible, but just because they are small.
All the same , there are several feasible strategies for finding them, if they are either there now, or have been in the past. One strategy has been mentioned by Isaac Kuo -- follow the water.
Another strategy is to look for the stuff microbes are made of -- follow the complex organic molecules.
I know Viking tried to do that, but it is no longer considered to have produced a reliable negative result. Next year the Curiosity rover will have another go at looking for organics.
Until Mars has been thoroughly investigated using strategies like these, I agree with Isaac.
It is simply too early to talk about a default position re small living organisms on Mars.
Ambiguous methane wisps notwithstanding, Mars offers nothing suggestive of billions of years of evolutionary adaptation of a proliferate expression of life as we know it, which is arguably a chief characteristic of life as we know it,...obvious and aggressive expansion and adaptation into any and all available niches of energy exploitation. It may turn out that there are deep rock organisms eeking out an existence somewhere in the Martian lithosphere, but the existence of such, currently, isn't much more dependable or verifiable than the transparent Kiblerites you mention.
Last edited by Paul Wally; 2011-Oct-12 at 11:21 AM. Reason: grammar
"Geology of possible Martian methane source regions" -
"Methane on Mars: A Perspective from Earth"
Earlier in this thread, you mentioned the free oxygen in Earth's atmosphere.
Before that, oxygen was already being produced, but it was reacting with elements such as iron to form oxides. So, yes, there were changes to the chemistry of surface layers.
But is the presence of iron oxides on a planetary surface an obvious sign of life?
Last edited by Colin Robinson; 2011-Oct-12 at 11:31 PM. Reason: grammar fix