Re: OT: Astronomy - we are small

On 18 Apr, 23:08, TT <g...@xxxxxxxxxxxx> wrote:
robinson.n...@xxxxxxxxx wrote:
On 18 Apr, 13:46, TT <g...@xxxxxxxxxxxx> wrote:
robinson.n...@xxxxxxxxx wrote:
On 17 Apr, 23:39, TT <g...@xxxxxxxxxxxx> wrote:
robinson.n...@xxxxxxxxx wrote:
On 17 Apr, 21:15, TT <g...@xxxxxxxxxxxx> wrote:
Scott wrote:
Holy ***!  We are small:
http://digg.com/d1ofQT
Astronomy fans probably will like this page.  I find it mind-boggling.
Nice. And we're definitely not alone. Too bad the distances are so long,
or maybe good...
What exactly are you saying? You believe that there is definitely
intelligent life on other planets?
Of course there is, probability for that is certain. Unless you believe
life on earth was created by some deity and it forgot to inhabit other
planets.
Unless you know the probability of intelligent life arising on any
given planet, there is no way you can rationaly make this argument. It
is perfectly feasible for there to be countless trillions of other
planets, but for the Earth to be the only one on which intelligent
life has arisen, if the aforementioned probability is low enough. You
have to remember that the question - "is there intelligent life on
other planets?" will only ever be asked on a planet on which there is
*already* intelligent life. We are necessarily a biased sample.
Yes we are a biased example and if there was only one such planet in
whole universe it would be ironic to use that as an example...which of
course we would.

But I think life is only about atoms and molecules. Imo it would be smug
to assume that these particles and conditions for life would be only met
on one planet in the whole universe.

The validity of an argument is not dependent on how 'smug' it is.
However, if you read my post you will see that my position is not to
assume that we are the only planet matching the preconditions for
life. My position is that we have no idea what the probability of life
occuring is on other planets. I would in fact argue that mine is the
least arrogant position on this subject.

Well what I meant by smug was that this is not just some outside
problem...meaning that us earthlings could feel smug of ourselves if we
were the only intelligent life in cosmos.

I wouldn't feel 'smug' about being alone in the universe, it would be
rather depressing, but that doesn't mean it isn't the case.


I agree we don't know what the probability is. (However, in theory we
might be able to figure that out...If we know enough on conditions in
our galaxy and beginning of the universe. Beginning of the universe
because if other galaxies/star systems etc come from same source there's
no reason to assume that conditions would be different...ie no water or
no life when there is water.)

Even if we could estimate the number of planets with suitable
conditions, we would still need to know the probability of life
emerging on a planet which has the necessary enviromental conditions.


But imo the probabilities are not important to the hypothesis whether
there is extraterrestrial life or not because of the big numbers.
Probabilities are important if we try to figure out whether there is
intelligent life close enough for us to witness it somehow(radio etc).

The problem with this argument is that we cannot know that the
probabilities don't involve infinitesimaly small numbers. If there are
a trillion planets in the universe but the probability of life
occuring on any given planet is one in a trillion, it would still be
quite feasible for us to be alone.


Here's a go at it:http://en.wikipedia.org/wiki/Drake_equation

I'll quote Michael Crichton, from that very wiki page...

"The problem, of course, is that none of the terms can be known, and
most cannot even be estimated. The only way to work the equation is to
fill in with guesses. [...] As a result, the Drake equation can have
any value from "billions and billions" to zero. An expression that can
mean anything means nothing. Speaking precisely, the Drake equation is
literally meaningless..."


Not to contemplate about other possible forms of life than what is met
on earth...There IS a huge amount of planets that have conditions for
liquid water. They've found ice on Mars recently too...I'd say it would
be fair to assume there is ice and water elsewhere in universe too.

It's not just about whether a planet can support life. What is the
probability of a planet able to support life actually having life
emerge? What is the probability of life on a planet resulting in
intelligent life emerging? These are questions to which there cannot
currently be an answer, hence you cannot be certain that we are not
alone - which is the statement of yours I objected to.

I disagree here. If the conditions are similar the probability ceases to
be important because of the huge amount of other galaxies...or planets
in even our own Milky Way.


Mean estimate of number of planets supporting life in the universe
= P(life emerges on a planet) * number_of_planets

P(life emerges on a planet)
= P(conditions on a planet can support life) * P(life emerges on a
planet that can support life)

Without the term - P(life emerges on a planet that can support life),
you cannot work this out. Even if number_of_planets is enourmous and P
(conditions on a planet can support life) is close to one, it is still
impossible.

I think your argument is like saying that if we flip a coin million
times we can't be sure that all wouldn't be "heads"...which is of course
correct in theory but not in practise.

No, it is not the same because we know the probability of a coin
giving a head.




Now you're going to say that liquid water doesn't necessarily mean
life...could be, I don't know. However look at earth and how many
different kind of animals and plants live here. According to this only
example we have so far it would seem that if conditions are correct,
development of many different kinds of lifeforms are likely.

Sure, but that tells us nothing of how likely life is to emerge in the
first place.

Whether these lifeforms are intelligent or not would be a matter of
definition. Maybe humans would not be seen different from earth plants
according to some extraterrestrial life form.

I recommend this short article by the great Marvin Minksy, on this
very subject....

http://web.media.mit.edu/~minsky/papers/AlienIntelligence.html

Well it's an article discussing what is intelligence. Imo many(all?)
animals can be described as intelligent, only the amount of intelligence
varies.

However if talk is about alien intelligence then the relevant norm for
intelligence would be being technologically advanced enough for us to
notice them or vice versa.

The main point is that we need to avoid the whole "intelligent in ways
we can't understand and thus wouldn't even notice" line of thinking,
because it is sophistry which leads absolutely nowhere. I'm not saying
aliens need to be able to do IQ tests to be considered intelligent,
but they had better be capable of representing concepts with symbols
and manipulating those symbols to solve problems. Otherwise, we might
as well define rocks and pieces of dog turd as intelligent.


Interesting counter argument for Drake equation...and counter arguments
to said paradox:http://en.wikipedia.org/wiki/Fermi_paradox

.

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