A single data point.

It seems that references for extrapolating from a single data
point are pretty much nonexistent, no one except SETI does it,
and everyone else understands that you cannot do probability
analysis with a single data point. Funny that.

BTW, the single data point is sufficient for one thing, it
disproves the assertion (which is silly on the face of it)
that there is no life in the universe. But beyond that no
conclusions can be drawn.

Another point that I forgot about is metals (to astronomers,
anything heavier than H or He). Population I stars are metal
poor, and even if everything else there was similar, it is not
clear that life could develop around such a star. Most of the
stars in globular clusters are pop 1. Indirect evidence for this
is that the sun is Population 2, and life on earth developed
somewhere around the universes 10 B birthday. Think of all the
candles.

============================


http://groups.google.com/groups?q=pr...ain.org&rnum=7

Likewise, until the discovery of the Mars samples, we had only one
data point for the existance of life. Thus it is intemperate to say
that life 'is' common. we can say that the chemical processes that
lead up to bacterial life appear basic and easy, and we can state that
_given_the_same_conditions_ life would be common. However, we (until
the Mars rock) do not have any evidence as to how common those initial
conditions are. As I've said before, you cannot make any probability
calculations with a single data point.

[ note, the Mars rock is quite controversial ]

http://groups.google.com/groups?q=pr...x.com&rnum =5

Somewhere along the line we drifted into another
speculation: predicting the specific low-probability
event. That's a horse of a different color. But it
has no particular relevance to the Creationist's
usage of the number.

Tied in with this was the use of a single data point
in measuring probability. *That* arument was interesting.
If you make one measurement and then develop a theory
that says that result has less than 1 chance in 10^50
of happening, are you justified in throwing it out?

The answer to that is always no. This is so because
you don't know the actual probabilities involved; your
theory is likely only an approximation to the real
physical situation. And if you did know the probabilities,
you don't need any further measurements. We make
measurements when (a) we don't know the probabilities
for sure and want to find them out or (b) when we want
to see if the setup we've got actually follows the
known probabilities. In either case we can tell
nothing from a single measurement.

---- Paul J. Gans


http://groups.google.com/groups?q=pr...ac.net&rnum=40

Then I won't ask for "metaphysical" proof, or even extraordinary proof.
I'm asking for some conclusive evidence, some *real* proof that the
positive assertion that there is life (not the possibility, but that there
IS life) elsewhere. There has yet to be any evidence. The fact that life
exists here is not proof that life exists elsewhere. It is proof that
given the precise starting point and all the same variables will make life
come about. There is no proof however, that this has happened elsewhere.

Agreed.

It's not even a probability, only a possibility.

This is debatable and seems to vary based on what assumptions one
chooses to emphasize. There is, in fact, a probability, but we don't
have enough information to define what the probability is. -- perhaps
that's unnecessary nit picking. The funny thing about having only a
single data point is that, as you agree, we have no information about
how rare or common life is in the universe. It may very well be that
Earth is the only planet in the whole universe with life; it may also be
that life appears quite readily from a variety of initial conditions and
that there are many millions of planets with life.

================================

From: John Rehling )
Subject: POLL: Exoplanets and life

Newsgroups: sci.astro, sci.astro.amateur, sci.astro.seti
Date: 2000/06/14

Jan writes:

Paul, don't you think that as there are billions (?) of stars
(just recently 300,000 new ones where identified in the bulge
in the middle of our own galaxy), that it would be weird
if this o'l earth had the patent for it ;-)?

I don't. The "sheer numbers" argument does little to impress me. If
life requires a few disparate elements to combine in a special way,
then the probability of biogenesis relates to combinatorics, and
numbers in combinatorics get much bigger than the number of stars.

Even if every star had one planet Earth-sized planet at Earthlike
temperatures orbiting it, I still doubt it. 60! is larger than the
number of molecules all those oceans would contain. 50! is
smaller. IMO, if life depends upon combinatorics, and the number of
elements that need to get thrown together in the right way is less
than about 50, *then* life will be found everywhere. If it is greater
than 60, then life will be found nowhere else. I certainly don't have
any a priori sense that it is less than 50 -- bacterial DNA looks
pretty complicated to me.

What I am trying to say is: very likely it (life) is a natural
exponent (result) of processes happening everywhere (that we, well
our concept of 'everywhere' anyways can observe).

I disagree. I suspect that it is a freakishly unlikely event that we
are only here to talk about because this is the place where it
happened to take place.

I'm open to the reasonable possibility that I am wrong, but I'm
bothered by the hegemony that Drake's opinion has.

-JAR
--
The only graceful way to accept an insult is to ignore it; if you
can't ignore it, top it. If you can't top it, laugh at it. If you
can't laugh at it, it's probably deserved.
-John Russell Lynes, Jr.


http://groups.google.com/groups?q=pr....net&rnum= 48


: form of life support. Therefore, it's not hard to extrapolate out the
: possibility that solar wind can carry such life to the rest of the solar
: system. Life might be found elsewhere in our system, but Ross insists, and I
: agree, that it will be transplanted Earth life.

Insisting where no data exists is a sign of poor science. The solar wind
is a mass of charged particles; it is very difficult to see that such a
wind could carry life outward in the solar system. Any cross-planet
panspermia would be more likely to occur as a result of meteor impacts,
and we know that meteor impacts can throw debris to other planets. But by
this, it's roughly equally as likely that life started elsehwere and was
seeded to Earth by such an impact; iEarth is not necessarily the
reservoir.

In any even, this is all fairly useless speculation. All we have is
precisely one data point of the existence of life: Earth. When all you
have is a single data point, you can't extrapolate *at all*.

http://groups.google.com/groups?q=pr...rk.net&rnum=58

From: )
Subject: Carl Sagan
View: Complete Thread (56 articles)
Original Format
Newsgroups: alt.paranet.ufo
Date: 1994-09-05 19:43:15 PST

MR JAMES EASTON ) wrote:

: I have accidentally come upon a text file which, given recent discussions
: concerning Mr Sagan, I though may be of particular interest.
: Obviously, I cannot verify it's authenticity, however, the original source
: is mentioned, should anyone be interested in doing so.
: [START]
: Appearing in the _Stars and Stripes_ (a US Military newspaper), Monday,
: November 26, 1962 (yes, 30+ years ago):

Snip, snip

The Drake Equation quoted in this article is simply a guess--nothing more.
With a single sample of intelligent life (I'm throwing us H. sapiens in
here as an example of intelligent life--perhaps I am in error) it is
impossible to extrapolate the true probability of other intelligent life
developing elsewhere in the universe let alone visiting us on Earth. That one
planet in the universe has developed sentient life is undeniable. That
this fact proves other sentient beings exist is untenable. Dr. Sagan's
enthusiastic predictions of years past can perhaps best be attributed to
youthful exuberance and ambition. I might suppose that he would blush
to read these quotations today.

From a statistical viewpoint, it does seem probable that other intelligent
beings exist. It is even possible that they have landed on Earth.
BUT, statistics are not proof even with good, solid data. Statistics
derived from a single data point are more useless than the astrology Dr.
Sagan sneers at.

We must demand to see the zebra before we are convinced that a horse
didn't leave the hoofprints.


http://groups.google.com/groups?q=pr....com&rnum =83

From: Brian Trosko )
Subject: Physics Question
View: Complete Thread (263 articles)
Original Format
Newsgroups: alt.games.diablo
Date: 2000/05/14

writes:
: We cannot assume there is life elsewhere in the universe. We cannot
: assume that there is no life elsewhere in the universe. We have a single
: data point. Extrapolation from a single data point is really, really,
: really stupid.
: It is only a single data point if you define it as that.

When the question being asked is "Is there life on other planets," then it
is a single data point.