In infinite wisdom Joseph Lazio answered:
"R" == Rich <someone@somewhere.com> writes:
R> In infinite wisdom Joseph Lazio answered:
Failure to find strong evidence of ETI in any given SETI program
is not a failure of the program, it is a scientific *result*.
R> I'm amazed at how many think that you can derive population
R> statistics from one example, the earth.
(Actually, in re-reading this, I just realized that one can derive
population statistics from this: The number of civilizations in the
Galaxy is at least 1.
We seem to have a different vision as to what population statistics are.
I would point you to any of the countless web-pages giving population
statistics for various things (usually demographics, but crime is also
popular) if I thought there were any point to it.
The question that SETI is trying to answer is
whether the number of civilizations in the Galaxy is more than 1.)
Agreed.
Re-read what Christopher wrote. He does not advocate deriving the
number of ET civilizations based on the Earth, but searching for
other ET civilizations to derive population statistics.
R> I'm referring to the Drake Equation, which many seem to think
R> proves the existence of anywhere from thousands to hundreds of
R> millions of ET civilizations in our galaxy alone. Is this not what
R> SETI is looking for?
Have I ever written that I think the Drake equation "proves" the
existence of ET civilizations?
Not where I have seen it (which is an expression of my ignorance as to
what you have said rather than an expression of doubt). But it remains
that it is usually portrayed in this light.
The Drake equation is really an illustration of our ignorance.
It illustrates nothing. It sheds no light.
It can be used to *motivate* a search, but that's it.
Generally, by my observation, by those who think it shows that there
are thousands of ETI's out there just trying to communicate with us.
And if it is your motivation, I think it's a very poor one.
By the same token, we can already set simple limits on the number
of ET civilizations.
R> The count is holding at zero. You cannot extrapolate from nothing
R> to population statistics dude.
There are clearly no super-advanced civilizations
[...]
in our neighborhood radiating at huge power levels or we'd have
seen them already.
R> Exactly. And were they transmitting at much lower power in our
R> direction, we'd have seen that already.
Well, yes, but "lower" here is relative.
Agreed. But I note that Lou Sheaffer is posting right now that 1 watt
would be sufficient. I suggest that this point is open to discussion.
[...]
If you'd like to read about an early attempt to set limits on the
number of civilizations in the Galaxy, visit the ADS and take a
look at the paper by Horowitz & Sagan (1993).
R> http://adsabs.harvard.edu/cgi-bin/bib_query?1993ApJ...415..218H
[...]
R> Interesting that they note "rare processor errors". Seems to be an
R> issue with seti@home as well.
Did you note the statement, "set limits on the prevalence of
supercivilizations transmitting Doppler-precompensated beacons at H I
or its second harmonic," which is really more relevant to the question
at hand?
Is it? I thought the question at hand was far more general. Above you
state it simply...
# The question that SETI is trying to answer is
# whether the number of civilizations in the Galaxy is more than 1.
[...]
Let me turn your statement around. How do you know that the Galaxy
contains no other civilizations, given that we know of one
civilization that can be detected over interstellar distances?
R> I make no claims to have such knowledge. I do claim that we just
R> don't know.
So why all of the posts to state something on which all of us agree?
I don't see that this is the common message at all.
-----
http://groups.google.com/groups?q=number+of+ET+civilizations&start=10&hl=en&lr=&ie=UTF-8&oe=UTF-8&scoring=d&selm=825fedc5.0404261920.358ffee9%40posting.google.com&rnum=12
[...]
Astrobiology Magazine (AM): Can you comment on how physics has
steadily moved Earth's place from one of uniqueness (or
anthropomorphism) to viewing our position as one tiny corner among
possibly billions of habitable worlds available for evolving complex
life?
Michio Kaku (MK): This question is no longer a matter of idle
speculation. Soon, humanity may face an existential shock as the
current list of a dozen Jupiter-sized extra-solar planets swells to
hundreds of earth-sized planets, almost identical twins of our
celestial homeland.
This may usher in a new era in our relationship with the universe: we
will never see the night sky in the same way ever again, realizing
that scientists may eventually compile an encyclopedia identifying the
precise co-ordinates of perhaps hundreds of earth-like planets.
Today, every few weeks brings news of a new Jupiter-sized extra-solar
planet being discovered, the latest being about 15 light years away
orbiting around the star Gliese 876. The most spectacular of these
findings was photographed by the Hubble Space Telescope, which
captured breathtaking photos of a planet 450 light years away being
sling-shot into space by a double-star system.
But the best is yet to come. Early in the next decade, scientists will
launch a new kind of telescope, the interferometry space telescope,
which uses the interference of light beams to enhance the resolving
power of telescopes.
[...]
----
Perhaps more important, given that we all agree that we do not know
how many radio transmitting ET civilizations there are in the Galaxy,
why do you object to trying to find out?
There are some pressing problems right here right now on earth. I
think we need to prioritize how we use the resources we have.
[And just a few other comments]
R> I'm not so sure about that. The dataset is still very small. It's
R> not clear, for example, that metal poor stars can have planets, or
R> perhaps planets not gas giants. There are whole populations of
R> stars that are metal poor, especially the populations of globular
R> clusters.
See the recent results on the planet detected around PSR B1620-26,
in the globular cluster M4.
R> http://www.extrasolar.net/planet.asp?PlanetID=30
R> Mass: 2.5 Jupiters
R> Seems like a gas giant near as I can tell.
[...]
Well, yes, but gas giants are planets, too. You stated, "It's not
clear [...] that metal poor stars can have planets, ...." We have one
counterexample.
It's disturbing that you cut the sentence in half to delte the part
where I said...
"or perhaps planets not gas giants."
The FULL sentence is...
# It's not clear, for example, that metal poor stars can have planets,
# or perhaps planets not gas giants.
You don't have a counter-example as I specifically and clearly excluded
gas giants.
R> As for earth-type planets, we can't detect them yet. But would you
R> expect that they would be found around stars in globular clusters?
I don't know. I do know that if we don't look for them, we'll never
be able to say.
It's not clear that even were we to resolve such a planet, we would be
able to say anything about ETI's. But what reason is there to expect
terrestrial planets around metal poor stars?
Rich