| Newsgroups: alt.sci.seti,sci.astro.seti |
"K" == Kerly2-Bill <curly-bill@comcast.net> writes:
K> Background I am a 79-year-old retired professor of information
K> science. I have long been interested in radio waves ever since my
K> days in WWII as a navy radio operator.
K> SETI thoughts
K> I am increasingly skeptical of ever making meaningful contact with
K> intelligent life on other planets.
These are fairly standard objections; just a few comments.
K> The Drake Equation just doesn't enumerate all the requirements for
K> intelligent life to exist: including high metal-content stars,
K> stable orbits, stable atmospheres,
The Drake equation doesn't attempt to enumerate all of the possible
conditions that could be required for life to develop. It simply
sketchs some broad categories that are required. All of the above
conditions are subsumed into two factors of the Drake equation: the
number of habitable planets per star system and the probability that
life develops on a potentially habitable planet.
For instance, if a particular star has no planets in stable orbits,
then it clearly will have no habitable planets. At this stage in the
game, though, we're not really interested in individual stars. We're
interested in the *average* number of stars that are orbited by
potentially habitable planets. If any given star doesn't have any
potentially habitable planets, that simply goes into the overall
average.
K> But my overriding reason is the enormous distances. Take a
K> nearby system: 100 light years. That means it takes 100 years from
K> the time a message is sent from another planet for us to receive
K> it, and then another 100 years for our reply to be heard by the
K> alien planet. That's 200 years round trip. A relatively nearby
K> system of a thousand light years takes two thousand years round
K> trip. And most star systems are well beyond a thousand light years.
Well, yes, though note that essentially all of the known planets are
within 150 light years. Also, from the standpoint of astrobiology,
even if we can't communicate with them, knowing that they exist is
still important.
K> Compared to other species on earth, mankind is extraordinarily
K> intelligent and has achieved mind-boggling things, all within the
K> last 7,000 years, but it has taken 5 million years for intelligent
K> man to develop. [...]
Humans are *not* extraordinarily intelligent. We think we are
intelligent, and our intellectual capabilities are clearly beyond that
of any other species. However, both chimpanzees and dolphins have
similar (specific) cranial sizes.
[...]
K> I think it far more likely that we will detect biology of sorts,
K> rather than intelligent life on an extrasolar planets. I think
K> it's hopeless.
I think you're being entirely too blase about even that discovery.
Re-read what you wrote. Finding life on another planet isn't
particularly exciting.(?!)
K> The Active Mind website,
K> http://www.activemind.com/Mysterious/Topics/SETI/drake_equation.html,
K> estimates that the number of planets per star that are capable of
K> sustaining life (ne in the Drake equation) is 1 to 5. I think,
K> from what we now know of extrasolar planetary systems, this figure
K> is far too high.
On the contrary, there are significant selection effects *against*
finding potentially habitable planets around stars. With our current
technology, we *cannot* find Earth-mass planets around other
main-sequence stars[*]. The best we can say is that there appear to
be more Neptune-mass planets than Jupiter-mass planets. From this, we
can predict that there might be more Earth-mass planets than
Neptune-mass planets, but we have no direct observational evidence, as
yet, to support this.
[*] O.k., that's not entirely true. We can find them via either
gravitational microlensing or by detecting radio signals from a
civilization on them. The technology used to find essentially all of
the known extrasolar planets cannot find Earth-mass planets.