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Old September 27th 18, 01:27 PM posted to sci.astro.amateur
Gary Harnagel
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Default Neil DeGrasse Tyson headed down same loony road as Carl Sagan?

On Thursday, September 27, 2018 at 4:42:54 AM UTC-6, Martin Brown wrote:

On 26/09/2018 20:07, Gary Harnagel wrote:

On Wednesday, September 26, 2018 at 6:52:19 AM UTC-6, Martin Brown wrote:

On 26/09/2018 12:11, Gary Harnagel wrote:
We don't know of any other ET civilisations though. As yet we haven't
found life arising independently on another planet either


That's because we haven't looked except in a very few places. Wanna
bet on the oceans of Enceladus?


Life in the oceans perhaps, intelligent at the level of an octopus maybe
but there is very little chance of them having any kind of technological
civilisation in water even if they reached the hunter gatherer stage.

Eventually they will get their opportunity when the sun expands and the
temperature rises enough so that there is liquid water at the surface.
(we will be toast by then)

although there may be hints of life having been on Mars back when
it had liquid water. (it may still be there deep in underground rocks
or dormant as cysts)


I wouldn't consider proof of life elsewhere in the solar system as proof
of interstellar life. It could have come from earth.


Depends whether or not it uses the same DNA code, handedness and amino
acids. If it uses different choices to those on Earth then the odds are
very good that it arose independently. If it uses the exactly the same
compounds as on Earth then terrestrial contamination is by far the most
likely reason. One reason to carefully sterilise anything sent to a
pristine potentially life supporting environment on another planet.


I suspect that ALL life will have the same DNA.

Until we have seen life arise in at least one other place then you are
on a hiding to nothing guessing at the probability of life elsewhere.


Some guesses are better than others. I think it's very arrogant to
believe that nobody's out there, and it's even more arrogant to believe
they haven't been around longer than we have.

I am inclined to think that it will arise spontaneously where ever and
when ever the conditions permit given how quickly it got going on Earth.
But until we see another example it is just an educated guess.


Educated versus arrogant.

Much life may remain stuck at the photosynthetic slime stage though.


I sometimes entertain panspermia thoughts.

You have a rather weak grasp of probability theory


You are very funny :-))

and an even weaker grasp of the Drake equation. Planets now appear
to be far more common than was once thought but a lot of them are
hot Jupiters tidally locked to their parent star (a side effect of
present experimental methods which are particularly good at detecting
planetary transits and Doppler shifts as the hefty planet orbits its
parent star close in).


And you seem to be very weak on present theory that posits Jupiter
having started out close to Sol.

Comparatively few have been found in the Goldilocks zone (although
that may be a selection effect of present observational techniques).


Indeed. We should be looking at OLD G and K-type stars for old civili-
zations. Tabby's Star may qualify although it's a 6-billion-year-old
F-type.

It is certainly possible. But whether or not it is common for life to
evolve beyond the single celled stage is still an open question.


"Life will find a way.” -- Michael Crichton


Just because your favourite science fiction writer said it does not make
it true.


He's not my favorite, but just because a SF writer said it doesn't make
it false.

One awkward upper bound on the timescale that a technological
civilisation can operate without having to develop space faring
technology is the time it takes to exhaust the finite resources
of their home planet.


As I said, it only takes ONE civilization to make it. It can then
spread to other galaxies in a few million years, a very short time in
the universe.


So why aren't they here then?


How do you know they aren't? Surely a billion-year-old civilization has
capabilities to completely hide themselves from us. OTOH, I sometimes
wonder about UFOs ....

I read Ruppelts "The Report on UFOs" back in the 50's, then a couple
of years ago I read his 1960 updated version where he said that no
credible sightings occurred with radar confirmation, so I switched back
to thinking they were natural phenomena. And then this happened:

https://video.search.yahoo.com/searc...b&action=click

If intelligent life was really common in our galaxy then there
should be some residual signals for our radio and optical
astronomers to see.


Not necessarily. The time that a civilization uses radio technology may
be quite short. Consider our own civilization. It's mostly beamed or
fiber.


If they were as common as you suppose there should be one inside the
range of our radio telescopes by now.


As you said, probability is a guess. What I said was that all that is
needed is ONE civilization. One civilization early in the galaxy's
life (say, 4 billion years ago in our 9-billion-year-old galaxy) can
spread a mere 100 thousand lightyears in a few million years.

Technological civilisations are not going to be non-thermally radio
bright for very long.


I'm having trouble with your triple negative :-|

I think you're saying that such civilizations will become radio bright
in a non-thermal manner in a short time? I say that radio-brightness
is a phase that civilizations go through in a fairly short time. They
may develop means for communication and energy distribution that we
can't detect at our present level of technology. IR brightness, OTOH,
is more difficult to control due to energy dissipation.

That or we would have seen self replicating probes by now a la Fermi
paradox.


Not if there is an over-arching civilization that has already been here..

The chemists and molecular biologists are slowly getting closer to
finding out answers. The tricky step is more likely to be the point
where single celled simple life makes the transition to complex
multicellular organisms. Science is always a step by step refinement
from present knowledge by way of experiments.

https://www.the-scientist.com/featur...-complex-42874

What they find will be way more convincing than a "Just So" story.


Indeed. But haven't complex organic molecules been found in the solar
system?


Plenty. It is amazing what sort of a cocktail you can brew in a dense
molecular cloud illuminated by fast burning brilliant young blue giants.

--
Regards,
Martin Brown


Yeah, and in the nursery where our sun was born, we may have been quite
close to one or two of those. Our DNA may be shared with a whole swarm
of stars spread all over the galaxy. Or maybe the biblical account is
not so far off: that old, old civilization may have planted us :-)