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Old October 2nd 18, 10:09 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 Tuesday, October 2, 2018 at 2:02:36 AM UTC-6, Paul Schlyter wrote:

On Mon, 1 Oct 2018 18:41:05 -0700 (PDT), Gary Harnagel
wrote:

On Saturday, September 29, 2018 at 3:55:55 AM UTC-6, Paul Schlyter
wrote:

Back then the galaxies were some 3 times closer to one another than
today, so the typical intergalactic distance were perhaps about a
million instead of millions of light years.

But, more importantly, back then there were few if any population I
stars in existence. All stars back then were population II stars,
which have very little, if any, elements heavier than H and He. Those
heavier elements are required to form life. So back then there was no
life in the universe, that we can say with great certainty. Back
then, our Sun and our Earth did not even exist. Life, of all kinds,
formed later.


9 billion years ago there certainly WERE stars with heavy elements:

http://www.astronomy.com/news/2016/0...rly-galaxies-c
hallenges-star-forming-theory

Although their metallicity was only 20% of stars near us, that's pretty
good for 11 billion years ago, wouldn't you say?


Lower metallicity means less material from which life can form.


Less, but not zero. You have NO idea how much less prevents life and neither
do I, so this is just yammering.

Such as wormholes? Or did you have something else in your mind?


Wormholes, Alcubierre=type drives, transit to other branes, and ways not
even a glimmer in the eyes of theoretical physicists.


Now you've entered the realm of science fiction...


So you believe only scientists can have new ideas? You DO realize that
some SF authors ARE scientists, don't you?

Not by much. Since the big bang happened 13.5 billion years ago, 5
billion years ago the intergalactic distances already had about 60%
of their current value.


And maybe there's a way to "wink out" there and "wink in" here vitually
instantaneously. We haven't had millions of years of scientific
development yet.


More sci-fi...


More lack of vision.

Do you consider one to be a large number? One is the number of
planets known to have life...

The law of large numbers say that if you repeat an experiment a large
number of times, the outcome will be very close to the expected
value. But, in the case of life in the universe, we have no idea what
the expected value is. So the law of large numbers does not help us
here.


Sure it does. We don't have to know the expectation value. We KNOW it
happened ONCE. Given ENOUGH chances, it will happen again.


Sure, but have there been ENOUGH chances? We don't know, we can only
guess or believe.


I BELIEEEVE!

Given what we know about planetary systems today, about the number of
stars in our galaxy, about the number of galaxies in just the VISIBLE
universe and the tininess of the visible universe, you don't believe it
hasn't happened MANY times? If so, you are an amazing pessimist!


You see? All we can do is believe, we don't know. We are getting to
know the first few factors of the Drake equation, but several factors
remain unknown to us. And these unknown factors are the hardest to
get to know. For instance, what is the typical lifetime of a
technologically advanced civilization? Apart from beliefs and
guesswork, hov can we actually get to KNOW that value?


It comes down to how much vision you have vs. how big a pessimist you are.

That's your guess, and it is a far cry from "absolutely certain" that
it actually is so.


YOU are the only one talking about "absolute certainty." I'm talking about
probabilities.


Even if you call it "very high probability' it's really the same thing. One
thing about extraterrestrial life is that ve cannot be "almost certain"
about anything.


I am.

You and I are working from different assumptions. Are you familiar
with Paul Steinhardt's Ekpyrotic theory?

https://arxiv.org/abs/hep-th/0103239

https://en.wikipedia.org/wiki/Ekpyrotic_universe

It posits a cyclic universe. If it has any credence it means that past
universes existed. If intelligent life is as rare as some here believe,
it becomes a virtual certainty that it developed in a previous genesis,
maybe millions of times. If some couldn't find a way to transport
itself from one genesis to the next, one would have. Imagine, a
civilization billions of years old appearing on the scene 13 billion
years ago!

But what if it doesn't have any credence? We don't know if it has, so
we can only guess. And you must do much better than guesswork to be
able to reliably claim that something is "almost certain".


Don't be such a pessimist! It's bordering on a mania :-)


Don't be such a dreamer...


Why not? Dreamers make reality happen. Pessimists just sit around moping.

When you talk about extraterrestrial life, don't you mean real life in the
real universe and not just your fantasies and wishes?


I believe in ET. Why wouldn't you?

You can fantasize as much as you want, but please stop trying to
misuse probability to claim something is "almost certain" when it
actually just is a guess of yours.


Pessimist!


No, I'm a realist.


No, you're a mope-around. And you cannot possibly be a "realist" since you
admit that we don't know.

There are no alternatives today that match empirical data so well.


Irrelevant since we're talking about billion-year-old civilizations.


You are then talking about something neither you nor anyone else on
Earth know anything about.


So you admit that calling yourself a realist is just as nonsensical as my
calling myself a visionary :-))

The discovery of the cosmic background radiation made the "big bang"
win over the "steady state" cosmology. But note that this is not
final. If and when a cosmology appears that matches empirical data
even better, then it will replace the "big bang" as the standard
cosmological model.


The standard model assumes inflation. There are scientists that dispute
that.

https://www.wired.com/2008/02/physic...ng-wasnt-the-b
eginning/


There are always people questioning, that's a natural part of the
scientific process. Time will tell who is right.


Indeed. As a human being, however, I want to have a "world view." It's
important to me. I have developed mine over many years and I'll hold it
until and if the evidence refutes it.