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4ab3b553$1@news.povray.org...
> Darren New wrote:
>> I'm pretty amazed it only takes 16 years to watch long enough to see
>> something orbiting the galaxy. :-)
>
> On what day of the week did God create black holes? :-)
>
When He got to go to Loo
Marc
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Darren New <dne### [at] san rrcom> wrote:
> http://www.youtube.com/watch?v=fgg2tpUVbXQ
The video posits that life in other planets is likely due to the humongous
amounts of stars and planets out there. On the other hand, the opposite
hypothesis is scientifically sound as well:
http://en.wikipedia.org/wiki/Rare_Earth_hypothesis
In short, the hypothesis states that life requires such ideal conditions
that most planets, and even most galaxies simply don't provide them.
The volume inside a galaxy in which any kind of life could possibly form
is quite small. If a star is too close to the core of the galaxy, radiation
will be too high, as well as the density of stars and other objects (which
greatly increases the likelihood of catastrophic events terminating any
possible life-producing conditions). Too far away from the core, and the
metallicity of star systems will be too low to produce any planets which
could produce life.
The shape and other features of the galaxy matter too. Some shapes make
it less likely for habitable conditions to form (because the above problems
will appear throughout the entire galaxy, among other things). This would
mean that only a small portion of all galaxies could support life of any
kind. It also means that most if not all early galaxies in the history of
the universe were inhospitable, and thus it's not very probable for life
to have been formed any time soon after the big bang.
Even inside the "habitable zone" the conditions must be very ideal.
A double star (which is relatively common) will be detrimental to any life.
Even single stars will require other conditions to be life-friendly (such
as having giant gass planets at an appropriate distance which vacuum the
stellar system from dangerous, life-terminating objects). The star itself
must be of a certain type: Too big or too small, too hot or too cold, or
too much radiation, and it will be unfriendly to life.
A planet must have certain conditions to produce life. Too close to the
star, and it won't have any water or other liquids (which is most probably
a prerequisite for life). Too far, and the water will be frozen. Also, the
orbit of the planet must be almost circular for this same reason.
A moon which causes tides, and plate tectonics also help in the process
of life forming. Even if a planet is otherwise ideal, if it lacks those,
it will be much less likely for life to form.
There are a big bunch of other conditions which must also be just right,
or else life will be much less likely. The video calls the Sun "unremarkable",
but in one thing it's extremely remarkable: It's probably one of the very
few stars in the galaxy, if not the entire universe, which has all the
necessary conditions for life.
A common concept is that the universe must be full of life, but that's
not necessarily so. Life might be extremely rare. Intelligent life even
rarer. (The conditions necessary to produce intelligent life make this
whole situation even more complicated.)
--
- Warp
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Warp escreveu:
> Darren New <dne### [at] sanrrcom> wrote:
>> http://www.youtube.com/watch?v=fgg2tpUVbXQ
>
> The video posits that life in other planets is likely due to the humongous
> amounts of stars and planets out there. On the other hand, the opposite
> hypothesis is scientifically sound as well:
>
> http://en.wikipedia.org/wiki/Rare_Earth_hypothesis
>
> In short, the hypothesis states that life requires such ideal conditions
> that most planets, and even most galaxies simply don't provide them.
>
> The volume inside a galaxy in which any kind of life could possibly form
> is quite small. If a star is too close to the core of the galaxy, radiation
> will be too high, as well as the density of stars and other objects (which
> greatly increases the likelihood of catastrophic events terminating any
> possible life-producing conditions). Too far away from the core, and the
> metallicity of star systems will be too low to produce any planets which
> could produce life.
>
> The shape and other features of the galaxy matter too. Some shapes make
> it less likely for habitable conditions to form (because the above problems
> will appear throughout the entire galaxy, among other things). This would
> mean that only a small portion of all galaxies could support life of any
> kind. It also means that most if not all early galaxies in the history of
> the universe were inhospitable, and thus it's not very probable for life
> to have been formed any time soon after the big bang.
>
> Even inside the "habitable zone" the conditions must be very ideal.
> A double star (which is relatively common) will be detrimental to any life.
> Even single stars will require other conditions to be life-friendly (such
> as having giant gass planets at an appropriate distance which vacuum the
> stellar system from dangerous, life-terminating objects). The star itself
> must be of a certain type: Too big or too small, too hot or too cold, or
> too much radiation, and it will be unfriendly to life.
>
> A planet must have certain conditions to produce life. Too close to the
> star, and it won't have any water or other liquids (which is most probably
> a prerequisite for life). Too far, and the water will be frozen. Also, the
> orbit of the planet must be almost circular for this same reason.
>
> A moon which causes tides, and plate tectonics also help in the process
> of life forming. Even if a planet is otherwise ideal, if it lacks those,
> it will be much less likely for life to form.
>
> There are a big bunch of other conditions which must also be just right,
> or else life will be much less likely. The video calls the Sun "unremarkable",
> but in one thing it's extremely remarkable: It's probably one of the very
> few stars in the galaxy, if not the entire universe, which has all the
> necessary conditions for life.
>
> A common concept is that the universe must be full of life, but that's
> not necessarily so. Life might be extremely rare. Intelligent life even
> rarer. (The conditions necessary to produce intelligent life make this
> whole situation even more complicated.)
carbon-based life.
--
a game sig: http://tinyurl.com/d3rxz9
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nemesis <nam### [at] gmailcom> wrote:
> carbon-based life.
Has any form of (intelligent) complex life which is not based on chemistry
similar to our own, and/or which is not heavily dependent on water, been
even seriously conjectured?
Complex life (ie. anything more complicated than something resembling a
virus) requires certain molecular structures, which in turn require certain
chemistry and certain chemical elements to appear in certain proportions.
For example, anything even remotely resembling proteins requires molecules
with certain structures and certain elements to be stable and feasible. If
these elements are not abundant enough, such complex molecules simply cannot
form.
AFAIK, it's physically impossible to get anything even remotely usable
for forming complex life from hydrogen and helium alone. This rules out
most star systems on the outer edges of galaxies, as well as most stars
in galaxies of certain type, for instance.
Also even non-carbon-based life won't survive a collision with an
enormous celestial body. No matter how exotic your lifeforms are, they
will most probably not survive if their planet collides with a star. Thus
star density in the galaxy is a key factor. (While direct collisions might
be less likely, close encounters may well fling the planet out of its orbit,
dooming any potential life to a slow death. You most probably can't have life
at 3 kelvin.)
--
- Warp
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Warp schrieb:
>
> A moon which causes tides, and plate tectonics also help in the process
> of life forming. Even if a planet is otherwise ideal, if it lacks those,
> it will be much less likely for life to form.
This is something that I find particularly intriguing about the place we
live on:
Not the fact that the earth does have a moon. Nor the fact that it is
the only one the earth does have. Not even the remarkable fact that it's
an incredibly huge chunk of rock for such a small planet.
No, what's most astonishing about this all is that its apparent size
matches so well with that of the sun.
I can only think of two possible conclusions for this:
(a) It may be due to the anthropic principle, i.e. there might be some
hidden mechanism in the creation of intelligent life that requires this
extraordinary property.
(b) It was /designed/ to be this way.
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Warp wrote:
> nemesis <nam### [at] gmailcom> wrote:
>> carbon-based life.
>
> Has any form of (intelligent) complex life which is not based on chemistry
> similar to our own, and/or which is not heavily dependent on water, been
> even seriously conjectured?
>
> Complex life (ie. anything more complicated than something resembling a
> virus) requires certain molecular structures, which in turn require certain
> chemistry and certain chemical elements to appear in certain proportions.
Carbon-based complex life certainly. ;)
Fact is we're used to what we're used to. We've never seen any other
life, carbon-based or not. BTW, this conversation just reminds me of
the XKCD strip of today someone posted here.
> For example, anything even remotely resembling proteins requires molecules
> with certain structures and certain elements to be stable and feasible. If
> these elements are not abundant enough, such complex molecules simply cannot
> form.
Reality is quite different inside neutron stars. There is the
possibility of giant earth-like worlds made of hot ice. If
self-replicating organisms would evolve in some of these environments,
how'd they turn out to be made of?
not really suggesting life would be possible inside stars, just
enumerating the weird places this universe has got...
> Also even non-carbon-based life won't survive a collision with an
> enormous celestial body. No matter how exotic your lifeforms are, they
> will most probably not survive if their planet collides with a star.
But they could send their last child to a world with a yellow sun! ;)
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clipka <ano### [at] anonymousorg> wrote:
> Warp schrieb:
> >
> > A moon which causes tides, and plate tectonics also help in the process
> > of life forming. Even if a planet is otherwise ideal, if it lacks those,
> > it will be much less likely for life to form.
>
> This is something that I find particularly intriguing about the place we
> live on:
>
> Not the fact that the earth does have a moon. Nor the fact that it is
> the only one the earth does have. Not even the remarkable fact that it's
> an incredibly huge chunk of rock for such a small planet.
>
> No, what's most astonishing about this all is that its apparent size
> matches so well with that of the sun.
>
> I can only think of two possible conclusions for this:
>
> (a) It may be due to the anthropic principle, i.e. there might be some
> hidden mechanism in the creation of intelligent life that requires this
> extraordinary property.
>
> (b) It was /designed/ to be this way.
(c) Lucky coincidence, since it did not and will not always appear to be the
same size of the sun.
-Reactor
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Warp wrote:
> nemesis <nam### [at] gmailcom> wrote:
>> carbon-based life.
>
> Has any form of (intelligent) complex life which is not based on chemistry
> similar to our own, and/or which is not heavily dependent on water, been
> even seriously conjectured?
Silicon, yes. Same column as carbon.
In any case, it's hard to say what life needs to survive, with only one
sample planet. Oxygen killed almost all the life, and now life flourishes
with it. We have worms living in the bottom of the ocean off sulphuric
vents. Etc.
I don't think we'll know one way or another until we either get out there,
or we build spectroscopes that can analyze the atmospheres of rocky planets
around other stars.
> AFAIK, it's physically impossible to get anything even remotely usable
> for forming complex life from hydrogen and helium alone.
That's probably true. :-)
> Also even non-carbon-based life won't survive a collision with an
> enormous celestial body.
I think if you had life on Jupiter, it could probably withstand quite a
whack. Not a star or a black hole, perhaps.
--
Darren New, San Diego CA, USA (PST)
I ordered stamps from Zazzle that read "Place Stamp Here".
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Reactor schrieb:
> (c) Lucky coincidence, since it did not and will not always appear to be the
> same size of the sun.
Quite mind-bogglingly unlike for intelligent life to "wake up" just at
such a time when it does.
(BTW, are you sure it will not? After all, not only does the lunar orbit
around earth change, but also earth's orbit around the sun. Maybe the
two effects will happen to cancel out?)
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nemesis <nam### [at] nospam-gmailcom> wrote:
> Warp wrote:
> > nemesis <nam### [at] gmailcom> wrote:
> >> carbon-based life.
> >
> > Has any form of (intelligent) complex life which is not based on chemistry
> > similar to our own, and/or which is not heavily dependent on water, been
> > even seriously conjectured?
> >
> > Complex life (ie. anything more complicated than something resembling a
> > virus) requires certain molecular structures, which in turn require certain
> > chemistry and certain chemical elements to appear in certain proportions.
> Carbon-based complex life certainly. ;)
Matter-based complex life in general. Complex life requires complex
molecules, and you can't have complex molecules made purely from the first
few elements a star produces, ie. hydrogen and helium.
Coincidentally, the next chemical element a star produces is, surprise
surprise, carbon. After that it only gets more complicated. Carbon is a
rather versatile molecule, besides being abundant in more developed star
systems, which is probably the reason why we are based on it.
(The elements in-between those are not formed in the core of the star at
all, but in supernova explosions, which means that any of the more complex
chemical elements must come from remnants of old supernovas (which might in
turn have been formed from remnants of even older supernovas, and so on).
AFAIK these stars don't tend to form at the edges of galaxies.)
I'd say that if you want complex life which is not carbon-based, the
conditions must be even more ideal than for us, so it's not like it makes
things simpler, but on the contrary, it probably makes life even less
likely.
> > For example, anything even remotely resembling proteins requires molecules
> > with certain structures and certain elements to be stable and feasible. If
> > these elements are not abundant enough, such complex molecules simply cannot
> > form.
> Reality is quite different inside neutron stars.
It's hard to imagine any kind of life (much less intelligent life) forming
on or in a neutron star. Matter density is way too high for any kind of
regular chemical reactions to happen. Molecules cannot form. Heck, even
atoms cannot form (due to temperature and pressure).
--
- Warp
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