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Suitable stars and the Drake Equation discussions



 
 
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  #11  
Old August 14th 12, 09:47 PM posted to sci.astro
Yousuf Khan[_2_]
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Posts: 1,692
Default Suitable stars and the Drake Equation discussions

On 11/08/2012 12:06 PM, dlzc wrote:
Dear Yousuf Khan:

On Friday, August 10, 2012 6:56:22 PM UTC-7, Yousuf Khan wrote:
...
The first 3 billion years was wasted in
single-cell form. Complex life only started
about 600 million years ago, probably after
the last Snowball Earth. If other planets
undergo quicker transitions from single-cell
to complex life, then they could save upto
3 billion years.


That is probably when the first DNA "virus" infected an RNA host cell. Corresponds reasonably well with the formation of free oxygen (at 500 million years).


The fact that complex life arose almost simultaneously with the end of
the Snowball Earth period, I would say that the environment had more to
do with the evolution of complex life than viruses changing DNA code.
Viruses must've been changing lots of DNA code prior to that, but
Snowball Earth happened only once (so far as we know).

If such is drifting on the stellar wind, being in a void as we are, could slow how long it took to get here. Cooler stars might be easier to let this stuff in...


What exactly are you referring to when you say, "let this stuff in"? Are
you talking about cosmic rays, interstellar dust, etc.?

Yousuf Khan
  #12  
Old August 14th 12, 11:12 PM posted to sci.astro
dlzc
external usenet poster
 
Posts: 1,426
Default Suitable stars and the Drake Equation discussions

Dear Yousuf Khan:

On Tuesday, August 14, 2012 1:47:20 PM UTC-7, Yousuf Khan wrote:
On 11/08/2012 12:06 PM, dlzc wrote:
On Friday, August 10, 2012 6:56:22 PM UTC-7, Yousuf Khan wrote:


...


The first 3 billion years was wasted in
single-cell form. Complex life only started
about 600 million years ago, probably after
the last Snowball Earth. If other planets
undergo quicker transitions from single-cell
to complex life, then they could save upto
3 billion years.


That is probably when the first DNA "virus"
infected an RNA host cell. Corresponds
reasonably well with the formation of free
oxygen (at 500 million years).


The fact that complex life arose almost
simultaneously with the end of the Snowball
Earth period, I would say that the
environment had more to do with the evolution
of complex life than viruses changing DNA code.


What if you produced a virus, or collection of viruses, to do your terraforming for you? If RNA organisms are the target...

Viruses must've been changing lots of DNA
code prior to that, but Snowball Earth happened
only once (so far as we know).


We have tidal rhythmites dating back to 2.2 Gy, not that that helps, but there were a few periods of glaciation indicated there, when lunar recession was nearly stagnant (no tides = "Snowball Earth").

If such is drifting on the stellar wind,
being in a void as we are, could slow how
long it took to get here. Cooler stars
might be easier to let this stuff in...


What exactly are you referring to when you
say, "let this stuff in"? Are you talking
about cosmic rays, interstellar dust, etc.?


Panspermia. Something like "The Chase",
http://en.wikipedia.org/wiki/The_Cha..._Generation%29
.... only instead of implanting on a planet, simply pumped into intrastellar flows, like dandelion seeds.

David A. Smith
  #13  
Old August 15th 12, 05:59 AM posted to sci.astro
Yousuf Khan[_2_]
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Posts: 1,692
Default Suitable stars and the Drake Equation discussions

On 12/08/2012 5:32 AM, Mike Dworetsky wrote:
Yousuf Khan wrote:
On 09/08/2012 2:42 PM, dlzc wrote:
Was only ~2.2 billion years from the Theia encounter, that wiped out
whatever might have been on Earth before.


The Theia encounter (if it happened), would've happened only a few
hundred million years after formation, maybe let's say 4.5 billion
years ago. Pretty much right at the beginning of the formation, so
almost no difference.


The Late Heavy Bombardment era was around 3.8-4.1 billion years ago,
maybe this is what he meant. The Moon was heavily cratered, and
presumably so was the Earth, resetting the clock for evolution of life.
The LHB does have some criticisms that I won't go into, but the Theia
event almost certainly happened very early on and is the only viable
explanation so far for the existence of Earth's large Moon and the
similarities of lunar and terrestrial isotope signatures, for example.


Well, the Late Heavy Bombardment makes more sense as a late event that
happened after solar system formation. However 3.8-4.1 billion years ago
is still a far cry from 2.2 billion years ago. So I wonder what event
might have happened 2.2 bya, that he might have been thinking of?

Yousuf Khan
  #14  
Old August 15th 12, 03:26 PM posted to sci.astro
dlzc
external usenet poster
 
Posts: 1,426
Default Suitable stars and the Drake Equation discussions

Dear Yousuf Khan:

On Tuesday, August 14, 2012 9:59:18 PM UTC-7, Yousuf Khan wrote:
On 12/08/2012 5:32 AM, Mike Dworetsky wrote:

Yousuf Khan wrote:


On 09/08/2012 2:42 PM, dlzc wrote:


Was only ~2.2 billion years from the Theia
encounter, that wiped out whatever might
have been on Earth before.


The Theia encounter (if it happened),
would've happened only a few hundred million
years after formation, maybe let's say 4.5
billion years ago. Pretty much right at the
beginning of the formation, so almost no
difference.


The Late Heavy Bombardment era was around
3.8-4.1 billion years ago, maybe this is what
he meant. The Moon was heavily cratered, and
presumably so was the Earth, resetting the
clock for evolution of life.


The LHB does have some criticisms that I
won't go into, but the Theia event almost
certainly happened very early on and is the
only viable explanation so far for the
existence of Earth's large Moon and the
similarities of lunar and terrestrial isotope
signatures, for example.


Well, the Late Heavy Bombardment makes more
sense as a late event that happened after solar
system formation. However 3.8-4.1 billion years
ago is still a far cry from 2.2 billion years
ago. So I wonder what event might have happened
2.2 bya, that he might have been thinking of?


I mostly wasn't. Mike was giving me too much credit. At 2.2 Gy, the month was 16 days long. So the Moon had receded from "ten hours" period to 16 days in 2 Gy.

Imagine the tides... even the loft of the Earth's crust...

David A. Smith
  #15  
Old August 18th 12, 12:23 AM posted to sci.astro
Yousuf Khan[_2_]
external usenet poster
 
Posts: 1,692
Default Suitable stars and the Drake Equation discussions

On 14/08/2012 6:12 PM, dlzc wrote:
Dear Yousuf Khan:

On Tuesday, August 14, 2012 1:47:20 PM UTC-7, Yousuf Khan wrote:
On 11/08/2012 12:06 PM, dlzc wrote:
On Friday, August 10, 2012 6:56:22 PM UTC-7, Yousuf Khan wrote:


...


The first 3 billion years was wasted in
single-cell form. Complex life only started
about 600 million years ago, probably after
the last Snowball Earth. If other planets
undergo quicker transitions from single-cell
to complex life, then they could save upto
3 billion years.


That is probably when the first DNA "virus"
infected an RNA host cell. Corresponds
reasonably well with the formation of free
oxygen (at 500 million years).


The fact that complex life arose almost
simultaneously with the end of the Snowball
Earth period, I would say that the
environment had more to do with the evolution
of complex life than viruses changing DNA code.


What if you produced a virus, or collection of viruses, to do your terraforming for you? If RNA organisms are the target...


Well, now we're getting into science fiction. So what intelligence were
terraforming us? And who terraformed them? Actually sounds a bit like
the god debate: who created god?

Viruses must've been changing lots of DNA
code prior to that, but Snowball Earth happened
only once (so far as we know).


We have tidal rhythmites dating back to 2.2 Gy, not that that helps, but there were a few periods of glaciation indicated there, when lunar recession was nearly stagnant (no tides = "Snowball Earth").


How do these indicate periods of glaciation?

If such is drifting on the stellar wind,
being in a void as we are, could slow how
long it took to get here. Cooler stars
might be easier to let this stuff in...


What exactly are you referring to when you
say, "let this stuff in"? Are you talking
about cosmic rays, interstellar dust, etc.?


Panspermia. Something like "The Chase",
http://en.wikipedia.org/wiki/The_Cha..._Generation%29
... only instead of implanting on a planet, simply pumped into intrastellar flows, like dandelion seeds.


That's assuming that panspermia is just allowed to drift in randomly. If
we were terraformed, then it was probably aimed at us pretty precisely,
rifle-style, rather than shotgun-style. If rifled at us, I doubt a puny
little solar wind is going to stop the stuff from coming in.

Yousuf Khan
  #16  
Old August 18th 12, 11:42 PM posted to sci.astro
dlzc
external usenet poster
 
Posts: 1,426
Default Suitable stars and the Drake Equation discussions

Dear Yousuf Khan:

On Friday, August 17, 2012 4:23:08 PM UTC-7, Yousuf Khan wrote:
On 14/08/2012 6:12 PM, dlzc wrote:
On Tuesday, August 14, 2012 1:47:20 PM UTC-7, Yousuf Khan wrote:
On 11/08/2012 12:06 PM, dlzc wrote:
On Friday, August 10, 2012 6:56:22 PM UTC-7, Yousuf Khan wrote:


The first 3 billion years was wasted in
single-cell form. Complex life only started
about 600 million years ago, probably after
the last Snowball Earth. If other planets
undergo quicker transitions from single-cell
to complex life, then they could save upto
3 billion years.


That is probably when the first DNA "virus"
infected an RNA host cell. Corresponds
reasonably well with the formation of free
oxygen (at 500 million years).


The fact that complex life arose almost
simultaneously with the end of the Snowball
Earth period, I would say that the
environment had more to do with the evolution
of complex life than viruses changing DNA code.


What if you produced a virus, or collection
of viruses, to do your terraforming for you?
If RNA organisms are the target...


Well, now we're getting into science fiction.


What is writing an equation to predict the probability of civilizations on other planets, based on assumptions of flatlanders like us?

So what intelligence were terraforming us? And who
terraformed them?


I doubt they were interested in ending up with us, just with our biosphere.

Actually sounds a bit like the god debate: who
created god?

Viruses must've been changing lots of DNA
code prior to that, but Snowball Earth happened
only once (so far as we know).


We have tidal rhythmites dating back to 2.2 Gy,
not that that helps, but there were a few
periods of glaciation indicated there, when lunar
recession was nearly stagnant (no tides =
"Snowball Earth").


How do these indicate periods of glaciation?


Free surface water does not exist if we are a snowball. No free surface water means the tides are not large enough to accelerate the Moon to a higher orbit.

If such is drifting on the stellar wind,
being in a void as we are, could slow how
long it took to get here. Cooler stars
might be easier to let this stuff in...


What exactly are you referring to when you
say, "let this stuff in"? Are you talking
about cosmic rays, interstellar dust, etc.?


Panspermia. Something like "The Chase",
http://en.wikipedia.org/wiki/The_Cha..._Generation%29
... only instead of implanting on a planet
simply pumped into intrastellar flows, like
dandelion seeds.


That's assuming that panspermia is just allowed
to drift in randomly. If we were terraformed,
then it was probably aimed at us pretty precisely,
rifle-style, rather than shotgun-style. If rifled
at us, I doubt a puny little solar wind is going
to stop the stuff from coming in.


Would have to be to get past a stellar sheath once the inner system was swept clear, and planets had formed.

David A. Smith
  #17  
Old August 19th 12, 02:23 AM posted to sci.astro
Yousuf Khan[_2_]
external usenet poster
 
Posts: 1,692
Default Suitable stars and the Drake Equation discussions

On 18/08/2012 6:42 PM, dlzc wrote:
Dear Yousuf Khan:

On Friday, August 17, 2012 4:23:08 PM UTC-7, Yousuf Khan wrote:
On 14/08/2012 6:12 PM, dlzc wrote:
On Tuesday, August 14, 2012 1:47:20 PM UTC-7, Yousuf Khan wrote:
On 11/08/2012 12:06 PM, dlzc wrote:
That is probably when the first DNA "virus"
infected an RNA host cell. Corresponds
reasonably well with the formation of free
oxygen (at 500 million years).


The fact that complex life arose almost
simultaneously with the end of the Snowball
Earth period, I would say that the
environment had more to do with the evolution
of complex life than viruses changing DNA code.


What if you produced a virus, or collection
of viruses, to do your terraforming for you?
If RNA organisms are the target...


Well, now we're getting into science fiction.


What is writing an equation to predict the probability of civilizations on other planets, based on assumptions of flatlanders like us?


That's just stastical extrapolation, based on factors we are currently
aware. As we become aware of more factors, then those factors get
incorporated into the stats later too. At some point there will be
enough factors accounted for that the equation will be right.

So what intelligence were terraforming us? And who
terraformed them?


I doubt they were interested in ending up with us, just with our biosphere.


So where are they now? If they spent all of that time and effort
terraforming us, then why didn't they stick around or leave any
archaelogical indications of their existence?

Viruses must've been changing lots of DNA
code prior to that, but Snowball Earth happened
only once (so far as we know).


We have tidal rhythmites dating back to 2.2 Gy,
not that that helps, but there were a few
periods of glaciation indicated there, when lunar
recession was nearly stagnant (no tides =
"Snowball Earth").


How do these indicate periods of glaciation?


Free surface water does not exist if we are a snowball. No free surface water means the tides are not large enough to accelerate the Moon to a higher orbit.


Okay, but what are rhythmites?

If such is drifting on the stellar wind,
being in a void as we are, could slow how
long it took to get here. Cooler stars
might be easier to let this stuff in...


What exactly are you referring to when you
say, "let this stuff in"? Are you talking
about cosmic rays, interstellar dust, etc.?


Panspermia. Something like "The Chase",
http://en.wikipedia.org/wiki/The_Cha..._Generation%29
... only instead of implanting on a planet
simply pumped into intrastellar flows, like
dandelion seeds.


That's assuming that panspermia is just allowed
to drift in randomly. If we were terraformed,
then it was probably aimed at us pretty precisely,
rifle-style, rather than shotgun-style. If rifled
at us, I doubt a puny little solar wind is going
to stop the stuff from coming in.


Would have to be to get past a stellar sheath once the inner system was swept clear, and planets had formed.


You can always bring it in on spaceships, no worries about stellar winds
then.

Yousuf Khan
  #18  
Old August 19th 12, 05:14 PM posted to sci.astro
dlzc
external usenet poster
 
Posts: 1,426
Default Suitable stars and the Drake Equation discussions

Dear Yousuf Khan:

On Saturday, August 18, 2012 6:23:33 PM UTC-7, Yousuf Khan wrote:
On 18/08/2012 6:42 PM, dlzc wrote:
On Friday, August 17, 2012 4:23:08 PM UTC-7, Yousuf Khan wrote:
On 14/08/2012 6:12 PM, dlzc wrote:
On Tuesday, August 14, 2012 1:47:20 PM UTC-7, Yousuf Khan wrote:
On 11/08/2012 12:06 PM, dlzc wrote:

....
Well, now we're getting into science fiction.


What is writing an equation to predict
the probability of civilizations on other
planets, based on assumptions of
flatlanders like us?


That's just stastical extrapolation, based
on factors we are currently aware. As we
become aware of more factors, then those
factors get incorporated into the stats
later too. At some point there will be
enough factors accounted for that the
equation will be right.


So, you agree it is just science fiction, the way the masters do science fiction.

So what intelligence were terraforming
us? And who terraformed them?


I doubt they were interested in ending
up with us, just with our biosphere.


So where are they now?


Civilization dead and gone, on a exoplanet near us perhaps. But could easily be anywhere in the Milky Way.

If they spent all of that time and effort
terraforming us,


Its just launching a probe, a chemical release weapon.

then why didn't they stick around or leave any
archaelogical indications of their existence?


They probably did, on their planet. If some race were propagating this way, they did not have any better idea to get between stars than we do. For that matter a supernova might have simply done the "spraying" for them.

Viruses must've been changing lots of DNA
code prior to that, but Snowball Earth happened
only once (so far as we know).


We have tidal rhythmites dating back to 2.2 Gy,
not that that helps, but there were a few
periods of glaciation indicated there, when lunar
recession was nearly stagnant (no tides =
"Snowball Earth").


How do these indicate periods of glaciation?


Free surface water does not exist if we
are a snowball. No free surface water means
the tides are not large enough to accelerate
the Moon to a higher orbit.


Okay, but what are rhythmites?


I would have thought you'd at least look...
http://www.mantleplumes.org/WebDocum...derESR2004.pdf
http://www.colby.edu/geology/RAG_356...rEtAl_1995.pdf
http://geology.gsapubs.org/content/32/10/841.abstract

It is a fossil record of tidally-influenced sediment. A big enough piece gives us length of month, length of year, and the sediment itself gives us *when* it was produced. Get enough pieces from enough places, and you get a pretty thorough record.

....
That's assuming that panspermia is just allowed
to drift in randomly. If we were terraformed,
then it was probably aimed at us pretty precisely,
rifle-style, rather than shotgun-style. If rifled
at us, I doubt a puny little solar wind is going
to stop the stuff from coming in.


Would have to be to get past a stellar
sheath once the inner system was swept
clear, and planets had formed.


You can always bring it in on spaceships,
no worries about stellar winds then.


Not if you died because you traveled at 0.1c or higher (the protons look like radiation then), or if your "century ships" systems failed. Only an FTL drive could get "corporeal" terraformers here to leave traces.

David A. Smith
 




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