Q: Red giant heating effects on earth-like planets over time

James Nicoll wrote:
In article ,
Bill Bonde ( ``Soli Deo Gloria'' ) wrote:

I'm aware of this future state for the Sun and the Earth, but what I'm
trying to figure out is whether there could be a time when a planet was
habitable and then a transition period to inhabitable that was short
enough to make an interesting story. It doesn't have to be the Sun and
the Earth. It could be any hypothetical star and planet possible. See,
if it takes a few million years to go from really bright to unliveable,
there would be a lot of incentive to learn how to fly away in space
craft.


I seem to recall (but can't find an URL) that once the hypothetical
oceans of Venus exceeded the magic number of mumble degrees, the boil-off
occured fairly rapidly,

Due to runaway green house I believe:
http://csep10.phys.utk.edu/astr161/l...reenhouse.html
During my casual Googling I couldn't find any pages that guesstimate how
long the transformation takes.

I found a few pages that opined it could happen on earth (without help
from a sun turning into a red giant)



--
Hop David
http://clowder.net/hop/index.html

In article ,
Hop David wrote:


James Nicoll wrote:
In article ,
Bill Bonde ( ``Soli Deo Gloria'' ) wrote:

I'm aware of this future state for the Sun and the Earth, but what I'm
trying to figure out is whether there could be a time when a planet was
habitable and then a transition period to inhabitable that was short
enough to make an interesting story. It doesn't have to be the Sun and
the Earth. It could be any hypothetical star and planet possible. See,
if it takes a few million years to go from really bright to unliveable,
there would be a lot of incentive to learn how to fly away in space
craft.


I seem to recall (but can't find an URL) that once the hypothetical
oceans of Venus exceeded the magic number of mumble degrees, the boil-off
occured fairly rapidly,

Due to runaway green house I believe:
http://csep10.phys.utk.edu/astr161/l...reenhouse.html
During my casual Googling I couldn't find any pages that guesstimate how
long the transformation takes.

I found a few pages that opined it could happen on earth (without help
from a sun turning into a red giant)

Well, it's not like we have to rely on mere theory here. Googling
seems to indicate the Earth is not all that much below the boil'n'bake
point. How hard could it be to push it over, if we gave it a serious try?

James Nicoll

--
Take the piston rings out of my stomach, And the cylinders out of my brain
Extract from my liver the crankshaft, And assemble the engine again!

[from 'The Dying Aviator']

On Fri, 20 Aug 2004 14:07:54 -0700, "Bill Bonde ( ``Soli Deo Gloria'' )"
wrote:

I'm aware of this future state for the Sun and the Earth, but what I'm
trying to figure out is whether there could be a time when a planet was
habitable and then a transition period to inhabitable that was short

Oddly enough, there is a time when Earth will be both habitable AND inhabitable at the same time!

In article , Darren
Garrison wrote:

On Fri, 20 Aug 2004 14:07:54 -0700, "Bill Bonde ( ``Soli Deo Gloria'' )"

wrote:

I'm aware of this future state for the Sun and the Earth, but what I'm
trying to figure out is whether there could be a time when a planet was
habitable and then a transition period to inhabitable that was short

Oddly enough, there is a time when Earth will be both habitable AND
inhabitable at the same time!

Yes, a large part of it is determined by whether the oxygen content and
climate in various regions make the local forests and grasslands
flammable or inflammable.

--
David M. Palmer (formerly @clark.net, @ematic.com)

In article ,
James Nicoll wrote:
I seem to recall (but can't find an URL) that once the hypothetical
oceans of Venus exceeded the magic number of mumble degrees, the boil-off
occured fairly rapidly,
I found a few pages that opined it could happen on earth (without help
from a sun turning into a red giant)

Well, it's not like we have to rely on mere theory here. Googling
seems to indicate the Earth is not all that much below the boil'n'bake
point. How hard could it be to push it over, if we gave it a serious try?

Quite difficult, last I heard. A paper in Science a few years ago
reported simulation results showing that even if you gave Earth the same
amount of atmospheric CO2 that Venus has, the oceans would not boil. (The
resulting climate would not be pleasant even at the poles, but the oceans
would remain liquid.) Earth doesn't get quite enough sunlight for that.

The reason things happened quickly on Venus once boiling started, by the
way, is that water vapor is a greenhouse gas.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

In article ,
Henry Spencer wrote:
In article ,
James Nicoll wrote:
I seem to recall (but can't find an URL) that once the hypothetical
oceans of Venus exceeded the magic number of mumble degrees, the boil-off
occured fairly rapidly,
I found a few pages that opined it could happen on earth (without help
from a sun turning into a red giant)

Well, it's not like we have to rely on mere theory here. Googling
seems to indicate the Earth is not all that much below the boil'n'bake
point. How hard could it be to push it over, if we gave it a serious try?

Quite difficult, last I heard.

Bugger. I know we get about 1/3 less light than Venus did when it
went runaway greenhouse, but I was hoping we could make up for that.

A paper in Science a few years ago
reported simulation results showing that even if you gave Earth the same
amount of atmospheric CO2 that Venus has, the oceans would not boil. (The
resulting climate would not be pleasant even at the poles, but the oceans
would remain liquid.) Earth doesn't get quite enough sunlight for that.

Would there actually be much range in temperature? I'd have
thought a 90 bar atmosphere would be good at moving heat around.

The reason things happened quickly on Venus once boiling started, by the
way, is that water vapor is a greenhouse gas.

I knew that.
--
Take the piston rings out of my stomach, And the cylinders out of my brain
Extract from my liver the crankshaft, And assemble the engine again!

[from 'The Dying Aviator']

Dear James Nicoll:

"James Nicoll" wrote in message
...
In article ,
Henry Spencer wrote:
....
A paper in Science a few years ago
reported simulation results showing that even if you gave Earth the same
amount of atmospheric CO2 that Venus has, the oceans would not boil.
(The
resulting climate would not be pleasant even at the poles, but the
oceans
would remain liquid.) Earth doesn't get quite enough sunlight for that.

Would there actually be much range in temperature? I'd have
thought a 90 bar atmosphere would be good at moving heat around.

There are hot spots in turbines too. The problem will be if/when there is
no night side to radiate heat to... a "less bright side" won't cut it.

David A. Smith

In article 8I2Wc.3566$L94.1968@fed1read07,
N:dlzc D:aol T:com \(dlzc\) N: dlzc1 D:cox wrote:
Dear James Nicoll:

"James Nicoll" wrote in message
...
In article ,
Henry Spencer wrote:
...
A paper in Science a few years ago
reported simulation results showing that even if you gave Earth the same
amount of atmospheric CO2 that Venus has, the oceans would not boil.
(The
resulting climate would not be pleasant even at the poles, but the
oceans
would remain liquid.) Earth doesn't get quite enough sunlight for that.

Would there actually be much range in temperature? I'd have
thought a 90 bar atmosphere would be good at moving heat around.

There are hot spots in turbines too. The problem will be if/when there is
no night side to radiate heat to... a "less bright side" won't cut it.

Awkward, yes, but the example of Venus susggest even having
a nightside may not help. The planet is this far from being in a 1:1
year: day relationship, and yet the long nights don't seem to have
helped.

--
Take the piston rings out of my stomach, And the cylinders out of my brain
Extract from my liver the crankshaft, And assemble the engine again!

[from 'The Dying Aviator']

"Eric Chomko" wrote in message
...
Bill Bonde ( ``Soli Deo Gloria'' ) ) wrote:
: Can anyone answer the following query or point me in a direction where I
: might find relevant information?: What are the supposed red giant
: heating effects on earth-like planets over time? I'm specifically
: interested in transition points, times, where a planet might be liveable
: for humans and then not be.

Well as I understand it when the Sun becomes a Red Giant, it will swell in
size to be as big as Mars' orbit. So, terrestial planets will be engulfed.
But don't worry that won't happen for another several billion years.

Actually, this is something of a misperception. When the sun swells up,
it will also be rapidly losing mass. This, in turn, will cause the orbits
of
the planets to be pushed outward. The sun may swell up to the current
orbit of Earth, or perhaps even as far as Mars, but Mars, Earth, and
possibly even Venus may survive being engulfed.

Bruce

In article ,
James Nicoll wrote:
amount of atmospheric CO2 that Venus has, the oceans would not boil. (The
resulting climate would not be pleasant even at the poles, but...

Would there actually be much range in temperature? I'd have
thought a 90 bar atmosphere would be good at moving heat around.

I don't remember, now, whether the paper addressed the issue or just quoted
a planetary average temperature. I do remember that the temperature number
quoted was unpleasantly high. :-)
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |