averting doom
John McCarthy
WASHINGTON (UPI) -- Life on Earth as we know it will
come to an end in 1,500 million years and the planet will
look more like its dusty, volcanic sister Venus in 2,500
million years, scientists said Wednesday.
But mirrors or shades potentially could shield Earth
from increasing heat from the sun and delay the catastrophic
consequences, they said. A collision with a comet or other
major change in the atmosphere could speed up the end of
life.
Ken Caldeira and James Kasting of Pennsylvania State
University calculated the doomsday estimates using computer
models of temperature and atmosphere changes and projections
of the sun's increasing heat.
As the sun continues to brighten and warm over time,
the amount of carbon dioxide in the atmosphere drops --
eventually to a point too low for plants to survive, the
scientists said in the British journal Nature.
.
.
.
``After 2 1/2 billion years, all of Earth's water
would have been lost to space. That's a pretty strong
barrier to life,'' said Caldeira, an Earth systems
scientist.
Tyler Volk, an applied science professor at New York
University, suggested there may be ways to delay or prevent
the eventual demise of life.
``Our descendants or descendant species would not
have to run from the devolution...they could fight,'' said
Volk. ``Shades in space or mirrors on the Earth that keep
out a small fraction of the elevated future (heat from the
sun) would be an option.''
Other possible solutions include constructing closed
environments such as the Biosphere 2 project in Arizona, in
which cycling of carbon dioxide, water and other essential
matter would be controlled. Establishing controlled
Earth-like environments in space also could be considered,
Volk said.
(Is it really true that mainly doom-seekers become Earth systems
scientists, and mainly problem-solvers become applied science
professors?)
The most straightforward way to avoid the death of the earth from the
overheating predicted by Caldeira and Kasting is to move the earth
farther from the sun on whatever schedule seems appropriate to our
descendants.
Here's the best way to do it that I have been able to think of. It is
along the same line as what Thomas Clarke offhandedly suggested in a
reply to my original post. The present post contains only a
qualitative discussion with a few numbers taken from calculations I
made for a slightly different project - moving Mars closer to the sun
in order to improve its climate. I need to work on the formulas and
the numbers some more before giving them.
The method involves no new science and only predictable improvement
in present technology.
Our object is to transfer energy from the orbit of Venus to the
orbit of the earth so that Venus will move closer to the sun and
the earth farther away. Jupiter could also be used. Unfortunately,
it seems that the matter is a bit more complicated than this, because
the process must not only conserve energy, but it must also conserve
angular momentum of the earth and Venus about the sun. Maybe this
can be done at the cost of giving Venus a more eccentric orbit, but
maybe it requires a third planet. (This is analogous to processes
in atomic physics that require a third body in order to satisfy
all the conservation laws.)
The problem is to arrange for a coupling between the orbits of the
earth and Venus and possibly another planet as well.
Our tool for doing this is what I shall call a *tame asteroid*.
A tame asteroid is one that has repeated encounters with planets.
A small deflection of the asteroid's orbit before an encounter
is magnified by the encounter. The asteroid is always controlled
so that it never stops having encounters. The deflections
(delta-v s) are accomplished as many encounters in advance as the
noise in the system will permit.
[This process is analogous to the trajectory of the spacecraft
Galileo, but apparently the plan with Galileo is to give up the close
encounters when it enters the Jovian system. It JPL were to keep
control of it by a sequence of encounters, it could be returned to the
vicinity of the earth after spending sufficient time in the Jovian
system. I have no idea what use this might be.]
The asteroid, say Ceres, has repeated encounters with the earth
and Venus. It passes in front of the earth and behind Venus on
each encounter. Thus it adds energy to the earth's orbit and takes
it from Venus's orbit.
When I was thinking about moving Mars, I made some calculations
involving the masses of Ceres, Mars and Venus and the ratio between
the escape velocity from Mars and the delta-v s needed to move
Mars to the more salubrious distance of the earth's orbit.
I got a figure of at least 330 encounters taking at least about
two years each. This assumed that each encounter with Mars
transferred the maximum possible amount of energy. Therefore, the
computation is optimistic by some small factor, say 5.
Since the earth is 9 times as massive as Mars, about 9 times as
many encounters would be required. At least at first, the encounters
would take less time, because the earth and Venus are closer to the
sun.
The problem with conserving angular momentum is one I only encountered
recently, so I haven't figured out what additional encounters might
be needed.
Keeping a Tame Asteroid Tame
Ceres has a mass of 10^21 kilograms, so it would be important to
make its deflections as much in advance as possible. I assume that
the gravitational fields of the bodies involved will have been
measured accurately long before the project is attempted, i.e. the
high order harmonics of the gravitational potentials will be accurately
known. What I don't know is this: What is the largest source of noise, i.e.
unpredictable deflections, in the system? I speculate that it is
weather in the sun causing unpredictable fluctuations in the sun's
gravitational field. I don't know if this is right, and I hope someone
else can shed light on how large they are likely to be.
Taming Ceres
I confess I haven't yet computed how large a delta-v must be imparted
to Ceres to tame it. Making its orbit eccentric enough to cross that
of Mars would suffice, because it could be arranged to encounter Mars
in an appropriate way to tame it. Besides doing this with a single
delta-v, it would probably be cheaper to put Ceres into a suitable
resonance with Jupiter, so that Jupiter would do the work of making
the orbit of Ceres eccentric enough to tame it. I don't know how
to do this kind of computation.
The most straightforward way to impart a delta-v to Ceres is to install
a large number of nuclear reactors on it, and use the energy to expel
fragments of Ceres in a desired direction and at an appropriate velocity.
If maximal energy efficiency is wanted, i.e. to impart the maximum
momentum per unit of energy used, then the appropriate velocity is
a simple optimization problem, and it turns out to be sqrt(2) vec,
where vec is the escape velocity from Ceres. The actual velocity
with which the matter leaves the Ceres gravitational field is then
vec.
The number of reactors needed is large. A million reactors each
of 1000MWE, would give Ceres a delta-v of 1 km/sec in 1,000 years -
if I did the arithmetic correctly. If our descendants installed
one reactor every thousand years, they would install a million in
a billion years, and that is time enough to avert the prophesied
doom. A non-trivial fraction of the mass of Ceres would be consumed
if energy is optimized and if 1 km/sec is needed. Our descendants
might decide to use a higher exhaust velocity. More likely, it
will turn out that a considerably smaller delta-v will do with the
aid of Jupiter. Our descendants might decide to use a smaller
asteroid.
The Broken Kepler Approximation
The full computations required to determine all these trajectories
will be quite large (though within the capacity of present computers).
Moreover, the required information about the gravitational fields
won't be available for a long time. Here is an approximation that
can give a qualitative picture and an estimate of the time required
to move earth out a given distance or to move Mars in (a shorter time
project).
Make the following assumptions:
1. The planets and the asteroid are point masses.
2. The system is planar.
3. The planets have masses small compared to the that of the sun.
4. The asteroid has a mass small compared to that of any planet
involved.
5. The encounters between the asteroid and a planet are elastic
collisions of point masses. However, we assume that the possible
angles of the collisions are limited by the radii of the planets.
6. Any individual collision has a small effect on the trajectory
of the planet.
7. The asteroid departs from each collision with a velocity that
ensures a subsequent collision with the same or a different planet.
Making these assumptions leads to the following conclusions.
1. The trajectory of the asteroid is a sequence of segments of
Keplerian ellipses about the sun. That's why we call the above
set of assumptions the broken Kepler approximation.
2. The segments are separated by elastic collisions with the planets
conserving energy and momentum.
3. For each collision there is a discrete set of deflections that
ensure subsequent collisions. They form a sort of spectrum.
4. Computing the next collision does not require the solution of
differential equations. Instead one has transcendental equations
to solve analogous to Kepler's equation (the one used to compute
the position of a planet as a function of time). However, it
looks like the transcendental equation will involve two unknown
parameters instead of the one that appears in Kepler's equation.
It would be nice to have a program that would compute broken
Kepler trajectories and display them for our contemplation.
I hope I have convinced you that our distant descendants can
survive the warming up of the sun until it becomes an actual
nova.
By the way, it seems to me that if the above idea is sound, it settles
the question of the stability of the solar system - in the negative.
Very likely an asteroid could be tamed over a sufficiently long time
with as small an expenditure of delta-v as might be desired. Once
tamed it could be used with infinitesimal external force to expel a
planet from the system. This tells us that the current trajectory of
the solar system is arbitarily close to one in which a planet is
expelled. Of course, the probability that a planet actually would be
expelled by this mechanism in some particular finite time is extremely
low, because maintaining the required sequence of encounters requires
an improbable precision in the initial conditions. I suppose a lower
bound on the probability could be computed and from it an expected
upper bound on the gravitational lifetime of the solar system could be
obtained.
Criticism and comments are welcome. For a certain reason, I even
welcome comments, however uninformed, to the effect that the whole
idea is preposterous. I prefer such comments to be postings rather
than email.
What would be most welcome is a collaborator on a paper that could
be published in _Nature_.
--
John McCarthy, Computer Science Department, Stanford, CA 94305
*
He who refuses to do arithmetic is doomed to talk nonsense.
Andrew - Palfreyman
trying to shield it), but what the heck's all this "elastic
collisions" stuff? Surely you're not serious about the "broken
Kepler" business?
Instead, I'd use the "tame asteroid" in a resonant slingshot
configuration between (say) Mars and Earth, in order to bring
Mars "down" and Earth "up" the Sun's gravitational potential
well. Hell, use a string of 'em to speed things up.....
--------------------------------------------------------------------------
| lord snooty @the giant | Would You Like Space Potatoes With That? |
| poisoned electric head | andrew_-_...@cup.portal.com |
--------------------------------------------------------------------------
Len Evens
>from a U.P. story
[Some very interesting speculation about the possibility of moving the
planet to avoid the consequences over hundreds of millions of years
---the last estimate I saw in a news story was just under a billion---
of the gradual heating of the sun.]
>
>
>By the way, it seems to me that if the above idea is sound, it settles
>the question of the stability of the solar system - in the negative.
If you don't mind a quibble from a mathematician, the mathematical question
of stability refers to whether a dynamical system following Newton's
laws and which is an idealization of the solar system stays bounded
for all time (or some related question of this type). McCarthy's
speculation proposes the use of nuclear explosions to deflect an
asteroid. This takes us out of the realm of dynamics. If we depart
from that realm, it is perfectly obvious that the solar system is
not a stable system. For example, what is likely to happen if the
the sun goes nova?
>Very likely an asteroid could be tamed over a sufficiently long time
>with as small an expenditure of delta-v as might be desired. Once
>tamed it could be used with infinitesimal external force to expel a
>planet from the system. This tells us that the current trajectory of
>the solar system is arbitarily close to one in which a planet is
>expelled. Of course, the probability that a planet actually would be
You would need a whole lot more mathematics than the rough estimates
made in McCarthy's exposition to establish this. I suspect the
clever people studying celestial mechanics have looked into
all the obvious small perturbations of this kind long ago, but
perhaps not. I will ask my local expert.
>expelled by this mechanism in some particular finite time is extremely
>low, because maintaining the required sequence of encounters requires
>an improbable precision in the initial conditions. I suppose a lower
>bound on the probability could be computed and from it an expected
>upper bound on the gravitational lifetime of the solar system could be
>obtained.
>
>Criticism and comments are welcome. For a certain reason, I even
>welcome comments, however uninformed, to the effect that the whole
>idea is preposterous. I prefer such comments to be postings rather
>than email.
>
It seems to me that this type of speculation takes us a bit beyond
science but perhaps not inexcusably. Those interested in the earth's
history, particularly future history, certainly can't propose experiments
or observations which will directly confirm such predictions over
what is often called deep time. McCarthy's point is basically that
the existence of intelligence may have profound effects. This point has
been made before. For example, Dyson proposed that advanced civilizations
might move all the mass in a star system into a sphere surrounding
the star thus capturing all its radiation and living on the inside
of the sphere. As Steven Jay Gould has pointed out, this may be
a limited perspective. We tend to think of evolution as an upward
process leading to us where it more or less stops. In fact, it is quite
possible that intelligence is an evolutionary side show which will shortly
disappear. There may be no ancestors around to engage in planetary
engineering when the time comes.
>What would be most welcome is a collaborator on a paper that could
>be published in _Nature_.
>--
>John McCarthy, Computer Science Department, Stanford, CA 94305
>*
>He who refuses to do arithmetic is doomed to talk nonsense.
>
I think the analysis needs a lot more mathematics than arithmetic.
Unforutnately, I don't know enough of the right kind to help, but
I will pass this idea on to my colleagues who do.
Leonard Evens l...@math.nwu.edu 708-491-5537
Dept. of Mathematics, Northwestern Univ., Evanston, IL 60208
Robert Frederking
theory and large computers to see whether the solar system is stable.
Their finding (I forget who it was now) was that millimeter
perturbations in the orbits of the planets do cause chaotic changes in
the long run. The good news (for people who don't like chaotic
orbits) is that the amount of time it takes for something ``really
bad'' to become probable is on the order of a trillion years [i.e.,
longer than the solar system will exist in its present form anyway].
``Really bad'' is for a planet to be ejected, a collission, etc.
Thomas Clarke
> By the way, it seems to me that if the above idea is sound, it settles
> the question of the stability of the solar system - in the negative.
> Very likely an asteroid could be tamed over a sufficiently long time
> with as small an expenditure of delta-v as might be desired. Once
> tamed it could be used with infinitesimal external force to expel a
> planet from the system. This tells us that the current trajectory of
> the solar system is arbitarily close to one in which a planet is
> expelled. Of course, the probability that a planet actually would be
> expelled by this mechanism in some particular finite time is extremely
> low, because maintaining the required sequence of encounters requires
> an improbable precision in the initial conditions. I suppose a lower
> bound on the probability could be computed and from it an expected
> upper bound on the gravitational lifetime of the solar system could be
> obtained.
Hurray! My Douglas Adamsian speculations were not totally hougwash :-)
More seriously, In the most recent Sci Am or Sky and Telescope
(I was reading both last night and get confused) there is piece about
work by the group at MIT with the special purspose celestial
mechanical computer (sorry for vagueness, but mags are at home)
concerning chaotic dynamics in the solar system. The original work
is reported in a July issue of Science, but I missed the original.
The upshot is they simulated the solar system's dynamics for some 100
million years and made several runs after slightly (1 millimeter !)
perturbing the position of each planet. The article showed a graph
of the expeonential (hence chaotic) divergence in the position of
Pluto for the 1 mm perturbation in Venus's position. After 100 myear
Plutos position had changed by quite some million miles.
Hey, maybe Pluto would be better than Ceres. Kick a periodic comet
so it ricochets of Pluto. Pluto Ricochets off Neptune, then off Jupiter
and into the inner solar system where it becomes tame!
--
Thomas Clarke
Institute for Simulation and Training, University of Central FL
12424 Research Parkway, Suite 300, Orlando, FL 32826
(407)658-5030, FAX: (407)658-5059, cla...@acme.ucf.edu
Thomas Clarke
Path: cs.ucf.edu!news
From: cla...@acme.ucf.edu (Thomas Clarke)
Subject: Re: averting doom
Message-ID: <1992Dec30.1...@cs.ucf.edu>
Sender: ne...@cs.ucf.edu (News system)
Organization: University of Central Florida
References: <1992Dec30.1...@cs.ucf.edu>
Date: Wed, 30 Dec 1992 19:41:39 GMT
In article <1992Dec30.1...@cs.ucf.edu> cla...@acme.ucf.edu (Thomas
Clarke) writes:
> In article <JMC.92De...@SAIL.Stanford.EDU> j...@SAIL.Stanford.EDU (John
> McCarthy) writes:
> > By the way, it seems to me that if the above idea is sound, it settles
> > the question of the stability of the solar system - in the negative.
> ... In the most recent Sci Am or Sky and Telescope
It was Sky and Telescope Feb '93 ppp 13-14.
I remembered wrong. A one millimeter perturbation of Mars' orbit
eventually caused a 500,000 kilometer difference in the position of
Pluto after 100 million years.
Gerald Sussman and Jack Wisdom used the Supercomputer Toolkit at MIT
to simulate the solar system.
>Hey, maybe Pluto would be better than Ceres. Kick a periodic comet
>so it ricochets of Pluto. Pluto Ricochets off Neptune, then off Jupiter
>and into the inner solar system where it becomes tame!
A further thought: sprinkle carbon black on the right part of the
comet and its natural outgassing will be modified. Done properely
in an orbit or two the comet will ricochet of Jupiter then into
Pluto and away we go.
This is a mission we could fly now!! A few hundred pounds of carbon
black in a comet fly by! I wonder is the MIT computer is up to
predicting comet outgassing :-)
Henry Spencer
>I like the simplicity of this idea (moving the Earth instead of
>trying to shield it), but what the heck's all this "elastic
>Instead, I'd use the "tame asteroid" in a resonant slingshot
That's what he's proposing. It turns out that gravity-assist maneuvers,
viewed from a distance, have exactly the behavior of elastic collisions
and can be analyzed as such.
--
"God willing... we shall return." | Henry Spencer @ U of Toronto Zoology
-Gene Cernan, the Moon, Dec 1972 | he...@zoo.toronto.edu utzoo!henry
Marvin Minsky
>Newsgroups: sci.astro
>Path: cs.ucf.edu!news
>From: cla...@acme.ucf.edu (Thomas Clarke)
>Subject: Re: averting doom
>Message-ID: <1992Dec30.1...@cs.ucf.edu>
>Sender: ne...@cs.ucf.edu (News system)
>Organization: University of Central Florida
>References: <1992Dec30.1...@cs.ucf.edu>
>Date: Wed, 30 Dec 1992 19:41:39 GMT
>
>In article <1992Dec30.1...@cs.ucf.edu> cla...@acme.ucf.edu (Thomas
>Clarke) writes:
>> In article <JMC.92De...@SAIL.Stanford.EDU> j...@SAIL.Stanford.EDU (John
>> McCarthy) writes:
>> > By the way, it seems to me that if the above idea is sound, it settles
>> > the question of the stability of the solar system - in the negative.
>> ... In the most recent Sci Am or Sky and Telescope
>
>It was Sky and Telescope Feb '93 ppp 13-14.
>I remembered wrong. A one millimeter perturbation of Mars' orbit
>eventually caused a 500,000 kilometer difference in the position of
>Pluto after 100 million years.
>
>Gerald Sussman and Jack Wisdom used the Supercomputer Toolkit at MIT
>to simulate the solar system.
McCarthy has been discussing the tame-asteroid proposal with Sussman
et al.
.
Dave Michelson
>trying to shield it), but what the heck's all this "elastic
>collisions" stuff? Surely you're not serious about the "broken
>Kepler" business?
>
approximation. Please correct me if I've misinterpreted this...
--
Dave Michelson
da...@ee.ubc.ca
Lamont Granquist
radius of the Sun would be quite a bit over one AU after it hits the
giant branch. If correct, I don't see how mirrors would help us out. Also,
according to the ASTR class, the Sun isn't going to explode -- it won't be
hot enough to fuse silicon, and instead it will shed it outer envelope and
turn into a white dwarf.
--
Lamont Granquist lam...@u.washington.edu
"When dogma enters the brain, all intellectual activity ceases."
-- Robert Anton Wilson
James Davis Nicoll
>Hmmmm... In my ASTR class, we did a rough calculation that showed that the
>radius of the Sun would be quite a bit over one AU after it hits the
>giant branch. If correct, I don't see how mirrors would help us out. Also,
>according to the ASTR class, the Sun isn't going to explode -- it won't be
>hot enough to fuse silicon, and instead it will shed it outer envelope and
>turn into a white dwarf.
Hmmm. Anyone know how long it takes a planet orbiting in the
outer fringes of a red giant to evaporate. Granted, red giants are
toasty (By Canadian standards), but wouldn't the plasma at 1 AU
be pretty thin? How fast would heat/momentum be transfered?
James Nicoll
ga...@stsci.edu
I mistakenly wrote:
> with an effective temperature of 4000 K and a luminosity of 10,000 K, then
^^^^^^^^^^^^^^^^^^^^^^
Which should have been "luminosity of 10,000 L(sun)". Luminosity is not
measured in Kelvins.
-Bill Gawne, Space Telescope Science Institute
Jay Scott
>By the way, it seems to me that if the above idea is sound, it settles
>the question of the stability of the solar system - in the negative.
>Very likely an asteroid could be tamed over a sufficiently long time
>with as small an expenditure of delta-v as might be desired. Once
>tamed it could be used with infinitesimal external force to expel a
>planet from the system. This tells us that the current trajectory of
>the solar system is arbitarily close to one in which a planet is
>expelled. Of course, the probability that a planet actually would be
>expelled by this mechanism in some particular finite time is extremely
>low, because maintaining the required sequence of encounters requires
>an improbable precision in the initial conditions. I suppose a lower
>bound on the probability could be computed and from it an expected
>upper bound on the gravitational lifetime of the solar system could be
>obtained.
Without being so rash as to do any actual calculations, I
would guess that this does not say much about the stability
question. I would guess that an asteriod is so much more likely
to be ejected from the solar system, or smashed to dust by
collisions, or fall into a planet, than to be captured into
a destructive resonant orbit that the asteriods will all be gone
before they destabilize the solar system.
I guess that light pressure effects or gravitational radiation
are more likely limiting factors. But don't listen to me, I don't
even know which one is bigger for planets (light pressure effects
are bigger for small objects).
Jay Scott
sc...@cs.uiuc.edu
Herman Rubin
>John McCarthy writes:
>>By the way, it seems to me that if the above idea is sound, it settles
>>the question of the stability of the solar system - in the negative.
.......................
>Without being so rash as to do any actual calculations, I
>would guess that this does not say much about the stability
>question. I would guess that an asteriod is so much more likely
>to be ejected from the solar system, or smashed to dust by
>collisions, or fall into a planet, than to be captured into
>a destructive resonant orbit that the asteriods will all be gone
>before they destabilize the solar system.
From the standpoint of stability as precisely defined in the theory
of dynamical systems, a gravitational system is not stable; the effects
of a perturbation do not die out. It is, for example, quite possible
that one of our space probes could alter the orbit of an asteroid so
that the gravitational attraction of another asteroid could cause it
to get a gravity boost from Jupiter which knocks it out of the solar
systme. Even more so, a change of one micron/second in the earth's
speed will eventually have a non-trivial effect on the paths of
Venus and Mars. I have not made any attempt to calculate how long
this will take.
--
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399
Phone: (317)494-6054
hru...@snap.stat.purdue.edu (Internet, bitnet)
{purdue,pur-ee}!snap.stat!hrubin(UUCP)
Len Evens
> In article <JMC.92De...@SAIL.Stanford.EDU> j...@cs.Stanford.EDU writes:
> >
> > WASHINGTON (UPI) -- Life on Earth as we know it will
> > come to an end in 1,500 million years and the planet will
> > look more like its dusty, volcanic sister Venus in 2,500
> > million years, scientists said Wednesday.
>
> climate prediction in 50 years, who would have any confidence in this
> speculation?
--
1> This has nothing to do with modelling weather. The difficulty
in weather prediction is that the kinds of dynamical systems being
modelled are too sensitive to small changes in initial conditions
for the models to be accurate over long periods of time.
2> Climate models are in fact much more accurate than weather
models. This is because they are concerned with average phenomena
and averages have much greater stability and predicitability.
Differences about climate models' prediction of global warming by
those who have studied such things are of the order of magnitude
of whether warming will be a bit over 1 degree C or two
or three times as high and whether it will take 50 years or 100
years. There is a very substantial amount agreement.
This fact has been obscured by the intense ideological
disputes over the issue.
3> The predictions of the ultimate history of the earth are based
on models of stars which are really fairly simple. If the
sun warms up, it is probably not too far out to suggest possible
physical responses here on earth over long periods of time. This
doesn't even require computer models. Of course, none of this
can be certain, but remember that we are
talking about periods of hundreds of millions of years. The
estimate of 1.5 billion is the largest I have seen. The most
recent news article that I saw suggested that a previous estimate
of 100 million years was too low and that it might be more like
900 million years. Clearly this analysis is all fairly new
and the arguments will be subject to intense scrutiny. However,
I don't see why a consensus couldn't develop on the
matter among geophysicists. This should be just a reliable and
scientific as beliefs now held about the early universe or other
events in deep space or deep time.
4> Except as interesting speculation, why should anyone care?
Remember that the real (plentiful) fossil record on earth is only about
500 million years old. Surely no one should worry seriously about
what sort of actions humanity should take to deal with such a problem.
Unfortunately, this may confuse people about the issue of global
warming which is something which may radically affect human societies
in the next several generations and which we may be able to do
something about.
Andrew Poutiatine
>In article <JMC.92De...@SAIL.Stanford.EDU> j...@cs.Stanford.EDU writes:
>>
>> WASHINGTON (UPI) -- Life on Earth as we know it will
>> come to an end in 1,500 million years and the planet will
>> look more like its dusty, volcanic sister Venus in 2,500
>> million years, scientists said Wednesday.
>
>climate prediction in 50 years, who would have any confidence in this
>speculation?
I believe the above prediction is based not on earth climate and weather
considerations (for which I must agree predictions of more than a few days
are not very dependable), but rather on the evolution of the sun.
I am not an astronomer, but as I recall, theory predicts that stars of our
sun's size go through a stage in their evolution at the end of their lives
when they become hotter and expand. It is this, I believe, that would
parch the earth, killing life "as we know it."
-AIP
ga...@stsci.edu
u10...@beta.lanl.gov (Andrew Poutiatine) writes:
Our understanding of the Sun is that it won't be at "the end of its life" for
another 4.5 or so *billion* years. The news article refers to predictions of
things to come in 1.5 to 2.5 billion years, when the Sun should still be a main
sequence star.
Any star will change slowly during its main sequence lifetime, and in the case
of the Sun and sunlike stars this means becoming slightly hotter and more
luminous. The prediction quoted above seems to be saying that this part
of the Sun's main sequence evolution will be sufficient to raise Earth's
temperature to the point Earth becomes unable to support life. While I've
no wish to dispute this claim (for now), it has nothing to do with the Sun's
predicted evolution into a red giant star after it leaves the main sequence
"at the end of its life".
Andrew Poutiatine
the sun would become a red giant by this point, only that it would become
hotter and grow, and the point I made was only that earth's drying up would
be due to our sun's evolution, not to long range terrestrial climate change,
although the former obviously causes the latter.
I said nothing about "the sun's predicted evolution into a red giant," that
was you. As I understand it, the earth is about 5 billion years old or
so, and if we assume the sun was born about the same time as the earth, then
I am calling "the end of it's (the sun's) life " to be 79% of its life
span. If you wish to define "the end of it's life" differently, go right
ahead, just don't argue semantics under the guise of astronomy.
Please take a moment to reread my post, it is above. I think upon more
careful examination you will see that you have simply (and in more detail
no less) restated my point.
-AIP, LANL
John McCarthy
4> Except as interesting speculation, why should anyone
care? Remember that the real (plentiful) fossil record on
earth is only about 500 million years old. Surely no one
should worry seriously about what sort of actions humanity
should take to deal with such a problem. Unfortunately,
this may confuse people about the issue of global warming
which is something which may radically affect human
societies in the next several generations and which we may
be able to do something about.
No comment except the above adverb.
Craig Powderkeg DeForest
> WASHINGTON (UPI) -- Life on Earth as we know it will
> come to an end in 1,500 million years and the planet will
> look more like its dusty, volcanic sister Venus in 2,500
> million years, scientists said Wednesday.
Not too likely, on a planet with over five billion potential planetary civil
engineers and over 10^9 years to think of a solution!
--
DON'T DRINK SOAP! DILUTE DILUTE! OK!
William VanHorne
>Do you seriously believe that a species capable of creating
>and enjoying The Love Boat is capable also of learning
>galactic engineering?
>
Son, if there's a buck to made doing it, It Will Be Done.
Amen.
---Bill VanHorne
-------------------------------------------------------------------------------
"And when the world is overcharged with inhabitants, the last remedy is Warre;
which provideth for every man, by Victory or Death" - Thomas Hobbes "Leviathan"
-------------------------------------------------------------------------------
Benjamin Weiner
>>> WASHINGTON (UPI) -- Life on Earth as we know it will
>>> come to an end in 1,500 million years ...
>Do you seriously believe that a species capable of creating
>and enjoying The Love Boat is capable also of learning
>galactic engineering?
A better question in my opinion is whether a species capable of
creating and enjoying The Love Boat *should* be saved from doom.
Blair P. Houghton
>In article <1iidds...@chnews.intel.com> bhou...@sedona.intel.com (Blair P. Houghton) writes:
>>Do you seriously believe that a species capable of creating
>>and enjoying The Love Boat is capable also of learning
>>galactic engineering?
>
>Son, if there's a buck to made doing it, It Will Be Done.
>Amen.
Exactly the reason we'll all die as cinders wearing Ronco's
Amazing New All-Polyester/Mylar Anti-Sol Suits with
Magnesium Chloride Eyeholes and Plastic Fan.
--Blair
"Hey, Doc, I picked up this
rash on my thighs from the
guest-host in the last episode;
you wanna take a look at it?"
Patricia C. Vener-Saavedra
about twice the luminosity it presently has. The average surface of
Earth will be about 100 degrees C. Some lakes and rivers will have
begun to boil. It will not be pleasant for homo sapiens.:-)
PCVS
--
*********************************************************************
ve...@stsci.edu | "I'm not bad, I'm just drawn this way."
| -- Jessica Rabbit
*********************************************************************
Nobody of Importance
]Hi there. As I recall, in about a billion years the sun will have
]about twice the luminosity it presently has. The average surface of
]Earth will be about 100 degrees C. Some lakes and rivers will have
]begun to boil. It will not be pleasant for homo sapiens.:-)
Who cares? By that time homo sapiens will be either:
a)extinct
or b)spread amongst the stars
OR c)fireproof ;)
]PCVS
Hit 'n' now to avoid an obnoxious sig thingie.
Subject: Patrick Chester |Words to live by:
Age: NOYB |"Military action is important to the
Address: A place |nation--it is the ground of death and
Email:wol...@ccwf.cc.utexas.edu |life, the path of survival and destruction
Political Views: Somewhere in orbit |so it is important to examine it."
Blackmarks: Politically Incorrect |Famous Last Words:
(hobbies) Anime Otaku/Trekker |--If you cut me down, I will only become
Technophile |more powerful...
Netrekker (claypigeon) |--Shhh!! There it is again....
Recommendation: Ignore |--Use the bazooka to open the door...
(not worth shoot-on-sight orders)|--I cut the red wire...
--
<***** INSERT LAWSUIT DEFLECTION TEXT*****>
I speak (type actually) for myself only. Even if I did decide to
speak for UT, no one would listen.
Flame away, I don't bleedin' care...
Tino
>about twice the luminosity it presently has. The average surface of
>Earth will be about 100 degrees C. Some lakes and rivers will have
>begun to boil. It will not be pleasant for homo sapiens.:-)
Don't Panic.
Tino
--
"Here are the young men, the weight on their shoulders..." - J.D.
----------------------------------------------------------------------------
Purdue University School of Nuclear Engineering
----------------------------------------------------------------------------
Marvin Minsky
>In article <1993Jan13.2...@stsci.edu> ve...@stsci.edu (Patricia C. Vener-Saavedra) writes:
>>Hi there. As I recall, in about a billion years the sun will have
>>about twice the luminosity it presently has. The average surface of
>>Earth will be about 100 degrees C. Some lakes and rivers will have
>>begun to boil. It will not be pleasant for homo sapiens.:-)
polymers of zirconium phosphide or something adequately thermophilic.
That is, unless the Rifkins succeed in outlawing evolutionary
engineering.
.
John C. Baez
>about twice the luminosity it presently has. The average surface of
>Earth will be about 100 degrees C. Some lakes and rivers will have
>begun to boil. It will not be pleasant for homo sapiens.:-)
Luckily homo sapiens will be not around by then. Even in terms of
biological evolution, a billion years is a long time. With
cultural-technological evolution, it's a *really* long time.
Mark Wilson
|Hi there. As I recall, in about a billion years the sun will have
|about twice the luminosity it presently has. The average surface of
|Earth will be about 100 degrees C. Some lakes and rivers will have
|begun to boil. It will not be pleasant for homo sapiens.:-)
Now this is what I call long range planning.
--
Mob rule isn't any prettier merely because the mob calls itself a government
It ain't charity if you are using someone else's money.
Wilson's theory of relativity: If you go back far enough, we're all related.
Mark....@AtlantaGA.NCR.com
Joshua Bell
>Hi there. As I recall, in about a billion years the sun will have
>about twice the luminosity it presently has. The average surface of
>Earth will be about 100 degrees C. Some lakes and rivers will have
>begun to boil. It will not be pleasant for homo sapiens.:-)
I would say that if Homo sapiens is still on Earth in a billion
years, it deserves it. :)
Joshua
| A shimmering net undulating like an infinite borealis. |
| - Chapterhouse: Dune |
| |
| jsb...@acs.ucalgary.ca Academic Computing Services, University of Calgary |
Nobody of Importance
]In article <1993Jan13.2...@stsci.edu> ve...@stsci.edu (Patricia C. Vener-Saavedra) writes:
]>Hi there. As I recall, in about a billion years the sun will have
]>about twice the luminosity it presently has. The average surface of
]>Earth will be about 100 degrees C. Some lakes and rivers will have
]>begun to boil. It will not be pleasant for homo sapiens.:-)
]
]I would say that if Homo sapiens is still on Earth in a billion
]years, it deserves it. :)
Finally! A kindred spirit. Besides, 1 billion years is a bit far down
the road anyway. I wouldn't worry about that quite yet anyway. I'd
worry more about getting large groups of humanity offplanet before
people like McGowen realize it is a "technocratic" solution. ;*)
]Joshua
]| A shimmering net undulating like an infinite borealis. |
]| - Chapterhouse: Dune |
]| |
]| jsb...@acs.ucalgary.ca Academic Computing Services, University of Calgary |
Hit 'n' now to avoid an obnoxious sig thingie.
Subject: Patrick Chester |Words to live by:
Age: NOYB |"Military action is important to the
Address: A place |nation--it is the ground of death and
Email:wol...@ccwf.cc.utexas.edu |life, the path of survival and destruction
Political Views: Somewhere in orbit |so it is important to examine it."
Blackmarks: Politically Incorrect |Famous Last Words:
(hobbies) Anime Otaku/Trekker |--If you cut me down, I will only become
Technocentric |more powerful...
Netrekker (claypigeon) |--Shhh!! There it is again....
Whole bunch of -isms |--Use the bazooka to open the door...
David E. Brahm
> about twice the luminosity it presently has. The average surface of
> Earth will be about 100 degrees C. Some lakes and rivers will have
> begun to boil. It will not be pleasant for homo sapiens.:-)
Don't worry; I hear Clinton has a plan...
--
Staccato signals of constant information, | David Brahm, physicist
A loose affiliation of millionaires and | (br...@cco.caltech.edu)
billionaires and Baby ... |---- Carpe Post Meridiem! --
These are the days of miracle and wonder, | Disclaimer: I only speak
And don't cry, Baby, don't cry, don't cry. | for the sensible folks.