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asteroid almost hits earth

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Don Coolidge

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Apr 24, 1989, 8:30:30 PM4/24/89
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>> ... This means that a *LARGE* (dinosaur killer) asteroid is not
>> likely to hit the Earth soon, and a meteor-crater-sized asteroid isn't likely
>> in our lifetimes.


> Nostradamus predicted an asteroid to hit the earth on May 7 1999 .

Aarrgghhh.

Neglecting for the moment that Nostradamus had never even _heard_ of
asteroids, didn't know that such objects existed, and therefore
couldn't possibly have predicted that one would hit the earth...no,
let's _not_ neglect it. That's really the point, after all.

The name of this talk group is sci.astro. That's "sci", as in "science".

Please take your Nostradamus postings somewhere else where they might
be appropriate (I almost said "relevant"). Jumbled, vague ramblings that
are so non-specific as to permit almost any possible interpretation
(yes, I have read Nostradamus) aren't science. Nor are they interesting.
And they don't belong here.

Don Coolidge

Robert Dinse

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Apr 27, 1989, 9:18:10 PM4/27/89
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> Nostradamus predicted an asteroid to hit the earth on May 7 1999 .

Please, get an english translation (or whatever language you happen
to speak semi-fluently) and read a straight translation of Nostradamus's
Quatrains.
I've seen wonderful television shows depicting a "prediction" in
which Nostradamus supposedly predicted the destruction of N.Y. by
nuclear weapons, also coincidentally in 1999.
After reading an english word-for-word (or as close as you can get)
translation, I've come to the conclusion that the folks that did the tv
show must have been doing some serious hallucinogens, and I would come
to a similiar conclusion in regards to your source.

George Regnery

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Apr 28, 1989, 10:37:50 AM4/28/89
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Do all of the people who think the Apocalypse will come before the millenium
realize that the millenium is really going to come sometime in 1996?
Well, if you are talking about the millenium of Jesus' birth anyway...
Historical records show that he was born in the year 749 AUC (Ab Urbe Condita,
or Anno Urbis Conditae, take your pick, The mean from the founding of the
City [Rome], and from the city having been founded respectively). Rome was
"founded" in 753 BC, based on the current calendar system.
Bet it will sure be a surprise to those people when Zippy the pinhead's
correction is correct- but due to his miscalculations the even will come on
December 25, 1994!


--
George M. Regnery ! Worcester ! "I function as a channel through
reg...@wpi.wpi.edu OR ! Polytechnic ! which music emerges from the chaos
reg...@wpi.bitnet ! Institute ! of noise." --Vangelis (composer of
CompuServe: 73300,3655 ! (Worc, Mass.) ! Albedo 0.39 and Chariots of Fire)

Timothy D Margeson

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Apr 28, 1989, 12:44:10 PM4/28/89
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In article <320...@hpindda.HP.COM> d...@hpindda.HP.COM (Don Coolidge) writes:
>> Nostradamus predicted an asteroid to hit the earth on May 7 1999 .
>Aarrgghhh.
>Neglecting for the moment that Nostradamus had never even _heard_ of
>asteroids, didn't know that such objects existed, and therefore
>couldn't possibly have predicted that one would hit the earth...no,
>Don Coolidge

Hi,

Let's not forget that Nostradamus was a seer and could foretell the future,
therefore the fact he could see that asteroids did exist long before we of
our time _discovered_ them.


Sure this belongs in other news groups, but hey, we need some humor in our
lives on occasion, after all, we're not all stiffs |-)


But how did they get 'efgdsj tuij sdfhs' to mean 'The year of the horse'?

--
Tim Margeson (206)253-5240
PO Box 3500 d/s C1-022 @@ 'Who said that?'
Vancouver, WA. 98668
e-mail replies to: timo...@tekigm2.UUCP or timo...@tekigm2.TEK.COM

William G. Hutchison

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May 1, 1989, 9:17:57 AM5/1/89
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In article <12...@ut-emx.UUCP>, et...@ut-emx.UUCP (Ethan Tecumseh Vishniac) writes:

> In article <12...@swan.ulowell.edu>, rgia...@hawk.ulowell.edu (Roy Giacchino) writes:
> >
> > Nostradamus predicted an asteroid to hit the earth on May 7 1999 .
> >
>

I am not convinced that Nostradamus did in fact predict this. Would you please
quote the specific "prophecy". Most writings by Nostradamus are so vague that
they cannot be interpreted until _after_ the event. Most of these
interpretations are garbage anyway: it would be more accurate to refer to them
as rationalizations.

A prediction with no predictive value is not a prediction at all!

--
Bill Hutchison, DP Consultant rutgers!cbmvax!burdvax!ubbpc!wgh
Unisys UNIX Portation Center
P.O. Box 500, M.S. B121 Jacobites unite: Scotland Free in '93!!
Blue Bell, PA 19424

Dani Eder

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May 3, 1989, 2:36:13 PM5/3/89
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If an asteroid misses the Earth by 500,000 km, that is about 80 Earth
radii. Let us comapre this to more familiar events and see how this
compares. The mean radius of a car is about 2 meters. 80 times 2
meters is 160 meters (525 feet.). If a car crosses a 4 way intersection
while you are that far away, do you call it a near miss? I think not.
The collision cross section of an irplane is 20 meters in the horizontal
radius and 4 meters in the vertical direction. A crossing at 1600
meters horizontal separation (1 mile) is hardly a near hit, as is
320 meters (1000 feet) in the vertical direction.

Another way to think about the event is to consider that the Earth
fills 1/6400 of the area of a circle with the miss distance above
as a radius. Thus we should expect an impact every 6400*(frquency
this size asteroid comes near earth) years. If such an asteroid
comes by once every year, we have a long time before we should
expect to get hit.


--
Dani Eder / Boeing / Space Station Program / uw-beaver!ssc-vax!eder
(205)464-4150(w) (205)461-7801(h) 1075 Dockside Drive #905 Huntsville,
AL 35824 34 40 N latitude 86 40 W longitude +100m altitude, Earth

Mike Ekberg, Sun {GPD-LEGO}

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May 4, 1989, 3:13:52 PM5/4/89
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In article <26...@ssc-vax.UUCP> ed...@ssc-vax.UUCP (Dani Eder) writes:
>
>If an asteroid misses the Earth by 500,000 km, that is about 80 Earth
>radii. Let us comapre this to more familiar events and see how this
>compares. The mean radius of a car is about 2 meters. 80 times 2
>meters is 160 meters (525 feet.). If a car crosses a 4 way intersection
>while you are that far away, do you call it a near miss? I think not.
>The collision cross section of an irplane is 20 meters in the horizontal
>radius and 4 meters in the vertical direction. A crossing at 1600
>meters horizontal separation (1 mile) is hardly a near hit, as is
>320 meters (1000 feet) in the vertical direction.
>

Carried to an absurd length(reducio ad absurtum(sd?)), let's assume
that instead of a another car crossing an intersection a couple of
blocks away, a 747 crashes. Or an atomic bomb goes off? (Phewww! just
missed me (:-).

Please note in the following re-post:

"His[ Eugene Shoemaker, a respected US Geological Survey scientist]
calculations suggest that asteroids packing the explosive energy of one
megaton should enter the atmosphere on an average of once every 30 years,
larger asteroids with a 20-megaton punch every 400 years, and a 1 km, 10,000
megaton comet or asteroid once in 100,000 years."

Maybe we should consider a cheap form of insurance, like a radar satellite
or two pointing out instead of in(of course the shuttle would carry them right)?

Note the Siberian comet/asteroid was estimated at 12-megaton, about 80 years
ago(so we have 320 years {:->).

[3 screen article follows]
From decwrl!ucbvax!hplabs!hp-pcd!hpcvlx!gvg Tue May 2 10:05:21 PDT 1989

Article 11311 of sci.space:
Path: sun!decwrl!ucbvax!hplabs!hp-pcd!hpcvlx!gvg
>From: g...@hpcvlx.HP.COM (Greg Goebel)
Newsgroups: sci.space
Subject: Re: Re: Asteroid Encounter
Message-ID: <1012...@hpcvlx.HP.COM>
Date: 1 May 89 15:21:48 GMT
References: <1012...@hpcvlx.HP.COM>
Organization: Hewlett-Packard Co., Corvallis, OR, USA
Lines: 93

Dealing With Threats From Space

Michael Lemonick

TIME / 9 JUN 86 / P 65

It is a sunny afternoon in Karachi, and streets of Pakistan's largest
city are crowded with shoppers, apparently unconcerned about the rising
tension between Pakistan and India. Suddenly a second sun bursts into
view overhead, so bright it temporarily blinds thousands and so hot it
blisters the skin. Thirty seconds later, the shock wave hits,
crumbling buildings and throwing people to the ground. To the
Pakistanis, only one explanation is possible for the tremendous blast:
India has launched a nuclear attack. They immediately order their bombers,
armed with atomic bombs, to strike back at India, which responds in kind.
Only later do the surviving officials learn of their mistake. The
object that exploded over Karachi was not a nuclear weapon but a large
meteor hurtling in from outer space.

Though this sounds like the plot for a TV movie, Eugene Shoemaker, a respected
US Geological Survey scientist, is concerned that just such an event -- and an
unwarranted reaction -- could occur. Shoemaker expressed his fears at a
Baltimore meeting of the American Geophysical Union (AGU): "The effect of a
meteor blast appears the same as a high-altitude nuclear explosion," he said.
"If this happens in the wrong place, people will think they've been nuked."

Meteors, which are asteroids or cometary debris that has entered the
atmosphere, continually shower the Earth. Most of them are small and either
break up or are burned to ash by friction. But, explains Shoemaker, the
incineration of larger asteroids is far more violent. As asteroid 80 feet
across, striking the atmosphere at 50,000 MPH, compresses the air in its path
so much that in effect the asteroid is stopped dead in its path, converting
kinetic energy almost instantaneously into heat, light, and a powerful shock
wave. That causes a tremendous explosion, in this case equivalent to a
one-megaton bomb.

If a meteor were to burst in the atmosphere tomorrow, Shoemaker says, "the
Soviets and the US would know what it was" and not react militarily. Their
detectors could distinguish between a nuclear explosion -- which generates
million-degree temperatures, X-rays, and gamma rays -- and an exploding meteor
-- which would produce considerably lower temperatures and no deadly radiation.
But smaller nations, unaware of the nature of the blast, might react violently.
Says Shoemaker: "Suppose it happens over Syria or Pakistan?" He proposes that
the US immediately try to determine whether the explosion was of cosmic origin
and notify the affected nation.

Since 1973, Shoemaker has been photographing the sky in search of asteroids
that periodically cross the Earth's orbit and thus pose a danger of collision.
To date, he says, 57 such asteroids at least 1 km in diameter have been
catalogued. In addition, about three Earth-crossing comets are detected each
year. From the rate at which new Earth-crossers are detected, Shoemaker
estimates that there are some 2,000 asteroids in this category and that 100
comets intersect the Earth's orbit every year.

His calculations suggest that asteroids packing the explosive energy of one
megaton should enter the atmosphere on an average of once every 30 years,
larger asteroids with a 20-megaton punch every 400 years, and a 1 km, 10,000
megaton comet or asteroid once in 100,000 years.

This century has already seen a major meteorite blast. In 1908, either an
asteroid or comet exploded about five miles above the remote Stony Tunguska
River region of Siberia, igniting and flattening trees over hundreds of square
miles. From descriptions of the blast and photographs of the damage,
scientists have estimated that the object was at least 200 feet across and
caused a 12-megaton explosion.

Depending on their velocity, size, and composition, some meteors survive the
fiery trip through the atmosphere at hit the ground, at which point they are
called meteorites. Most are in the form of pebbles or small rocks, but
occasionally they are much larger. Scientists think it was a 130-foot chunk of
meteoric iron that hit Arizona with a force of 15 megatons between 20,000 and
50,000 years ago, digging a crater three-quarters of a mile across and 600 feet
deep.

But even greater menace lurks in the darkness of space. Scientists have
speculated that objects as large as several miles across have crashed into the
Earth, spewing millions of tons of debris into the atmosphere, blotting out the
Sun for months or years, and causing mass extinctions of life -- including,
many believe, the dinosaurs. Of the known larger Earth-crossers, none seem to
pose a threat in the near future. But, says Shoemaker, "until we have tracked
all of them, something could sneak up on us."

What if a large asteroid or comet is discovered heading for the Earth? At the
AGU meeting, Shoemaker and colleage Alan Harris, of the Jet Propulsion
Laboratory in Pasadena, California, suggested that the intruder could be
diverted by landing a thrusting device on it. As a last-ditch effort, a small
nuclear warhead could be detonated on or near it. Says Shoemaker: "We have
the technology to do that right now." But if the explosion simply broke the
meteorite into large chunks, the danger would only be multiplied. "The more
prudent solution," says Harris, "is to burrow a substantial charge into the
object and blow it to smithereens."

[<>]


# mike (sun!mae), M/S 8-04
"I'd rather sniff French shit for 5 years then eat
Chinese shit the rest of my life" -Ho Chi Minh-

David L. Cox

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May 4, 1989, 9:33:59 PM5/4/89
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In article <66...@xenna.Encore.COM> da...@xenna.UUCP (David L. Cox) writes:
>>In article <26...@ssc-vax.UUCP>, ed...@ssc-vax.UUCP (Dani Eder) writes:
>>
>>Well...up to a point...cars and aircraft aren't attracted to each other,
>>especially not by a force which goes as 1/(R^2).
>
>Why not, I thought gravity attracted all objects?
>
This may have sounded confusing. I meant that if you take any two objects,
there was a gravitational attraction between them which is proportional to
1
---
2
R


David Cox +-------+
++------+|
da...@multimax.encore.com ||ENCORE||
da...@xenna.encore.com |+------++
da...@encore.com +-------+
COMPUTER CORPORATION

Jeff Hunter

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May 5, 1989, 12:24:54 AM5/5/89
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In article <26...@ssc-vax.UUCP>, ed...@ssc-vax.UUCP (Dani Eder) writes:
>
> If an asteroid misses the Earth by 500,000 km, that is about 80 Earth
> radii. Let us comapre this to more familiar events and see how this
> compares. The mean radius of a car is about 2 meters. 80 times 2
> meters is 160 meters (525 feet.). If a car crosses a 4 way intersection
> while you are that far away, do you call it a near miss? I think not.

A human has average radius of about two feet. If you're out
watering the lawn one morning and a random sniper blows out a window
halfway down the block don't you think you'd be a trifle concerned?
Now I agree that with only a few sizeable shots per decade (in
your block) the odds of you getting your hair parted much less getting
your kidneys plugged is pretty low. We don't need to blow the budget for a
huge space-defence network, but I'd feel safer if we had good sightings of
all the hefty earth-crossing rocks. Given two year's notice I think we
could put up enough megatonnes to nudge anything smaller than Mt. Everest
out of the way.
--
___ __ __ {utzoo,lsuc}!censor!jeff (416-595-2705)
/ / /) / ) -- my opinions --
-/ _ -/- /- No one born with a mouth and a need is innocent.
(__/ (/_/ _/_ Greg Bear

Stuart Warmink

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May 4, 1989, 1:05:11 PM5/4/89
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In article <26...@ssc-vax.UUCP>, ed...@ssc-vax.UUCP (Dani Eder) writes:
> If an asteroid misses the Earth by 500,000 km, that is about 80 Earth
> radii. Let us comapre this to more familiar events and see how this
> compares. The mean radius of a car is about 2 meters. 80 times 2
> meters is 160 meters (525 feet.). If a car crosses a 4 way intersection
> while you are that far away, do you call it a near miss? I think not.
> [another example for an aircraft]

Well...up to a point...cars and aircraft aren't attracted to each other*,
especially not by a force which goes as 1/(R^2). An asteroid which might
otherwise have passed by at quite a distance would get much closer to Earth
because of the Earth's gravity - effectively "funneling" the asteroids
towards the Earth.
But, as you say, 80 Earth radii is not exactly plunging into the atmosphere.

(* Except perhaps for cars here in New Jersey :-)

--
------------------------------------------------------------------------------
"Captain, I see no reason to stand here | Stuart Warmink, Whippany, NJ, USA
and be insulted" - Spock | s...@cbnewsl.ATT.COM (att!cbnewsl!sw)
-------------------------> My opinions are just that <------------------------

Bill Wyatt

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May 5, 1989, 10:30:06 AM5/5/89
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>> If an asteroid misses the Earth by 500,000 km, that is about 80 Earth
>> radii. [...]

> Well...up to a point...cars and aircraft aren't attracted to each other*,
> especially not by a force which goes as 1/(R^2).

?? Of course they are. It's just a tiny amount, that's all.

> An asteroid which might
> otherwise have passed by at quite a distance would get much closer to Earth
> because of the Earth's gravity - effectively "funneling" the asteroids

> towards the Earth. [...]

Actually, the cross section is smaller than you might think - about
two Earth radii (I'm not sure if this is measured from the Earth's
center or surface). I.e., if an object would have passed a point two
(or three) radii from the Earth's center, it will be deflected
enough to hit.
Bill Wyatt, Smithsonian Astrophysical Observatory
UUCP : {husc6,cmcl2,mit-eddie}!harvard!cfa!wyatt
ARPA: wy...@cfa.harvard.edu
SPAN: cfa::wyatt BITNET: wyatt@cfa

jo...@prism.tmc.com

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May 5, 1989, 10:33:00 AM5/5/89
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Would it be possible for the Earth to acquire a second moon by capturing
an asteroid, or comet, without its striking the Earth? Just
curious.
----
JOHN DOWD jo...@mirror.TMC.COM
{mit-eddie, ihnp4, harvard!wjh12, cca, cbosgd, seismo}!mirror!john
Mirror Systems Cambridge, MA 02140

car...@s.cs.uiuc.edu

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May 7, 1989, 2:48:00 PM5/7/89
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/* Written 9:30 am May 5, 1989 by wy...@cfatst.HARVARD.EDU in s.cs.uiuc.edu:sci.astro */

Actually, the cross section is smaller than you might think - about
two Earth radii (I'm not sure if this is measured from the Earth's
center or surface). I.e., if an object would have passed a point two
(or three) radii from the Earth's center, it will be deflected
enough to hit.
/* End of text from s.cs.uiuc.edu:sci.astro */

Doesn't that depend on the speed of the object? I.e., if the object is moving
*very* slowly, then it could be much farther out than that and would hit
Earth (i.e., it were moving at, say, 1 nm/s, it would hit from a lot farther
than 2 radii out). Conversely, if it's moving fast enough, it won't hit
(consider a satellite - it's closer than 2 radii, and it doesn't get deflected
into the planet). Or were you assuming "standard" solar sytem speeds for
objects? If so, about what would that be?

Alan M. Carroll "And there you are
car...@s.cs.uiuc.edu Saying 'We have the Moon, so now the Stars...'"
CS Grad / U of Ill @ Urbana ...{ucbvax,pur-ee,convex}!s.cs.uiuc.edu!carroll

Clayton Cramer

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May 8, 1989, 5:24:56 PM5/8/89
to
In article <202300024@prism>, jo...@prism.TMC.COM writes:
>
> Would it be possible for the Earth to acquire a second moon by capturing
> an asteroid, or comet, without its striking the Earth? Just
> curious.
> ----
> JOHN DOWD jo...@mirror.TMC.COM

I've seen the assertion made that it is impossible for an object
passing near a planet to be captured unless its velocity is reduced
by a collision with some other object, or skimming the atmosphere.
Supposedly, the sum of the vectors involved guarantees that the
object passing by will exceed escape velocity for the primary.

However, this was a popular book on astronomy -- there were no
equations to make my eyes glaze over.


--
Clayton E. Cramer {pyramid,pixar,tekbspa}!optilink!cramer
Assault rifle possession is a victimless crime.
----------------------------------------------------------------------------
Disclaimer? You must be kidding! No company would hold opinions like mine!

Bill Wyatt

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May 9, 1989, 9:35:42 AM5/9/89
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>> Actually, the cross section is smaller than you might think - about
>> two Earth radii (I'm not sure if this is measured from the Earth's
>> center or surface). [...]
>
> Doesn't that depend on the speed of the object? [...]
> [...] Or were you assuming "standard" solar sytem speeds for

> objects? If so, about what would that be?

Yes, about 15-25 km/sec.

John H. Kim

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May 9, 1989, 10:44:49 AM5/9/89
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In article <13...@optilink.UUCP> cra...@optilink.UUCP (Clayton Cramer) writes:
>In article <202300024@prism>, jo...@prism.TMC.COM writes:
>>
>> Would it be possible for the Earth to acquire a second moon by capturing
>> an asteroid, or comet, without its striking the Earth? Just
>> curious.
>
>I've seen the assertion made that it is impossible for an object
>passing near a planet to be captured unless its velocity is reduced
>by a collision with some other object, or skimming the atmosphere.
>Supposedly, the sum of the vectors involved guarantees that the
>object passing by will exceed escape velocity for the primary.

I just thought of a simple example of how this could happen. There
was a computer analysis of a three body problem done some time ago.
It involved (you guessed it!) three bodies in orbit about each other.
It ended up with two of the bodies orbiting each other and the third
being flung off into space. Now, since gravity is such a wonderfully
conservative force, you could imagine the same sequence of events in
reverse order. Then, you would have one body being "captured" by the
other two. I don't think the orbit is stable, although it might
appear to be if one or more of the bodies is much smaller than the
other(s). So (assuming everything I've recalled is correct) an
asteroid might appear to be captured but eventually will leave
(like in a couple million years).
--
John H. Kim | (This space to be filled when I
jo...@jarthur.Claremont.EDU | think of something very clever
uunet!muddcs!jarthur!jokim | to use as a disclaimer)

Pawel Gburzynski

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May 9, 1989, 7:00:15 PM5/9/89
to
In article <13...@optilink.UUCP>, cra...@optilink.UUCP (Clayton Cramer) writes:
> In article <202300024@prism>, jo...@prism.TMC.COM writes:
> >
> > Would it be possible for the Earth to ....
>
> I've seen the assertion made that it is impossible for an object ....

>
> However, this was a popular book on astronomy -- there were no
> equations to make my eyes glaze over.
>
You don't need any equations, just a bit of common sense.

An object approaching the Earth is either orbiting it already (so it is a
second moon) or is approaching the Earth with the escape velocity (we can
ignore birds' droppings for simplicity).

Pawel Gburzynski

Nichael Cramer

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May 9, 1989, 10:16:18 PM5/9/89
to
In article <13...@optilink.UUCP> cra...@optilink.UUCP (Clayton Cramer) writes:
>In article <202300024@prism>, jo...@prism.TMC.COM writes:
>> Would it be possible for the Earth to acquire a second moon by capturing
>> an asteroid, or comet, without its striking the Earth? Just
>> curious.
>I've seen the assertion made that it is impossible for an object
>passing near a planet to be captured unless its velocity is reduced
>by a collision with some other object, or skimming the atmosphere.
>Supposedly, the sum of the vectors involved guarantees that the
>object passing by will exceed escape velocity for the primary.

A free body has energy>0, a captured body has energy<0. So an _isolated_
body can't _gravitationally_ capture a free body (in short because the
excess energy has no place to go; in a little more detail, you can't
capture and still conserve both the energy and the momentum).

You can, however, capture the free body if you dissipate the excess energy;
e.g., as Clayton suggests, via atmospheric drag.

Alternatively, if the captor is not an _isolated_ body but a _system_ (e.g.
Earth + Moon) it is possible to gravitationally capture the free body
because the system can absorb some of the energy (i.e. the distances
between original bodies will change).

NICHAEL
(the other Cramer on the nets)

Robert J Woodhead

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May 10, 1989, 6:44:27 AM5/10/89
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In article <5...@cadomin.UUCP> pa...@alberta.UUCP (Pawel Gburzynski) writes:
> [ In re, capture of an asteroid into Earth orbit ]

>An object approaching the Earth is either orbiting it already (so it is a
>second moon) or is approaching the Earth with the escape velocity (we can
>ignore birds' droppings for simplicity).

Ah, but it is not quite that simple. Consider that the
Gravity-well Slingshot used by deep-space probes can not
only be used to extract momentum from the planet, but also
to dump momentum as well. Thus it is possible for an object
to be captured into orbit. In addition, you must add in the
complicating effects of the Moon.

Consider the case of Comets, all of which start out in
hyperbolic (escape) orbits. Occasionally, an encounter with
Jupiter or one of the other large planets pertubates the
orbit into one of short period (for example, Halley's)

This example clearly shows that it is possible for the
Earth-Moon system to capture an asteroid. Just very very
unlikely.

--
Robert J Woodhead, Biar Games, Inc. !uunet!biar!trebor | tre...@biar.UUCP
"The lamb will lie down with the lion, but the lamb won't get much sleep."
-- Woody Allen.

Jude Anand George

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May 10, 1989, 4:18:06 PM5/10/89
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pa...@alberta.UUCP (Pawel Gburzynski) writes:
> An object approaching the Earth is either orbiting it already (so it is a
> second moon) or is approaching the Earth with the escape velocity (we can
> ignore birds' droppings for simplicity).

I don't think so. This is true for a free body approaching another free
body in space, but doesn't have to apply in the solar system. An asteroid
traveling around the sun with nearly the same orbital velocity as the
earth may find it very easy to fall into earth orbit. Likewise, an asteroid
approaching the solar system from deep space is approaching with escape
velocity for the solar system, but not necessarily for the earth. The
initial assertion is valid only for point masses, not for systems with
multiple objects traveling at different relative velocities.


+====================\ Internet: jg...@andrew.cmu.edu \=======================+
| Jude Anand George \ BITNET: jg2f+@ANDREW | jg2f+%andrew@{CMCCVB|CMCCVMA} |
| redden Augean jog \ UUCP: the_known_world!harvard!andrew.cmu.edu!jg2f+ |
+=======================\ CIS: 72307,1752 Jude George \====================+

Walter L. Peterson, Jr.

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May 11, 1989, 12:56:31 AM5/11/89
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In article <12...@jarthur.Claremont.EDU>, jo...@jarthur.Claremont.EDU (John H. Kim) writes:
> ...
> I just thought of a simple example of how this could happen. There
> was a computer analysis of a three body problem done some time ago.
> It involved (you guessed it!) three bodies in orbit about each other.
> It ended up with two of the bodies orbiting each other and the third
> being flung off into space. Now, since gravity is such a wonderfully
> conservative force, you could imagine the same sequence of events in
^^^^^^^

> reverse order. Then, you would have one body being "captured" by the
> other two. ...


Yes, one *could* imagine such a situation. One could also watch a
simulation of a bouncing ball slowly coming to rest and then IMAGINE
a stationary ball spontaneously begining to bounce higher and higher
'til it vanishes off the top of the screen. HOWEVER - the Laws of
Thermodynamics (especially the Second Law) forbid such an occurance.

I am certain that there *ARE* situations in which "incoming" body can
be captured by an n-body (where n > 1) system; however, I am equally
certain that the dynamics of such a capture are quite different from
the scenario given above.

--
Walt Peterson. Prime - Calma San Diego R&D (Object and Data Management Group)
"The opinions expressed here are my own and do not necessarily reflect those
Prime, Calma nor anyone else.
...{ucbvax|decvax}!sdcsvax!calmasd!wlp

Geo Swan

unread,
May 11, 1989, 2:20:23 AM5/11/89
to

The original question for this discussion asked how possible it was for
the Earth to capture an asteroid, so that we acquired a second moon.
Several previous articles have stated that some of the outer moons of
the outer planets are believed to be captured moons. These articles
didn't say why.

I believe the reason is that while the orbits of the well-known moons
are well-behaved, some of the more recently discovered moons are not.
The well-known moons orbit in the same plane as their companions, they
are not markedly eccentric, and they are reasonably close to their
principal. For some of the other moons these conditions do not hold.
Are there a couple retrograde orbits out there? I don't recall.

My recollection is that for an asteroid to be captured its original
orbit around the sun must be sufficiently similar to that of the planet
that captures it that it receives _regular_ perturbations over a long
period of time. These perturbations have the effect of making its
orbit more like that of the target planet. If they go on long enough
the difference in velocity between the two bodies is reduced to where
it can be captured. So far as the Earth is concerned, I don't believe
any of the known asteroids qualifies.

Nichael Cramer

unread,
May 10, 1989, 10:36:14 PM5/10/89
to

In article <5...@biar.UUCP> tre...@biar.UUCP (Robert J Woodhead) writes:
>In article <5...@cadomin.UUCP> pa...@alberta.UUCP (Pawel Gburzynski) writes:
>> [ In re, capture of an asteroid into Earth orbit ]
>>An object approaching the Earth is either orbiting it already (so it is a
>>second moon) or is approaching the Earth with the escape velocity (we can
>>ignore birds' droppings for simplicity).
>
> Ah, but it is not quite that simple. Consider that the
> Gravity-well Slingshot used by deep-space probes can not
> only be used to extract momentum from the planet, but also
> to dump momentum as well. Thus it is possible for an object
> to be captured into orbit. In addition, you must add in the
> complicating effects of the Moon.

To clarify slightly, you HAVE to add in the effects of the moon. The
slingshot effect will not work with an isolated body (if you work through
the equations you will see that you can't conserve both energy and momentum
in the system). The slingshot effect works by stealing energy from the
*system* of, say, Jupiter and its moons.

> This example clearly shows that it is possible for the
> Earth-Moon system to capture an asteroid. Just very very
> unlikely.

Consider the moons of some of the Jovian planets (If the hypothesis that
some of them are captured astroids is correct).

NICHAEL

Michael C Nolan

unread,
May 11, 1989, 10:26:36 PM5/11/89
to
>One could also watch a simulation of a bouncing ball slowly coming to
>rest and then IMAGINE a stationary ball spontaneously begining to
>bounce higher and higher 'til it vanishes off the top of the screen.
>HOWEVER - the Laws of Thermodynamics forbid such an occurance.

The bouncing ball isn't a conservative system though, it has losses.
As a pure F=ma problem (no drag), if you reverse the velocities, the
system will evolve backwards, so that three body capture is in fact the
reverse of three body escape.

no...@hiips.lpl.arizona.edu; ...!noao!solpl!hiips
--
no...@hiips.lpl.arizona.edu; ...!noao!solpl!hiips

Henry Melton

unread,
May 11, 1989, 10:40:38 PM5/11/89
to
> >> Would it be possible for the Earth to acquire a second moon by capturing
> >> an asteroid, or comet, without its striking the Earth? Just
> >> curious.
> >
> I just thought of a simple example of how this could happen. There
> was a computer analysis of a three body problem done some time ago.
> It involved (you guessed it!) three bodies in orbit about each other.
> It ended up with two of the bodies orbiting each other and the third
> being flung off into space. Now, since gravity is such a wonderfully

I discovered a wonderful Macintosh program named 'Gravitation' or
something like that, which models bodies under gravitational attraction.
It is a lot of fun. You get to set up up to ten bodies (position, mass,
and velocity), then turn it loose.

I tested it with a number of setups and although the simulation fails
because time is not really in small jumps, the failure only shows up in
extreme conditions (high-speed perigee swings in highly elliptical
orbits) so it is a nice test bed to play with orbits. It was fun to set
up the Saturn co-orbital situation and watch the moons dance their jig.

One other thing I have been trying to accomplish is to set up the
maximum number of objects in stable orbits. It is a lot harder than it
sounds. While is is fairly easy to set up a situation where a third
body can approach a planet-moon pair and give up enough energy to put it
into an orbit of its own, this situation is only partially stable. Give
it enough cycles, and harmonic interactions between the two moons will
eventually peak again and the smaller will either be ejected or drop to
a orbit that intersects the primary (oops).

If I had a graphics terminal I would like to port the program to my unix
system. I wrote a version for my Model 100 Tandy portable, but it was
SLOW.

hjm
--

Keith Dancey

unread,
May 12, 1989, 5:08:30 AM5/12/89
to
In article <103...@sun.Eng.Sun.COM> m...@sun.UUCP (Mike Ekberg, Sun {GPD-LEGO}) writes:

>
>But even greater menace lurks in the darkness of space. Scientists have
>speculated that objects as large as several miles across have crashed into the
>Earth, spewing millions of tons of debris into the atmosphere, blotting out the
>Sun for months or years, and causing mass extinctions of life -- including,
>many believe, the dinosaurs. Of the known larger Earth-crossers, none seem to
>pose a threat in the near future. But, says Shoemaker, "until we have tracked
>all of them, something could sneak up on us."
>

My understanding is that the demise of the dinosaurs extended over a period
of order of magnitude of a thousand years. Certainly long enough to place
doubt upon the viability of a single catastrophy such as the one mentioned.

If the palaeontological evidence is not contradicted (and I have understood
it correctly) then a *series* of such catastrophic strikes would be required.

That is not say a single catastrophy is ruled out, but it looks as though
its effects must be longer-lived than a few years.

As for tracking "all" large, earth-crossing asteriods, there is
a danger of conveying the unspoken idea that the number may be fixed and
finite for all time. I think such a concept is also under question.
There is just the possibility that these bodies are disturbed out of
an otherwise harmless state by the dynamics of the galaxy. This means
their numbers may be added to at any time unexpectedly.

--
Keith Dancey, UUCP: ..!mcvax!ukc!rlinf!kgd
Rutherford Appleton Laboratory,
Chilton, Didcot, Oxon, England OX11 0QX
Tel: (0235) 21900 ext 6756 JANET: K.DA...@uk.ac.rl.inf

Joshua M. Alden

unread,
May 12, 1989, 2:36:47 PM5/12/89
to
In article <7...@hutto.UUCP> he...@hutto.UUCP (Henry Melton) writes:
>I discovered a wonderful Macintosh program named 'Gravitation' or
>something like that, which models bodies under gravitational attraction.
>It is a lot of fun. You get to set up up to ten bodies (position, mass,
>and velocity), then turn it loose.
>
>hjm
>--

Hello.

I tried to get mail to you, but you have an unknown host, according
to our system here. Could you mail me a copy of this program if it's
PD or Shareware, or tell me where I can get a copy?


-Josh Alden
Joshua...@dartmouth.edu

Scott Bayes

unread,
May 12, 1989, 2:49:06 PM5/12/89
to

I should think there are small differences due to tidal effects. The tidal
deformations would steal energy at different points in the interaction,
causing slightly differing orbits between running forwards and running
backwards. I should think these differences would almost never matter
as to whether an ejection event could succefully be reversed and become a
capture event.

In other words, the n-body problem should be _almost_ conservative.

Scott Bayes
physicist gone walkabout in computer land

Jude Anand George

unread,
May 12, 1989, 3:56:44 PM5/12/89
to
jg...@andrew.cmu.edu (Jude Anand George) writes:
> pa...@alberta.UUCP (Pawel Gburzynski) writes:
> > An object approaching the Earth is either orbiting it already (so it is a
> > second moon) or is approaching the Earth with the escape velocity (we can
> > ignore birds' droppings for simplicity).
.
.

> earth may find it very easy to fall into earth orbit. Likewise, an asteroid
> approaching the solar system from deep space is approaching with escape
> velocity for the solar system, but not necessarily for the earth. The

Bob Ayers points out to me in email that I may be wrong; if you fall into
any gravity well, you will have enough energy to climb back out of that
gravity well. Now I can't decide... perhaps a simulation is in order :-)


+====================\ Internet: jg...@andrew.cmu.edu \=======================+
| Jude Anand George \ BITNET: jg2f+@ANDREW | jg2f+%andrew@{CMCCVB|CMCCVMA} |

| Andean judge goer \ UUCP: the_known_world!harvard!andrew.cmu.edu!jg2f+ |

Paul Durham

unread,
May 12, 1989, 6:09:40 PM5/12/89
to
In article <5...@cbnewsl.ATT.COM> s...@cbnewsl.ATT.COM (Stuart Warmink) writes:
>
>Well...up to a point...cars and aircraft aren't attracted to each other*,
>especially not by a force which goes as 1/(R^2).

Well, actually they are.

It's the same force which attracts astronomical bodies.
( or so Newton said :-) ).


P. Durham

Henry Melton

unread,
May 13, 1989, 12:32:02 AM5/13/89
to
In article <13...@dartvax.Dartmouth.EDU>, jal...@eleazar.dartmouth.edu (Joshua M. Alden) writes:
> In article <7...@hutto.UUCP> he...@hutto.UUCP (Henry Melton) writes:
> >I discovered a wonderful Macintosh program named 'Gravitation' or
> I tried to get mail to you, but you have an unknown host, according
>
> -Josh Alden

Sorry, 'hutto' hasn't made it to the maps yet, a new site. I got my
copy from the CD-ROM available from the Boston Computer Society. It is
freeware (the author would like a postcard). Unfortunately, since I am
new at this, I don't think I have the tools necessary to copy it to the
net.

The author is:
Jeff Rommereide
PO Box 600
Sicklerville, NJ 08081


If you come up empty:

Henry Melton
Rt. 1 Box 274E
Hutto, TX 78634 (I can always mail a floppy)


--

Jason

unread,
May 13, 1989, 9:03:55 AM5/13/89
to

In article <61...@nfs4.rl.ac.uk> k...@inf.rl.ac.uk (Keith Dancey) writes:
>>Sun for months or years, and causing mass extinctions of life -- including,
>>many believe, the dinosaurs.
>My understanding is that the demise of the dinosaurs extended over a period
>of order of magnitude of a thousand years.

...etc....

Please correct me if I am wrong, but is this one of the theories (proofs) behind
the "asteroid theory" of the extinction of the dinosaurs ?:

Layers of Iridium were found deep into the earth's crust ( i.e. in the layers
of the Grand Canyon). Now, being that Iridium is rare on earth but found
to be relatively more bountiful in asteroids and meteors, it is suggested
that the layer of this element was put on our planet by an extremely large
(or as previously mentioned a few extremely large) asteroid(s) which hit
earth and caused the clouds of dust ...etc., which eventually killed off the
dinosaurs. This dust, if the theory is accurate, was filled with Iridium and
when settled created a solid layer over years of rain, erosion ...etc...

Is this a widely accepted view? What are the opposing ideas?

___ ___ __ ___ )___ __________________________________
( | '__| (__ / / / / | II Corinthians 10:17 |
\ | (__)\ __) /__/ / / +--------------------------------+
\_| Internet: jygabler@ucdavis |"Why me?!", Garion said. "Do we |
| BITNET: jygabler@ucdavis | we have to go thru that again",|
| UUCP: ucdavis!jygabler | the dry voice retorted. |

Eugene Miya

unread,
May 13, 1989, 8:21:08 PM5/13/89
to
If you are really interested in this. I recommend the work and writings of
Preston Cloud.

Longish signature follows "Type 'n' now"

Another gross generalization from

--eugene miya, NASA Ames Research Center, eug...@aurora.arc.nasa.gov
resident cynic at the Rock of Ages Home for Retired Hackers:
"You trust the `reply' command with all those different mailers out there?"
"If my mail does not reach you, please accept my apology."
{ncar,decwrl,hplabs,uunet}!ames!eugene
Live free or die.

Robert Wier

unread,
May 16, 1989, 2:44:15 PM5/16/89
to

I got a copy of MacGravity, and if it's a reasonably accurate
simulation, it's as scary as h*ll. Its VERY hard to get a
nice, stable solar system type planetary arrangement going, and
if a fairly massage object passes thru (say, on a planetary scale)
, well, that's the ol ball game unless any civilizations have the
technology to leave or stand off a ways till things settle down...


- Bob Wier College of Engineering
Flagstaff, Arizona Northern Arizona University
...arizona!naucse!rrw | BITNET: WIER@NAUVAX | *usual disclaimers*

Kevin Bagley

unread,
May 16, 1989, 5:34:58 PM5/16/89
to
In article <39...@bbn.COM> ncr...@BBN.COM (Nichael Cramer) writes:
>
>In article <5...@biar.UUCP> tre...@biar.UUCP (Robert J Woodhead) writes:
>>In article <5...@cadomin.UUCP> pa...@alberta.UUCP (Pawel Gburzynski) writes:
>>> [ In re, capture of an asteroid into Earth orbit ]
>>>An object approaching the Earth is either orbiting it already (so it is a
>>>second moon) or is approaching the Earth with the escape velocity (we can
>>>ignore birds' droppings for simplicity).
>>
>> Ah, but it is not quite that simple. Consider that the
>> Gravity-well Slingshot used by deep-space probes can not
>> only be used to extract momentum from the planet, but also
>> to dump momentum as well. Thus it is possible for an object
>> to be captured into orbit. In addition, you must add in the
>> complicating effects of the Moon.

>To clarify slightly, you HAVE to add in the effects of the moon.

[stuff relating to slingshot and object capturing deleted]
>NICHAEL

I disagree. You do not HAVE to have a moon in order to obtain the
slingshot effect. All you do have to do is approach an orbiting body
at the side opposite the direction of the orbit. Consider the following
where 'O' is in orbit a 't' approaches according to the path

<- Orbit direction
________
--_
*****O\***
**** \ ****
*** \ ***
** \ **
Approaching t
body

In this example. 'O' will loose velocity in direct proportion to the velocity
gained by 't' (assuming equal mass). A different approach by 't' may slow
't' while increasing 'O'. If 't' is in an orbit with perihelion at or near
the orbit of 'O', it may be captured by O. This is actually a 3 body system
since we are assuming 't' and 'O' are in orbit around a more massive body
as in an asteroid in orbit around the sun.

*****O*****
**** xxx ****
*** x x ***
** x x **
* x x *
* x x *
x x
x x
x x

As a further consideration, consider two ice-skaters in motion (a and b).
'b' is approaching 'a' at a velocity slightly faster than 'a'. Skater 'a'
grabs skater 'b' and with a spinning motion, launches 'b' faster than
'b' was originally moving. 'a' of course ends up slower than before the
encounter, however, no energy is lost or gained, merely transferred.

I am not an astronomer, and what I remember is old, so feel free to
shoot any bugs in the above. :)

--
_____ Kevin Bagley Global Tech. Int'l Inc., Mukilteo WA 98275 206-742-9111
)___) __ _ _ UUCP:uw-beaver!uw-nsr!uw-warp!gtisqr!kevin
_/___) (__(__(_)_/_)_ ARPA:uw-nsr!uw-warp!gtisqr!ke...@beaver.cs.washington.edu
_______________/ Disclaimer... "I did not say this. I am not here."

AIDE Hugh Hazelrigg

unread,
May 17, 1989, 2:16:59 AM5/17/89
to
In article <61...@nfs4.rl.ac.uk> k...@inf.rl.ac.uk (Keith Dancey) writes:
>My understanding is that the demise of the dinosaurs extended over a period
>of order of magnitude of a thousand years. Certainly long enough to place
>doubt upon the viability of a single catastrophy such as the one mentioned.

What prevents the effects of a "single catastrophy [sic]" from propagating over
a period of a thousand years? On a geological scale of time, the events of a
thousand years constitute less than a footnote in a billion-page volume.

Life on this planet seems to be pretty durable, in spite of its perceived
fragility. We, the living, while certainly not immune from geological,
meteorological, or cosmological influences, won't go away overnight unless the
whole planet is blasted to smithereens in one swell foop!

Look: a thousand years (or even five or ten) really is just a one-nighter
(what a party!). The earth may have lost a host of magnificent species, but
did life disappear?

I believe the metorite/asteroid collision theory to be the best put forward to
date to explain the demise of the dinosaurs and their ecosystem. Your objection,
Keith, is ill-considered.

Hugh Hazelrigg
ha...@unm-la.lanl.gov
Disclaimer: None. I don't work for anyone who doesn't trust me implicitly.

saouter yannick

unread,
May 17, 1989, 5:28:23 AM5/17/89
to
In article <43...@ucdavis.ucdavis.edu>, ccs...@castor.ucdavis.edu (Jason) writes:
>
> In article <61...@nfs4.rl.ac.uk> k...@inf.rl.ac.uk (Keith Dancey) writes:
> >>Sun for months or years, and causing mass extinctions of life -- including,
> >>many believe, the dinosaurs.
> >My understanding is that the demise of the dinosaurs extended over a period
> >of order of magnitude of a thousand years.
>
> ...etc....
>
> Please correct me if I am wrong, but is this one of the theories (proofs) behind
> the "asteroid theory" of the extinction of the dinosaurs ?:
>
> Layers of Iridium were found deep into the earth's crust ( i.e. in the layers
> of the Grand Canyon). Now, being that Iridium is rare on earth but found
> to be relatively more bountiful in asteroids and meteors, it is suggested
> that the layer of this element was put on our planet by an extremely large
> (or as previously mentioned a few extremely large) asteroid(s) which hit
> earth and caused the clouds of dust ...etc., which eventually killed off the
> dinosaurs. This dust, if the theory is accurate, was filled with Iridium and
> when settled created a solid layer over years of rain, erosion ...etc...
>
I have heard about it,too. Dinosaurs might have been killed, in this theory for
few reasons :
- Herbivorous ones starved to death as the big forests burned with the energy
developped with the hit,and as the others plants died because of the Sun to be
darkened by the clouds. Then carnivorous ones starved to death,too.

- They might have choked with the carbonic anhydrid developped by the fires.

- The fishes died with the disappearance of the plancton, due to the first
reason.

- They could have died with the chill of the Earth due to the clouds.

- Moreover Iridium is poisonous.

However, all the dinosaurs would have been to disappear, that is to say, even
turtles and iguanes. And when all the creatures to be killed, then a great time
would be needed to repair this catastrophe (the first oxygen producers appears
in the sea 2 000 000 000 years ago, and this hit occurs 65 000 000 years ago).

sao...@sigle.irisa.fr

John K Hayes

unread,
May 17, 1989, 10:06:08 AM5/17/89
to

It just so happens there is an article in the current issue of Nat'l
Geographic (June, I think) that deals with mass extinctions. It says that
most scientists now believe that the extinction of the dinasaurs was caused by
a single event as opposed to a gradual dying out. They define the time
boundary of the Cretaceus (sp?) period (when there were dinasaurs) and the
Tertiary (sp?) period (when there weren't) as the K-T boundary. There have
been samples of quartz crystals found that date to around the K-T boundary
that show signs of stress to a degree such as that caused by a nuclear
explosion or an impact of a very large meteor.
There has also been found a pencil thin layer in a chunk of rock of an element
commonly found in meteors but rarely on earth. The layer in the rock where
this occurs corresponds roughly to the K-T boundary. They estimate the meteor
to have been about 6 miles across which would produce the equivilent of
10,000 times all the world's nuclear explosives.

As for what happened after the impact, scientists differ. Some propose that
90 % of the earth's forests caught fire. Some say that if the impact were on
land it would produce a thick smog that would cause extreme cold; but if it
were at sea, it would send so much water vapor into the atmosphere that a
greenhouse effect would produce extreme heat. One scientist who has been
studying the Yellowstone fire proposes that even if the impact were at sea
it would have produced an explosion so great that most of the world would have
caught fire (I forget the specifics she detailed, but they were very
interesting).

Still others (but a minority now, I believe) maintain that the cataclysm
can be explained by earthly causes such as ice ages, volcanic activity,
shifting of the continents, etc. But, there seems to be evidence that
suggests otherwise.
--
---{john hayes} Old Dominion University; Norfolk, Virginia USA
internet: ai...@cs.odu.edu
Home: (804) 622-8348 Work: (804) 460-2241 ext 134

<++++++++++++++++++++++++++++++++++>
Are you a Have or a Have_Not? Because if you're a Have_Not, you've probably
had it; whereas, if you're a Have, you've probably got it and are going to
give it away at some point in the future! --- The Clash
<++++++++++++++++++++++++++++++++++>

Ethan Tecumseh Vishniac

unread,
May 17, 1989, 10:42:34 AM5/17/89
to
In article <12...@irisa.UUCP>, sao...@irisa.UUCP (saouter yannick) writes:
>
> - Moreover Iridium is poisonous.

In sufficient quantities it is. In this case the amounts are probably not
biologically significant.

>
> However, all the dinosaurs would have been to disappear, that is to say, even
> turtles and iguanes. And when all the creatures to be killed, then a great time
> would be needed to repair this catastrophe (the first oxygen producers appears
> in the sea 2 000 000 000 years ago, and this hit occurs 65 000 000 years ago).

Actually, turtles and iguanas are not dinosaurs, and they did not disappear
at the end of the Mesozoic. My understanding is that the extinction of
terrestrial life can be summed up with the statement that everything weighing
more than 20kg died off. However, the extinction was more sweeping than
this and many tiny (and, of course, large) oceanic organisms died as well.
It is also true that this is not the most dramatic mass extinction in the
fossil record.
--
I'm not afraid of dying Ethan Vishniac, Dept of Astronomy, Univ. of Texas
I just don't want to be {charm,ut-sally,emx,noao}!utastro!ethan
there when it happens. (arpanet) et...@astro.AS.UTEXAS.EDU
- Woody Allen (bitnet) ethan%astro.as....@CUNYVM.CUNY.EDU

These must be my opinions. Who else would bother?

Eugene Miya

unread,
May 17, 1989, 4:42:10 AM5/17/89
to
> Alverz et al extinction theory as plausible.

Wait a minute! You make a good point that 1K years is just a small
amount of time on a geologic or planetary (or many other) time scales.
I don't quibble about that, but I can't agree you can't look at this
without so skepticism (like fusion, conductors, etc.)

Several years I went on one of the yearly Caltech ski trips, when
this theory was fresh on every's brain (probably about 1982/3). Okay
we discuss work on ski trips (we all get our turn).
Luis and Walter (and all the others) still got lots of respect,
but one of the people who came up, Peter Ray, a botanist at Stanford,
I won't just say "He shot holes thru the theory," but he did raise
interesting unanswered questions from the botanical community.
None of the original LBL people addressed this questions. You have
to study some of these questions in great depth and say, "Oh yeah?!
I didn't think about that simple idea which remains unanswered..."
Happens all the time. Theories are scientific fads. Good find
some serious skeptics, I won't try to paraphrase Peter's questions.

Roy Smith

unread,
May 18, 1989, 8:01:45 AM5/18/89
to
In article <6...@gtisqr.UUCP> ke...@hindmost.UUCP (Kevin Bagley) writes:
> Consider that the Gravity-well Slingshot used by deep-space probes can
> not only be used to extract momentum from the planet, but also to dump
> momentum as well.

Jeeze, that's the problem with our disposable society. Everywhere
we go, we pollute. Miles offshore, you can find floating beer cans. Now
we've taken it just one step further. You have some momentum you no longer
want, no problem, just dump it on a convenient planet! When are people
going to learn?

Momentum:
nature's most precious non-renewable resource.
Don't waste it.
--
Roy Smith, System Administrator
Public Health Research Institute
{allegra,philabs,cmcl2,rutgers,hombre}!phri!roy -or- r...@phri.nyu.edu
"The connector is the network"

saouter yannick

unread,
May 18, 1989, 9:16:50 AM5/18/89
to
In article <13...@ut-emx.UUCP>, et...@ut-emx.UUCP (Ethan Tecumseh Vishniac) writes:
> It is also true that this is not the most dramatic mass extinction in the
> fossil record.

Such collisions occurs about every 50 000 000 years and I've heard that others
species have disappeared as suddenly as the dinosaurs did, so earlier
collisions might be the cause for that, too.

Does anyone knows others example of strange disappearance ?

Nichael Cramer

unread,
May 18, 1989, 11:00:45 PM5/18/89
to
In article <6...@gtisqr.UUCP> ke...@hindmost.UUCP (Kevin Bagley) writes:
>In article <39...@bbn.COM> ncr...@BBN.COM (Nichael Cramer) writes:
>>
>>>In article <5...@cadomin.UUCP> pa...@alberta.UUCP (Pawel Gburzynski) writes:
>>>> [ In re, capture of an asteroid into Earth orbit ]

>>To clarify slightly, you HAVE to add in the effects of the moon.


> [stuff relating to slingshot and object capturing deleted]
>>NICHAEL
>
> I disagree. You do not HAVE to have a moon in order to obtain the
> slingshot effect. All you do have to do is approach an orbiting body

> at the side opposite the direction of the orbit....
> ...[Diagram deleted]


> In this example. 'O' will loose velocity in direct proportion to the velocity
> gained by 't' (assuming equal mass). A different approach by 't' may slow
> 't' while increasing 'O'. If 't' is in an orbit with perihelion at or near
> the orbit of 'O', it may be captured by O. This is actually a 3 body system
> since we are assuming 't' and 'O' are in orbit around a more massive body
> as in an asteroid in orbit around the sun.

You are right that you don't have to have a *MOON*, but you *MUST HAVE* the
THIRD body for this to work (this was the point in the original posting; I
think it's clearer in context).

In your example above, if both bodies are intially free, thery will remain
free. Moreover their respective speed will NOT change overall.

>....[DIAGRAM 2 DELETED]


> As a further consideration, consider two ice-skaters in motion (a and b).
> 'b' is approaching 'a' at a velocity slightly faster than 'a'. Skater 'a'
> grabs skater 'b' and with a spinning motion, launches 'b' faster than
> 'b' was originally moving. 'a' of course ends up slower than before the
> encounter, however, no energy is lost or gained, merely transferred.

Wrong.

1) Energy HAS entered the system. Namely the muscular energy exerted by
skater 'a' (this is important for reasons listed below).

2) This is not a valid comparison to the free graviational bodies (in part
because you are introducing this "internal structure" of the body).

3) This, also, is a three body system. The two skaters and, through the
friction of the their skates, the earth. If the skaters were in free fall,
this would be a much trickier move to execute.

4) Even if the final velocities of the skaters are exactly right so that
the total kinetic energy of the system does not change, you will find --if
you work through the numbers-- that you have not conserved the net momentum
of the system.

This last is the bottom line. Two free bodies cannot "slinshot" one
another and still conserve both energy and momentum

NICHAEL

------------------------------------------------------------
| Nichael Lynn Cramer | Pull down, |
| -- Nic...@BBN.Com | Tear Up. |
| -- NCr...@BBN.Com | -- Don Martin |
------------------------------------------------------------

Nichael Cramer

unread,
May 18, 1989, 11:18:20 PM5/18/89
to

I don't remember the numbers (in species/yr) offhand, but I've read
arguements (e.g. by S J Gould) that claim that we are *now* in the midst of
the one of greatest (if not in fact _the_ greatest) of mass extinctions of
all time.

If I recall right, the numbers work out to ~1 species/100,000 increase in
human population.

Clayton Cramer

unread,
May 19, 1989, 12:11:10 PM5/19/89
to
In article <40...@bbn.COM>, ncr...@bbn.com (Nichael Cramer) writes:
> In article <12...@irisa.UUCP> sao...@irisa.UUCP (saouter yannick) writes:
> >In article <13...@ut-emx.UUCP>, et...@ut-emx.UUCP (Ethan Tecumseh Vishniac) writes:
# ## It is also true that this is not the most dramatic mass extinction in the
# ## fossil record.
# #
# #Such collisions occurs about every 50 000 000 years and I've heard that others
# #species have disappeared as suddenly as the dinosaurs did, so earlier
# #collisions might be the cause for that, too.
# #
# #Does anyone knows others example of strange disappearance ?
#
# I don't remember the numbers (in species/yr) offhand, but I've read
# arguements (e.g. by S J Gould) that claim that we are *now* in the midst of
# the one of greatest (if not in fact _the_ greatest) of mass extinctions of
# all time.
#
# If I recall right, the numbers work out to ~1 species/100,000 increase in
# human population.

I've read that the current rate of extinction is about 15 species/century --
which is clearly far lower than ~1 species/100,000 increase in human
population.

Of course, we still don't know all the species on the planet, and I
very much doubt that we notice many that come and go anyway.

One of the Paleozoic extinctions involved 99% of all species then alive
being killed off. But over what time scale?

--
Clayton E. Cramer {pyramid,pixar,tekbspa}!optilink!cramer
Assault rifle possession is a victimless crime.
----------------------------------------------------------------------------
Disclaimer? You must be kidding! No company would hold opinions like mine!

Roy Smith

unread,
May 19, 1989, 10:47:47 PM5/19/89
to
In article <6...@gtisqr.UUCP> ke...@hindmost.UUCP (Kevin Bagley) writes:

Nichael Cramer

unread,
May 20, 1989, 2:36:07 AM5/20/89
to
In article <14...@optilink.UUCP> cra...@optilink.UUCP (Clayton Cramer) writes:
>In article <40...@bbn.COM>, ncr...@bbn.com (Nichael Cramer) writes:
># #Does anyone knows others example of strange disappearance ?
>#
># I don't remember the numbers (in species/yr) offhand, but I've read
># arguements (e.g. by S J Gould) that claim that we are *now* in the midst of
># the one of greatest (if not in fact _the_ greatest) of mass extinctions of
># all time.
>#
># If I recall right, the numbers work out to ~1 species/100,000 increase in
># human population.
>
>I've read that the current rate of extinction is about 15 species/century --
>which is clearly far lower than ~1 species/100,000 increase in human
>population.

CLAYTON

I checked my source for the above after I got home last night, and he was
claiming a loss of 10,000 species/yr but he didn't cite any sources. This
does sound very high. But on the other hand, it seems equally difficult to
believe we've only lost 13-14 species in all of the 20th century. (I've
also seen figures in the 1-10/yr range.)

Do you (or anyone else) have specific references for what the actual value
of this rate is?

Thanks
NICHAEL

The Daimyo

unread,
May 20, 1989, 6:52:07 PM5/20/89
to
In article <40...@bbn.COM> ncr...@labs-n.bbn.com (Nichael Cramer) writes:
>In article <14...@optilink.UUCP> cra...@optilink.UUCP (Clayton Cramer) writes:
>>In article <40...@bbn.COM>, ncr...@bbn.com (Nichael Cramer) writes:
>># #Does anyone knows others example of strange disappearance ?
>>#
>># I don't remember the numbers (in species/yr) offhand, but I've read
>># arguements (e.g. by S J Gould) that claim that we are *now* in the midst of
>># the one of greatest (if not in fact _the_ greatest) of mass extinctions of
>># all time.
>>#
>># If I recall right, the numbers work out to ~1 species/100,000 increase in
>># human population.
>>
>>I've read that the current rate of extinction is about 15 species/century --
>>which is clearly far lower than ~1 species/100,000 increase in human
>>population.
>
>I checked my source for the above after I got home last night, and he was
>claiming a loss of 10,000 species/yr but he didn't cite any sources. This
>does sound very high. But on the other hand, it seems equally difficult to
>believe we've only lost 13-14 species in all of the 20th century. (I've
>also seen figures in the 1-10/yr range.)
>
>Do you (or anyone else) have specific references for what the actual value
>of this rate is?

There is a theory that was proposed by the late Dr. Luis Alvarez and Dr.
Richard Muller on the topic of mass extinctions. In the geological
record there is evidence of mass extinctions at regular intervals thru
out earth's history. These extinctions occurred (don't quote me on
this, I'm doing it by memory) I think every 300 million years, at a
almost frightening regular interval. The extinctions of the dinosaurs
was one and about 300 million years later, the extinction of pre-historic
mammals another. Before then, the geological record shows extinction
after extinction at roughly 300 million year intervals. The theory
proposed states that our Sun may have a companion star. For years,
astronomers and astrophysicists had assumed that our sun was different
from the rest of the stars in the universe in that it was not part of
a binary system. This theory states that our sun may have a companion
star that at its closest point to the earth (it still looks like a normal
star from a telescope at its closest point) crosses thru the comet belt
with enough gravitational disturbance to knock about a 300,000 (I think)
or so comets out of the cloud into the inner solar system. The odds
worked out that one would hit the earth.
For more information consult the book "Nemesis: the Death Star"
by Dr. Richard Muller.

Extinctions on the smaller scale, aka caused by man, continue on this
planet in several key places : 1South America 2Africa ...etc. the list
goes on. The destruction of the Amazon to make farm land is by far
one of the fastest destruction of both animal and plant species in the
world. The uniqueness of the Amazon enviroment is such that the plant
and animal species that live there cannot be found anywhere in the world.
In fact in a recent shuttle picture, the Amazon area was nothing but
smoke as the forest is being burned down. In Africa, the desert grows.
Man's own folly is to blame for that disaster as well. The interference
of well meaning foreigners to help the people has led to the destruction
of thousands of acres of land. The digging of wells in areas with lush
vegetation was not only not productive but is the direct cause of the
growing deserts. Herd animals, wild life, and man flock for miles around
just to get to this plentiful source of water. In their rampage, the
vegetation is stripped, trees are cut down and tender vegetation
trampled. What's left in a matter of months is a wasteland, a addition
to already expanding desert. Destruction of trees has had a direct
impact on the ecosystem in Africa. In areas where there are trees it
rains. In areas where there were trees not long ago, it will rain for
a few years more. In areas where trees were cut down a long time ago,
there is desert. The ecosystem is destroyed the moment the native
habitat is destroyed, and the weather adjusts accordingly. The famine
in Africa will continue, probably and sadly, forever, unless the the
ecosystem is restored. In the United States, coal burning plants have
destroyed forest land on the Eastern Sea Board and all over Eastern
Canada. Lakes have so much acid content in them that the water is
poisonous. In Europe, a similar situation exists in Germany, where
a huge portion of forest land has been labeled as doomed from the acid
rain. In Chicago, the marble off the buildings is being dissolved by the
acid rain, of which sulfuric acid is a member. When the habitats go,
so do the life forms that live within them. Hopefully something can
be done to stop this. Soon I hope.

Albert Sze-Wei Wang
------------------------------
The Daimyo |
c60a...@widow.berkeley.edu |
------------------------------

Clayton Cramer

unread,
May 21, 1989, 2:42:57 PM5/21/89
to
In article <40...@bbn.COM>, ncr...@bbn.com (Nichael Cramer) writes:
> In article <14...@optilink.UUCP> cra...@optilink.UUCP (Clayton Cramer) writes:
> >In article <40...@bbn.COM>, ncr...@bbn.com (Nichael Cramer) writes:
# ## #Does anyone knows others example of strange disappearance ?
# ##
# ## I don't remember the numbers (in species/yr) offhand, but I've read
# ## arguements (e.g. by S J Gould) that claim that we are *now* in the midst of
# ## the one of greatest (if not in fact _the_ greatest) of mass extinctions of
# ## all time.
# ##
# ## If I recall right, the numbers work out to ~1 species/100,000 increase in
# ## human population.
# #
# #I've read that the current rate of extinction is about 15 species/century --
# #which is clearly far lower than ~1 species/100,000 increase in human
# #population.
#
# CLAYTON
#
# I checked my source for the above after I got home last night, and he was
# claiming a loss of 10,000 species/yr but he didn't cite any sources. This
# does sound very high. But on the other hand, it seems equally difficult to
# believe we've only lost 13-14 species in all of the 20th century. (I've
# also seen figures in the 1-10/yr range.)
#
# Do you (or anyone else) have specific references for what the actual value
# of this rate is?
#
# Thanks
# NICHAEL

Nope. I sure would like to see some numbers. Now that I think about
it, I think what I had read (in a newspaper, so probably false) was
that over the time man has been on the planet, there has been an
average loss of 15 species/century -- not the same as the rate for
this century.

Kevin Bagley

unread,
May 22, 1989, 12:57:15 PM5/22/89
to
In article <40...@bbn.COM> ncr...@labs-n.bbn.com (Nichael Cramer) writes:
>In article <6...@gtisqr.UUCP> ke...@hindmost.UUCP (Kevin Bagley) writes:
>>In article <39...@bbn.COM> ncr...@BBN.COM (Nichael Cramer) writes:

>>>>In article <5...@cadomin.UUCP> pa...@alberta.UUCP (Pawel Gburzynski) writes:
>>>>> [ In re, capture of an asteroid into Earth orbit ]

>>>To clarify slightly, you HAVE to add in the effects of the moon.
>> [stuff relating to slingshot and object capturing deleted]
>>>NICHAEL

>> I disagree. You do not HAVE to have a moon in order to obtain the
>> slingshot effect. All you do have to do is approach an orbiting body
>> at the side opposite the direction of the orbit....

The above still remains valid. It may also be appied to a two body system
wherre the above statement would be changed to...

You do not HAVE to have a moon in order to obtain the
slingshot effect. All you do have to do is approach an orbiting body

at the side opposite it direction of movement.

>You are right that you don't have to have a *MOON*, but you *MUST HAVE* the
>THIRD body for this to work (this was the point in the original posting; I
>think it's clearer in context).

Disagree. Acceleration/deceleration may be obtained in a two body encounter.
No conservation laws are violated by the method I described. In the encounter,
one body gains velocity, while the other body looses velocity. Energy is
transferred, not lost or gained.


>In your example above, if both bodies are intially free, thery will remain
>free. Moreover their respective speed will NOT change overall.

Part one of the above statement is correct. Part two is not.
Since the engergies available in the description I provided may be
transferred, it is easily possible for one body to be accelerated while
the other is slowed down. Capture will not take place, but the velocity
changes *will* happen.

>>....[DIAGRAM 2 DELETED]

>> As a further consideration, consider two ice-skaters in motion (a and b).

[Skater description deleted]

>Wrong.

Not wrong.

>1) Energy HAS entered the system. Namely the muscular energy exerted by
>skater 'a' (this is important for reasons listed below).

The muscular energy is equivalent to the gravity well of a massive body.

>2) This is not a valid comparison to the free graviational bodies (in part
>because you are introducing this "internal structure" of the body).

The analogy of muscular energy is a valid representation of the gravity
well of massive bodies.

>3) This, also, is a three body system. The two skaters and, through the
>friction of the their skates, the earth. If the skaters were in free fall,
>this would be a much trickier move to execute.

The friction of the skates does not help the energy transfer, it hinders
it. Actually, the maneuver would be (slightly) more effective in free fall.

>4) Even if the final velocities of the skaters are exactly right so that
>the total kinetic energy of the system does not change, you will find --if
>you work through the numbers-- that you have not conserved the net momentum
>of the system.

The numbers work. Again, no energy is lost or gained, it is merely
transferred. These are the maneuvers performed by all deep space inter-
planetary probes. Not only can it work, It DOES. Jupiter was actually
slowed by the passage of voyager... a VERY minute slowing since Jupiter
is so massive, however the effect on Voyager was a significant increase
in velocity.

>This last is the bottom line. Two free bodies cannot "slinshot" one
>another and still conserve both energy and momentum

This is the next last bottom line. In a two-free-body system where both
bodies have relative motion, one of the bodies can gain in velocity while
the other will loose velocity.

>NICHAEL

>------------------------------------------------------------
>| Nichael Lynn Cramer | Pull down, |
>| -- Nic...@BBN.Com | Tear Up. |
>| -- NCr...@BBN.Com | -- Don Martin |
>------------------------------------------------------------

^^^^^^^^^^^^^^^^^^^^^^^^^^^
I remember that issue of MAD.

Since this has been hashed around quite a bit. If you want to respond,
please us email.

James S. Larson @ St. Olaf College

unread,
May 22, 1989, 6:22:09 PM5/22/89
to
There has been recent discussion as to the rate of extinction of species.
Some sources said that the rate was only a few dozen a century. While
that may have been true in the past, the rate has increased dramatically
this century.

According to Gaia: An Atlas of Planet Management (edited by Dr. Norman
Meyers, 1984), the annual rate of extinction was less than 1 before
1900. In 1950 it grew to 6/yr. In 1975 it was 400/yr. The projection
for 1990 was 10,000/yr. and the forecast for 2000 was 50,000/yr!!!!

They say "Current estimats suggest that we are losing one species a day
from the 5-10 million species thought to exist. By the time human
populations reach some sort of ecological equilibrium with their
one-Earth habitat, at least a quarter of all species could have
disappeared." (p. 155)

This is getting off the topic of the newsgroup, but it illustrates that
we don't need to wait for a one-in-a-million-years asteroid in order
to destroy life on earth.

--
-------------------------------------------------------------------------------
| Jim Larson | "What? You mean behind the rabbit?" |
| lars...@thor.acc.stolaf.edu | -Monty Python and the Holy Grail |
-------------------------------------------------------------------------------

Wayne D. T. Johnson

unread,
May 22, 1989, 1:23:10 PM5/22/89
to
I have also heard a story about a mammoth that was found frozen in Siberia,
death was purported to have been caused by freezing, with tropical plants
still in its mouth.

I know Van Donigan (sp?, author of charriots of the gods and other such drivle) used this as proof that an advanced intellegent life existed back then.

Last I heard, he was doing 5-10 for fraud...

--
Wayne Johnson (Voice) 612-638-7665
NCR Comten, Inc. (E-MAIL) W.Jo...@StPaul.NCR.COM or
Roseville MN 55113 joh...@c10sd1.StPaul.NCR.COM
These opinions (or spelling) do not necessarily reflect those of NCR Comten.

Keith Dancey

unread,
May 23, 1989, 5:15:43 AM5/23/89
to
In article <11...@unm-la.UUCP> ha...@unm-la.UUCP (Hugh Hazelrigg) writes:
>In article <61...@nfs4.rl.ac.uk> k...@inf.rl.ac.uk (Keith Dancey) writes:
>>My understanding is that the demise of the dinosaurs extended over a period
>>of order of magnitude of a thousand years. Certainly long enough to place
>>doubt upon the viability of a single catastrophy such as the one mentioned.
>
>What prevents the effects of a "single catastrophy [sic]" from propagating over
>a period of a thousand years? On a geological scale of time, the events of a
>thousand years constitute less than a footnote in a billion-page volume.
>
True. But you are forgetting that geology was not the issue in the
article on the relatively sudden extinction of dinasaurs.
The issue was whether a single impact could effect *meteriological*
conditions such that a species would become extinct. For instance,
whether polluted skies would effect food chains and temperature. But
if that scenario was to be true, then SURELY a species would die within
its lifetime. If one dinosaur could survive its entire life under these
conditions, then so could another, and so on. If dinosaurs took a
thousand years to become extinct, what finished off the last one that
*didn't* manage to kill its immediate forbears. If anything, one would
assume that survivors of the first five hundred years would have been
selected to manage better under the austere conditions, rather than
the opposite. It is also reasonable to assume that these hostile
conditions would *gradually* improve with time, thus *increasing*
the chances of species survival, rather than the opposite.

>
>Look: a thousand years (or even five or ten) really is just a one-nighter
>(what a party!). The earth may have lost a host of magnificent species, but
>did life disappear?
>
When you are talking about *dramatic* changes in climate and food chains
critically effecting species survival, then the time scales involved must
be of the order of seasons, rather than thousands of years. One year of
darkness is all that it would take to destroy vegetarian dinosaurs. But
they lasted for generations. How? And if even a single generation could
survive lower temperatures, why couldn't others?

>I believe the metorite/asteroid collision theory to be the best put forward to
>date to explain the demise of the dinosaurs and their ecosystem. Your objection,
>Keith, is ill-considered.
>

Far from it. There are enormous problems with a *single* catastrophy such
as an asteriod strike *if* the palaeontological evidence is to be believed
(unless dinosaurs lived a thousand years, that is :-).
--
Keith Dancey, UUCP: ..!mcvax!ukc!rlinf!kgd
Rutherford Appleton Laboratory,
Chilton, Didcot, Oxon, England OX11 0QX
Tel: (0235) 21900 ext 6756 JANET: K.DA...@uk.ac.rl.inf

Jonathan Patrick Leech

unread,
May 23, 1989, 2:10:43 PM5/23/89
to
In article <61...@nfs4.rl.ac.uk> k...@inf.rl.ac.uk (Keith Dancey) writes:
>My understanding is that the demise of the dinosaurs extended over a period
>of order of magnitude of a thousand years. Certainly long enough to place
>doubt upon the viability of a single catastrophy such as the one mentioned.
>If the palaeontological evidence is not contradicted (and I have understood
>it correctly) then a *series* of such catastrophic strikes would be required.
>
>That is not say a single catastrophy is ruled out, but it looks as though
>its effects must be longer-lived than a few years.

There is some belief that a gravitational perturbation of the
cometary cloud could produce "showers" of comets in the inner solar system.
Don't take "showers" too literally - it means a handful of hits over
long periods of time - but this has some bearing on your comments.

Yow! Get off the net for two weeks, come back to 600 articles in
sci.space. :-)

Jon Leech (le...@apple.com)
Apple Integrated Systems, San Jose
__@/

Larry Wall

unread,
May 24, 1989, 8:58:16 PM5/24/89
to
In article <62...@nfs4.rl.ac.uk> k...@inf.rl.ac.uk (Keith Dancey) writes:
: True. But you are forgetting that geology was not the issue in the

: article on the relatively sudden extinction of dinasaurs.
: The issue was whether a single impact could effect *meteriological*
: conditions such that a species would become extinct. For instance,
: whether polluted skies would effect food chains and temperature. But
: if that scenario was to be true, then SURELY a species would die within
: its lifetime. If one dinosaur could survive its entire life under these
: conditions, then so could another, and so on.

Yes, but that's not really the issue. To guarantee eventual extinction
you only have to reduce the rate of survival (to reproductive age) to
less than 2 per dinosaur family. We all know that changes in
temperature affect fertility, not to mention fecundity... :-)
And there could well be some relationship between temperature and
mortality. Especially with large egg layers. So meteorology can
certainly have long term effects on a species.

(What actually happened was the dinosaurs had an industrial revolution with
all the iron in the asteroid, and the standard of living went too high,
and too many of them became dinks.)

: If dinosaurs took a

: thousand years to become extinct, what finished off the last one that
: *didn't* manage to kill its immediate forbears.

Probably loneliness. Only 1/3 :-)

: If anything, one would


: assume that survivors of the first five hundred years would have been
: selected to manage better under the austere conditions, rather than
: the opposite. It is also reasonable to assume that these hostile
: conditions would *gradually* improve with time, thus *increasing*
: the chances of species survival, rather than the opposite.

There are several things to say about that. If you trigger a mini ice
age it could well last longer than 1000 years. Moreover, as the
dinosaurs get sparser, it becomes more difficult to find a mate and
de-sparsify the dinosaurs, a nasty form of feedback. And even if
conditions are improving gradually, the land is now overrun with little
varmints who have a faster selection cycle and took advantage of the
new conditions while the bigger folk were still squeaking by. Perhaps
the initial catastropic conditions favored small critters that could
get by eating almost anything, even tough dinosaur eggs. Or malnourished
dinosaurs trying to babysit their eggs.

It's also vaguely possible that the dinosaurs adapted to the cold, but at
the price of losing the ability to adapt to the heat again. We don't know
enough about dinosaur genetics to rule it out. (At least, I don't.)

: >Look: a thousand years (or even five or ten) really is just a one-nighter

: >(what a party!). The earth may have lost a host of magnificent species, but
: >did life disappear?
: >
: When you are talking about *dramatic* changes in climate and food chains
: critically effecting species survival, then the time scales involved must
: be of the order of seasons, rather than thousands of years. One year of
: darkness is all that it would take to destroy vegetarian dinosaurs. But
: they lasted for generations. How? And if even a single generation could
: survive lower temperatures, why couldn't others?

Maybe they were allergic to the ragweed that grew so well in the cooler
climate. I think every day I spend in these Santa Ana winds takes several
hours off my life. (Beats having the smog though.)

If the chaoticists are to be believed, something much less dramatic
than an asteroid is capable much greater consequences than mere
extinction of dinosaurs. Why, the flap of a butterfly's wing today may
influence whether the universe collapses next week... well, perhaps
that's a wee bit exagerated... Still and all, non-linear systems (and
we're not just talkin' weather) can behave oddly under seemingly mild
perturbations. Let's remember that ecological niches aren't cast in
concrete, but at least partly in the flesh of whatever else wants to
occupy the neighboring niches, not to mention the same niche. And
precedence matters--last one there is a rotten dinosaur egg!

: >I believe the metorite/asteroid collision theory to be the best put forward


: >to date to explain the demise of the dinosaurs and their ecosystem. Your
: >objection, Keith, is ill-considered.
: >
: Far from it. There are enormous problems with a *single* catastrophy such
: as an asteriod strike *if* the palaeontological evidence is to be believed
: (unless dinosaurs lived a thousand years, that is :-).

It doesn't take much imagination to see that *something* changed to off
all the dinosaurs. Just because we have difficulty imagining how the
bullet got from the smoking gun to the victim doesn't mean it didn't (or did).
To bend another saying to our use, we might say that "Absense of imagination
implies imagination of absence." Just because I can't see the connection
doesn't mean there isn't one. The "enormous problems" with a single
catastrophe are mostly problems in our head, because we ain't smart enough.
(Nothing personal, Keith. :-)

I've got it now! The asteroid hit an oil field situated over a fluorite
deposit sitting on a huge salt dome, and filled the atmosphere with
chlorofluorocarbons. Anything that couldn't hide under a log and didn't
have fur or feathers had increased risk of skin cancer for the next
N thousand years. :-)

Yes, unlikely. But we don't know how many times Mother Nature tried before
she hit the jackpot. Unlikeliness isn't a big problem in my book.

Go ahead, flame me, I've already reproduced.

Larry Wall
lw...@jpl-devvax.jpl.nasa.gov
"So many programs, so little time..."

j.a.welsh

unread,
May 26, 1989, 9:50:56 AM5/26/89
to

The Voyagers used gravity slingshots to get where they are and
as far as I know, they only used the planets gravity for a
boost. Isn't there a planned interplanetary probe that is supposed
to slingshot past Venus twice (or is it Venus once and Earth once?)
to get out to Jupiter? These would be single body slingsots.

Michael Starr

unread,
May 28, 1989, 4:08:05 PM5/28/89
to
In article <22...@thor.acc.stolaf.edu> lars...@thor.stolaf.edu (James S. Larson @ St. Olaf College) writes:
>They say "Current estimats suggest that we are losing one species a day
>from the 5-10 million species thought to exist. By the time human
>populations reach some sort of ecological equilibrium with their
>one-Earth habitat, at least a quarter of all species could have
>disappeared." (p. 155)

According to the June 1989 National Geographic (editorial page):
"Humans for the first time are the cause and the ultimate victims. It's
said that before humans appeared, extinctions of flora and fauna
ran about one species a year. Now it is estimated that four
species go belly-up per hour, indicating a total of a million by the
year 2015."

----
__/\__ ******************** __/\__ | st...@shuxd.att.com
\ / * Michael L. Starr * \ / | att!shuxd!starr
|/\| ******************** |/\| | attmail!starr

Alan Silverstein

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May 31, 1989, 1:38:36 PM5/31/89
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> ...it should be obvious what killed off the dinasours: An Intelligent
> Dinasour!

The only problem is, we haven't found any of their Coke bottles... or
geosync satellites.

William O'Shaughnessy

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May 30, 1989, 7:49:22 PM5/30/89
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With man as an example of what an intelligent species can do to a planet

it should be obvious what killed off the dinasours:
An Intelligent Dinasour!

Look at what man is doing now. Within a hundred years most formerly wild
mammals will only exist in zoos. It'll take us longer to do in the
oceans but we're working on it.
Bill O'Shaughnessy

pe...@ohstpy.mps.ohio-state.edu

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Jun 1, 1989, 4:52:27 PM6/1/89
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That tells you they were really intelligent.

William O'Shaughnessy

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Jun 2, 1989, 12:38:01 PM6/2/89
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Ahhh, but we have found their spark plugs imbedded in rocks in Southern
California, and nails in rock in a deep mine in South Dakota.

Timothy D Margeson

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Jun 2, 1989, 7:16:33 PM6/2/89
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In article <463...@hpfcdc.HP.COM> a...@hpfcdc.HP.COM (Alan Silverstein) writes:
>
>The only problem is, we haven't found any of their Coke bottles... or
>geosync satellites.

Weel that may be true, but remember that we would be hard pressed to locate
our own if we didn't know where to look!


--
Tim Margeson (206)253-5240
PO Box 3500 d/s C1-022 @@ 'Who said that?'
Vancouver, WA. 98668
e-mail replies to: timo...@tekigm2.MEN.TEK.COM

Clayton Cramer

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Jun 5, 1989, 12:34:08 PM6/5/89
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In article <781...@hpcupt1.HP.COM>, will...@hpcupt1.HP.COM (William O'Shaughnessy) writes:
> Ahhh, but we have found their spark plugs imbedded in rocks in Southern
> California, and nails in rock in a deep mine in South Dakota.

I've seen something like a spark plug supposedly encased in rock found
in Southern California. Does anyone have the whole story on this?


--
Clayton E. Cramer {pyramid,pixar,tekbspa}!optilink!cramer

Governments that don't trust most people with weapons, deserve no trust.

William O'Shaughnessy

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Jun 7, 1989, 4:43:20 PM6/7/89
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The spark plug like object imbedded in a rock and nails imbedded in rock in
a deep mine are from real news stories from >5 yrs. back as best my memory
can recall them. They were not National Enquirer stories. The spark plug
story was on a PBS show mannnnnnnnnnnny years ago.

Bill O'Shaughnessy

Jordan Kare

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Jun 8, 1989, 5:02:01 PM6/8/89
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In article <50...@jpl-devvax.JPL.NASA.GOV> lw...@jpl-devvax.JPL.NASA.GOV (Larry Wall) writes:
>.... Let's remember that ecological niches aren't cast in
>concrete...

What about all those alligators living in the New York City sewer system??

Jordin Kare

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