PLEASE NOTE:
*
CCNet DEBATE, 12 October 1998
-----------------------------
(1) ASTEROID WEAPON-THREAT SHOULD BE DISMISSED OUT OF HAND
Richard A Kowalski <bitnik@bitnik.com>
(2) ASTEROID DEFLECTION
James D. Perry <AJDPerry@aol.com>
(3) THE LAST MAGICIAN
Sir Arthur C Clarke
(4) THE COMET OF 1680/81
Wolfgang Kokott <W.Kokott@lrz.uni-muenchen.de>
(5) ARE THERE CYCLES OF CLIMATIC DOWNTURNS?
Mike Baillie <m.baillie@qub.ac.uk>
(6) A PROPOSED MECHANISM FOR THE GENERATION OF COMET SHOWERS
Roy Tucker <tucker@noao.edu>
=====================
(1) ASTEROID WEAPON-THREAT SHOULD BE DISMISSED OUT OF HAND
From Richard A Kowalski <bitnik@bitnik.com>
Personally, I think that the use of an asteroid as a weapon
actually
requires too much forethought, planning and "threat
time" for even a
"madman" to use.
The idea of a threat is to create terror and chaos. It must also
be
such that the "enemy" cannot counteract the weapon.
In other words, "Mad man X" builds or obtains an
interplanetary launch
vehicle and the needed warheads or other technologies needed to
change
the objects orbit to one of earth intercept. Then (s)he needs a
large
lead time to allow for this "weapon" to
"find it's target", which can
be years or decades.
How likely is it that all of this could remain a secret until it
is too
late to respond? I think very unlikely.
It is much cheaper, easier and much less costly to produce
biological
or chemical or even obtain nukes, to do the job.
I think the threat from this type of weapon should be dismissed
out of
hand when there are so many more realistic threats already being
used.
Anyone for fuel oil and fertilizer, Sarin or Anthrax, et al?
-- Richard A Kowalski
Quail Hollow Observatory http://www.bitnik.com/QHO
761 Zephyrhills
==================
(2) ASTEROID DEFLECTION
From James D. Perry <AJDPerry@aol.com>
Dear Benny,
Oliver Morton said,
"While I'm not greatly invested in the Sagan/Ostro
threat, I thought
James Perry was a little too dismissive. His confidence
that a
strangelove-style madman would be easily controlled
through PALs,
etc, ignores the fact that most nuclear powers do not have
universal
PALs or similar controls."
The US, Britain, France, and Russia use PALs (or some
analogue).
Therefore the majority of all nuclear weapons are under PAL
control. I
don't know what the Chinese, Israelis, Indians, and Pakistanis
use, but
this is a moot point, since these would probably not be the
powers who
installed and operated an asteroid deflection system.
"What's more, he assumes at some points that the risk
is of a global
catastrophe, while engineered regional devestations are also
possible.
They'd be harder to pull off, I agree, but politicians and
generals
have been known to attempt things they couldn't pull off while
all the
time convinced that they could..."
I did address the issue of regional devastation, and concluded
that
asteroids were not the best way to inflict such
devastation. It is
highly unlikely that the powers who would probably control the
asteroid
deflection system (perhaps the Permanent Members of the UN
Security
Council) would want to cause a regional catastrophe, but if they
did,
they have more effective, reliable, and controllable means at
their
disposal (nuclear-armed ICBMs) than asteroids.
"He also assumes that a collision would be engineered using
an existing
deflection system, which is not necessarily the case. "
I'm not quite sure what you're getting at here. How do you
engineer a
collision with a deflection system that does not exist?
"And he ignores the fact that an asteroid, while unwieldy,
might when
used as a weapon provide benefits in terms of leverage and
deniability."
One could address this risk by ensuring that the operations of
the
asteroid deflection system were completely transparent.
When asteroids
were detected -- or deflected -- this information would be made
available to scientists and the public worldwide in a timely
manner.
It would be hard to redirect an asteroid (or permit an asteroid
to
continue on a dangerous course) if the world was looking over
your
shoulder, so to speak. Moreover, one must assume that
professional and
amateur astronomers would continue to hunt for asteroids
independently
of the asteroid detection system -- indeed, civilian scientists
may
even be part of the detection system. This redundant capability
would
make a "plausibly deniable" deflection that much harder
to execute
successfully. Finally, if the detection/deflection effort
were
international, then a large number of countries would have to
collude
to effect an "accidental" collision, which seems
unlikely to me.
"Jens Kieffer-Olsen assumes that use of nuclear explosives
means the
involvement of the military. While in the rest of the world this
might
be the case, in the US nuclear explosives come under the remit of
the
Department of Energy. As I understand it, this is the result of a
decision -- in the Eisenhower administration, or earlier -- that
nukes
were too important to leave to the generals. It is the DoE that
designs
and makes the things; nuclear tests were, when they used to
occur, DoE
responsibilities, I believe. So a civilian use of nuclear
explosives is
conceivable -- indeed, precedent suggests that American public
opinion
and political prractice would both point to civilian control of
non-military nukes in such a context."
This is not precisely accurate. In 1946, the Truman
administration
established the Atomic Energy Commission, and gave the AEC
physical
possession of all nuclear weapons, to be handed over to the
military
only at the President's discretion. This practice did not last
very
long, however. In the early 1950s, the military began to assume
custody
of weapons, and by the late 1950s the entire stockpile had been
handed
over to the military. The principal impetus for this was the
development of ICBMs, whose short time of flight rendered
impractical
any scheme in which the military could not respond immediately to
an
enemy attack. After its establishment in the 1970s, the
Department of
Energy became responsible for the research, development, testing,
production, and retirement of nuclear weapons. However, the
operational
deployment (and potential employment) of the weapons is in the
hands of
the Department of Defense.
It is true that "civilian use of nuclear weapons is
conceivable" -- and
a reasonable case could be made that asteroid deflection is a
"civilian
use" of nuclear weapons. Note that there is a strong
correlation
between timely detection and nuclear control/safety. The
sooner a
dangerous object is detected, the more time we will have to plan
the
deflection, and the safer the operation will be.
James D. Perry
=================
(3) THE LAST MAGICIAN
From Sir Arthur C Clarke
Dear Benny,
Amused by Brian's reference to 'the rather bizzarre (sic - it's a
word
I've never been able to spell either) character who succeeded
Newton'.
I'd have given Sir Isaac 9 out of 10 in that category...
All best,
Arthur Clarke 8 Oct 98
=========================
(4) THE COMET OF 1680/81
From Wolfgang Kokott <W.Kokott@lrz.uni-muenchen.de>
Great scientists are quoted constantly, but read rarely. Edmond
Halley
shares this fate. He had noticed that his parabolic orbits for
the
comets of 1531, 1607 and 1682 were quite similar and on these
grounds
tried successfully to represent the older observations by means
of the
1682 elements -- ending up with the famed 76-years periodicity.
Subsequently, he noticed that prior to 1680, comets had appeared
in 531
and 1106, and <lacking observational evidence> conjectured
that IF these
three apparitions were again of the same object, a period of 575
years
would result. On this basis, he again adapted his parabola. The
big
'if' is by Halley himself <the 'Synopsis', both the 1705 and
the 1749
versions>, and it did not work out. Up to now, the spurious
evidence of
531 and 1106 did not lead to reliable orbits for these objects.
The
definite orbit of C/1680 was finally computed by J.F.Encke in
1818;
he did make use of the modern theory of planetary perturbations.
His
orbit is also an ellipse, albeit with a period of about 9600
years and a
marked 'uncertain' tagged to this value.
Regards,
W.Kokott
=========================
(5) ARE THERE CYCLES OF CLIMATIC DOWNTURNS?
From Mike Baillie <m.baillie@qub.ac.uk>
Thanks to Brian Marsden for clarifying the debunking of Halley's
575
year return time on the 1680 comet. By way of explanation let me
inform
the readership of a rather curious coincidence. In studying
tree-ring
records and writing odd articles it happens that among other
dates I
have covered (without prior knowledge of Halley's 575 year
period) are
2911 BC, the 2354-2345 BC inundation event, the 1628 BC possibly
Santorini event, the 1159 BC so called Hekla 3 event, the 207 BC
and
536-545 AD events. For good measure and prompted by Kevin Pang's
Chinese history and Val LaMarche's 43 BC frost ring event, I have
discussed the 44 BC event (for which we have no Irish oaks).
Now the curious thing about this list of dates, independently
derived
from tree-ring series, is the proximity of several of them to the
531
AD, 44 BC, 1194 BC, 2344 BC and 2919 BC "Halley 1680
returns".
Obviously this is just a bizarre coincidence. Or is it? How would
we
know? Is it possible that there are 'episodes', which might
involve
comets or their debris, at around the interval that Halley
proposed? I
wouldn't pretend to know.
Incidentally, the reason I refer to the 2354-2345 BC event as
'the
inundation event' is that we have pretty good tree-ring evidence
that
just at that time the level of Lough Neagh in Northern Ireland,
the
largest water body in the British Isles, rose suddenly.
Even more
curious is that the prehistoric section of the Irish Annals
records
"lakes breaking out" in 2341 "BC", while
Archbishop Usher (aka Ussher)
of County Armagh (just south of Lough Neagh) was the individual
who
provided the biblical date 2349/48 "BC" for the Flood
of Noah; the very
date that Halley and Whiston used.
Part of my interest is how scientists are supposed to deal with
such
loose clusters of information. Bluntly, how can one assess
significance
with intrinsically weak data, but quite a lot of it? This
is very much
in keeping with Bob Kobres' recent listing on how do we infer
significance from mythological information which is intrinsically
weak,
though there is a lot of it.
Mike Baillie
Palaeoecology Centre
School of Geosciences, Queen's University, Belfast
(01232) 335147
============================
(6) A PROPOSED MECHANISM FOR THE GENERATION OF COMET SHOWERS
From Roy Tucker <tucker@noao.edu>
Dear Dr. Peiser,
If the following text is deemed appropriate, I would appreciate
its
posting to the Cambridge Conference forum. Thank you very much.
Sincerely yours,
Roy Tucker
-------------------------------------------------------------------
A proposed mechanism for the generation of comet showers
The geological record contains
tantalizing evidence of the
occurence of 'comet showers', geologically brief periods during
which
impact events were much more frequent than at the present time.
Speculations regarding the causes of such showers have involved
gravitational perturbations of the Oort cloud by passing stars or
a
faint red dwarf companion of the sun or passage of the sun
through
molecular clouds in the galaxy. I wish to offer, for comment by
the
members of this forum, another possible mechanism.
I would first like to call attention to
a few facts or conjectures:
Fact 1 - Chiron and other known outer solar system minor planets
can be
quite large, approximately 200 kilometers in diameter.
Fact 2 - Chiron, originally thought to be a minor planet, has in
recent
years displayed a cometary coma and is apparently a huge comet.
This may be
generally true of these outer solar system bodies.
Fact 3 - Many of these bodies are in unstable orbits that will
evolve
greatly in periods of time much shorter than the age of the solar
system. This may offer them the occasional opportunity to
interact with the
major outer planets.
Conjecture 1 - Many Oort cloud comets may indeed have highly
eccentric
orbits that permit them to approach the outer giant planets.
Fact 4 - The Kreutz family of sun-grazing comets, consisting of
apparently many hundreds of fragments, is likely to have resulted
from the
disruption of a single parent body at around 371 BC (Marsden, AJ
1989,
98:2306).
Fact 5 - Close approaches to a giant planet can either eject a
comet
from the solar system or greatly reduce its semimajor axis so
that it
becomes a short-period comet.
Fact 6 - At least one comet (Shoemaker-Levy 9) has been observed
to be
disrupted by a close approach to a giant planet (Jupiter) into
kilometer-sized fragments.
Hypothesis:
It is possible for a large Chiron-class object
or Oort cloud comet
to pass within the Roche limit (approximately 2.456 planetary
radii or
about 108,000 km for Jupiter) of a major planet and not only be
disrupted into a large number of fragments but these fragments
may also
be injected into short-period orbits with perihelia deep within
the
inner solar system. Bear in mind that a 200 km object such as
Chiron
would produce 8,000,000 one km fragments if equally divided. This
is an
extreme but plausible example. The high orbital inclination of
the Kreutz
family clearly demonstrates that it was not disrupted by an
encounter with
a major planet but it does show that, at least in a single case,
a large
parent comet has been disrupted into hundreds of smaller ones.
The population of outer solar system
minor planets is only now
being investigated and their abundance, sizes, and average
orbital
characteristics are not well known. The frequency with which
large,
outer solar system minor planets may approach the giant planets
is not
well known since we have had the ability to detect such objects
for only
a very few decades.
For such a disruption and comet shower
to occur, the object must
pass within the Roche limit but not impact the planet. The ratio
of the
circular area within the Roche limit in a plane perpendicular to
a
tangent of the object's path at periapse to the cross-sectional
area of
the planet is approximately six. It is more than five times more
likely to
be disrupted and pass the planet than to impact the planet.
This is, I believe, a plausible
mechanism whereby the passage of a
single outer solar system minor planet/comet near a giant planet,
such
as Jupiter, may result in a cosmic shotgun blast at the inner
solar
system.
Thank you very much for your attention
and consideration. I will
appreciate receiving your comments.
- Roy Tucker
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