PLEASE NOTE:
*
CCNet DIGEST, 9 June 1998
-------------------------
(1) NEW CALCULATIONS LEAVE CRITICS SPEECHLESS
Benny J Peiser <b.j.peiser@livjm.ac.uk>
(2) 1997 XF11 WAS NOT DANGEROUS AT ANY TIME
Clark Chapman <cchapman@boulder.swri.edu>
(3) USAF NEWS RELEASE ON THE GREENLAND METEOROID IMPACT
Duncan Steel <dis@a011.aone.net.au>
(4) A CLIMATE OF SECRECY IS THE GREATER EVIL
Jens Kieffer-Olsen <dstdba@post4.tele.dk>
(5) STRANGE NATURAL EVENTS IN LATE ANTIQUITY
Alfonso López Borgoñoz <borgonoz@mx2.redestb.es>
(6) THE AD 540 EVENT
Mike Baillie <m.baillie@qub.ac.uk>
===============
(1) NEW CALCULATIONS LEAVE CRITICS SPEECHLESS
From Benny J Peiser <b.j.peiser@livjm.ac.uk>
In yesterday's CCNet Digest, Brian Marsden presented astronomical
data
which show that, prior to Helin's and Lawrence's discovery of the
1990
films of asteroid 1997 XF11, there was "a small, but
real" possibility
that this PHO could have collided with earth in the next century.
I am
in no position to comment on whether or not Brian's sums add up.
But
one thing seems obvious to me: Should Brian's data and
calculations be
verified, this new twist in the XF11 controversy would prove his
rather
outspoken "zero-risk" critics wrong.
Now, Brian has offered his opponents to "peer review"
his data. So far,
however, no one seems prepared to come forward with an attempt to
falsify his calculations. Only Clark Chapman has responded to
Brian's
challenge. But his reaction is somewhat contradictory and often
difficult to follow. As far as I understand, Clark's main
objection is
that orbital calculations (even if they show the possibility of
an
actual impact) are simply worthless since "background
probability" as
such would rule out an impact in the first place. I don't know
whether
I got this right, but this line of argument sounds exactly like
the one
I was concerned about in the last question of my interview with
Alan
Harris six weeks ago (see CNet Debates 28 April). If Clark is now
confirming that statistical "background probability"
will become the
battle cry against actual orbit calculations, one wonders why we
should
continue with the search for PHOs and calculate earth-crossing
orbits
at all.
What is more, Clark's response to Brian's hard data provides an
impressive example of the enormous difficulties we still have -
are are
prone to have in the future - in dealing with the uncertainties
of NEO
research. Just imagine we wouldn't have the 1990 films of XF11.
On 11
March 1998, Brian Marsden would send out to a dozen of
astronomers
yesterday's calculations, showing a small, but probable impact
scenario
in 2037. After consultations with his colleagues, seven of them
agree
that the public should be informed about this data and the very
small,
but possible risk this object might - due to future perturbations
-
pose in 40 years time. Three other colleagues, however, argue
that
"background probability" would rule out any risk and
that no "scary"
statement should be issued before the year 2028. Since no
'consensus'
can be reached among the group of NEO experts, NASA officials
veto the
submitted statement by the MPC and instead issue their own
"zero-risk"
statement which follows the argumentation of the minority group.
As a
response to NASA's decision, three of the seven scientists issue
a
personal statement in which they present their own research
findings
and calculations.
Now, you may think that this is a highly unlikely scenario. But I
would
argue that this is how science has always been working, at least
in
since the end of official censorship in England the 1640s. As far
as I
can see, it is neither possible nor desirable to force scientists
into
a 'consensus' on an issue so pervaded by uncertainties as the
nature,
number and hazards of Near-Earth Objects.
Benny J Peiser
P.S. I should add that Brian Marsden provided the heading for his
statement in yesterdays's CCNet Digest. The heading for Clark's
statement below, however, is mine.
=========================
(2) 1997 XF11 WAS NOT DANGEROUS AT ANY TIME
From Clark Chapman <cchapman@boulder.swri.edu>
Dear Benny,
It is a shame that Brian Marsden can't say, in simple English, in
your
Digest: "I am sorry. We are overworked and underfunded here.
In my
excitement on March 11th, I failed to make an elliptical error
analysis
of 1997 XF11 that would have proven that the asteroid could not
hit the
Earth in 2028. I furthermore mistook the one-dimensional error
that I
did calculate to be a 3-sigma error when it was actually a
1-sigma
error, and therefore said things that weren't correct (e.g. that
XF11
almost certainly would come within the lunar distance). Most
regrettably, I failed to check with my other colleagues around
the
world who could have shown me my errors before I went public, and
people got confused and scared. Finally I regret waiting more
than 5
weeks, until April 18th, to acknowledge that data were available
months
earlier that would have showed, had I or anyone else chosen to
examine
them, that 1997 XF11 had no realistic possibility of hitting the
Earth
in 2028. I've learned my lesson from Comet Swift-Tuttle and now
again
from 1997 XF11, and I promise not to make these errors
again."
It would be so wonderful to hear that from Brian. Instead, he
continues
to obfuscate matters. And he succeeds. A few days ago, on
National
Public Radio's "Morning Edition," it was reported -- in
a piece dealing
with the role of scientists interacting with journalists -- that
Brian's "initial calculation [was] based on that single
sighting...and
then all the other scientists started saying, 'hey, have we seen
that,
have we seen that?' and they came up with other sightings, and
they
instantly went back out into the mass media world and said, 'we
need to
correct this.'"
Now, that piece does ill credit to National Public Radio.
"Single
sighting," indeed! But it carries the essence of
Brian's continuing
tale (repeated numerous times in news stories referenced in this
Digest) about the role of the 1990 observations in proving 1997
XF11
"safe". To be sure, those data may have helped educate
*Brian* about
the impossibility of 1997 XF11 striking the Earth in 2028, but as
the
CNN story (item #2 in today's CCDigest) says, Paul Chodas had
found an
effectively zero threat the previous evening, "15 minutes
after he had
the XF11 data in hand." Even when informed about Chodas'
result, Brian
wouldn't admit his errors to the media (so some reporters told me
on
March 12th).
In CCDigest, you have printed Brian's remarks under the heading,
"I'm
Sorry, Clark, but 1997 XF11 Was Dangerous." I don't know if
those are
Brian's words, or yours, Benny, but the heading should have ended
with
the first two words. That's because the last four words are
*false*.
1997 XF11 was *not* dangerous at any time from its discovery by
Jim
Scotti through today, if one uses anything resembling a
common-sense
definition of the word "dangerous" [dictionary:
"able to or likely to
do harm"]. A particular asteroid is "dangerous"
and potentially worthy
of the interest of the broader astronomical world and the news
media
if, after it has been observed, it is found to present a
significant
fraction of that tiny, but potentially devastating, risk we live
with
all the time: namely, that one of those 1,750 km-wide asteroids
that
have *not* (yet) been found will strike without warning.
I don't quibble with Brian's fascination with the calculating
games he
describes in today's Digest. No doubt, there may be some tiny
little
place(s) in that original extremely elongated error ellipse of
1997
XF11 which -- if it happened to pass through that place
(extremely
unlikely!) -- would have resulted in subsequent evolution of its
orbit
that might have been interesting, or even dangerous. But the
chances
that it would have passed through that exact place and that all
the
subsequent evolution would happen, so that 1997 XF11 could
actually
strike the Earth in the next century were always extraordinarily
tiny.
Why don't you just say that, Brian, instead of once again saying
that
the asteroid was actually "dangerous" and that we live
in "peril"
[dictionary: "imminent danger"] unless every remote
contingency isn't
checked out?
Brian continues to be confused by the concept of "exactly
zero."
Experts in risk management long ago concluded that you can never
reduce
the risk of any hazard to "exactly zero". Just
because Brian can tweak
the numbers and find *some* way to have gotten 1997 XF11 to hit
next
century, based on the data available last December or March, does
not
mean that the asteroid was *ever* "dangerous" or
newsworthy. No
credible person claims that something is "dangerous"
just because the
probability of it happening isn't "exactly" zero.
Otherwise, we would
all cower in fear throughout our lives about countless near-zero
dangers.
Readers who have been following the 1997 XF11 saga will recall
that I
was, also, highly critical of Don Yeomans for his "that's
zero folks"
description of Paul Chodas's result. Brian's example of an
impact in
2037 surely illustrates why a claim of "exactly zero"
misrepresents the
larger reality. It is perhaps as confusing to non-technical
people as
Brian's claim that an extraordinarily improbable contingency is
evidence
of "danger".
It's all well and good that Helin and Lawrence found the earlier
data
that tie down XF11's orbit. But it's a red herring to say that
*those
observations* were responsible for proving XF11 was not
dangerous.
There *never was* a correctly calculated error probability
(including
Brian's "what-if?" examples in today's Digest) of 1997
XF11 colliding
with the Earth at any time during the next century that remotely
approaches the "background" probability that we live
with all the time.
It's time to admit it, Brian, and move on to more constructive
endeavors. I, for one, am working today on my response to the
request
from Congress that I provide it with an "action plan"
on how to get
NASA (and other national and international entities) working on
an
adequate Spaceguard Survey. Certainly (and this is for Mr.
Kobres) it
will include a recommendation for much enhanced funding for the
MPC (or
some equivalent entity) to hire the people to analyze all of
these data
comprehensively, and to double-check the results before going
public
with scary mistakes.
Clark R. Chapman
8 June 1998
===============
(4) USAF NEWS RELEASE ON THE GREENLAND METEOROID IMPACT
From Duncan Steel <dis@a011.aone.net.au>
USAF NEWS RELEASE
From: Headquarters Air Force Technical Applications
Center
Office of Public
Affairs
Patrick AFB, Fl.,
32925-3002
(407)-494-9915
Date: June 8, 1998
****************************************************************************
On 9 December 1997 at approximately 08:15:55.2 UT, sensors aboard
a
U.S. Department of Defense satellite recorded the bright flash of
an
apparent meteoroid disintegrating in the atmosphere over
Greenland. The
peak radiated intensity recorded on this event was 9.5E10
watts/sr
(using a 6000K blackbody model for the radiation).
Correspondingly, the
total radiated energy of the event was 2.7E11 Joules.
If you have questions call MSgt Rene Uzee, Air Force Technical
Applications Center Public Affairs at, (407) 494-4403.)
*****************************************************************************
PLEASE NOTE: THIS USAF BOLIDE INFORMATION RELEASE AND ALL
PREVIOUS
RELEASES CAN BE FOUND ON THE WWW AT
http://phobos.astro.uwo.ca/~pbrown/usaf.html
*****************************************************************************
Individuals interested in obtaining graphical lightcurve
information
for this event should send an email with their names, fax numbers
and
a description of their intended use of this information to
peter@danlon.physics.uwo.ca
===========================
(4) ANOTHER COSMIC IMPACT MOVIE
From Steve Koppes <SKoppes@aol.com>
Another new made-for-TV impact movie, titled
"Meteorites!" aired last
Wednesday evening (June 3) on the USA network. There were no big
names
in this movie, which helps account for the dismal acting.
The plot involved a fictional Arizona town menaced by a deadly
shower
of meteorites during a UFO festival (picture the meteorite shower
of
Holbrook, Arizona, in 1912, only with many fatalities, crossed
with the
celebration of aliens in Roswell, New Mexico, last summer). The
movie
made reference to other parts of the country also sustaining
damage
from the meteorite shower over several days, but the movie
focused on
the little town in Arizona.
The movie did address the difference between a meteor and a
meteorite,
and the fact that even small objects can leave relatively large
holes
in the ground. There were the inevitable mistakes, however,
probably
even more numerous than I am able to point out.
One of the actors -- I think it was the man portraying the
director of
the Flandrau Planetarium -- said "the comet" had
unexpectedly changed
course. He was actually referring not to a comet but to cometary
debris, which was being tracked by radar. I don't know much about
orbital mechanics, but is it really possible for a stream of
meteors to
change course unexpectedly?
Another part that was rather hard to swallow was how so many of
the
meteorites -- especially the earliest ones in the stream -- had
such an
amazing propensity for landing on people. Nearly an entire family
was
destroyed in one early scene. In another scene, a group of
outdoorsmen
had the misfortune of experiencing their campsite turned into a
crater.
I couldn't help but laugh out loud when an arrogant newspaper
reporter
suffered a direct hit by a meteorite at the UFO festival. He was
vaporized, leaving behind only the smoke billowing from his shoes
(is
that snickering I hear out there?).
Regards.
Steve Koppes
=======================
(5) A CLIMATE OF SECRECY IS THE GREATER EVIL
From Jens Kieffer-Olsen <dstdba@post4.tele.dk>
Re: AT LONG LAST: US SCIENTISTS REJECT NASA'S INTERIM PROCEDURES
ON
REPORTING PHOs
>"You can't control the flow of news but you can be as
truthful as
>possible up front," said Allan Lindh of the U.S.
Geological Survey.
>"The press, public and public officials seem to deal
well with
>uncertainty, but they don't deal well with the suggestion you
might
>hold out on them."
The public has been accustomed to sensationalism to such a degree
that
the XF11 scare was treated as a lark by the layman. I therefore
agree
with Allan Lindh that a climate of secrecy is the greater evil.
Illogical as it may seem, I suspect that a genuine scare could
result
from a report by astronomers of an object due to pass safely at
GEO
distance. Despite such an event being treated as a lark by
scientists!
Jens Kieffer-Olsen
=======================
(5) STRANGE NATURAL EVENTS IN LATE ANTIQUITY
From Alfonso López Borgoñoz <borgonoz@mx2.redestb.es>
Dear Benny,
I have received this, do you know something about this?
----------------
Date: Sat, 30 May
1998 18:11:11 +0300
Sender: Late Antiquity
Discussion Forum <LT-ANTIQ@VM.SC.EDU>
From: korgianitis
Dimitris <trim@OTENET.GR>
Subject: Fw: Strange natural
phenomens during Late Ant.
It is well known from several resources that strange natural
phenomena
took place during the 5th and 6th. One of the most anusual is
that
about the dissappearence of the sun. This is connected with
earthquales, fires falling from the sky into the sea and floods
that
has caused major damages all over the world. Does anyone know
about any
possible cross-checking that maybe has been done by
scientists?
Thinking that if that`s true it could had a major effect to the
mentality of his age.
---------------
From: Morten
Axboe <m_axboe@IMAGE.DK>
Subject: Strange natural phenomens
during Late Ant.: AD 536
One such phenomenon was the 'dust-veil' or 'dry fog', which in
536
dimmed the sun for almost a year, leading to severe colds and
failure
of crops. It is mentioned by Procopius, Cassiodorus and other
mediterranean writers, but also by Chinese sources, and can be
demonstrated dendrochronologically both in Europe and in Northern
America. The reason for this phaenomenon is disputed, but in
itself it
seems beyond doubt and must have been serious on the whole
Northern
hemisphere. The quotes I have found (see below) mention nothing
about,
how Christian people actually reacted to this ominious
'dust-veil';
only that 'there was distress.. among men.. from the evil
things.' But
what did they actually do to ward off the anger of God? Burn
candles?
built new churches? Walk in processions? I am very interested if
anybody has any hints or references on this!
Some references:
Stothers & Rampino: Volcanic Eruptions in the Mediterranean
Before A.D.
630 From Written and Archaeological Sources. Journal of
Geophysical
Research Vol. 88, No. B6, pp. 6357-6371, Aug. 1983
M.G.L. Baillie: Marking in marker dates: towards an archaeology
with
historical precision. World Archaeology Vol. 23 No. 2, pp.
233-243,
1991
M.G.L. Baillie: Dendrochronology raises questions about the
nature of
the AD 536 dust-veil event. The Holocene 4,2, pp. 212-217,
1994
M.G.L. Baillie: A Slice Through Time. Dedrochronology and
precision
dating. London 1995.
-------------
From: Ralph
Mathisen <N330009@UNIVSCVM.SC.EDU>
Subject: Strange Natural
Phenomena....
OK, for fires in the sky and volcanos, try :) R. Mathisen,
"Nature or
Nurture - What Caused the Famines of Late ROman Gaul?", The
Ancient
World 24(1993) 91-105.
-------------
From: Matthias
Bode <Bode@STUD-MAILER.UNI-MARBURG.DE>
Subject: AW: Strange natural
phenomens during Late Ant.: AD 536
One such phenomenon was the 'dust-veil' or 'dry fog', which in
536
dimmed the sun for almost a year, leading to severe colds and
failure
of crops. It is mentioned by Procopius, Cassiodorus and other
mediterranean writers, but also by Chinese sources, and can be
demonstrated dendrochronologically both in Europe and in Northern
America.
Well, sounds quite like the special effects in DEEP IMPACT,
doesn't it?
But seriously: Has anybody asked geologists if they have any
impact
crater at hand that fits the year? And what about Greenland ice
drill
cores? They were quoted on the list just recently in connection
with
lead poisoning. A solution could be in the ice layers.
------
From: Dio <dionysios@EARTHLINK.NET>
Subject: Re: AW: Strange natural
phenomens during Late Ant.: AD 536
Well, this is from memory and not specific, but just a couple of
weeks
ago in the USA a television program aired on Discovery channel, I
believe, in concert with the release of Deep Impact, and went
into as I
recall fairly scientifically (?) past evidence of real impacts.
One was
described for the 6th century and a gentleman from Ireland was
interviewed who had been looking into dendrological evidence
there. He
was convinced from it that indeed there was an impact somewhere
in the
first halff of that century. Certainly it seemed to be one more
than
usually fraught with earthquakes, etc,, unless the ancient
sources are
just exaggerating for rhetorical effect, etc.
--------
From: Matthias
Bode <Bode@STUD-MAILER.UNI-MARBURG.DE>
Subject: AW: Strange Natural
Phenomena....
In our department library I found the following book:
D. Justin Schove & Alan Fletcher: Chronology of Eclipses and
Comets AD 1 -
1000. The Boydell Press. 1984.
This book does not only list the things mentioned in the title,
but
also all sorts of strange things that can be found in written
sources.
For 536 they have ample evidence for some sort of dust-veil or
dust
clouds blocking sunlight for almost a year. For example in
Procopius
[dots already in the book]:
"during this winter Belisarius remained in Syracuse and
Solomon in
Carthage. And ... during this year a most dread portent took
place. For
the Sun gave forth its light without brightness, like the moon,
during
this whole year, and it seemed exceedingly like the sun in
eclipse, for
the beams it shed were not clear nor such as it is accustomed to
shed.
... And it was the time when Justinian was in the tenth year of
his
reign." (Wars 4 = Vandal War 2, Ch 14.; Loeb 1916: p.
326-329)
The authors also quote a certain Michael the Syrian (12th C) as
follows:
"...in the year of the Greeks 848 [AD 536] there was a sign
in the sun.
Such a thing had never been seen before and it is nowhere written
that
anyting similar had happened in the world ... the sun was dimmed,
and
the darkening lasted a year and a half, that is to say, 18
months. Each
day it shone about four hours and even then the light was merely
that
of a weak shadow. Everybody declared that its original light
would
never return. The fruits did not ripen and wine had the taste of
acid
grapes."
They also quote evidence from Greenland ice:
Hammer, C.U., Clausen, H.B. and Dansgaard, W. 1980
"Greenland ice-sheet
evidence of post-glacial volcanism and its climatic impact".
NATURE
(288), 230-235. and: R.B. Stothers "Mystery cloud of AD
536" NATURE
(accepted) 1984.
That's all there is in the book by Schove and Fletcher. I haven't
been
able to look into the articles in Nature yet. Schove and Fletcher
think
the whole phenomenon is volcanic in origin.
==================
(6) THE AD 540 EVENT
From Mike Baillie <m.baillie@qub.ac.uk>
Having lived for some years with the AD 540 event (I call it the
AD 540
event because the various effects in tree-ring chronologies
centre on
AD 540, although the event itself is better defined as 536-545),
and
having tried to find hints in ancient, and other, sources for the
most
likely cause, I have found myself drawn away from the original
Stothers
and Rampino volcano hypothesis (because of the lack of any clear
dramatic acid signal in the Greenland ice-core records) to what I
believe is the next most likely cause. To account for the
environmental
downturn in the trees, and in human food crops, in the later
530s, and
to account for the dust-veil descriptions as picked up by the
volcanologists, the most likely cause has to be "loading of
the
atmosphere by cometary debris" either through direct contact
with a
comet (though obviously not a direct impact) or through
interaction
with one of Clube and Napier's "cosmic swarms" of
Tunguska class and
super-Tunguska class impacts. The obvious place to search for
evidence
is in the ice core records. However as outlined in "A Slice
Through
Time", page 104,(Routledge, London, 1995) there are problems
with the
ice-core records in the sixth century AD. The worst problem is
the loss
of 14 metres of the American GISP2 ice record between
"545-613" on
their dating. I have therefore turned to historical and
mythological
sources relevant to the period. In my view, these sources do not
rule
out the possibility of a cometary interaction. I have written the
story
up in a popular book format which will, with any luck, be
published
this summer. MB
Mike Baillie
Palaeoecology Centre
School of Geosciences, Queen's University, Belfast
(01232) 335147
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