PLEASE NOTE:
*
Date sent: Fri, 27 Feb 1998 12:37:10 -0500 (EST)
From: Benny J Peiser B.J.PEISER@livjm.ac.uk
Subject: Re: CC COMMENTS, 27/02/98
To: cambridge-conference@livjm.ac.uk
Priority: NORMAL
CAMBRIDGE-CONFERENCE COMMENTS, 27 February 1998
----------------------------------------------
From: Rob McNaught rmn@aaocbn.aao.gov.au
VISUAL FIREBALL SIGHTINGS: A CONSUMER WARNING!
I applaud the comments of David Morrison and Jeremy Tatum. With
about
two decades of interest in following up fireball reports and 25
years of
operating all-sky fireball cameras, I have come across this sort
of hype
and exaggeration regularly.
The appearance of a story in the media need not have anything to
do with
the magnitude of the event. In the USA with such a high
population
density, it would be difficult for a fireball to occur away from
some
major centre of population. Here in Australia, it is commonplace
for a
bright fireball to be photographed over western NSW and have no
mention
in the media. Also, an evening fireball is much more likely to be
reported than a morning fireball. When however, a fireball occurs
over
a major town and sonic booms are widely heard, the event
invariably
makes the national news within hours. Early maps of tornado
distribution in the USA showed a similar bias due to the uneven
population density.
Other news items that compete for space can oust a fireball from
being
covered. During the recent huge Pilliga forest fire near here, a
bright
fireball was photographed by the one camera station operating
that night
(others were affected by smoke). It was weeks before I knew of it
when the
film was processed (the long delay caused by the fire).
Once a journalist takes interest in a fireball, it is easy to
hunt down
reports of other events. After all, fireballs that light up the
ground
occur monthly from any dark location. Thus one fireball suddenly
becomes several with the attendant speculation about increased
rates.
It is probably unfair to critise a journalist for having no
scientific
training, but it is certainly fair to critise the organisations
they work
for, the larger ones at least, if they either do not have
scientifically
trained journalists on their staff, or they ask a scientifically
illiterate
journalist to cover a fireball report. This results in
misinterpretations and accepting highly questionable statements
from highly questionable sources. As an example of the former, I
was once quoted as saying a fireball had exploded causing
devastation similar to a nuclear explosion and I was seeking help
in finding where it had occurred!!! Well, to be fair, I had said
that, but only when asked about Tunguska. More recently, a
potential meteorite fall near here was widely reported in the
press (at sunset, no cameras operating, over 50 in-situ
eyewitness
interviews indicate an end height below 20km and low velocity). A
local newspaper ran a front page story about it, having spoken to
two "experts". One, a local amateur astronomer who
operates an
all-sky fireball camera, gave a good factual account of the
event,
but his comments were lost in the nonsense and half truths of a
local operator of a public observatory. The story ended up
being about the $ value of the "meteorites". Of course,
he may
have been misquoted!
Certainly, scientists do not always agree on the details, or even
the
fundamentals, but I am unaware of any serious questions regarding
the
physics of small fireballs (centimetre to meter size.
Electrophonic sounds may be one issue). It is thus depressing to
have ill informed comments from people with no background in this
field (planetarium directors, operators of public observatories
and astrophysicists included).
Regarding the perception of a fireball by the human eye/mind,
Jeremy is
actually incorrect in saying that there is no information on the
actual 3D
motion of the fireball. The human mind has evolved to correctly
interpret changing angular velocity as motion of an object
relative to the observer. Usually this occurs in a rich visual
environment with many other cues to size and distance. In the
case
of a fireball, these other cues are lacking (changing size,
shape,
intervening haze, obscuration of distant or by near objects
etc.),
which certainly results in indeterminacy of the distance, but in
my experience, the observer usually correctly interprets the
general direction of motion of a fireball. The linear
deceleration
of the fireball in the atmosphere certainly affects this
judgement, but the changing angular velocity is a strong cue. But
Jeremy is certainly correct in that the projected path across the
sky
give the essential data from which the real trajectory is
determined.
[A single photograph with timed interruptions CAN result in the
derivation of the radiant (orientation of the real path), by
assuming
the early part of the path has near constant linear velocity and
fitting the changing angular velocity to the angular distance
covered.
The distance cannot be derived from this technique, but plausible
assumptions can be made.]
Regarding the problem of misperception of the distance of a
fireball, this
is where the lack of cues leaves the mind floundering. Almost
certainly, the human mind UNCONSCIOUSLY and directly interprets
the
event in terms of more familiar objects with the following
result:
it was bright, therefore it is close
it has a high angular velocity, therefore it is close
it is large, therefore it is close
Once it is "seen" to be close, this sets one parameter
that many others must
follow. If it appeared to be say, 300 metres away, and was seen
at 30
deg altitude, then it will appear to have a height of 150 metres.
If
the distant hills are say 500 metres above the observer, this can
result in the PERCEPTION that the fireball was below the height
of the
hills, despite being of higher angular altitude. It is unlikely
that
this perception once made can be altered, and one has to be very
tactful in explaining this illusion. It can result in resentment
at the
arrogance of scientists who ignore what people actually see.
[When
sonics are heard some minutes later, the eye-witness is usually
aware
of a problem with the perceived distance.] Aurorae
"seen" in front of
hills, is presumably caused by the same psychological process.
Another
result of this misperceived distance is that the size of the
object
becomes fixed. "It was the size of a dinner plate".
Asking "The size
of a dinner plate at what distance?" really doesn't help, as
the
angular size of the object becomes secondary to the
(mis)perceived 3D
size, despite the angular size having primacy as the original
sense data.
UFO reports caused by Venus "following" a car is the
same overall
psychological process of misperceived distance with all its
consequences.
Once the observer becomes fearful of the "UFO", a
correct interpretation is
not likely to be possible and again there is resentment if the
observed
phenomenon is questioned. The perceptual process most at play
here is
called "constancy".
As a final point, I'd like to point out that meteoric fireballs
are
probably some 100 times or so more common than satellite re-entry
fireballs. I'm only aware of three satellite re-entries having
been
photographed by fireball networks, whereas many hundreds of
meteoric
fireballs have been recorded. Re-entries are rarely much brighter
than
Venus and typically last for many tens of seconds, going from
horizon
to horizon usually with dozens of fragments trailing. Whilst some
meteoric fireballs may be of long duration with numerous
fragments
(like Peekskill), they would typically be very much brighter than
Venus. A fireball lasting a few seconds is unlikely to ever be a
satellite re-entry, regardless of the fact that re-entries are
much
less common.
Recent events suggest to me that too much importance is being
placed on
visual observations of fireballs when there is little or no hard
data to back
up the claims. The extent of reporting in the media (including
the
internet) may indicate little more than hype or lack of
background
knowledge. As Jeremy says, it takes quite a bit of foot slogging
(and $
of petrol) to make in situ measurements of visual sightings and
usually
for poorly defined results. With the photographed Pribram
meteorite
fall, Ceplecha mentions both systematic and large random errors
in the
visual observations. In the Eastern Australian Fireball Network,
we are
awaiting the next bright fireball, to compare the photographic
real
trajectory with that derived solely from visual sightings to
assess the
nature of these effects in visual observations. This is necessary
in
interpreting eye-witness reports of satellite detected
"superbolides".
Without a satellite detection, or good physical data, I fear that
most
reported "impacts" will turn out to be hype. If this
were to go on for
much longer, there will be widespread cynicism about the
phenomenon.
Rob McNaught (rmn@aaocbn.aao.gov.au)
======================
From: Simon Mansfield simon@spacer.com
Benny,
maybe the "increased activity" is mistaken for Iridium
satellite
flashes.
Simon
*
Date sent: Fri, 27 Feb 1998 11:24:09 -0500 (EST)
From: Benny J Peiser B.J.PEISER@livjm.ac.uk
Subject: CC DIGEST, 27/02/98
To: cambridge-conference@livjm.ac.uk
Priority: NORMAL
CAMBRIDGE-CONFERENCE DIGEST, 27 February 1998
---------------------------------------------
(1) SORRY PEOPLE, BUT I MADE A BIT OF A BOO-BOO
Charles Darwin C.R.Darwin@Westminster.Abbey.uk
(2) A MODEL OF MASS EXTINCTION
M.E.J. Newman, CORNELL UNIVERSITY
(3) EJECTA LAYER AT THE K/T BOUNDARY IN NEW JERSEY
R.K. Olsson et al., RUTGERS STATE UNIVERSITY
(4) ROADBLOCKS ON THE KILL CURVE: TESTING THE RAUP HYPOTHESIS
C.W. Poag, US GEOLOGICAL SURVEY
(5) MASS EXTINCTIONS AND THE SUN'S ENCOUNTERS WITH SPIRAL ARMS
E.M. Leitch and G. Vasisht, CALTECH
(6) LOOKING AT THE K/T BOUNDARY IN THE WESTERN PYRENEES
E. Apellaniz et al., EUSKAL HERRIKO UNIBERTSITATEA
(7) EVALUATING THE FLUCTUATION OF MASS EXTINCTIONS AND RECOVERY
M.L. Droser et al., UNIVERSITY OF CALIFORNIA RIVERSIDE
(8) THE CRETACEOUS-TERTIARY BIOTIC TRANSITION
N. Macleod et al., NATURAL HISTORY MUSEUM
(9) NONLINEAR DYNAMICS AND MASS EXTINCTIONS
R.V. Sole et al., UNIVERSITY POLITECHNIC OF CATALUNYA
=====================================
(1) SORRY PEOPLE, BUT I MADE A BIT OF A BOO-BOO
From: Charles Darwin C.R.Darwin@Westminster.Abbey
Hi folks,
Having followed your research and debates for some while, I think
it's
about time to confess that I no longer adhere to the main
conclusions (attached below) of my controversial book published
some 140 years ago. I am sure you will be lenient with me; after
all, I used to be a fellow catastrophist in my early days. I've
come to realise that I got it terribly wrong when I converted to
Lyell's uniformitarian creed. After more than 90 years of
sessions
with my psycho-analyst, I now believe that the crisis which
triggered this sudden conversion was not so much due to my
relationship to my mother but rather caused by post-traumatic
stress syndrom from which I suffered under the impact of the
Chilean earthquake. So leave Oedipus out of the deabte.
Cheers, Charly
P.S. I have attached the main paragraph of my flawed theory which
has now become merely of historical interest:
"As all living forms of life are the lineal descendants of
those which lived long before the Silurian epoch, we may feel
certain that the ordinary succession by generation has never
been broken, and that no cataclysm has desolated the whole
world. Hence we may look with some confidence to a secure
future of equally inappreciable length. And as natural
selection works solely by and for the good of each being, all
corporeal and mental environments will tend to progress towards
perfection" (On the Origin of Species by Means of Natural
Selection: or the Preservation of Favoured Races in the
Struggle for Life, 1859)
=====================
(2) A MODEL OF MASS EXTINCTION
M.E.J. Newman: A model of mass extinction. JOURNAL OF THEORETICAL
BIOLOGY, 1997, Vol.189, No.3, pp.235-252
CORNELL UNIVERSITY, CTR THEORY, RHODES HALL, ITHACA, NY, 14853,
USA
In the last few years a number of authors have suggested that
evolution
may be a so-called self-organized critical phenomenon, and that
critical processes might have a significant effect on the
dynamics of
ecosystems. In particular it has been suggested that mass
extinction
may arise through a purely biotic mechanism as the result of
'coevolutionary avalanches'. In this paper we first explore the
empirical evidence which has been put forward in favor of this
conclusion. The data center principally around the existence of
power-law functional forms in the distribution of the sizes of
extinction events and other quantities. We then propose a new
mathematical model of mass extinction which does not rely on
coevolutionary effects and in which extinction is caused entirely
by
the action of environmental stress on species. In combination
with a
simple model of species adaption we show that this process can
account
for all the observed data without the need to invoke coevolution
and
critical processes. The model also makes some independent
predictions,
such as the existence of 'aftershock' extinctions in the
aftermath of
large mass extinction events, which should in theory be testable
against the fossil record. (C) 1997 Academic Press Limited.
=========================
(3) EJECTA LAYER AT THE K/T BOUNDARY IN NEW JERSEY
R.K. Olsson*), K.G. Miller, J.V. Browning, D. Habib, P.J.
Sugarman:
Ejecta layer at the Cretaceous-Tertiary boundary, Bass River, New
Jersey (Ocean Drilling Program Leg 174AX). GEOLOGY, 1997, Vol.25,
No.8,
pp.759-762
*) RUTGERS STATE UNIVERSITY, DEPARTMENT OF GEOLOGICAL SCIENCE,
PISCATAWAY, NJ, 08855
A continuously cored borehole drilled at Bass River, New Jersey,
recovered a Cretaceous-Tertiary (K-T) succession with a dcm-thick
spherule layer immediately above the boundary. Below the spherule
layer, the Cretaceous glauconitic clay is extensively burrowed
and
contains the uppermost Maastrichtian Micula prinsii calcareous
nannofossil zone. Spherical impressions of spherules at the top
of the
Cretaceous indicate nearly instantaneous deposition of ejecta
from the
Chicxulub impact. The thickest ejecta layer shows clearly that a
single
impact occurred precisely at K-T boundary time. Above the
spherule
layer, the glauconitic clay contains the planktonic foraminiferal
PO
and Pa Zones, indicating (1) a complete K-T succession and (2)
continuous deposition interrupted only by fallout of the ejecta
layer.
Clay clasts within a 6 cm interval above the spherule layer
contain
Cretaceous microfossils and may be rip-up clasts from a tsunami
or
possibly a megastorm event. Extinction of the Cretaceous
planktonic
foraminifers and burrowing organisms occurs abruptly at the K-T
boundary. Thus, the Bass River K-T succession unequivocally links
the
Chicxulub bolide impact to the mass extinctions at the end of the
Mesozoic. Copyright 1998, Institute for Scientific Information
Inc.
=============================
(4) ROADBLOCKS ON THE KILL CURVE: TESTING THE RAUP HYPOTHESIS
C.W. Poag: Roadblocks on the kill curve: Testing the Raup
hypothesis.
PALAIOS, 1997, Vol.12, No.6, pp.582-590
US GEOLOGICAL SURVEY, 384 WOODS HOLE RD, WOODS HOLE, MA, 02543
The documented presence of two large (similar to 100-km
diameter),
possibly coeval impact craters of late Eocene age, requires
modification of the impact-kill curve proposed by David M. Raup.
Though
the estimated meteorite size for each crater alone is large
enough to
have produced considerable global environmental stress, no
horizons of
mass mortality or pulsed extinction are known to be associated
with
either crater or their ejecta deposits. Thus, either there is no
fixed
relationship between extinction magnitude and crater diameter, or
a
meteorite that would produce a crater of > 100-km diameter is
required
to raise extinction rates significantly above a similar to 5%
background level. Both impacts took place similar to 1 - 2 m.y.
before
the ''Terminal Eocene Event'' (= early Oligocene pulsed
extinction).
Their collective long-term environmental effects, however, may
have
either delayed that extinction pulse or produced threshold
conditions
necessary for it to take place. Copyright 1998, Institute for
Scientific Information Inc.
=====================
(5) MASS EXTINCTIONS AND THE SUN'S ENCOUNTERS WITH SPIRAL ARMS
E.M. Leitch and G. Vasisht: Mass extinctions and the sun's
encounters
with spiral arms. NEW ASTRONOMY, 1997, Vol.3, No.1, pp.51-56
CALTECH,PASADENA,CA,91125
The terrestrial fossil record shows that the exponential rise
in biodiversity since the Precambrian period has been punctuated
by
large extinctions, at intervals of 40 to 140 Myr. These mass
extinctions represent extremes over a background of smaller
events and
the natural process of species extinction. We point out that the
non-terrestrial phenomena proposed to explain these events, such
as
boloidal impacts (a candidate for the end-Cretaceous extinction)
and
nearby supernovae, are collectively far more effective during the
solar
system's traversal of spiral arms. Using the best available data
on the
location and kinematics of the Galactic spiral structure
(including
distance scale and kinematic uncertainties), we present evidence
that
arm crossings provide a viable explanation for the timing of the
large
extinctions. (C) 1998 Elsevier Science B.V.
================================
(6) LOOKING AT THE K/T BOUNDARY IN THE WESTERN PYRENEES
E. Apellaniz*), J.I. Baceta, G. Bernaola Bilbao, K. Nunez Betelu,
X. Orue Etxebarria, A. Payros, V. Pujalte, E. Robin, and R.
Rocchia:
Analysis of uppermost Cretaceous lowermost Tertiary hemipelagic
successions in the Basque Country (western Pyrenees): evidence
for a
sudden extinction of more than half planktic foraminifer species
at the
K/T boundary. BULLETIN DE LA SOCIETE GEOLOGIQUE DE FRANCE, 1997,
Vol.168, No.6, pp.783-793
*) EUSKAL HERRIKO UNIBERTSITATEA,ZIENTZI FAK,ESTRATIG &
PALEONTOL
SAILA, 644 POSTAKUTXA, BILBAO, BASQUE COUNTRY, SPAIN
This paper summarises our current knowledge about 21 sections
across
the K/T boundary from the Basque Country (western Pyrenees), all
of
them comprising intermediate-deep basinal facies. This study
allowed us
to establish that Sopelana III and Bidart are the best sections
for
analysing the extinction of the planktic foraminifers at the K/T
boundary. Detailed analyses of planktic foraminifers from four
new
sections allow us to differentiate four biozones, one at the end
of the
Cretaceous and three at the beginning of the Tertiary. These
analyses
further show that 63 Upper Maastrichtian planktic foraminifers
species
reached the boundary where 33 species became extinct. The study
also
shows that some species decrease markedly in abundance in the
last few
metres of the Cretaceous prior to the extinction event which
could be
related to environmental changes at the end of the Maastrichtian.
More
than 50 % of the planktic foraminifers, that is 33 species,
became
extinct at the end of the Cretaceous. However, most of the
extinct
species were rare and only about 20 % of the total Cretaceous
assemblages are involved in the extinction event. The 30
surviving
species, that is less than 50 % of the Cretaceous species, later
disappear through the Pr. longiapertura and P. pseudobulloides
biozones
of the beginning of the Tertiary. Above the K/T boundary, samples
are
far poorer in planktic foraminifer specimens than those from the
uppermost Maastrichtian and include 16 Tertiary species.
Moreover,
together with this extinction event there are impact markers
(iridium
and Ni-rich spinels), as well as a high concentration of soot at
the
beginning of the Danian at the Sopelana III section. This
strengthens
the hypothesis of a causal link between the impact and WT
extinctions.
Copyright 1998, Institute for Scientific Information Inc.
========================
(7) EVALUATING THE FLUCTUATION OF MASS EXTINCTIONS AND RECOVERY
M.L. Droser*), D.J. Bottjer, and P.M. Sheehan: Evaluating the
ecological architecture of major events in the Phanerozoic
history of
marine invertebrate life. GEOLOGY, 1997, Vol.25, No.2, pp.167-170
*) UNIVERSITY OF CALIFORNIA RIVERSIDE, DEPARTMENT OF EARTH
SCIENCE, RIVERSIDE,CA,92521
Paleoecological changes associated with Phanerozoic mass
extinctions
and radiations can be categorized into four nonhierarchical,
nonadditive levels. First-level changes include colonization of a
new
ecosystem. Structural changes within an established ecosystem
represent
the second level, changes within an already established
ecological
structure are the third level, and taxonomic changes within a
community
represent the fourth level. Applying these levels to the
Ordovician
radiation, end-Ordovician extinction and Silurian recovery, as
well as
the end-Permian extinction and Triassic recovery, demonstrate
that
paleoecological changes associated with these major events can be
evaluated and compared in a more rigorous manner than previously
done.
Results of this analysis demonstrate that use of these levels
indicates
that the relative magnitude of an event as measured by taxonomic
criteria may be decoupled from its paleoecological significance.
Copyright 1998, Institute for Scientific Information Inc.
========================
(8) THE CRETACEOUS-TERTIARY BIOTIC TRANSITION
N. Macleod*), P.F. Rawson, P.L. Forey, F.T. Banner, M.K.
Boudagher
Fadel, P.R. Brown, J.A. Burnett, P. Chambers, S. Culver, S.E.
Evans, C.
Jeffery, M.A. Kaminski, A.R. Lord, A.C. Milner, A.R. Milner, N.
Morris,
E. Owen, B.R. Rosen, A.B. Smith, P.D. Taylor, E. Urquhart, J.R.
Young:
The Cretaceous-Tertiary biotic transition. JOURNAL OF THE
GEOLOGICAL
SOCIETY, 1997, Vol.154, No.Pt2, pp.265-292
*) NATURAL HISTORY MUSEUM, DEPT PALAEONTOLOGY, CROMWELL RD,
LONDON SW7
5BD, ENGLAND
Mass extinctions are recognized through the study of fossil
groups
across event horizons, and from analyses of long-term trends in
taxonomic richness and diversify. Both approaches have inherent
flaws:
and data that once seemed reliable can be readily superseded by
the
discovery of new fossils and/or the application of new analytical
techniques. Herein the current state of the Cretaceous-Tertiary
(K-T)
biostratigraphical record is reviewed for most major fossil
clades,
including: calcareous nannoplankton, dinoflagellates, diatoms,
radiolaria, foraminifera, ostracodes, scleractinian corals,
bryozoans,
brachiopods, molluscs, echinoderms, fish, amphibians, reptiles
and
terrestrial plants (macrofossils and palynomorphs). These reviews
take
account of possible biasing factors in the fossil record in order
to
extract the most comprehensive picture of the K-T biotic crisis
available. Results suggest that many faunal and floral groups
(ostracodes, bryozoa, ammonite cephalopods, bivalves, archosaurs)
were
in decline throughout the latest Maastrichtian while others
(diatoms,
radiolaria, benthic foraminifera, brachiopods, gastropods, fish,
amphibians, lepidosaurs, terrestrial plants) passed through the
K-T
event horizon with only minor taxonomic richness and/or diversity
changes. A few microfossil groups (calcareous nannoplankton,
dinoflagellates, planktonic foraminifera) did experience a
turnover of
varying magnitudes in the latest Maastrichtian-earliest Danian.
However, many of these turnovers, along with changes in
ecological
dominance patterns among benthic foraminifera, began in the
latest
Maastrichtian. Improved taxonomic estimates of the overall
pattern and
magnitude of the K-T extinction event must await the development
of
more reliable systematic and phylogenetic data for all Upper
Cretaceous
clades. Copyright 1998, Institute for Scientific Information Inc.
=============================
(9) NONLINEAR DYNAMICS AND MASS EXTINCTIONS
R.V. Sole*), S.C. Manrubia, M. Benton, P. Bak: Self-similarity of
extinction statistics in the fossil record. NATURE, 1997,
Vol.388,
No.6644, pp.764-767
*) UNIVERSITY POLITECHNIC OF CATALUNYA, DEPT PHYS FEN, CAMPUS
NORD,
MODUL B4,ES-08034 BARCELONA,SPAIN
The dynamical processes underlying evolution over geological
timescales
remain unclear. Analyses of time series of the fossil record have
highlighted the possible signature of periodicity in mass
extinctions,
perhaps owing to external influences such as meteorite impacts.
More
recently the fluctuations in the evolutionary record have been
proposed
to result from intrinsic nonlinear dynamics for which
self-organized
criticality provides an appropriate theoretical framework. A
consequence of this controversial conjecture is that the
fluctuations
should be self-similar, exhibiting scaling behaviour like that
seen in
other biological and socioeconomic systems. The self-similar
character
is described by a 1/f power spectrum P(f), which measures the
contributions of each frequency f to the overall time series. If
self-similarity is present, then P(f) approximate to f(-beta)
with 0 <
beta < 2, This idea has not been sufficiently tested, however,
owing to
a lack of adequate data. Here we explore the statistical
fluctuation
structure of several time series obtained from available
palaeontological data bases, particularly the new 'Fossil Record
2'. We
find that these data indeed show self-similar fluctuations
characterized by a 1/f spectrum. These findings support the idea
that a
nonlinear response of the biosphere to perturbations provides the
main
mechanism for the distribution of extinction events. Copyright
1998,
Institute for Scientific Information Inc.
--------------------------------
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