PLEASE NOTE:
*
Addendum: Impact event associated with oldest stone tools found in China.
*
CCNet-SPECIAL, 3 March 2000
ARMAGEDDON: THE REAL STORY -COSMIC OPTIMISTS, PESSIMISTS AND
REALISTS
-----------------------------------------------------------------------
From Benny J Peiser <b.j.peiser@livjm.ac.uk>
The theme under which this year’s AAAS Annual Meeting in
Washington,
D.C. took place was telling in its honesty: "Science in an
Uncertain
Millennium." It could have just as well been titled
"Scientific
uncertainty in the new Millennium". After all, if we have
leaned one
major lesson from the study of science history, it is that
science can
no longer provide us with the "certainties" and
"truths" it used to be
associated with by its most zealous missionaries. This shift in
the
perception of what science can, and cannot achieve, enfolded
mostly
during the 20th century and has come about, as I believe, chiefly
in
response to the sobering realisation of our rather precarious
place in
space.
It was therefore not completely surprising that the AAAS accepted
a
rather exotic sounding session on "unpredictable events of
extra-terrestrial origin and their impact on humanity." As
the
session’s synopsis pointed out, human affairs on Earth have
and often
have been directly associated with astonishing events taking
place in
the visible sky. "The very imagery of the skies, which is
usually so
predictable, can sometimes change without warning. This symposium
will
explore these often-unpredictable extraterrestrial inputs and the
profound effect they have had on human culture.
Yet, the presentations at the AAAS meeting and some of the
reactions to
the arguments and questions raised have demonstrated, once again,
that
current research on the history of cosmic impacts differs quite
notably
between why I have tentatively called the British and the
American
schools of thought (see today’s CCNet-Essay).
This controversy, an often bitter conflict within the NEO
research
community and largely unnoticed by the interested public, has
been
going on for more than 20 years - ever since a number of
Britain’s
leading astronomers started to look at historical catastrophism
as a
legitimate field of scientific study in the late 70s and early
80s.
I have attached below a lengthy expose by the WHY FILES team
about this
ongoing controversy that was rekindled in reaction to our AAAS
session.
In a separate mailing, I have circulated my recent article in
ASTRONOMY
NOW which tries to add further background information on this
dispute.
If, as a result of our debate, we could at least agree that the
issue
of historical impact catastrophes has been ignored (if not
ridiculed
altogether) for far too long, and that this field of
investigation
should be taken more earnestly in the future, perhaps something
good may still come out of the often acrimonious encounters of
the
past.
In short, today’s two CCNet mailing will hopefully provide
you with
sufficient food for thought for your weekend break.
Benny J Peiser
-------------------------
ARMAGEDDON: THE REAL STORY
From WHY FILES, 2 March 2000
http://whyfiles.news.wisc.edu/106asteroid/index.html
COLOSSAL CATACLYSM - FACING THE ASTEROID THREAT
2 Mar 2000 The Near Earth Asteroid Rendezvous satellite has
settled
into orbit around the 21-mile long asteroid Eros for a year of
observation. The American Museum of Natural History is in court,
trying
to keep possession of a large meteorite claimed by an Oregon
Indian
group.
The Why Files is starting to fret about asteroids, comets and
other
junk from space. We know asteroids and comets can wreak havoc
when they
strike Earth. Think of it as yesteryear's science fiction -- and
today's science fact. According to a presentation at a national
scientific meeting, asteroid impacts over the past 10,000 years
had a
hand in shaping the climate and the nature of civilization
itself.
The alarm over asteroids has even reached the tabloids. "The
end
of the world?" bellowed the cover of the Weekly World News
(see "A
Message from God" in the bibliography). "Shell-shocked
NASA
scientists are scrambling to come to grips with a top-secret
radio
transmission received from the icy vastness of deep space that
appears to be a communication from God Himself." An asteroid
detected earlier this year -- its threat since discounted by
legit
astronomers -- appears destined to impact in January, 2022, the
World gushed, with the predictable catastrophic consequences. We
don't know about that -- and we'd hate to impeach the veracity of
our colleagues in the fiber-media, but....
Will you be squashed by an asteroid? Probably not today, probably
not tomorrow, but someday, and perhaps soon, a fast-flying rock
from outer space could run your account seriously in the red --
along, perhaps, with the rest of civilization. It all depends on
whether you believe the optimists or the pessimists in the
festering debate about asteroid hazards. As we'll see, both sides
use essentially the same facts, but reach radically divergent
conclusions.
DOIN' THE BUMP
One thing that's no longer in dispute, however: Space jams of the
sort we'll be discussing are the only natural events -- save
perhaps epidemics -- that could terminate civilization. If you
worry about earthquakes and volcanoes, then you gotta at least
think about getting rocked by rocks that are ignoring the speed
limit.
But hey, just because hardballs from outer space put the
dinosaurs
(and half the other species on their team) into the cosmic cellar
65 million years back, look at the bright side. A true fastball
--
remember -- these objects may cross home plate at more than 15
kilometers per second, could strike out "I want to be a
Millionaire" -- and toss the McLaughlin Group from the game
for
good measure.
A collision with a comet or asteroid would be no soap opera, yet
as the world turns, it's continually assaulted by rocks and ice
from space. These old and restless objects are dregs from the
formation of the solar system, and they orbit through the days of
our lives, waiting to slam into New York, maybe looking for
a
guest appearances on Oprah...
One glance at the cratered face of the asteroid, and you know
fast-moving rocks can really ding things up on the bold and
beautiful planets and moons in our solar system. None of this
destruction is likely to be featured in "America's funniest
home
videos." Considering the blast, the fires and smoke, the
gigantic
waves caused by oceanic impacts, the death and the destruction,
maybe we should be talking General Hospital meets ER.
Got a gambler's stomach? Then look at the odds of cosmic
catastrophe, extraterrestrial style.
ASTEROIDAL ASSASSINS
People have been worrying about cosmic collisions for a long
time,
but the field only gained scientific legitimacy in the 1980s when
the
extinction of the dinosaurs was pinned on a single strike of a
comet
or asteroid. (Asteroids are rocky; comets are dirty snowballs.
because they cause similar results when they hit Earth, and
asteroids
are more common, we'll refer to both bodies as
"asteroids.")
Now we have the assertion, based on a computer simulation by
Australian engineer Michael Paine, that during the last 10,000
years,
Earth was hit about 350 times by asteroids as large as the rock
that
wasted 2,000 square kilometers of Siberian forest in 1908.
According
to the simulation, during the next 10,000 years, cosmic junk
could
kill 13 million people, and perhaps cause wars, famines and
general-purpose chaos. Although the assertion was not published
in a
refereed journal, the alarming news was discussed at a national
scientific meeting in February.
Before we get to the details, let's jump back in time with our
we're-paranoid-for-a-reason collision chronology:
65 million years ago -- A 10-kilometer asteroid strikes north of
the
Yucatan Peninsula, causes a global firestorm, then a cold snap
and
finally a global warming that extinguishes the dinosaurs. Mammals
move to center stage. Some eventually make important discoveries
like
bingo, the Edsel, and the painful effects of asteroids.
3.3 million years ago -- An impact in Argentina precedes numerous
extinctions and a global cooling trend (more on this later).
50,000 years ago -- An iron meteorite a few dozen meters across
gouges the 1.2 kilometer Barringer meteorite crater in Arizona.
1490 -- About 10,000 people die in the Chinese city of
Chi1ing-yang
when an asteroid breaks overhead.
1908 -- An asteroid estimated at 50 meters across explodes above
Tunguska, Siberia, blowing down trees across 2,000 square
kilometers
and killing a thousand reindeer, but apparently no people.
Because
the stony object exploded in the atmosphere, there's no crater.
1937 -- Asteroid Hermes -- about a kilometer in diameter --
misses
Earth by 600,000 miles. Hermes, although smaller than the 'roid
that
snuffed the dinosaurs, could have been a true "category
killer," able
to cause epic devastation and kill millions.
1950 -- Immanuel Velikovsky publishes "Worlds in
Collision" (see
bibliography), a pseudoscientific warning about impact hazards.
In
equal parts bogus and frightening, Velikovsky casts the entire
field
of impact studies into disrepute.
1980 -- Spacewatch program starts at the University of Arizona,
intent on cataloging asteroids. The goal is to get a statistical
picture of orbiting rocks anywhere in the solar system.
1980 -- Physicist Luis Alvarez and his team blames the dinosaur
extinction on the environmental havoc of a collision. The
resulting
firestorm and a global soot and dust cloud, they argue, cooled
the
planet enough to make the dinos long for a package vacation in
Cancun. Many scientists, including renowned comet hunters, smirk
in
their beer about this ridiculous notion, which only gains
acceptance
after a 180-kilometer wide crater is discovered north of the
Yucatan.
1994 -- Comet Shoemaker-Levy 9 breaks apart, then smashes
into
Jupiter under the watchful eye of dozens of telescopes. The
resulting
zone of chaos is estimated to be as large as the Earth and lends
urgency to the search for asteroids and comets.
"Shoemaker-Levy was a
turning point," says Benny Peiser, an anthropologist at
Liverpool
John Moores University at the 2000 meeting of the American
Association for the Advancement of Science in Washington, D.C. In
the
course of presenting results of the computer simulation on
asteroid
impacts, Peiser adds, "If it can happen in front of your
nose --
practically in your backyard -- it can also happen on
Earth."
1998 -- Astronomers announce that an asteroid may be on a
collision
course for Earth. The warning is quickly withdrawn after further
observations.
1998 -- Peter Schultz, a professor of planetary geology at Brown
University, associates greenish glass bodies found in Argentina
with
the extinction of 36 local animals (including one we'd love to
see, a
carnivorous, flightless bird). The glass contains iridium, the
same
chemical that helped prove the impact theory of dinosaur
extinction.
Still, correlation is not proof. "The climate change -- the
sudden,
dramatic cooling came immediately after the impact," Schultz
says.
"My gut says it's direct cause and effect, but we were
careful to
call this a coincidence." More on the story)..
2000 -- NASA's Near-Earth Asteroid Tracking System announces new
data
about large asteroids. "Until now, scientists thought the
population
of large, near-Earth asteroids was between 1,000 and 2,000, but
we've
downgraded that number significantly," said David
Rabinowitz, now at
Yale University. "We now believe there are between 500 and
1,000
near-Earth asteroids larger than one kilometer in diameter."
2000 -- Michael Paine, an Australian engineer, announces a new
computer analysis of asteroid impacts indicating that asteroids
may
cause considerable chaos over a 100,000-year period. Most
disturbing
was a 5-kilometer asteroid, which exploded with a power of 23
million
megatons, easily enough to wipe out the human population. Paine
ignored this unsettling occurrence, since it was highly unlikely
to
occur in any given 100,000-year span. Still, he estimated the
annual risk of a fatal asteroid impact at one in 90, and
concluded
that an average of 120,000 people died per event. A particular
concern was tsunamis. When an asteroid hits the ocean, which
covers
about 70 percent of the planet, it can trigger a tsunami.
According
to the simulation, the average tsunami would kill 470,000 people.
The Why Files hates to base a story on a computer projection --
especially one done by a newcomer to the field of impact studies
--
but when it comes to asteroidal impact, there's little else to go
on.
As we'll see, only about 3 percent of impacts leave a crater, and
even when a crater does form, it is eventually buried by
sediment, as
happened to the Yucatan crater, or by the shifting of tectonic
plates. On Earth, crater-counting can cause a false sense of
security.
Have asteroids terminated civilizations? What to make of the
terrestrial impact of cosmic impacts?
HE SAID, SHE SAID
Listening to the debate over asteroid hazards, it's hard to
remember
that both sides are talking about projections based on the same
data.
On the one hand, the optimists say that impacts that would cause
a
global catastrophe (defined as killing more than one-quarter of
humanity), will occur about every 330,000 years (see p. 59 of
"Hazards... " in the bibliography).
On the other hand, Tom Gehrels, who edited "Hazards..."
and founded
Spacewatch, an asteroid search at the University of Arizona, says
impact is "a horrible problem. Do I lie awake at night?
Yes."
Gehrels is not alone. Radio astronomer Gerrit Verschuur of the
University of Memphis writes that while the asteroid hunters are
concentrating on 1-kilometer objects, "It is the smaller
impacts that
pose the greater danger, and they occur more frequently"
(see p. 108
in "Impact!" in the bibliography).
We asked astronomer Duncan Steel, of the University of Salford in
the
United Kingdom, whether, as the Paine simulation indicates, the
crater record understates the true number of impacts. He wrote
back,
"This is what one can infer to have happened, based simply
upon our
knowledge of the influx (i.e., physics). Now we need to look into
the
historical record and also the archeological record in this
light. In
the past scholars have dismissed tales of exploding rocks from
space
and vast cataclysms because 'such things do not happen'. But now
we
know they do."
Anthropologist Peiser is one of those who suspect that history
and
anthropology have suggestive evidence of impacts. If, he asks,
the
computer simulation was correct, and 350 Tunguska-size objects
struck
the Earth within the last 10,000 years, how would that have
affected
human society? He says the decline of many ancient civilizations,
including that of the Roman Empire, "may be associated with
episodes
of increased cosmic activity. Up to eight major [social] events
in
the last 10,000 years were associated with major impacts,"
Peiser
maintains. He argues that estimates of asteroid activity reflect
present conditions, even though Earth may have occupied far more
hazardous regions of space in the past.
Trying to carry arguments across disciplines is risky, writes
Verschuur. "The reaction to any proposal that we have
anything of
geological, paleontological or astronomical value to learn from
history is a direct parallel to the reaction met by the Alvarez
team
when they first dared to suggest a connection between
astronomical
events and mass extinctions. The prejudice of scientists against
anything that does not come from within their own discipline ...
is
considerable."
I'M FROM MISSOURI ... SHOW ME
At about this point, the optimists on the other side of the issue
start to echo a famous ad campaign: "Got data?"
To Peiser's assertion that, "Some 100 surface impacts,
including more
than a dozen oceanic impacts, have repeatedly devastated whole
regions, small countries and early civilizations around the
globe"
during the past 10,000 years, Clark Chapman, an asteroid expert
at
the Southwest Research Institute in Colorado, wrote that this
reflects "historical anecdotes and the ancient versions of
'urban
legends.' I regard these as having little probative
[substantiating]
value, unless accompanied by sound physical and geological
evidence.
But there are some neo-catastrophists, located mainly in Britain,
who
have an almost Velikovskian pseudo-scientific take on this matter
and
have argued that such impacts are more frequent..."
Velikovsky, of
course, is the guy who gave asteroid impacts such a bad name back
in
1950.
Responding to the same statement, David Morrison, director of
astrobiology and space research at NASA Ames Research Center,
argues
that the 100 impacts number is "highly speculative. I know
of no
convincing evidence that any 'small countries' or 'early
civilizations' have been devastated by a cosmic impact. It is
possible that one or more have (one thinks of the Biblical story
of
Sodom) but the evidence is weak. And of course there would be no
way
to know about most oceanic impacts."
John Lewis, the University of Arizona astronomer who created the
software that cranked out the numbers so worrisome to Peiser and
others, notes that if you run a simulation for a million years,
you
get "an astronomical number of casualties." Even if a
billion people
are cooked by asteroids over a million years, he says, "The
total
number of people who will die in that time is in the
trillions." The
danger of dying from an impact, he says, is "comparable to
flying an
airplane, it's about the same risk."
You tell me. Should we be searching harder for asteroids?
ONE POINT OF AGREEMENT
What with the Shoemaker-Levy crackup on Jupiter, and the growing
awareness that an asteroid whacked the dinos, it's clear that
something must be done about whirling space junk. The
current
searches focus on asteroids at least one kilometer across. The
reason for this focus, says astronomer John Lewis, is that
"civilization might not be able to survive a 2-kilometer
impact.
Morrison, who directed a 1992 survey of asteroid hazards for
NASA,
says "The actual risk of having your tombstone say 'killed
by an
asteroid' are at least 10 times as great" for asteroids
larger than 1
kilometer, "so certainly it's a proper priority to deal with
the
larger ones first."
Only about 40 percent of the kilometer-plus objects are known;
most
of the rest are expected to be identified within 10 years. At
present, no known planet-killing asteroids in this size range --
or
any size, for that matter -- is on a collision path with Earth.
Still, a 300-meter object might have a global impact, causing a
week
or two of climate disruption and could kill crops in the northern
hemisphere if it struck while crops were growing. Morrison agrees
"It
might be nice" to track smaller objects, but searching for
objects
like the 50-meter asteroid that devastated part of Siberia last
century would be a big job.
HOW MUCH MONEY YOU GOT?
Asteroid numbers are inversely related to size, which is a fancy
way
of saying that most are small. If you decrease the size by a
factor
of 10, says Gehrels, the population grows by a factor of 100. To
Lewis, that means that the cost of discovering and tracking the
smaller --- but potentially deadly -- asteroids would be, well,
in
his words, "astronomical. It's ridiculous, would require
mobilizing
the armed forces of the world to search for them."
Lewis adds that while many people may die over the next million
years
due to impacts, many more will die from other causes. "If
your sole
concern is avoiding destruction of global civilization, you can
limit
your search for things that are easy" to see. Objects that
are 500
meters and up in diameter are big, relatively rare, and large and
bright.
Let's repeat. No known asteroid is aiming for us, but 60 percent
of
the largest ones remain undiscovered. Still, Lewis expects that
the
present search for Earth-killer asteroids should identify about
90
percent of the large, near-Earth asteroids in the next 20
years, so "Basically, you have eliminated the [catastrophic]
hazard
within a fraction of a lifetime." However, Gehrels maintains
that
while the original identification is under control, money is
lacking
for following the orbits of faint, newly discovered asteroids.
Many
of them are tracked by amateur astronomers, who lack telescopes
of
sufficient size for the job.
IS THAT GOOD ENOUGH?
While most of the action centers on 1-kilometer asteroids,
Gehrels
says much smaller ones could "make a helluva mess. With our
society
expanding, even in Siberia [the Tunguska impact] would hit people
today. The world has become so interwoven, if you had a hit
anywhere
with a 100-meter object, it would really upset the society on
a
global scale." (Remember, the 50-meter Tunguska asteroid
packed the
punch of 40 million tons of TNT.)
An asteroidal bolt from the blue could even be interpreted as a
nuclear strike, possibly setting off a retaliatory strike. If,
for
example, Karachi, Pakistan, were to be obliterated by an
asteroid,
would the Pakistani military wait for confirmation, or strike
India
first with its nukes, and ask questions later?
That's a nice segue into one proposal -- deflecting asteroids
with
nuclear bombs. The idea is not to disintegrate the asteroid, but
rather to cook one side so hot that lots of material would
vaporize
and shoot off into space. In accord with the laws of mechanics,
that
motion would beget an equal and opposite motion, altering the
trajectory enough to miss Earth. Depending on the accuracy of the
orbital predictions and explosion, it might be best to strike an
asteroid millions of miles distant, at which point a gentle nudge
would have the most effect.
We won't get into the geopolitical impact of such a system, which
has
already aroused controversy because it involves using nuclear
weapons
in space and may contravene the Anti-Ballistic Missile treaty.
We got to wondering. Are the optimists and pessimists actually
talking about the same hazard?
IS THIS SCIENCE?
The asteroid debate raises a larger issue. How can scientists
reach
radically different conclusions from similar data? The optimists
say
there are just three chances of a catastrophic impact every
million
years. Yet given the intensity of human population and
habitation,
smaller objects that might once have been benign may be fatal
today,
and that in our interconnected world, the ensuing war, famine and
chaos
could be more destructive than the actual impact.
The optimists deride the historical and anthropological signs
that
impacts spelled doom for civilizations as exceedingly flimsy. The
pessimists say that since many smallish impacts probably occurred
over the past 10,000 years, it makes sense to search for their
effects,
one of which might be the sudden demise of civilizations.
The optimists demand to see the evidence, but the pessimists
counter
that the most convincing signs -- craters -- are misleadingly
rare.
Most of the Earth is covered by water, where craters don't form,
and
only about 3 percent of asteroids are iron. The remainder, like
the
Tunguska object, are stony objects that break up in the
atmosphere.
Thus, as asteroid hunter Gehrels says, "3 to 4 percent of
asteroids
would come through -- that's an accurate number."
Furthermore, as he observes, craters that do form are eventually
wiped
out by erosion or plate tectonic movement.
The optimists say that for any individual, the chance of
asteroidal
assassination is equivalent to the chance of dying in a jet
crash. The
pessimists say that a civilization is, well, a precious thing to
waste,
so it only makes sense to look for objects large or small before
they
come looking for us. Both sides agree that a well-aimed Tunguska
object
could obliterate any city on the planet.
ARISTOTLE’N ASTEROIDS
Although the debate can sink to the level of a hissing match,
both
sides point to some wiggle room in the argument. Are the
pessimists
blowing things out of proportion? Lewis, who compares the risk to
flying in an airplane, says the "whole mindset may turn out
to be
justified, but at the moment, it should be treated as
speculation."
Indeed, Morrison, who's never been associated with the
pessimists, says
"It's a legitimate scientific debate" about whether
societies have been
obliterated in the past. I don't know how you resolve it
easily."
Are the optimists whistling past the graveyard, ignoring
gargantuan
threats to society? Perhaps, but even Peiser does not claim proof
that
asteroids have played such an important role in history: "I
don't say
these theories are correct. I say it's possible that [the hazard
estimate of] the NASA establishment is off by orders of
magnitude."
Perhaps it's not a case of scientific disagreement but rather a
philosophical dispute. As Morrison says, "Given the same
data, people
will still come to different conclusions about the correct
resources to
devote to the search [for various types of asteroids]. It's a
perfectly
legitimate social question about what risks you want to deal
with."
Gehrels says completing the search for 100-meter objects would
"be a
reasonable goal," and notes that Spacewatch is attempting a
statistical
survey of these smaller but still deadly objects. Nevertheless,
he sees
signs of progress in the ongoing searches. With carefully chosen
words,
he says, "The asteroid hazard is the most serious thing that
humanity
faces, because it's the only one that can eliminate society at
once.
But we are on the way to taking care of it."
Astronomer Steel, however, is less sanguine. Asked via e-mail if
current search programs are adequate, he fired back: "I take
it you are
joking. There is NO SOUTHERN HEMISPHERE SEARCH
PROGRAMME [emphasis his].
Ipso facto, current efforts are not sufficient. However, the only
real
Northern Hemisphere search projects -- wonderful efforts operated
from
the U.S. -- are only covering (i) a minor portion of the northern
sky;
(ii) Not covering that sky to an adequate faintness limit: They
are
using only one-meter telescopes, and the laws of physics, which
may not
be contravened, dictate that telescopes with apertures larger
than two
meters are required... The great scientists are doing the best
they can
with very limited funds, but globally we are doing rather less
than 10
percent of what needs to be done lest we go the way of the
dinosaurs."
The controversy continues in our asteroid attack bibliography.
©2000, University of Wisconsin, Board of Regents.
The Why Files Staff includes: Terry Devitt, editor; S.V. Medaris,
designer/illustrator; David Tenenbaum, feature writer; Amy
Toburen,
content development executive; Eric G.E. Zuelow, content
development
executive
FOR MORE INFORMATION PLEASE VISIT THE WHY FILES WEBSITE AT
http://whyfiles.news.wisc.edu/106asteroid/index.html
----------------------------------------
THE CAMBRIDGE-CONFERENCE NETWORK (CCNet)
----------------------------------------
The CCNet is a scholarly electronic network. To
subscribe/unsubscribe,
please contact the moderator Benny J Peiser <b.j.peiser@livjm.ac.uk>.
Information circulated on this network is for scholarly and
educational use only. The attached information may not be copied
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reproduced for any other purposes without prior permission of the
copyright holders. The fully indexed archive of the CCNet, from
February 1997 on, can be found at http://abob.libs.uga.edu/bobk/cccmenu.html
*
CCNet ESSAY: COSMIC UNCERTAINTY
-------------------------------
From ASTRONOMY NOW, March 2000, pp. 53-55
http://astronomynow.com
IS THE EARTH DUE FOR ANOTHER CATACLYSMIC
IMPACT? THE SEARCH FOR PAST
IMPACTS IS HELPING TO SAFEGUARD OUR FUTURE.
By Benny Peiser
Ever since Sir Isaac Newton, we have learned to see our world
through
the lens of order and stability. In this deeply ingrained view,
the
world works like a giant clockwork according to set a universal
laws
and patterns that can be recognised and understood. Perhaps the
greatest triumph of Newtonian cosmology was the scientific
comprehension of comets. It was the ability to predict their
movements
which laid to rest the ancestral fear of comets as random
portents of
an unpredictable universe. The main message of this optimistic
cosmology was that human society could be assured of the
constancy,
predictability and stability of our world.
. . . [continued]