[meteorite-list] Re:Comet hit Britain in mid sixth century, AD?

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Sat Jul 22 01:33:29 2006
Message-ID: <00b501c6ad50$77cb02e0$7f45e146_at_ATARIENGINE>

Hi,

    The scientist you're referring to is Michael Baillie,
an Irish dentrochronologist (not Bailey). His evidence
of remarkably sharp climatic deviations ("years without
summers") is striking and solid. Dentrochronologists
have no trouble with his evidence and indeed a considerable
body of other evidence of sharp dramatic "drop-outs" of
1 or 2 years has been found in many locations by other
dentrochronologists. The argument is all about why, not
what, It's really hard to argue with a tree...

    The suggestion of comet airburst or other such event is
not new to the time period you're talking about (530's
and 540's AD) and Baillie has only taken up previous
hypotheses and refined them with dentrochronological
data. Napier and Clube first suggested something of the
kind in the 1970's, so it's a case of an hypothesis that
is acquiring more physical evidence as time goes by.

    Their suggestion arose from uncovering a 19th century
account of an excavation on the island of Anglesey (which
is the least forested portion of the UK, less than 0.5%)
of an ancient forest which had been flattened and crushed
wholesale and apparently instantaneously and which to
them greatly resembled a naive description of the flattened
forest on the Tungus River caused by the Tunguska object,
only much larger.

    There are many collateral lines of evidence for SOME
extreme phenomenon in the 530's, whether a cometary
airburst, a chondritic airburst, an oceanic strike, an immense
episode of vulcanism. Distinguishing between such events
by either by the contemporary accounts or physical evidence
of today is just not as easy as it sounds.

    The 535 AD "catastrophe" seems to have been much
worse in south China than anywhere else (or perhaps just
better documented?), so it has been suggested that an earlier
and much vaster eruption of Krakatoa is responsible for
the event.

    I quote the estimable Wikipedia: "...an eruption in 535 CE,
also referred to in the Javanese Book of Kings, and for which
there is geological and some corroborating historical evidence.
David Keys and others have postulated that the violent eruption
of Krakatoa in 535 may have been responsible for the global
climate changes of 535-536. Keys explores what he believes
to be the radical and far ranging global effects of just such
a putative 6th century eruption in his book Catastrophe:
An Investigation into the Origins of Modern Civilization.
Additionally, in recent times, it has been argued that it was this
eruption which created the islands of Verlaten and Lang
(remnants of the original) and the beginnings of Rakata -
all indicators of early Krakatoa's caldera's size. However,
there seems to be little, if any, datable charcoal from that
eruption, even if there is plenty of circumstantial evidence."
(Note: there is NO datable material for this earlier
eruption of Krakatoa, which could nave been any time
between 300 BC and 900 AD.)

    There's lots of "circumstantial evidence" for many
hypotheses, because something big and nasty happened,
only what? The variety of catastrophe is broad and not
all (any?) big nasty events are well understood.

    List member E. P. Grondine has done an amazing
amount of research on this very topic, and I'm surprised
he hasn't jumped in here already! Go to Google and
type in "E. P. Grondine" and "comet" or "catastrophe"
or "impact" or "Cambridge Conference" and read the
results that he posted in the Cambridge Conference
on these topics. And, no, I'm not his press agent...

    Also, you should not imagine (none of these theorists
suppose) that a catastrophe kills all the British Celts
nor all the Anglo-Saxons! Crop failures, famine, darkness,
fires, black days, ill luck, plagues, bad times a-plenty!
Folks move on, look for a happier spot, with better
living conditions and fewer big nasty events to deal
with or having another way to survive... Like ancient
Okies in a Super Dust Bowl... Put Gramma on top
of the ox cart full of house goods and the plough and
head for California or the ancient equivalent thereof.

    Yes, Marco, History is Change. But there are also
those "with a known fetish" AGAINST impacts or any
other physical event as a source" for any historical change.
The sudden collapse of the "Byzantine" or eastern Roman
Empire after 534 AD is without known social, political,
economic, military nor other human cause. It is the sudden
commencement of the Dark Ages for no apparent reason.
Dark Ages are rare, and always without apparent explanation
(1200 BC to 800 BC is another, and there was another
about 4000 years ago, too).

    Some things are just not worked out yet. In the longer
term, there is the unexplained history of eustatic sea level
changes. "Eustatic" sea level changes are the rise and
fall of sea level on a timescale too rapid to be caused by
the elevation or subsidence of continents or the displacement
of water by growing mid-oceanic ridges. 50 years ago and
more, most geologists worked for oil companies and their
data was "secret." In the 1970's, the great geologist Vail
talked his oil company into letting him divulge their vast
records of eustatic sea level changes to other geologists.
To get eustatic changes you have to radically change
the amount of water in the oceans, pretty difficult to do...

    There are great sharp drops in the Earth's sea level, as
great or greater than those of the severest ice ages (when
water is tied up in glaciers miles thick covering vast swathes
of continents) that only lasted a few years to perhaps 500-1000
years, far too short for an "ice age" (which takes many thousands
of years). They have never been "explained," because the only
plausible cause would be a vast world-wide glaciation in
which most of the planet froze over instantly and caused
the atmospheric water to fall out as snow or ice but only for
a very few years, then took up to centuries to melt all that ice
after the climate returned to normal. These odd, potentially
"super-cooling," events are NOT associated with extinctions
nor any other known phenomenon (vulcanism, magnetic
reversals, etc.). They are completely out of the blue
(and fortunately quite rare) and very difficult to explain.
They are sometimes called "false" ice ages, a totally ridiculous
term. At least for the last 35 years, they have been impossible
to explain. I got no theory, except that I tend look up at the
sky for big nasty unexplained events.

    After-thought: Ever hear of the form of ice called
"diamond dust?" Google that, too. Now, there's a really
nasty possibility...


Sterling K. Webb
---------------------------------------------------
meteorite-list_at_meteoritecentral.com>
Sent: Friday, July 21, 2006 11:59 AM
Subject: Re: [meteorite-list] Re:Comet hit Britain in mid sixth century, AD?


>> Baileys comet impact hypothesis is
>> quite contested, it certainly is not an
>> accepted main stream hypothesis. So I
>> quite surprised by the tone of that
>> newspaper clipping that suggested so.
>> The astrophysicist supporting it are, by
>> the way, astrophysicists with a known
>> fetish for impacts as a source for every
>> historical change.
>
> Thanks Marco,
> In general, I think the theory is very dubious. The guy was trying to
> explain how small numbers of Anglo-Saxon migrants replaced a much larger
> indigenous Celtic/British population both genetically and linguistically.
> But if the Britons were dying off in the 530s because of poor crop yields
> and cold nights or whatever caused by cometary dust in the atmosphere,
> then the Anglo-Saxons would too.
>
> Unless of course somebody postulates an actual impact which wiped out a
> large part of the (British) population on the west side of the island, but
> was survived by larger numbers on the east which is where the
> Anglo-Saxons were. But then that's not a good model either,
> because Ireland is where it
> would have hit... and there is no evidence of such an event from there.
>
> Just as a matter of interest if someone has time to fiddle with it, what
> parameters would such a hypothetical body have to have to kill people
> within a radius of 300 km (so along the whole western coast of England
> and
> Wales) but leave those beyond still alive? [I could not get the Arizona
> Earth
> Impact Effects Program http://www.lpl.arizona.edu/impacteffects/ to give
> the > result I wanted - just curious].
>
> Paul Barford
>
Received on Sat 22 Jul 2006 01:34:13 AM PDT