"Eric Stevens" <eric.stevens@sum.co.nz> wrote in message
news:si9530l8ts5qdqtgn8oplqp273l9rrsijl@4ax.com...
On Tue, 17 Feb 2004 22:23:26 -0000, "Jim Webster"
Jim@feeswerve.spam.co.uk> wrote:



I suggest you read what Baillie has written. It's too long for me to
quote.

It better be an awfully good explanation to explain away why a historian
renown for his love of anecdote and juicy stories, and who actually wrote a
secret history to be produced after his death never mentioned the equivalent
of a Krakatoa eruption which happened for several years in succession (as
with the crossing of cometary trails). I am afraid that this predisposes me
to be sceptical



You seem to be torn between three concepts.
1) A Tunguska like impact. Fine, but where in the crater?

There is no crater with Tunguska events. Its a monstrous air-blast.
This is the chacteristic of virtually all high-speed bolides. They do
not reach the ground.

Yet at Tunguska the event was visible on the ground for many years
afterwards.

And what were the climate effects of Tunguska?

And what signs of bubonic plague?

If you want Tunguska style events, you really have to show that Tunguska
actually produced the sorts of effects you are looking for.
Remember Tunguska was in 1908. Russian Harvests in 1913 were larger than any
year until 1956. There is no evidence that a Tunguska incident had the sort
of climatic or disease effects that you are looking for.

2) Cometary dust belt left by a comet. Yes, but this happens twice a
year,
every year. Now if you look at old descriptions they can occasionally be
quite spectacular, but the amount of dust that has to be left to have any
sort of major climatic effect effectively demands the comet break up in
front of us for us to run into. Certainly I am aware of no evidence of
climate change because of the trails we know of.

There is evidence of climate change associated with dust layers in ice
cores. Some are probably due to volcanoes but others lack the acid
trace characteristic of volcanoes. I again refer to you to 'Exodus to
Arthur'.

Volcano emissions are well known to produce climate effects but look at the
numbers I produced in the other post, comparing Krakatoa to the sort of muck
you pick up in a comet trail

3) A comet seen in the sky. Our ancestors were pretty good at recording
them.

There is absolutely no ned for the parent comet to be visible at the
same time as the earth runs into its debris trail. Having said that,
there may have been one well described situation when the earth
appears to have had a very near miss with a comet. This has come down
to us in all kinds of stories from the Epic of Gilgamesh, to the story
of Phaethon to the chinese dragons. See
http://abob.libs.uga.edu/bobk/phaeth.html

See the figures for the amount of waste you need in a comet trail

On Wed, 18 Feb 2004 08:39:01 -0000, "Jim Webster"
Jim@feeswerve.spam.co.uk> wrote:

The other option is the cometary trail. So let us do the maths, let us
assume that the trail deposits on earth the same volume of material as
the
Karkatoa eruptuion. (21 cubic km). But some of this burns up as it
enters
the atmosphere so let us assume that there was 42 cubic km.
Now the Atmosphere is 480 km thick. So for ease assume the earth
sweeps
up
the muck spread over 1000km of cometary trail. So the comet sheds
0.042
cubic km per kilometre. Now Earth is 93 million miles from the sun.
The
comet starts shedding material as it moves toward the sun and
continues
as
it goes round the sun and comes out the other side. The amount shed
isn't
uniform, so as an approximation we will just assume it starts shedding
as
it
enters earths orbit. Sublimation starts when the comets are closer
than
about three astronomical units from the Sun (one astronomical unit
[AU]
equals about 150,000,000 km, or 93,000,000 miles). So assume that this
comet
only sheds material for 2 astronomical units, this is 7,812,000 cubic
km.
As a comparison, the nucleus of Halley's comet, is about 15 by 4 km
(about
9 by 2.5 miles).

The size of comet needed is several orders of magnitude larger than
any
comet recorded. So I would suggest that unless you can come up with
examples
of the appropriate size the explanation isn't particularly useful

There is something wrong with your thesis. For a start, I suggest that
you try to catch up with the last 20 years on the subject.

The maths is there, show what is wrong. Just because the maths doesn't
fit
your model doesn't mean the maths is wrong, it may mean your model is
wrong


Mathematics is merely a formalised system of logic used to reach
conclusions on the basis of an initial series of axioms. If a
mathematical conclusion can be shown to be wrong then it must be that
one of the initial axioms must be wrong. The question is 'which one?'.

The logical structure of your mathematics may be perfectly correct as
it stands but if your conclusions don't fit the real-world
ovservations, there must be something wrong with one or more of your
starting points. You cannot properly accept or reject any particular
theory on the basis of such simple arithmetic as you have just used
unless you can also show that both your starting points and your
conclusions are consistent with what is already known.

I don't want to get bogged down in a prolonged argument. Nor do I want
to start arguing from authority. But, it is clear to me, that your
model is an inaccurate oversimplification of what is already known
about comets and, for this reason, the conclusions you have drawn from
it are suspect.

Just to make life interesting, the ground may have shifted again. Dr.
Michael R. Rampino [Associate Professor, Earth & Environmental Science
Program, New York University] has just written to the CCNet mailing
list:

"Claus Hammer and his co-workers have now substantiated and
redated the volcanic ice-core peak that Richard Stothers
and I believed for many years to be associated with the
dim sun conditions of AD 536.

There is absolutely no physical evidence for a comet impact or
airburst at that time, so speculation about this "impact event"
should now end."

Rampino and Stothers have worked together for a long time and for this
reason Rampino can be expected to have early access to Stothers'
conclusions. That may explain why I can as yet find no refrence to
work by Stothers which explains Rampino's comments. However, if the
ice core dating must truly be revised it follows that so will the
theories and hypothesese which depend on it. Where it all is presently
going is a mystery to me. The dendrochronologists are likely to be the
ultimate authorities on dating and it will be interesting to see what
they make of whatever Stothers has recently been doing.

dendrochronologists may show that trees had a bad year, they do not show the

But they are an order of magnitude less than some events of the
reorded past. They are probably two orders below Tunguska level
events. A civilization on the end of a Tunguska level of attack would
surely remember it, even if they could not possibly understand the
reality of what was happening,

See http://abob.libs.uga.edu/bobk/bronze.html for some possibilities.


To have a Tunguska you need a crater, where is the crater?

The other option is the cometary trail. So let us do the maths, let us
assume that the trail deposits on earth the same volume of material as
the
Karkatoa eruptuion. (21 cubic km). But some of this burns up as it enters
the atmosphere so let us assume that there was 42 cubic km.
Now the Atmosphere is 480 km thick. So for ease assume the earth sweeps
up
the muck spread over 1000km of cometary trail. So the comet sheds 0.042
cubic km per kilometre. Now Earth is 93 million miles from the sun. The
comet starts shedding material as it moves toward the sun and continues
as
it goes round the sun and comes out the other side. The amount shed isn't
uniform, so as an approximation we will just assume it starts shedding as
it
enters earths orbit. Sublimation starts when the comets are closer than
about three astronomical units from the Sun (one astronomical unit [AU]
equals about 150,000,000 km, or 93,000,000 miles). So assume that this
comet
only sheds material for 2 astronomical units, this is 7,812,000 cubic km.
As a comparison, the nucleus of Halley's comet, is about 15 by 4 km
(about
9 by 2.5 miles).

The size of comet needed is several orders of magnitude larger than any
comet recorded. So I would suggest that unless you can come up with
examples
of the appropriate size the explanation isn't particularly useful

I've responded to this previously but I've now had some time to do a
little more digging .... :-)

http://www.solarviews.com/eng/kuiper.htm
"The Kuiper belt remained theory until the 1992 detection of a
150-mile wide body, called 1992QB1 at the distance of the
suspected belt. Several similar-sized objects were discovered
quickly confirming the Kuiper belt was real. The planet Pluto,
discovered in 1930, is considered the largest member of this
Kuiper belt region. Also, Neptune's satellites, Triton and
Nereid, and Saturn's satellite, Phoebe are in unusual orbits
and may be captured Kuiper belt objects."

The kinds of things we are considering are not mere rocks from the
sky. The 150mile diameter object would, if it had the same density as
water, have a mass of 7.25e15 tons. Even after it has broken up, its
mass would not be any less significant.

Jim,

Planetoids (or planetessimals) are different from comets. The
distinction needs to be maintained. Yes, there are very large
comet cores, and they are likely to be equally damaging if they
hit Earth. But comets and asteroids of the same size are not
equally visible, and don't have the same potential for
'residuals' hitting Earth.

Also, IIRC there are very few not very powerful mechanisms for
planetoids or asteroids to shed debris; while there are several
quite powerful mechanisms for comets doing so.
Planetoids/asteroids seldom have even 'moons' (although at least
one does, and it's an extremely interesting system), much less
mobile debris that can be stripped off by the solar wind,
although coronal mass ejections I'm sure could do a good job of it.

AFAIK, the orbiting debris fields are cometary remnants, and
danger from them is separable from the danger of comets or
asteroids/planetoids.

Tom McDonald

On Wed, 18 Feb 2004 08:37:33 -0000, "Jim Webster"
Jim@feeswerve.spam.co.uk> wrote:


"Eric Stevens" <eric.stevens@sum.co.nz> wrote in message
news:si9530l8ts5qdqtgn8oplqp273l9rrsijl@4ax.com...
On Tue, 17 Feb 2004 22:23:26 -0000, "Jim Webster"
Jim@feeswerve.spam.co.uk> wrote:



I suggest you read what Baillie has written. It's too long for me to
quote.

It better be an awfully good explanation to explain away why a historian
renown for his love of anecdote and juicy stories, and who actually wrote
a
secret history to be produced after his death never mentioned the
equivalent
of a Krakatoa eruption which happened for several years in succession (as
with the crossing of cometary trails). I am afraid that this predisposes
me
to be sceptical



You seem to be torn between three concepts.
1) A Tunguska like impact. Fine, but where in the crater?

There is no crater with Tunguska events. Its a monstrous air-blast.
This is the chacteristic of virtually all high-speed bolides. They do
not reach the ground.

Yet at Tunguska the event was visible on the ground for many years
afterwards.

See the opening page of http://www-th.bo.infn.it/tunguska/
Visible affects did not include a crater.

And what were the climate effects of Tunguska?

I gather that they were only minor. That should tell you something.
I'm not sure what.

And what signs of bubonic plague?

None that I know of but should there be?

If you want Tunguska style events, you really have to show that Tunguska
actually produced the sorts of effects you are looking for.
Remember Tunguska was in 1908. Russian Harvests in 1913 were larger than
any
year until 1956. There is no evidence that a Tunguska incident had the
sort
of climatic or disease effects that you are looking for.

Not a single incident.


2) Cometary dust belt left by a comet. Yes, but this happens twice a
year,
every year. Now if you look at old descriptions they can occasionally
be
quite spectacular, but the amount of dust that has to be left to have
any
sort of major climatic effect effectively demands the comet break up
in
front of us for us to run into. Certainly I am aware of no evidence of
climate change because of the trails we know of.

There is evidence of climate change associated with dust layers in ice
cores. Some are probably due to volcanoes but others lack the acid
trace characteristic of volcanoes. I again refer to you to 'Exodus to
Arthur'.

Volcano emissions are well known to produce climate effects but look at
the
numbers I produced in the other post, comparing Krakatoa to the sort of
muck
you pick up in a comet trail

You are entitled to be sceptical about an argument but your scepticism
will carry more weight if you know the argument which you are
questioning.
Having seen half a dozen variants on the same theme over the last few years

3) A comet seen in the sky. Our ancestors were pretty good at
recording
them.

There is absolutely no ned for the parent comet to be visible at the
same time as the earth runs into its debris trail. Having said that,
there may have been one well described situation when the earth
appears to have had a very near miss with a comet. This has come down
to us in all kinds of stories from the Epic of Gilgamesh, to the story
of Phaethon to the chinese dragons. See
http://abob.libs.uga.edu/bobk/phaeth.html

See the figures for the amount of waste you need in a comet trail

Every part of that calculation is hypothetical. None is based on
reality.

On Wed, 18 Feb 2004 20:52:40 -0000, "Jim Webster"
Jim@feeswerve.spam.co.uk> wrote:


"Eric Stevens" <eric.stevens@sum.co.nz> wrote in message
news:2dh7309lvvo25iq3njvb68ehf3h2hg34on@4ax.com...
But they are an order of magnitude less than some events of the
reorded past. They are probably two orders below Tunguska level
events. A civilization on the end of a Tunguska level of attack
would
surely remember it, even if they could not possibly understand the
reality of what was happening,

See http://abob.libs.uga.edu/bobk/bronze.html for some
possibilities.


To have a Tunguska you need a crater, where is the crater?

The other option is the cometary trail. So let us do the maths, let us
assume that the trail deposits on earth the same volume of material as
the
Karkatoa eruptuion. (21 cubic km). But some of this burns up as it
enters
the atmosphere so let us assume that there was 42 cubic km.
Now the Atmosphere is 480 km thick. So for ease assume the earth
sweeps
up
the muck spread over 1000km of cometary trail. So the comet sheds
0.042
cubic km per kilometre. Now Earth is 93 million miles from the sun.
The
comet starts shedding material as it moves toward the sun and
continues
as
it goes round the sun and comes out the other side. The amount shed
isn't
uniform, so as an approximation we will just assume it starts shedding
as
it
enters earths orbit. Sublimation starts when the comets are closer
than
about three astronomical units from the Sun (one astronomical unit
[AU]
equals about 150,000,000 km, or 93,000,000 miles). So assume that this
comet
only sheds material for 2 astronomical units, this is 7,812,000 cubic
km.
As a comparison, the nucleus of Halley's comet, is about 15 by 4 km
(about
9 by 2.5 miles).

The size of comet needed is several orders of magnitude larger than
any
comet recorded. So I would suggest that unless you can come up with
examples
of the appropriate size the explanation isn't particularly useful

I've responded to this previously but I've now had some time to do a
little more digging .... :-)

http://www.solarviews.com/eng/kuiper.htm
"The Kuiper belt remained theory until the 1992 detection of a
150-mile wide body, called 1992QB1 at the distance of the
suspected belt. Several similar-sized objects were discovered
quickly confirming the Kuiper belt was real. The planet Pluto,
discovered in 1930, is considered the largest member of this
Kuiper belt region. Also, Neptune's satellites, Triton and
Nereid, and Saturn's satellite, Phoebe are in unusual orbits
and may be captured Kuiper belt objects."

The kinds of things we are considering are not mere rocks from the
sky. The 150mile diameter object would, if it had the same density as
water, have a mass of 7.25e15 tons. Even after it has broken up, its
mass would not be any less significant.


except that we have no evidence for these objects ever entering the inner
solar system. After all, you don't need the Kuiper belt, you could
postulate
an asteroid, we know they come much closer, but they do not leave trails
of
dust.

It is now accepted that at least some asteroids are larger fragments
left over from a parent comet.

If you are looking for a Tunguska type event, then there isn't a problem
with sourcing the asteroid. It is finding something that will leave a
dense
trail behind it, and I am unaware of any comet (a remarkably well studied
phenomena) which will do that.

You don't need a particularly dense trail.

Eric Stevens

"Eric Stevens" <eric.stevens@sum.co.nz> wrote in message
news:2me730tc9ppatfc2f7cbthesvd68pf09u4@4ax.com...
On Wed, 18 Feb 2004 08:39:01 -0000, "Jim Webster"
Jim@feeswerve.spam.co.uk> wrote:

The other option is the cometary trail. So let us do the maths, let us
assume that the trail deposits on earth the same volume of material as
the
Karkatoa eruptuion. (21 cubic km). But some of this burns up as it
enters
the atmosphere so let us assume that there was 42 cubic km.
Now the Atmosphere is 480 km thick. So for ease assume the earth
sweeps
up
the muck spread over 1000km of cometary trail. So the comet sheds
0.042
cubic km per kilometre. Now Earth is 93 million miles from the sun.
The
comet starts shedding material as it moves toward the sun and
continues
as
it goes round the sun and comes out the other side. The amount shed
isn't
uniform, so as an approximation we will just assume it starts shedding
as
it
enters earths orbit. Sublimation starts when the comets are closer
than
about three astronomical units from the Sun (one astronomical unit
[AU]
equals about 150,000,000 km, or 93,000,000 miles). So assume that this
comet
only sheds material for 2 astronomical units, this is 7,812,000 cubic
km.
As a comparison, the nucleus of Halley's comet, is about 15 by 4 km
(about
9 by 2.5 miles).

The size of comet needed is several orders of magnitude larger than
any
comet recorded. So I would suggest that unless you can come up with
examples
of the appropriate size the explanation isn't particularly useful

There is something wrong with your thesis. For a start, I suggest that
you try to catch up with the last 20 years on the subject.

The maths is there, show what is wrong. Just because the maths doesn't
fit
your model doesn't mean the maths is wrong, it may mean your model is
wrong


Mathematics is merely a formalised system of logic used to reach
conclusions on the basis of an initial series of axioms. If a
mathematical conclusion can be shown to be wrong then it must be that
one of the initial axioms must be wrong. The question is 'which one?'.

The logical structure of your mathematics may be perfectly correct as
it stands but if your conclusions don't fit the real-world
ovservations, there must be something wrong with one or more of your
starting points. You cannot properly accept or reject any particular
theory on the basis of such simple arithmetic as you have just used
unless you can also show that both your starting points and your
conclusions are consistent with what is already known.

I don't want to get bogged down in a prolonged argument. Nor do I want
to start arguing from authority. But, it is clear to me, that your
model is an inaccurate oversimplification of what is already known
about comets and, for this reason, the conclusions you have drawn from
it are suspect.


Actually if you look at the amount of dust that would be needed to cause
climatic effects from cometry dust, we would probably be able to detect the
trails. Given that the nature of atmosphere is such that dust tends to burn
up on entry....

... I suggest the cometary dust hypothesis suffers from serious
impracticality. As we have no proven real world observations of vast amounts
of cometary dust impacting on the weather, purely when we cross the comets
path, I suggest that actually my maths is pretty well in keeping with the
real world situation

Just to make life interesting, the ground may have shifted again. Dr.
Michael R. Rampino [Associate Professor, Earth & Environmental Science
Program, New York University] has just written to the CCNet mailing
list:

"Claus Hammer and his co-workers have now substantiated and
redated the volcanic ice-core peak that Richard Stothers
and I believed for many years to be associated with the
dim sun conditions of AD 536.

There is absolutely no physical evidence for a comet impact or
airburst at that time, so speculation about this "impact event"
should now end."

Rampino and Stothers have worked together for a long time and for this
reason Rampino can be expected to have early access to Stothers'
conclusions. That may explain why I can as yet find no refrence to
work by Stothers which explains Rampino's comments. However, if the
ice core dating must truly be revised it follows that so will the
theories and hypothesese which depend on it. Where it all is presently
going is a mystery to me. The dendrochronologists are likely to be the
ultimate authorities on dating and it will be interesting to see what
they make of whatever Stothers has recently been doing.

dendrochronologists may show that trees had a bad year, they do not show the
cause.
Volcanic activity is entirely possible, we know that it does have the
desired effect and it is entirely possible that we will be able to pin the
effect down to a specific eruption. They have the advantage that they create
dust within the atmosphere which is far more "efficient" than trying to
bring dust into the atmosphere from outside, given the proportion that would
burn up on entry

Jim Webster

"Eric Stevens" <eric.stevens@sum.co.nz> wrote in message
news:2dh7309lvvo25iq3njvb68ehf3h2hg34on@4ax.com...
But they are an order of magnitude less than some events of the
reorded past. They are probably two orders below Tunguska level
events. A civilization on the end of a Tunguska level of attack would
surely remember it, even if they could not possibly understand the
reality of what was happening,

See http://abob.libs.uga.edu/bobk/bronze.html for some possibilities.


To have a Tunguska you need a crater, where is the crater?

The other option is the cometary trail. So let us do the maths, let us
assume that the trail deposits on earth the same volume of material as
the
Karkatoa eruptuion. (21 cubic km). But some of this burns up as it enters
the atmosphere so let us assume that there was 42 cubic km.
Now the Atmosphere is 480 km thick. So for ease assume the earth sweeps
up
the muck spread over 1000km of cometary trail. So the comet sheds 0.042
cubic km per kilometre. Now Earth is 93 million miles from the sun. The
comet starts shedding material as it moves toward the sun and continues
as
it goes round the sun and comes out the other side. The amount shed isn't
uniform, so as an approximation we will just assume it starts shedding as
it
enters earths orbit. Sublimation starts when the comets are closer than
about three astronomical units from the Sun (one astronomical unit [AU]
equals about 150,000,000 km, or 93,000,000 miles). So assume that this
comet
only sheds material for 2 astronomical units, this is 7,812,000 cubic km.
As a comparison, the nucleus of Halley's comet, is about 15 by 4 km
(about
9 by 2.5 miles).

The size of comet needed is several orders of magnitude larger than any
comet recorded. So I would suggest that unless you can come up with
examples
of the appropriate size the explanation isn't particularly useful

I've responded to this previously but I've now had some time to do a
little more digging .... :-)

http://www.solarviews.com/eng/kuiper.htm
"The Kuiper belt remained theory until the 1992 detection of a
150-mile wide body, called 1992QB1 at the distance of the
suspected belt. Several similar-sized objects were discovered
quickly confirming the Kuiper belt was real. The planet Pluto,
discovered in 1930, is considered the largest member of this
Kuiper belt region. Also, Neptune's satellites, Triton and
Nereid, and Saturn's satellite, Phoebe are in unusual orbits
and may be captured Kuiper belt objects."

The kinds of things we are considering are not mere rocks from the
sky. The 150mile diameter object would, if it had the same density as
water, have a mass of 7.25e15 tons. Even after it has broken up, its
mass would not be any less significant.


except that we have no evidence for these objects ever entering the inner
solar system. After all, you don't need the Kuiper belt, you could postulate
an asteroid, we know they come much closer, but they do not leave trails of
dust.

If you are looking for a Tunguska type event, then there isn't a problem
with sourcing the asteroid. It is finding something that will leave a dense
trail behind it, and I am unaware of any comet (a remarkably well studied
phenomena) which will do that.

"Eric Stevens" <eric.stevens@sum.co.nz> wrote in message
news:5vh730p2893g811983burnfimda68gqno0@4ax.com...
On Wed, 18 Feb 2004 08:37:33 -0000, "Jim Webster"
Jim@feeswerve.spam.co.uk> wrote:


"Eric Stevens" <eric.stevens@sum.co.nz> wrote in message
news:si9530l8ts5qdqtgn8oplqp273l9rrsijl@4ax.com...
On Tue, 17 Feb 2004 22:23:26 -0000, "Jim Webster"
Jim@feeswerve.spam.co.uk> wrote:



I suggest you read what Baillie has written. It's too long for me to
quote.

It better be an awfully good explanation to explain away why a historian
renown for his love of anecdote and juicy stories, and who actually wrote
a
secret history to be produced after his death never mentioned the
equivalent
of a Krakatoa eruption which happened for several years in succession (as
with the crossing of cometary trails). I am afraid that this predisposes
me
to be sceptical



You seem to be torn between three concepts.
1) A Tunguska like impact. Fine, but where in the crater?

There is no crater with Tunguska events. Its a monstrous air-blast.
This is the chacteristic of virtually all high-speed bolides. They do
not reach the ground.

Yet at Tunguska the event was visible on the ground for many years
afterwards.

See the opening page of http://www-th.bo.infn.it/tunguska/
Visible affects did not include a crater.

No but there were many many miles of flattened trees etc etc. It was visible
on the ground for many years after and I believe that the effects are still
visible if you try to cross the area

And what were the climate effects of Tunguska?

I gather that they were only minor. That should tell you something.
I'm not sure what.

It shows that you need a much larger effect to create weather/climate
changes which makes it even harder to leave no physical trace on the ground

And what signs of bubonic plague?

None that I know of but should there be?

If you want Tunguska style events, you really have to show that Tunguska
actually produced the sorts of effects you are looking for.
Remember Tunguska was in 1908. Russian Harvests in 1913 were larger than
any
year until 1956. There is no evidence that a Tunguska incident had the
sort
of climatic or disease effects that you are looking for.

Not a single incident.


2) Cometary dust belt left by a comet. Yes, but this happens twice a
year,
every year. Now if you look at old descriptions they can occasionally
be
quite spectacular, but the amount of dust that has to be left to have
any
sort of major climatic effect effectively demands the comet break up
in
front of us for us to run into. Certainly I am aware of no evidence of
climate change because of the trails we know of.

There is evidence of climate change associated with dust layers in ice
cores. Some are probably due to volcanoes but others lack the acid
trace characteristic of volcanoes. I again refer to you to 'Exodus to
Arthur'.

Volcano emissions are well known to produce climate effects but look at
the
numbers I produced in the other post, comparing Krakatoa to the sort of
muck
you pick up in a comet trail

You are entitled to be sceptical about an argument but your scepticism
will carry more weight if you know the argument which you are
questioning.
Having seen half a dozen variants on the same theme over the last few years
my comments pretty well apply to most.



3) A comet seen in the sky. Our ancestors were pretty good at
recording
them.

There is absolutely no ned for the parent comet to be visible at the
same time as the earth runs into its debris trail. Having said that,
there may have been one well described situation when the earth
appears to have had a very near miss with a comet. This has come down
to us in all kinds of stories from the Epic of Gilgamesh, to the story
of Phaethon to the chinese dragons. See
http://abob.libs.uga.edu/bobk/phaeth.html

See the figures for the amount of waste you need in a comet trail

Every part of that calculation is hypothetical. None is based on
reality.

In that it shares a great deal with the theory that cometary trails could
have caused the climate changes. But if you don't like the figures, produce
better ones. Remember you are dealing with astronomy and that is a very
mathematical science

I'm not particularly concerned about whether or not I convince you. I

On Wed, 18 Feb 2004 21:07:44 -0000, "Jim Webster"
Jim@feeswerve.spam.co.uk> wrote:


"Eric Stevens" <eric.stevens@sum.co.nz> wrote in message
news:5vh730p2893g811983burnfimda68gqno0@4ax.com...
On Wed, 18 Feb 2004 08:37:33 -0000, "Jim Webster"
Jim@feeswerve.spam.co.uk> wrote:


"Eric Stevens" <eric.stevens@sum.co.nz> wrote in message
news:si9530l8ts5qdqtgn8oplqp273l9rrsijl@4ax.com...
On Tue, 17 Feb 2004 22:23:26 -0000, "Jim Webster"
Jim@feeswerve.spam.co.uk> wrote:



I suggest you read what Baillie has written. It's too long for me to
quote.

It better be an awfully good explanation to explain away why a
historian
renown for his love of anecdote and juicy stories, and who actually
wrote
a
secret history to be produced after his death never mentioned the
equivalent
of a Krakatoa eruption which happened for several years in succession
(as
with the crossing of cometary trails). I am afraid that this
predisposes
me
to be sceptical



You seem to be torn between three concepts.
1) A Tunguska like impact. Fine, but where in the crater?

There is no crater with Tunguska events. Its a monstrous air-blast.
This is the chacteristic of virtually all high-speed bolides. They
do
not reach the ground.

Yet at Tunguska the event was visible on the ground for many years
afterwards.

See the opening page of http://www-th.bo.infn.it/tunguska/
Visible affects did not include a crater.

No but there were many many miles of flattened trees etc etc. It was
visible
on the ground for many years after and I believe that the effects are
still
visible if you try to cross the area

Which has got what to do with your expectation of a crater?

And what were the climate effects of Tunguska?

I gather that they were only minor. That should tell you something.
I'm not sure what.

It shows that you need a much larger effect to create weather/climate
changes which makes it even harder to leave no physical trace on the
ground

You are obviously not aware of the latest work on high velocity
impacts.

Every part of that calculation is hypothetical. None is based on
reality.

In that it shares a great deal with the theory that cometary trails could
have caused the climate changes. But if you don't like the figures,
produce
better ones. Remember you are dealing with astronomy and that is a very
mathematical science

I'm not particularly concerned about whether or not I convince you. I
would count it a success if you took it upon youreself to research the
subject. The references I gave you earlier are not primary sources but
they give you links to primary sources.

Eric Stevens

"Eric Stevens" <eric.stevens@sum.co.nz> wrote in message
news:rdq730dp6pshsc2gq013bu9l4iueb45asn@4ax.com...
On Wed, 18 Feb 2004 21:07:44 -0000, "Jim Webster"
Jim@feeswerve.spam.co.uk> wrote:


"Eric Stevens" <eric.stevens@sum.co.nz> wrote in message
news:5vh730p2893g811983burnfimda68gqno0@4ax.com...
On Wed, 18 Feb 2004 08:37:33 -0000, "Jim Webster"
Jim@feeswerve.spam.co.uk> wrote:


"Eric Stevens" <eric.stevens@sum.co.nz> wrote in message
news:si9530l8ts5qdqtgn8oplqp273l9rrsijl@4ax.com...
On Tue, 17 Feb 2004 22:23:26 -0000, "Jim Webster"
Jim@feeswerve.spam.co.uk> wrote:



I suggest you read what Baillie has written. It's too long for me to
quote.

It better be an awfully good explanation to explain away why a
historian
renown for his love of anecdote and juicy stories, and who actually
wrote
a
secret history to be produced after his death never mentioned the
equivalent
of a Krakatoa eruption which happened for several years in succession
(as
with the crossing of cometary trails). I am afraid that this
predisposes
me
to be sceptical



You seem to be torn between three concepts.
1) A Tunguska like impact. Fine, but where in the crater?

There is no crater with Tunguska events. Its a monstrous air-blast.
This is the chacteristic of virtually all high-speed bolides. They
do
not reach the ground.

Yet at Tunguska the event was visible on the ground for many years
afterwards.

See the opening page of http://www-th.bo.infn.it/tunguska/
Visible affects did not include a crater.

No but there were many many miles of flattened trees etc etc. It was
visible
on the ground for many years after and I believe that the effects are
still
visible if you try to cross the area

Which has got what to do with your expectation of a crater?

I said "Yet at Tunguska the event was visible on the ground"

And what were the climate effects of Tunguska?

I gather that they were only minor. That should tell you something.
I'm not sure what.

It shows that you need a much larger effect to create weather/climate
changes which makes it even harder to leave no physical trace on the
ground

You are obviously not aware of the latest work on high velocity
impacts.

Obviously Tunguska wasn't either. Any latest work still has to take this
into account

Every part of that calculation is hypothetical. None is based on
reality.

In that it shares a great deal with the theory that cometary trails could
have caused the climate changes. But if you don't like the figures,
produce
better ones. Remember you are dealing with astronomy and that is a very
mathematical science

I'm not particularly concerned about whether or not I convince you. I
would count it a success if you took it upon youreself to research the
subject. The references I gave you earlier are not primary sources but
they give you links to primary sources.

I have been reading round the primary astronomical sources for some years
although it is not a major interest of mine. It is because of this that I
have so little respect for the secondary sources and the somewhat casual
attitude they have to the sort of numbers needed

I said "Yet at Tunguska the event was visible on the ground"

You also said in Message-ID: <c0u55c$eik$1@newsg1.svr.pol.co.uk

---- snip ----

"1) A Tunguska like impact. Fine, but where in the crater?"

I took it that was a typo for "Fine, but where is the crater?". It
doen't make much sense otherwise.

And what were the climate effects of Tunguska?

I gather that they were only minor. That should tell you something.
I'm not sure what.

It shows that you need a much larger effect to create weather/climate
changes which makes it even harder to leave no physical trace on the
ground

You are obviously not aware of the latest work on high velocity
impacts.

Obviously Tunguska wasn't either. Any latest work still has to take this
into account

The latest work shows that a much smaller bolide than previously
recognised can create a nuclear winter. Tunguska was still to small to
creat much of an effect.

Re you quest for numbers, I am working on it.

"Eric Stevens" <eric.stevens@sum.co.nz> wrote in message
news:sjg8309sdnsvsh5kf0hj7kdhf1cvart2jv@4ax.com...


I said "Yet at Tunguska the event was visible on the ground"

You also said in Message-ID: <c0u55c$eik$1@newsg1.svr.pol.co.uk

---- snip ----

"1) A Tunguska like impact. Fine, but where in the crater?"

I took it that was a typo for "Fine, but where is the crater?". It
doen't make much sense otherwise.

Because it is obvious that to have any climate effects the impact would have
to be bigger than Tunguska. Therefore you are getting to a size where you
are going to get a crater

And what were the climate effects of Tunguska?

I gather that they were only minor. That should tell you something.
I'm not sure what.

It shows that you need a much larger effect to create weather/climate
changes which makes it even harder to leave no physical trace on the
ground

You are obviously not aware of the latest work on high velocity
impacts.

Obviously Tunguska wasn't either. Any latest work still has to take this
into account

The latest work shows that a much smaller bolide than previously
recognised can create a nuclear winter. Tunguska was still to small to
creat much of an effect.

Which is what I said, you need something bigger than Tunguska. Tunguska left
very noticeable traces on the ground. Anything bigger would leave even more
traces on the ground. And remember we are only talking about 1500 years ago,
not millennia.

Re you quest for numbers, I am working on it.


Jolly good

Jim Webster

On Thu, 19 Feb 2004 08:36:53 -0000, "Jim Webster"


The only obvious effects of Tunguska was blast damage to trees. There
will be no sign of this in 1500 years. There are more subtle traces
but these can only be found by specifically looking for them with
appropriate analytical techniques. The problem is that if there was a
similar event in 536AD, where do we start our specific search for
evidence?

Re you quest for numbers, I am working on it.


Jolly good