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Main
Date: 10 Aug 2007 00:22:08
From: Sam Wormley
Subject: What happens when a meteor is on a collision course with Earth
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What happens when a meteor is on a collision course with Earth
http://www.helium.com/tm/498146/there-seems-perception-community
There seems to be a perception in the community that the Earth would
somehow be better off being struck by an icy comet rather than by a
similar sized rocky or metal object. This is, generally, not the case.
Let's take a look at why not.
For the purpose of our discussion, we are going to assume that a one
cubic mile object is about to strike the Earth traveling at the
relatively slow speed of the Perseid Meteor Shower. That's about 33,000
miles per hour. An object coming directly from deep space or a comet
approaching the sun could go much faster. I once got stuck for four
hours in a traffic jam outside the baseball stadium in St. Louis and
missed a very good concert so we'll assume the stadium is ground zero.
The common argument is that an icy object would be less dense and so
would cause less damage. On a global scale, there would be less total
energy in the impact and slightly less particulate matter in the
atmosphere and ejected back into orbit after the event but only
slightly less and I'm afraid it would make no difference what-so-ever
to our doomed baseball fans.
Here's the problem. At a velocity of 33,000 miles per hour. When the
object begins to be warmed and slowed by the atmosphere, say 100 miles
up give or take, it is only 10.8 seconds from impact. This means that
the entire column of air underneath it only has about 11 seconds to
leave the area. Or, put another way, the air between the Earth and the
object would have to move at 33,000 miles an hour to get out of the
way.
Super computer modeling shows that this is not what happens. What
happens is that the leading edge of the object, regardless of material,
superheat into a gas or plasma, the air superheat into a gas or
plasma, the stadium superheat into a gas or plasma, the upper level of
the earth superheat. As for the fans, well, go ahead and put the onions
on your hot dog, you'll never live to regret it.
Once things have gotten hot enough to to turn concrete dugouts and Sy
Young award winners into plasma, the issue of rocky vs. icy is only
going to be interesting only to scientist in bunkers on other
continents who are wondering when it's going to stop snowing mud.
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Date: 11 Aug 2007 01:03:50
From: thad@thadlabs.com
Subject: Re: What happens when a meteor is on a collision course with Earth
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On Aug 10, 7:45 am, Chris L Peterson <c...@alumni.caltech.edu > wrote:
> On Fri, 10 Aug 2007 02:48:13 -0700, "t...@thadlabs.com"
> [...]
> Not that Tunguska couldn't be a pure air-burst, of course.
Eyewitness reports (of which there are many, surprisingly, found
in many citations on the Web) support an aerial detonation of
"something".
> But compared
> with the size of parent required to produce the Carolina Bays, Tunguska
> was a pebble (or ice cube).
And with the (alleged) force of 1,000 Hiroshima-sized nukes given the
destruction. That's a lot of energy! :-)
> Essentially all of the physical modeling
> performed in recent years (something largely impossible when the
> referenced paper was published) demonstrates that a body of this size,
> of any reasonable density, does not disrupt entirely. A large crater
> should exist, and doesn't.
Which suggests the models are inaccurate, likely due to not really
knowing the makeup of the object (assuming we're still referring to
the Tunguska event).
> [...]
> Furthermore, it is now strongly suspected that cometary material is
> loaded with dust and debris that will leave a characteristic signature
> in sediments- something not seen with the Carolina Bays.
The <http://abob.libs.uga.edu/bobk/cbayint.html > paper projects
vectors determined from the Carolina Bays' craters' orientations
suggesting the (primary) detonation occurred over Ohio or Indiana,
far from the shock waves (allegedly) creating the Bays, thus the
absence of ET material is not surprising. This is seen in Fig. 5.
> [...]
> Research continues, but the consensus is that the structures are
> geophysical, and there are models for their production that work well.
I literally have 100s of papers concerning both the Tunguska event
and the Carolina Bays, and I have yet to find a supportable theory
better than the one in the UGA paper (URL above) re: the Bays.
There's a tremendous amount of research still being conducted re:
the Tunguska event; one that's very interesting is:
<http://pumpkin.aquila.infn.it/gabri/downld/tunguska_eng.ppt >
which I converted to PDF format the day before the presentation,
and available here:
<http://thadlabs.com/FILES/tunguska_eng.pdf >
You might also find this interesting:
<http://www.astro.hr/spaceguard/html/solution.html >
<http://www.astro.hr/spaceguard/html/scenario.html >
(Scenario Tunguske eksplozije) for the pictures, etc.
I haven't found much present activity surrounding the
Carolina Bays.
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Date: 11 Aug 2007 07:56:49
From: Chris L Peterson
Subject: Re: What happens when a meteor is on a collision course with Earth
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On Sat, 11 Aug 2007 01:03:50 -0700, "thad@thadlabs.com"
<thad@thadlabs.com > wrote:
>Which suggests the models are inaccurate, likely due to not really
>knowing the makeup of the object (assuming we're still referring to
>the Tunguska event).
We are not. Tunguska was certainly an airburst. It is the models that
try to explain the Carolina Bays as such that don't work. Yes, the
models may have problems, but nobody seems to be able to come close to
explaining how something so massive could disrupt entirely. That's one
reason why most researchers have abandoned the notion that the Bays were
produced by airbursts. And of course, the fact that they weren't
produced at the same time.
<http://abob.libs.uga.edu/bobk/cbayint.html > paper projects
>vectors determined from the Carolina Bays' craters' orientations
>suggesting the (primary) detonation occurred over Ohio or Indiana,
>far from the shock waves (allegedly) creating the Bays, thus the
>absence of ET material is not surprising. This is seen in Fig. 5.
The paper used a primitive model. More current work shows that a large
high altitude detonation should not produce such oriented craters
(nobody has tried an actual experiment <g >).
>There's a tremendous amount of research still being conducted re:
>the Tunguska event; one that's very interesting is:
I wouldn't say "a tremendous amount", but certainly there is active
research. That's because there's little doubt it was the result of a
meteoroid of some sort, the site has become increasingly accessible, and
chemical and physical techniques now promise to let us find material
from the parent body. Impact research in general is strong now, as fast
computers and good simulation code is finally lending rich insight into
an area that until recently was only coarsely understood.
>I haven't found much present activity surrounding the
>Carolina Bays.
I think that's because the question is settled, that natural processes
largely associated with surface water produced the Bays over tens of
thousands of years. They are of some interest to geomorphologists, but
not to most impact researchers.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 10 Aug 2007 09:15:44
From: Uncle Al
Subject: Re: What happens when a meteor is on a collision course with Earth
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Sam Wormley wrote:
>
> What happens when a meteor is on a collision course with Earth
> http://www.helium.com/tm/498146/there-seems-perception-community
>
> There seems to be a perception in the community that the Earth would
> somehow be better off being struck by an icy comet rather than by a
> similar sized rocky or metal object. This is, generally, not the case.
> Let's take a look at why not.
[snip]
> Here's the problem. At a velocity of 33,000 miles per hour. When the
> object begins to be warmed and slowed by the atmosphere, say 100 miles
> up give or take, it is only 10.8 seconds from impact. This means that
> the entire column of air underneath it only has about 11 seconds to
> leave the area. Or, put another way, the air between the Earth and the
> object would have to move at 33,000 miles an hour to get out of the
> way.
Given a large hypersonic object either
1) rifle bullet and leading edge shock compression is
pseudoadiabatic. Diesel engine cylinder on the compression upstroke
with a vengeance. Impactor causes major grief after impact, too.
2) shot shell and compression is pseudoadabatic until
fragmentation. Even if 100% of incoming energy is dumped into the
lower atmosphere the ground surface still disappears. Total lofted
debris is very small compared to a ground hit. Vaporizaiton and
condensation of the object itself is still a big bunch of stuff.
Major production of NOx from combusting the atmosphere.
Consider the ground surprises attendant to the USSR's 50 (possibly 75)
megaton Tsar Bomba air detonation, 13,000 feet altitude, 30 October
1961 at Mityushikha Bay test range, Novaya Zemlya Island. 27 tonne
device, Tu-95 drop.
> Once things have gotten hot enough to to turn concrete dugouts and Sy
> Young award winners into plasma, the issue of rocky vs. icy is only
> going to be interesting only to scientist in bunkers on other
> continents who are wondering when it's going to stop snowing mud.
As with nuclear ground burst vs. air burst, lofted debris is much more
serious for a (penetrating) ground hit. NOx production is much mores
serious for an air burst.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2
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Date: 10 Aug 2007 11:03:56
From: Richard Tobin
Subject: Re: What happens when a meteor is on a collision course with Earth
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In article <QcOui.38481$Xa3.8918@attbi_s22 >,
Sam Wormley <swormley1@mchsi.com > wrote:
> Here's the problem. At a velocity of 33,000 miles per hour. When the
> object begins to be warmed and slowed by the atmosphere, say 100 miles
> up give or take, it is only 10.8 seconds from impact. This means that
> the entire column of air underneath it only has about 11 seconds to
> leave the area. Or, put another way, the air between the Earth and the
> object would have to move at 33,000 miles an hour to get out of the
> way.
This reasoning is incorrect. You don't have to run at 30mph to get
out of the way of a car.
Is this article intended seriously? Has anyone ever suggested that a
one-cubic-mile icy comet might be less dangerous than a rock one to
people anywhere near the impact point?
-- Richard
--
"Consideration shall be given to the need for as many as 32 characters
in some alphabets" - X3.4, 1963.
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Date: 10 Aug 2007 02:48:13
From: thad@thadlabs.com
Subject: Re: What happens when a meteor is on a collision course with Earth
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On Aug 9, 11:50 pm, Chris L Peterson <c...@alumni.caltech.edu > wrote:
> On Thu, 09 Aug 2007 18:31:04 -0700, "t...@thadlabs.com"
>
> <t...@thadlabs.com> wrote:
> >You may find this interesting (re: the Carolina Bays):
>
> ><http://abob.libs.uga.edu/bobk/cbayint.html>
>
> >Note the paper's date: April 1975.
>
> Well, yes, but the evidence that the Carolina Bays are of
> extraterrestrial origin is very weak. Not many geologists (or
> meteoriticists) consider it likely they were produced by either
> asteroidal or cometary collisions. The theory has grown less popular
> over the decades.
I have yet to find any better explanation given the evidence cited
at the above URL. Aerial detonations do happen and cause very
widespread damage -- consider the 1908 Tunguska event as one
recent example.
The claim a crater (a nearby lake) was found was soundly refuted
as you can read here:
<http://www.theregister.co.uk/2007/06/27/lake_crater_tunguska/ >
In which Dr Gareth Collins, a research associate at Imperial College
London, told the BBC: "The impact-cratering community does not accept
structures as craters unless there is evidence of high temperatures
and high pressures. That requires evidence of rocks that have been
melted or rocks that have been ground up by the impact."
The Tunguska event took place on June 30, 1908. The blast, which had
the energy of about 1,000 Hiroshima-sized nukes, was so bright it was
even seen in the London skies. No debris from the explosion has ever
been found, much less any traces of an impact.
Dr Collins says the lake Longo and his team have studied is not
consistent with what we already know about Tunguska. The angle of
impact is wrong, any fragments surviving the initial blast would be
moving too slowly, and there are trees older than 100 years still
standing near the lake, making it unlikely anything from space crashed
nearby.
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Date: 10 Aug 2007 08:45:32
From: Chris L Peterson
Subject: Re: What happens when a meteor is on a collision course with Earth
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On Fri, 10 Aug 2007 02:48:13 -0700, "thad@thadlabs.com"
<thad@thadlabs.com > wrote:
>I have yet to find any better explanation given the evidence cited
>at the above URL. Aerial detonations do happen and cause very
>widespread damage -- consider the 1908 Tunguska event as one
>recent example.
It is far from widely accepted that Tunguska was caused by a cometary
parent body. In fact, much recent work with the structural integrity of
large meteoroids and asteroids suggests the parent may have been just
that.
>The claim a crater (a nearby lake) was found was soundly refuted
>as you can read here:
>
><http://www.theregister.co.uk/2007/06/27/lake_crater_tunguska/>
That is hardly a sound refutation! One person, who hasn't seen any
primary evidence, disagrees. In fact, there is much that is interesting
about the lake that was found, and until core samples are recovered in
the next season, nobody is doing more than guessing.
Not that Tunguska couldn't be a pure air-burst, of course. But compared
with the size of parent required to produce the Carolina Bays, Tunguska
was a pebble (or ice cube). Essentially all of the physical modeling
performed in recent years (something largely impossible when the
referenced paper was published) demonstrates that a body of this size,
of any reasonable density, does not disrupt entirely. A large crater
should exist, and doesn't.
Furthermore, it is now strongly suspected that cometary material is
loaded with dust and debris that will leave a characteristic signature
in sediments- something not seen with the Carolina Bays.
Research continues, but the consensus is that the structures are
geophysical, and there are models for their production that work well.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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Date: 10 Aug 2007 09:43:09
From: Paul Schlyter
Subject: Re: What happens when a meteor is on a collision course with Earth
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In article <QcOui.38481$Xa3.8918@attbi_s22 >,
Sam Wormley <swormley1@mchsi.com > wrote:
> What happens when a meteor is on a collision course with Earth
Well, it becomes a meteor instead of a meteoroid.....
As a matter of fact, a collision course with Earth is a _requirement_ for
a meteoroid to become a meteor. If it's not on a collision course with
the Earth, it won't become a meteor.....
That's the proper answer to that question.
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
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Date: 09 Aug 2007 18:31:04
From: thad@thadlabs.com
Subject: Re: What happens when a meteor is on a collision course with Earth
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On Aug 9, 5:22 pm, Sam Wormley <sworml...@mchsi.com > wrote:
> What happens when a meteor is on a collision course with Earth
> http://www.helium.com/tm/498146/there-seems-perception-community
>
> There seems to be a perception in the community that the Earth would
> somehow be better off being struck by an icy comet rather than by a
> similar sized rocky or metal object. This is, generally, not the case.
> Let's take a look at why not.
> [...]
You may find this interesting (re: the Carolina Bays):
<http://abob.libs.uga.edu/bobk/cbayint.html >
Note the paper's date: April 1975.
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Date: 10 Aug 2007 00:50:45
From: Chris L Peterson
Subject: Re: What happens when a meteor is on a collision course with Earth
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On Thu, 09 Aug 2007 18:31:04 -0700, "thad@thadlabs.com"
<thad@thadlabs.com > wrote:
>You may find this interesting (re: the Carolina Bays):
>
><http://abob.libs.uga.edu/bobk/cbayint.html>
>
>Note the paper's date: April 1975.
Well, yes, but the evidence that the Carolina Bays are of
extraterrestrial origin is very weak. Not many geologists (or
meteoriticists) consider it likely they were produced by either
asteroidal or cometary collisions. The theory has grown less popular
over the decades.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
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