🚀 go-pugleaf

In article <5236@uwmcsd1.UUCP> markh@csd4.milw.wisc.edu
 (Mark William Hopkins) writes about Velikovsky:
>No.  It was because his book related to possible celestial events in the
>past giving Mythological evidence to support it (and geological and
>paleontological in the following work Earth In Upheaval).  His interpretation
>of the evidence he collected boiled down to the assertion that Electromagnetic
>forces play a large role in shaping the orbits of our planets and that the
>solar system is electromagnetically active (something that was not accepted
>back in the late '40's.)

It isn't accepted now, either. The solar wind is intricate, but puny.
The Jovian system does some fun stuff, but only the Jovian moons care.

>This is true in part.  Obviously, Astronomers know astronomy.  However, they
>usually know next to nothing about geology, ancient history or mythology nor
>do many appreciate how one goes about gathering evidence in these fields.

Odd you should mention geology. When geology and astronomy are put together,
it gets titles like "planetary science". Are you aware that there has been
considerable work on subjects like the crustal effects of tides ?
Velikovsky's near-collisions would have caused earthquakes sufficient to
flatten the world's limestone caverns. (They are quite fragile - look up
"Karst topography".) Since the world contains limestone caverns which were
here in Moses' day, I would say that planetary science has fairly thoroughly
disproved Velikovsky.

>>>	 Never mind that the very same kind of hypothesis has been 
>>>	 invoked to explain the extinction of the dinosaurs.
>>The dinosaur-extinction hypothesis, as I understand it, is that dust
>>raised by a large meteorite striking the earth caused climactic changes
>>that the dinosaurs couldn't survive.
>Velikovsky's hypothesis was that the climatic change brought about by the
>near collision caused the mass extinction at the end of the Ice Age ... the
>very same kind of hypothesis.

A planet floating by, and an asteroid ramming us, are not "the same kind of
hypothesis". The observational evidence is that there are a lot of asteroids
with eccentric orbits, but no planets acting like recent arrivals. (Recent
meaning 4000 years, on a scale of billions.)

There was no mass extinction at the end of the Ice Age. A few species
vanished, but absolutely zip as mass extinctions go. Furthermore, there is
no evidence of an unreasonably major climatic change. Personally, I wouldn't
try to explain something that didn't happen.

-- 
	Don		lindsay@k.gp.cs.cmu.edu    CMU Computer Science

In article <5236@uwmcsd1.UUCP> markh@csd4.milw.wisc.edu
 (Mark William Hopkins) writes about Velikovsky:
>>>	 Never mind that the very same kind of hypothesis has been 
>>>	 invoked to explain the extinction of the dinosaurs.
>>The dinosaur-extinction hypothesis, as I understand it, is that dust
>>raised by a large meteorite striking the earth caused climactic changes
>>that the dinosaurs couldn't survive.
>Velikovsky's hypothesis was that the climatic change brought about by the
>near collision caused the mass extinction at the end of the Ice Age ... the
>very same kind of hypothesis.


Don't we have a little problem with time scales here?
Moses a "little" time ago 
Dinosaurs a "long" time ago










Disclaimer: Individuals have opinions, organizations have policy.
            Therefore, these opinions are mine and not any organizations!
Q.E.D.
jwm@aplvax.jhuapl.edu 128.244.65.5

In article <1138@PT.CS.CMU.EDU> lindsay@K.GP.CS.CMU.EDU (Donald Lindsay) writes:
>In article <5236@uwmcsd1.UUCP> markh@csd4.milw.wisc.edu
> (Mark William Hopkins) writes about Velikovsky:
>>No.  It was because his book related to possible celestial events in the
>>past giving Mythological evidence to support it (and geological and
>>paleontological in the following work Earth In Upheaval).  His interpretation
>>of the evidence he collected boiled down to the assertion that Electromagnetic
>>forces play a large role in shaping the orbits of our planets and that the
>>solar system is electromagnetically active (something that was not accepted
>>back in the late '40's.)
>
>It isn't accepted now, either. The solar wind is intricate, but puny.
>The Jovian system does some fun stuff, but only the Jovian moons care.
>
>>This is true in part.  Obviously, Astronomers know astronomy.  However, they
>>usually know next to nothing about geology, ancient history or mythology nor
>>do many appreciate how one goes about gathering evidence in these fields.
>
>Odd you should mention geology. When geology and astronomy are put together,
>it gets titles like "planetary science". Are you aware that there has been
>considerable work on subjects like the crustal effects of tides ?
>Velikovsky's near-collisions would have caused earthquakes sufficient to
>flatten the world's limestone caverns. (They are quite fragile - look up
>"Karst topography".) Since the world contains limestone caverns which were
>here in Moses' day,

Dating methods?

>I would say that planetary science has fairly thoroughly disproved Velikovsky.

Qualify that. I would like to better understand what you are referring to.

>
>>>>	 Never mind that the very same kind of hypothesis has been 
>>>>	 invoked to explain the extinction of the dinosaurs.
>>>The dinosaur-extinction hypothesis, as I understand it, is that dust
>>>raised by a large meteorite striking the earth caused climactic changes
>>>that the dinosaurs couldn't survive.
>>Velikovsky's hypothesis was that the climatic change brought about by the
>>near collision caused the mass extinction at the end of the Ice Age ... the
>>very same kind of hypothesis.
>
>A planet floating by, and an asteroid ramming us, are not "the same kind of
>hypothesis".

Very descriptive of you. Unfortunately, such words can exxagerate superficial 
differences.  In both cases we are talking about collisions or near collisions.

>The observational evidence is that there are a lot of asteroids
>with eccentric orbits, but no planets acting like recent arrivals. 
>(Recent meaning 4000 years, on a scale of billions.)

Which evidence are you referring to?  Current observations of actual bodies
out there right now?  The time window of our observation is only a couple 
hundred years, not enough to provide negative evidence.

Or extrapolations of the planetary orbits into the past?  This is a common
argument used, but a little consideration of the conditions under which these
calculations are carried out will show that they need not be valid.

This is the puzzle I pose to you.  I've already solved it. 

What is it that will make the perturbation analysis invalid that extrapolates
the planets' orbits into the past?  There is one answer consistent with Newton's
law of gravity, but I will let you exercise your imagination in trying to figure
it out.

Or could you be referring to the fact that none of the planetary orbits cross
one another at present (ignore Pluto and Neptune, they do not lie in the same 
plane anyhow.)  This is the other major argument that has been used against
Velikovsky. 

This is another puzzle I pose to you, that I have already solved.  Find a
mechanism that will circularize planetary orbits in a small time span.  No
cheating, you can't use electromagnetic forces, only gravity.  Further, it
has to be consistent with today's observations.

Actually, if you answer the first question, you will have answered the 
second, but I'll leave that to you.

It is not too well known, but there are actually an uncountably infinite
number of past models of the solar system consistent with today's orbital 
parameters. Here, I am even assuming that the parameters are precisely
specified and precisely known.

>There was no mass extinction at the end of the Ice Age.

To the best of my knowledge, all the horses and camels (!) on this continent  
died out.  The mammoths became extinct, the saber tooth tiger, to name a few.  I
would call this a mass extinction.  In any case, this is what I am referring to.
Particularily the mammoths in Siberia.

Siberia itself went from a warmer climate (the mammoths can not live in the
present climate of northern Siberia) to its present state in such a small time
that many of the mammoths that were killed did not even have time to putrify.
In one case food was even found in the stomach of one of these animals -- food
consisting of plants that can only grow in southern Siberia today.

In fact, neither Western Alaska nor Siberia were covered by glaciers in this
period.

This is some of the evidence that Velikovsky brought up. There are probably
500 to 1000 other similar items that were brought up by his book Earth In 
Upheaval.

If this is all true, then I am willing to question things further.

> Furthermore, there is no evidence of an unreasonably major climatic change.
>Personally, I wouldn't try to explain something that didn't happen.

In article <5250@uwmcsd1.UUCP> markh@csd4.milw.wisc.edu (Mark William Hopkins) writes:
>>>The dinosaur-extinction hypothesis, as I understand it, is that dust
>>>raised by a large meteorite striking the earth caused climactic changes
>>>that the dinosaurs couldn't survive.
>>>Velikovsky's hypothesis was that the climatic change brought about by the
>>>near collision caused the mass extinction at the end of the Ice Age ... the
>>>very same kind of hypothesis.
>>
>>A planet floating by, and an asteroid ramming us, are not "the same kind of
>>hypothesis".
>
>In both cases we are talking about collisions or near collisions.

No. Read carefully. A planet floating by is a near-collision. It is not a
collision.  An asteroid ramming us is a collision. It is not a near-
collision. 

If an asteroid missed the Earth, it would have no serious tidal effect.  If
it grazed the atmosphere, it would do at most local damage. (A side note:
some mountain climbers once photographed a grazing meteor that was **going**
**up** ! ) The lack of damage follows from the fact that it retained enough
energy to escape, hence didn't leave the energy here. So, the asteroids that
do damage are the ones that collide. Their kinetic energy is turned into
heat, there is a shock wave, and material is flung clean into space. Dust
may take years to come out of the atmosphere, hence the climate can change
world-wide. The shock can cause local volcanoes, which put out dust, ditto.
Smaller asteroids may cause localized extinctions, just through the shock
(particularly if they hit an ocean and cause habitat flooding). However,
these smaller events are localized: the big ones, global.

A planet is maybe 10 to the tenth times heavier.  If a planet hit us, I
would expect no multicellular life forms to survive. If that. So, we are
talking about near-collisions, only, since life is in fact present.  All
interaction would be via tidal effects. (If the atmospheres mixed, then the
planets would have to be separated by about one percent of their diameters,
and the tides would shatter every continental plate.) So.  Let's look at
tidal effects. If the earth's rotation stopped and restarted (as Velikovsky
claimed) then volcanoes should have broken out simultaneously everywhere.
(Dust again.) Earthquakes everywhere should have flattened all the limestone
caverns that are in fact still there. Or, the near-collision could have been
at quite a distance, in which case the effects Velikovsky used as his
"evidence", wouldn't have happened. 

>This is another puzzle I pose to you, that I have already solved.  Find a
>mechanism that will circularize planetary orbits in a small time span.  No
>cheating, you can't use electromagnetic forces, only gravity.  Further, it
>has to be consistent with today's observations.

It also has to be consistent with the currently-best topographic map of
Venus, and its greenhouse effect, and its atmospheric composition, and its
rotation rate. Don't let me stop you trying.

>>There was no mass extinction at the end of the Ice Age.
>To the best of my knowledge, all the horses and camels (!) on this continent
>died out.  The mammoths became extinct, the saber tooth tiger, to name a few.
>I would call this a mass extinction.  In any case, this is what I am 
>referring to. Particularily the mammoths in Siberia.

A "mass extinction" is the extinction of a major fraction of all species in
the fossil record - like, 40% of them. At the end of the ice age, the
extinction was not massive at all. I have the impression that it was mostly
higher mammals, and that the extinctions were localized - American horses,
but not Asian, for example. Also, the last I heard, there was some reason to
believe that Man killed off e.g. the saber tooth tiger. Note that a near
collision with a planet should not have localized effects.
-- 
	Don		lindsay@k.gp.cs.cmu.edu    CMU Computer Science

In article <1167@PT.CS.CMU.EDU> lindsay@K.GP.CS.CMU.EDU (Donald Lindsay) writes:
>In article <5250@uwmcsd1.UUCP> markh@csd4.milw.wisc.edu (Mark William Hopkins) writes:
>>>>The dinosaur-extinction hypothesis, as I understand it, is that dust
>>>>raised by a large meteorite striking the earth caused climactic changes
>>>>that the dinosaurs couldn't survive.
>>>>Velikovsky's hypothesis was that the climatic change brought about by the
>>>>near collision caused the mass extinction at the end of the Ice Age ... the
>>>>very same kind of hypothesis.
>>>
>>>A planet floating by, and an asteroid ramming us, are not "the same kind of
>>>hypothesis".
>>
>>In both cases we are talking about collisions or near collisions.
>
>No. Read carefully. A planet floating by is a near-collision. It is not a
>collision.  An asteroid ramming us is a collision. It is not a near-
>collision. 

Okay.  However, the difference is still superficial because in both cases
we are talking about a catastrophe caused by a collision OR a near collision
bringing about the extinction of species.  This is what Velikovsky had 
hypothesized about the Ice Age extinctions *and also prior extinctions*.  He
had stated that the dinosaurs had probably become extinct either through a
collision or the after effects of one.

What these ideas were going against was the ingrained belief of that time that
extinctions were brought about naturally, as per Darwin (as opposed to 
extinction by catastrophe.)  I hope this clears things up, because we do not
really disagree on matters here.

>
>If an asteroid missed the Earth, it would have no serious tidal effect.  If
>it grazed the atmosphere, it would do at most local damage. (A side note:
>some mountain climbers once photographed a grazing meteor that was **going**
>**up** ! ) The lack of damage follows from the fact that it retained enough
>energy to escape, hence didn't leave the energy here. So, the asteroids that
>do damage are the ones that collide.

Large bodies will do damage regardless of whether they collide or not.  If 
orbits intersect, near collision is more probable in any case (something to
be thankful for.)

The real question to focus on, as far as Velikovsky is concerned, is why the
orbits of Venus and Earth (or Mars and Earth) do not STILL intersect.  It has
supposedly been only a few thousand years or so.

>interaction would be via tidal effects. (If the atmospheres mixed, then the
>planets would have to be separated by about one percent of their diameters,
>and the tides would shatter every continental plate.) So.  Let's look at
>tidal effects. If the earth's rotation stopped and restarted (as Velikovsky
>claimed) then volcanoes should have broken out simultaneously everywhere.
>(Dust again.) Earthquakes everywhere should have flattened all the limestone
>caverns that are in fact still there. 

IF they were formed PRIOR to the event.  Having dating methods that are 
consistent with both views is crucial here.  Methods that use radiation counts
to date things prior to a supposed catastrophe cannot be used to disprove the
catastrophe existed.
Formation rates cannot be assumed to be uniform either, given the existence of
a prior catastrophe.

The best test I can think of would use tree ring analysis.  Tree rings are
perfectly reliable calendars for determining past dates and past climate
accurate to the year, once one has calibrated the rings.

>>This is another puzzle I pose to you, that I have already solved.  Find a
>>mechanism that will circularize planetary orbits in a small time span.  No
>>cheating, you can't use electromagnetic forces, only gravity.  Further, it
>>has to be consistent with today's observations.
>
>It also has to be consistent with the currently-best topographic map of
>Venus, and its greenhouse effect, and its atmospheric composition, and its
>rotation rate. Don't let me stop you trying.

Venus is a strange planet no matter what how think of it.

Trying what?  My point is that most of the disproofs of the collision hypothesis
that I have seen are not valid.  This includes the one that attempts to show
that no catastrophes existed in the past by extrapolating planetary orbits into
the past.  It's a simple fact that if an EXPULSION had taken place in the past
then the perturbation analysis would not be valid beyond the time of the 
expulsion.  This is one thing I can think of that will put a wrench into the
whole process.  "Imagination" is the word.

>
>>>There was no mass extinction at the end of the Ice Age.
>>To the best of my knowledge, all the horses and camels (!) on this continent
>>died out.  The mammoths became extinct, the saber tooth tiger, to name a few.
>>I would call this a mass extinction.  In any case, this is what I am 
>>referring to. Particularily the mammoths in Siberia.
>
>A "mass extinction" is the extinction of a major fraction of all species in
>the fossil record - like, 40% of them. At the end of the ice age, the
>extinction was not massive at all. I have the impression that it was mostly
>higher mammals, and that the extinctions were localized - American horses,
>but not Asian, for example. Also, the last I heard, there was some reason to
>believe that Man killed off e.g. the saber tooth tiger. Note that a near
>collision with a planet should not have localized effects.

Right.  It should have global effects.  That point is a two edged sword when
we find that the effects actually were global.

But listen, I'm not going to stand around playing V.'s advocate.  We've gotten
quite beyond the point made by the example in my posting: Velikovsky was wronged
and the conditions that led to this happening have not changed all that 
greatly.

   "Radiation counts used to date things before a supposed catastrophe cannot b
     "used"


    Why?  The two have nothing to do with each other.

In article <4006@cup.portal.com> roger_warren_tang@cup.portal.com writes:
>
>   "Radiation counts used to date things before a supposed catastrophe cannot b
>     "used"
>
>
>    Why? ... 

Because the catastrophe itself may be a large source of radiation.

In article <4006@cup.portal.com> roger_warren_tang@cup.portal.com writes:
>   "Radiation counts used to date things before a supposed catastrophe cannot b
>     "used"
>    Why?  The two have nothing to do with each other.


As an example of how a catastrophe could mess up radiodating, how about one 
which altered the background levels?  The dating assumes a steady level
(at least C14.  The other stuff has the same assumptions, but it
would be REALLY tough to change that.  Say you put a lot of radiation
loose in the air. C14 levels go up.  The clock gets badly gummed.
The decay rate would stay the same, but the starting level you are
calculating from would not be the actual starting level.

Of course, nothing grossly mechanical could do something like this.
Just wanted to throw in mt $.02 worth.  

Velikovsky is still out to lunch.....


Disclaimer: Individuals have opinions, organizations have policy.
            Therefore, these opinions are mine and not any organizations!
Q.E.D.
jwm@aplvax.jhuapl.edu 128.244.65.5

   That a catastrophe is a large source of radiation has very little to do
with most of the radioactive dating methods.
    As well, such a catastrophe would be recognizable by the neutron tracks and
other radiation markers.  As well, such radiation would be stopped within the
first few feet of solid ground cover.  If you postulate such intense radiation
as to penetrate ground cover, this too would be quite evident.

In article <5300@uwmcsd1.UUCP>, markh@csd4.milw.wisc.edu (Mark William Hopkins) writes:
> In article <4006@cup.portal.com> roger_warren_tang@cup.portal.com writes:
> >   "Radiation counts used to date things before a supposed catastrophe cannot b
> Because the catastrophe itself may be a large source of radiation.
External radiation is irrelevant to radiometric dating. The technique involves
measuring the amounts of specific radioactive isotopes (e.g., Rb^87) and
their stable daughter products (Sr^87 in this case). Crudely, the Rb/Sr
ratio is controlled by the age of the rock as Rb converts to Sr at a
known rate. External radiation has no influence on the rate of decay.
The fact that the rock may emit radiation, from whatever source, is
irrelevant as the isotope abundances are generally measured on a mass
spectrometer. A more detailed explanation can be found in most books
on igneous petrology (e.g., Hyndman). I teach this subject in my classes
so I think I can claim at least minimal expertise.

>,>>> markh@csd4.milw.wisc.edu (Mark William Hopkins)
>>,>>>> lindsay@K.GP.CS.CMU.EDU (Donald Lindsay)
>>>>>Velikovsky's hypothesis was that the climatic change brought about by the
>>>>>near collision caused the mass extinction at the end of the Ice Age ... the
>>>>>very same kind of hypothesis.
>>>>A planet floating by, and an asteroid ramming us, are not "the same kind of
>>>>hypothesis".
>>>In both cases we are talking about collisions or near collisions.
>>No. Read carefully. A planet floating by is a near-collision. It is not a
>>collision.  An asteroid ramming us is a collision. It is not a near-
>>collision. 
> Okay.  However, the difference is still superficial because in both cases
> we are talking about a catastrophe caused by a collision OR a near collision
> bringing about the extinction of species.

Of course, by this standard, the differences between evolution and
special creation are superficial because in both cases we are talking
about origins caused by mutation and natural selection OR direct divine
intervention.

The point is, Mark has displaced most of the material that explains why
a collision with an asteroid is very different from a near collision
with an object many orders of magnitude more massive.  The only thing
they have in common is "a body approaches the earth" in each scenario,
just as about the ony thing evolution and special creation have in
common is "species result from the process".

> Methods that use radiation counts
> to date things prior to a supposed catastrophe cannot be used to disprove the
> catastrophe existed. [...]
> The best test I can think of would use tree ring analysis.  Tree rings are
> perfectly reliable calendars for determining past dates and past climate
> accurate to the year, once one has calibrated the rings.

Just out of curriosity, why is this any better than radiation dating?
After all, catastrophic changes may have occured to change the rate of
ring formation, or obliterate some of the rings of all the trees you are
using.  (This is the direct analog of the argument Mark just used
against isotope dating methods, and is even used against other
yearly-depsosition methods by creationists and Velikovsky enthusiasts.)
(Note that I'm not trying to group the above two groups in the same
camp... I'm just using them as two examples.)

> Velikovsky was wronged
> and the conditions that led to this happening have not changed all that 
> greatly.

True, but important to remember that being wronged doesn't make him
correct.  It merely makes him wronged.  (I would also argue that the
extent of the "wrong" is very small, and did not in the least succeed in
supressing Velikovsky's theories.  They are rejected not because they
are unknown, they are rejected because *are* known, and they don't make
sense.)

--
A program without a loop and a structured variable isn't worth writing.
                                        --- Alan J. Perlis
-- 
Wayne Throop      <the-known-world>!mcnc!rti!xyzzy!throopw

Please bear in mind that the appropriate newsgroup for
Velikovsky discussions is talk.origins.  You can get all sorts
of wonderful arguments, pro and con, there.
-- 
 I'm not afraid of dying     Ethan Vishniac, Dept of Astronomy
 I just don't want to be     {charm,ut-sally,ut-ngp,noao}!utastro!ethan
 there when it happens.      (arpanet) ethan@astro.AS.UTEXAS.EDU
    - Woody Allen            (bitnet) ethan%astro.as.utexas.edu@CUNYVM.CUNY.EDU

In article <702@xyzzy.UUCP> throopw@xyzzy.UUCP (Wayne A. Throop) writes:
>True, but important to remember that being wronged doesn't make him
>correct.  It merely makes him wronged.

Likewise, criticizing his critics does not make one his supporter.  You're
not going to tell me that you fell into that trap too, are you?.  If so then
why do you keep on making the same fallacy over and over that some others have 
about where I stand?

Is it so difficult for you to conceive of a person who can merely MENTION the
man's name and talk about what he said without necessarily taking his side.
You and a few others owe me an apology on that point.  It was an insult to my
intelligience and others' on this net.

Next time: ASK, if you're not sure what someone said.

Now about knowing what the man said : I doubt you know that much at all except
what you have heard through second-hand quotes and the like.  The extent of his 
being wronged in this respect (CRITICISING SOMEONE'S CLAIMS WHERE YOU DO NOT
EVEN KNOW WHAT THAT PERSON SAID) has been well demonstrated in this newsgroup
on my account.

Correct me if I'm wrong by publicly posting what you know about him.  As they 
say : "either put up or shut up", no more bluffing.

>>In article <4006@cup.portal.com> roger_warren_tang@cup.portal.com writes:
>>>"Radiation counts used to date things before a supposed catastrophe cannot
[be trusted etc; I never saw the original, only mangled quotations]

>In article <5300@uwmcsd1.UUCP> markh@csd4.milw.wisc.edu (Mark
>William Hopkins) writes:
>>Because the catastrophe itself may be a large source of radiation.

In article <116@slu70.UUCP> guy@slu70.UUCP (Guy M. Smith) writes:
>External radiation is irrelevant to radiometric dating.

Right.  The key to understanding this is that the dating is based on
*ratios* of particular isotopes:

>The technique involves measuring the amounts of specific radioactive
>isotopes (e.g., Rb^87) and their stable daughter products (Sr^87 in
>this case). Crudely, the Rb/Sr ratio is controlled by the age of the
>rock as Rb converts to Sr at a known rate. External radiation has no
>influence on the rate of decay.

If I may say so, markh has the right idea but the wrong details,
something he seems to do all too often.  In this case the details are
the important part.  The point is not that the event (`catastrophe')
may be a source of radiation, but rather that it may be a source of the
isotopes used in dating.  This changes the whole focus of the argument.

If the absolute counts of either Rubidium-87 or Strontium-87 were
influenced by the event, the ratio function [Rb/Sr](t) might have a
sudden discontinuity.  This can be checked, however, by choosing two
more isotopes; as the number of isotopes checked goes up, the
probability of error goes down.  Moreover, there may be an independent
means of verifying that the event did not affect the isotope ratio.
Whether this is in fact the case I cannot say, although I doubt that
anyone doing such dating would not anticipate this line of argument
and have countered it before it even began.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris

In article <11009@mimsy.UUCP> chris@mimsy.UUCP (Chris Torek) writes:
 >If the absolute counts of either Rubidium-87 or Strontium-87 were
 >influenced by the event, the ratio function [Rb/Sr](t) might have a
 >sudden discontinuity.  This can be checked, however, by choosing two
 >more isotopes; as the number of isotopes checked goes up, the
 >probability of error goes down.

As an example of the danger of using a single isotope ratio, several
historic (19th centry) lava flows at Mauna Kea (sp?) have a Rb/Sr date
of several hundred million years.

Hal Chambers

In article <11009@mimsy.UUCP>, chris@mimsy.UUCP (Chris Torek) writes:
> If the absolute counts of either Rubidium-87 or Strontium-87 were
> influenced by the event, the ratio function [Rb/Sr](t) might have a
The problem with this idea is that you need to insert these isotopes into
solid rock. Most geochronologists start with a large chunk of solid
unaltered (hopefully) rock and take steps to eliminate contamination
(like removing the weathering rind, etc). They then either grind
up the whole rock or they extract certain minerals (generally a better
technique). Uranium-lead dating is commonly done with zircons extracted
from the original sample (you need 50-100 kg to start). It is difficult
to see how an event of the sort under discussion could affect the
elements buried centimeters or meters below the surface of a solid
igneous rock. It would affect sediments but they are generally unsuitable
for radiometric dating. As discussed by another poster, the exception
is carbon-14 dating.