>Do you consider this a fair analogy? If so, perhaps you will admit that
>the 'old earth' scenario stands on shaky ground. If not, perhaps you
>would care to identify the divergencies.
IMO this analogy (attributed to R.L Wysong?) is a very poor analogy of
radiometric clocks and a very good example of sloppy thinking or basic
lack of understanding displayed by some well-quoted young earth
creationist authors. Since there are many who follow this list that
may not recognize how this bad this analogy is, I will give my reasons
below.
>Concerning the questionable use of 'radiometric clocks' in estimating
>the Earth's age, I came across the following interesting analogy:
>"We can compare radioactive dating methods to the melting of an ice
>cube. If we know how fast ice cubes melt and we are presented with a
>tray of water that is alleged to have been derived from the ice, we
>could calculate how large the original ice cube was and how long it took
>to melt.
**Bad Analogy Reason #1: "If we know how fast ice cubes melt ..."
Common experience tells us that the rate at which an ice cube melts
varies immensely ... The extremes being almost instantaneously when
tossed into a blast furnace or almost never when stored at temperatures
below 0 degrees Celsius (32 degrees Fahrenheit). In other words, the
rate at which an ice cube melts is totally *dependent* upon the
environment in which the ice cube sits. Conversely, the rate at which
a population of radioactive isotopes decay is *independent* of its
environment. (The only known exceptions to this independence of rate -
such as the environment in the heart of a supernovae - have been
pointed out in earlier posts by Glenn Morton, Pim van Meers, and David
Bowman. See especially the post at
http://www.calvin.edu/archive/evolution/199808/0200.html)
**Bad Analogy Reason #2: New math - "... we could calculate how large
... and how long"
The word problem about math calculations is simply wrong since there is
insufficient information to calculate both of the results desired.
Knowing the volume of water present, we can calculate the volume of an
original ice cube. However, even if we assume a constant temperature
of the surrounding environment (a necessary assumption to get a
"constant melting rate"), we cannot calculate how long it took for the
tray of ice to reach it's current liquid state. In addition, we need
to know the starting temperature and the final temperature. An ice
cube starting at -100 deg. C will take much longer to reach a 5 deg. C
liquid than one with a starting temperature of -2 deg. C.
This may seem to be a minor point, but it is indicative of the lack of
critical thinking involved in creating the "ice cube analogy"
>But what if we don't know if all the water we are presented
>with has come from the ice? What if water was already present in the pan
>before the cube was put there to begin melting? Or what if water was
>added to or removed from the pan during the course of the melting?
**Bad Analogy Reason #3: ... leaving the refrigerator door open
This author of this analogy has (deliberately?) chosen a situation
which is extremely open to the problems of material "addition" or
"subtraction". Because of this extreme openness, the analogy becomes a
caricature or a strawman of radiometric age determination methods.
Some radiometric methods, like potassium[40]-argon[40] (K-Ar), are
susceptible to material additions or subtractions and dependent on
knowing the amount of "decay product" originally present in the rock.
Because of this, rock samples for K-Ar age determinations are collected
with great care to obtain the most pristine samples possible. I spent
this past spring backpacking in remote parts of Alaska to collect
samples for various purposes ... including age determinations. To
collect the freshest rock possible, we carried 5-pound long-handled
sledge hammers in addition to all of our other gear. That's a
considerable investment in weight to carry when hiking but it was
necessary for exposing the center of large boulders or for getting deep
into an outcrop. Even more care was taken with the samples back in the
lab to remove any possible altered material BEFORE submitting them for
analyses.
Other radiometric methods, like the U-Th-Pb isochron techniques, are
independent of the amount of "decay product" originally present in the
rocks and, because of the multiple analyses of different minerals in
the same rock, immediately reveal if unsuspected additions or
subtractions of material has occurred. Data from these open systems are
commonly thrown out, not because the ages don't fit some desired number
but because the sample was obviously flawed. i.e. the assumption of
no additions or subtractions was not applicable to that sample.
>What
>if we don't know if the ice cube was melting under the exact conditions
>we used to determine the rate of melting, i.e. what if the conditions
>were warmer, colder or windier than the conditions used to determine
>cube 'half-life'? Are we sure that some of the ice did not sublimate, or
>some of the water in the pan evaporate? Was the water in this cube as
>pure as the water in the cube we determined cube 'half-life' on?
**Bad Analogy Reason #4: Ice cube 'half-lifes'
A common problem with almost all analogies of radiometric methods is
that the analogy uses a simple straight line decay rate while
radioactive decay is logarithmic. For those unfamiliar with this idea,
the following chart should illustrate the difference:
Amount of original parent material left
Straight Line Decay Logarithmic Decay
Beginning Time 1 1
1 half life 1/2 1/2
2 half lifes 0 1/4
3 half lifes 0 1/8
4 half lifes 0 1/16
5 half lifes 0 1/32
The term "half life", when describing decay rates, most appropriately
refers to a logarithmic decay and really shouldn't be used for simpler
Straight Line rates - it becomes meaningless after just 2 half lifes!
**Bad Analogy Reason #5: Rhetorical questions?
This list of rhetorical questions, though of serious importance to the
melting rate of an ice cube, are mostly irrelevant to the issue of
radiometric clocks. The first is a repeat of the false notion of rate
changes due to environment conditions ("warmer, colder or windier").
The second is a repeat of the strawman caricature of openness
("sublimation" and "evaporation"). And the third is embarrassingly
ridiculous. How can an atom of U[235] be impure??? How can any atom
be impure in the same way that we talk about water being impure?
Again, the basic lack of understanding present in someone who would
assume to teach about problems with a technical subject is appalling.
Rhetorical questions are a sales technique that is commonly used to get
the listener to buy anything. I personally detest them. The salesman
... or anyone with a idea to sell which could include teachers,
preachers, seminar speakers, lawyers, business persons, scientists,
media investigators, UFO theorists, Chariots of the Gods books ... The
salesman using rhetorical questions gets the listeners to agree with a
series of simple questions whose answers are painfully obvious and then
slips in the hook hoping that you will keep nodding yes. Beware of the
list of rhetorical questions, there is almost always a hook waiting and
you need to be ready to evaluate it separately ... even if you really
do agree with the hook!
>"... If one were to argue that the age of the pan could be absolutely
>determined by ice cube decay he would certainly be on tenuous grounds
>unless he could answer with certainty each of the questions raised
>above.
**Bad Analogy Reason #6: The hook ... and switching baits.
Note that the list of rhetorical questions all deal with determining
the rate at which water melts ... something that most people have
experience with and therefore will readily assent to the obvious
rhetorical "answers". However, the hook line deals not with the
melting water but with the age of the pan! ... he switched baits and
hopes you will keep nodding Yes!
Of course, not even the most hardened anti-Christian uniformitarian
geochronologist could now disagree with this conclusion that the
melting ice rate will not give us the absolute age of the pan. The
idea is ridiculous. But actually the analogy author has committed a
serous error with this statement. We will all agree that the ice
melting rate will not give use an absolute age of the pan, but using
only the information and assumptions needed for this situation we CAN
calculate a MINIMUM age of the pan. ... Assuming the ice tray was taken
from the freezer and allowed to thaw on the table at room temperature,
we know that the pan (tray) itself is AT A MINIMUM about 1 hour old -
even if the tray of ice were created _ex nihilo_ in the freezer.
All radiometric dates are "minimum" dates and not "absolute" dates.
The problem is that radiometric dates tell us that Wysong's(?) "ice
cube tray" has been sitting on the table AT A MINIMUM of 450,000 times
longer than the 10,000 or so years that he is willing to accept.
>"... Until the assumptions in a dating method are known and scrutinized,
>the calculated data cannot be given serious consideration."(R.L.Wysong).
Over 50 years ago, most scientists would have agreed with this
statement about caution in accepting radiometric dates. But since
then, the assumptions for each 'dating method' have been determined and
scrutinized to the point where the calculated data CAN be given serious
consideration ... and consequently scientists do. The only ones who
can still make this statement today, are those who have not personally
scrutinized the data, or those unwilling to accept the research of
those who have scrutinized the data, or those are unable to accept the
results regardless of what the data says.
---------
For those who had the stamina to read this far, I leave you with some
humor which explains why geochronologists seldom use the term "dating"
in their technical writing. The mental pictures which arise are too
funny for a serious paper in a scientific journal.
age dating: a phenomena which commonly occurs in nursing homes - also
known as geriatric dating. Related topics include Mixed Age Dates.
dating methods: a hot discussion topic among high school and
college-age adolescents - often encompassing large amounts of
misinformation.
dating rocks: a questionable relationship between geologists and their
samples which can occur at or near the end of a long and lonely
field season.
radioactive dating: 1) v. a intimate relationship between two co-workers
at a nuclear power plant. 2) n. attending a social event with a
radioactive companion; or 3) a engagement with an explosive ending.
radioactive age dates: 1) Two person social events that occur during
the Radioactive Age which followed the Great Nuclear War; or
2) Social events occurring after a couple has advanced in age to
a point where only radiometric age determination methods can
verify the birth date on their ID's - an important factor when
serving or selling alcoholic beverages. See also Age Dating.
3) The sweet, oblong, once-edible fruit of the Nuclear War-
contaminated date palm trees, now used in homeopathic medicinal
preparations.
-------------
Steve
[Disclaimer: The opinions expressed here are my own
and are not to be attributed to my employer.]
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