From: glenn r morton
To: All
Subject: Evidence #11 for a Young World
From: xdegrm@oryx.com (glenn r morton)
Organization: Oryx Energy
In article Alan Scott wrote:
>#11. Not enough helium in Earth's atmosphere
>
> All naturally occurring families of radioactive elements generate
>helium as they decay. If such decay took place for billions of years, as
>alleged by evolutionists [there they go messing with nuclear physics], much
>helium should have found its way into the earth's atmosphere. Taking into
>account the slow rate of escape of helium from the atmosphere into space,
>and assuming no helium was in the atmosphere to begin with, it would take
less
>than (bold) two million years (end bold) to accumulate the small amount of
>helium in the air today.[23]
> This means the atmosphere is much younger than the evolutionary
>(italics) five billion years (end italics) - again consistent with a recent
>creation (6,000-10,000 years) of functional atmosphere.
>
>[23] Vardiman, L., 'The age of the earth's atmosphere estimated by its
> helium content', PROCEEDINGS OF THE FIRST INTERNATIONAL CONFERENCE
> ON CREATIONISM, Vol.2, Creation Science Fellowship, Pittsburgh,
> 1987, pp.187-195
I have briefly looked at the above article and it has some major problems.
Vardiman uses an equation which I think was taken from J.H.Jeans _The
Dynamical Theory of Gases_ Cambridge 1916 or E. Leonard Jones, Trans.,
Cambridge Phil. Coc., Vol 22, 1923. The equation is
F= n(g He/2pi)^1/2 (1+(R+z)/He)exp(-(r+z)/He) where n is the particle density
z is the height, g is the acceleration due to gravity and He is the scale
height at the base of the exosphere. The equation reference is quite old
so I don't know if it is still considered correct.
He admits that there is a great difficulty with estimating the influx of
helium to the atmosphere out of the crust. As near as I can tell at this
point, he uses a 4.5 billion year earth and an amount of helium of 6 x 10^38
atoms entering the atmosphere yields a rate of 2 x 10^6 atoms/cm^2-sec.
6 x 10^38 atoms is the number of atoms of helium in the atmosphere according
to him.
The guts of his argument is found in the following quote.
"To evaluate equation 2 we assume the reference density is 3.4 x 10^13 atoms/
cm^3 at a height of about 100 km. The temperature at the homopause is
approximately 185 degrees K and the exospheric temperature is 1500 degrees K.
The concentration is further adjusted by the helium mixing ratio shown in
Table 1. With these assumptions, the value of the helium flux is calculated
to be 5 x 10^4 atom/cm^2-sec. This escape rate is about 40 times less than
the
average source rate estimated to be coming into the atmosphere from the
crust of the earth. By dividing this escape flux into the column density of
helium in the atmosphere (1.1 x 10^20 atoms/cm^2), the characteristic escape
time for atmospheric helium is found to be about 70 million years. By divid-
ing the source flux of 2 x 10^6 particles / cm^2-sec into the column
density, the residence time is found to be about 2 million years. The
characteristic residence time for helium is much smaller than the character-
istic escape time. In other words, it takes a much longer time for a
given quantity of helium to escape from the atmosphere to space than it
does to enter the atmoshere through the crust." p. 191 of above article e
First, the data he is referring to in table 1 is the atmospheric composition.
My gut feeling is that there should be more helium in the upper atmosphere
than there is in the average atmosphere. Helium is much lighter than
the other atmospheric constituents and so should preferentially be on the
top. Secondly, the output flux is what he calculated would be required to
account for the helium in the atmosphere in 4.5 billion years. He allowed
for no primordial helium and considering that there should have been some
helium in the pre-solar nebula, his rate of escape from the crust would
be too high.
He then discusses very briefly three other escape mechanisms. Polar wind
escape which is the escape of He+ through the open field lines at the poles.
He then says "Axford(22) has applied the polar wind model specifically
to the escape of helium and calculated an escape flux of about 1 x 10^5
atoms /cm^2-sec. much lower than even Jean's escape."
Last time I checked 1 x 10^5 is greater than 1 x 10^4 unless the laws of math
have changed since I left college many years ago. Axford's article is cited
as Journal of Geophysical Research Space Physics 73, 1968, p. 6317-6323
He claimed that the solar wind mechanism escape flux would be quite low but
gives no numbers. The last mechanism of escape he talks about is hot ion
exchange but once again gives no numbers. One must wonder whether the work
he refers one to Fahr and Shizgal Rev. of Geophys. and Space Physics, 21, 1983
, pp 75-124 has numbers which are embarrassing for his position.
He also pooh-poohs a suggested mechanism of escape proposed by Spitzer and
Hunten (Spitzer, "The Terrestrial Atmosphere above 300 km", in _The
Atmospheres of
the Earth and Planets_ Univ. Chicago Press, 1949 p. 211-247 and Hunten "The
Escape of light gases from planetary atmospheres" J. of the Atmos. Sci. 30,
1973, p. 1481-1494). Their mechanism is that the earth's outer atmosphere
is periodically heated by large solar storms to 2000 deg. K which then allows
the helium to escape. He of course provides no numbers.
He ends the article with the silliest idea of the distribution of radioactive
elements I have heard in a while. He says.
"The recent discoveries of helium coming through the crust from the mantle
where no radioactive decay process is known to produce helium, has led to
the statement that primoridal helium exists in the mantle. Why then, is it
so hard to believe that primordial helium still exists in the atmosphere?
The lack of an escape mechanisms and the likelihood that, the helium we
observe in the atmosphere is primordial provides evidence that the
earth's atmosphere is quite young." p. 193
It is believed that there is not as much radioactivity in the mantle as there
is in the crust but to make the claim that there is none is quite a stretch.
I have not looked at the articles he cited I will order them now and take a
look when they come in.
