Hi, citizena-ga:
Dr. LaViolette's Web site has many colorful elements. To present a
critique of his "scientific theories" it is necessary to limit the
discussion to certain aspects that fall within the purview of science.
For example, I do not think that the claim that a secret message from
10,000 years ago was encoded in the constellations of the Zodiac is
capable of any scientific analysis.
However I've looked critically at those two of his claims that are
more clearly within the realm of science.
A. "A study of astronomical and geological data reveals that cosmic
ray electrons and electromagnetic radiation from a similar outburst
of our own Galactic core (Figure 1-b), impacted our Solar System near
the end of the last ice age. This cosmic ray event spanned a period of
several thousand years and climaxed around 14,200 years ago."
B. "Although far less intense than the PG 0052+251 quasar outburst,
it was, nevertheless, able to substantially affect the Earth's climate
and trigger a
solar-terrestrial conflagration the initiated the worst animal
extinction episode of the Tertiary period."
These are related claims, obviously, in the context of Paul
LaViolette's theory of a "galactic superwave". However I propose to
make separate evaluations of the astrophysical and the paleontological
evidence that he presents or fails to present in support of his
claims.
We may take as a ground rule of science that the burden lies with the
one proposing a novel scientific theory to present evidence which is
more satisfactorily explained by it than by any competing theory.
"Precisely because of human fallibility, extraordinary claims require
extraordinary evidence." -- Carl Sagan
http://www.pbs.org/wgbh/nova/aliens/carlsagan.html
1. Obscurantism
The first criticism to make of Dr. LaViolette's claims of a "galactic
superwave" (or variations elsewhere like "Galactic Explosion
Hypothesis") is that he's couching them in terminology that is
colorful but lacking any accepted definition in astrophysics or other
scientific discipline but pretending that the reader ought to know
well enough what is meant. It may be necessary at times to invent new
terminology (this often is the case in mathematics), but unless one
deliberately wants to obscure their meaning, the effort to define ones
terms is of critical importance!
"Galactic Wave" is in fact the title of an art print by Jon Lomberg,
who worked closely with Carl Sagan to illustrate books and the TV
series "Cosmos":
[Galactic Wave -- Giclée Prints]
http://www.jonlomberg.com/dp_galacticwave.html
"Jon Lomberg pays homage to the great Japanese artist Katsushika
Hokusai (1760-1849) who created a famous woodcut of a giant wave with
Mt. Fuji seen on the horizon. Lomberg reinterprets this image in an
astronomical context, showing the disk of the galaxy as a cresting
wave, with young stars spraying out from the wave. The galactic center
can be seen in the background, in the position Mt. Fuji occupies in
the woodcut."
Let us therefore ask what this phrase should mean in LaViolette's
context. He says above that an "outburst" of radiation from the
galactic core lasted several thousand years and peaked around 14,200
years ago. Alternatively his GEH (Galactic Explosion Hypothesis)
states that "these outbursts recur every ten thousand years or more
and last anywhere from several hundred to several thousand years."
Elsewhere he states: "Galactic core explosions actually occur about
every 13,000 - 26,000 years for major outbursts and more frequently
for lesser events."
If the timings of these outbursts seem unpredictable to almost a point
of vagueness, their contents are even less well described. He says
they consist of "cosmic ray electrons and electromagnetic radiation"
travelling "outward from the Galactic Center at very close to the
speed of light." They also inject "large amounts of cosmic dust over
a period of thousands of years", which has a dramatic effect on the
earth's climate "in a period of less than one hundred years."
The galactic superwave is "similar" to but "far less intense than the
PG 0052+251 quasar outburst." Or it was "equivalent to the energy
released from five to ten million highly energetic supernova
explosions." Then again he seems to paint a continuum of "major
superwaves" scaling down to more frequent "minor superwave emissions"
every 500-700 years, and to further make some passing comparison
between superwaves and gamma-ray bursts lasting on the order of
seconds.
By poorly characterizing his theorized phenomenon Dr. LaViolette opens
himself to a criticism that he is willing to aggregate observations
many dissimilar events to lend support to his claims.
As we are about to see, though, in some critical respects the evidence
he claims to support his theory is either badly misrepresented or
nonexistent.
2. Evidence in Ice
In looking over the literature citations given by Dr. LaViolette, one
is struck by the fact that after 1988 none of them are other than
self-attributions (the most recent being his 1997 book, Earth under
Fire).
Here is what he says about one key item on the list of independent confirmations:
[Galactic Center (Page 2)]
http://www.etheric.com/GalacticCenter/Galactic2.html
"Astronomical observations show the last major Galactic core explosion
occurred as recently as 10,000 to 15,000 years ago.(16, 17) Data
obtained from polar ice core samples show evidence of this cosmic ray
event as well as other cosmic ray intensity peaks from earlier times
(Figure 2).(1, 18)"
One must click ahead to "Page 4" and scroll to the bottom to find what
references are being mentioned. Citations 16 and 17 do not appear to
supply evidence of a "major Galactic core explosion" as Dr.
LaViolette's framing suggests. Indeed their titles refer to gas
density and ionization within 2-3 parses of the galactic center, but
the latter paper's title contains the desultory phrase "possible
evidence for infall"!
Citation 1 is Dr. LaViolette's own book. Citation 18 is the paper
which you asked about:
18) Raisbeck, G. M., et al. "Evidence for two intervals of enhanced
10Be deposition in Antarctic ice during the Last Glacial Period."
Nature 326 (1987): 273.
The graph (Figure 2) which Dr. LaViolette places just beneath this
attribution on "Page 2" is _not_ taken from this paper. Raisbeck et
al do have a graph (covering the estimated past 140,000 years) that
might have clarified matters for the interested reader, but it shows
no 10Be peak whatsoever around the 10-14ka timeline contended. Indeed
the authors write up the graph as follows:
10 18
"The most dramatic difference between the Be and ? O curves are the
two fairly well defined peaks in the 10Be concentration, at ~925m and
~600m. According to the timescale adopted by Lorius et al., these
levels correspond to times of ~60,000 and ~35,000 yr BP, respectively.
Each of the peaks is estimated to last ~1,000-2,000 years, depending
on the assumed precipitation rate and how one chooses to define the
peak shapes."
So what in this, if anything, supports Dr. LaViolette's theory? There
is no peak at ~14,000 yr BP. Indeed the authors concur with later
papers in finding that in these more recent times the 10Be
concentrations are significantly lower than any other time since about
120,000 years ago:
"[T]he 10Be concentration appears to increase quite steadily from the
previous interglacial until the glacial maximum at ~20,000 yr BP,
followed by a rather rapid decrease to Holocene levels."
So the lowered baseline of 10Be would make any peak during this recent
interglacial stand out clearly. But it is not in the data! Also the
two observed peaks last one or two thousand years, scarcely the
several thousand years that Dr. LaViolette speaks of.
It is worth a second look at the exact wording chosen for this citation:
"Data obtained from polar ice core samples show evidence of this
cosmic ray event as well as other cosmic ray intensity peaks from
earlier times (Figure 2)."
After reading the cited paper carefully, I am virtually forced to
conclude that Dr. LaViolette is being "cute" with the evidence by
mentioning "peaks from earlier times". He provided no independent
polar ice core evidence of what he claims (though this 1987 paper is
hardly the last research that was done on these cosmogenic isotopes)
and appears to be playing for "wiggle room" by throwing in the phrase
about "earlier times".
For the sake of clarity, the conventional explanation of variations in
10Be concentrations in ice is twofold, that there are climate induced
variations, due to precipation rate and perhaps changes in atmospheric
circulation, together with changes in the rate of production of 10Be
in the atmosphere. For the latter there are three possibilities:
variation in primary cosmic ray flux, changes in solar modulation, and
changes in geomagnetic field intensity.
Even if it were granted that the peaks observed were due to an
increase in cosmic ray flux, rather than to a reduction in solar
modulation (the solar winds, dying down, would reduce the magnetic
field that deflects much of the cosmic radiation from earth), there is
a lack of evidence for a central galactic source of the radiation, and
no credible attempt to tie the magnitude or duration of the
hypothetical cosmic ray increase to the isotopic peaks.
3. "Worst Animal Extinction of the Tertiary Period"
Again we are faced with a preliminary difficulty in identifying to
what Dr. LaViolette is referring. He presents a brief excerpt from
his 1983 dissertation:
[The Terminal Pleistocene Extinction Episode]
http://www.etheric.com/Superwave/Ch10.html
that strongly suggests identification with what is more commonly
called the megafaunal extinction of the late Quaternary period:
[Megafaunal extinction in the late Quaternary
and the global overkill hypothesis -- Wroe et al]
http://www.bio.usyd.edu.au/staff/swroe/Wroeetal2004MegafaunalextinctionintheLateQuaternaryAbstr.pdf
What Dr. LaViolette thought worth putting forth in this short excerpt
is instructive. The argument he makes is that because "many
radiocarbon dates assigned to the remains of Pleistocene megafauna
should not be trusted", he will assign his own favored date of ~14,000
yr BP.
The paper above by Wroe et al is a recent and lengthy critique of the
three main theories of causation for this extinction: human
intervention (eg. overhunting of prey, but possibly less directly
effected), disease, and climate induced.
A recent news story you may have seen mentions the use of DNA to
suggest a timetable for the population decline that predates the
arrival of man:
[Climate helped wipe out large mammals]
http://www.newscientist.com/news/news.jsp?id=ns99996726
"An analysis of the genetic diversity of bison shows that the decline
in Beringia - the prehistoric land mass joining Alaska and Siberia -
began 37,000 years ago, more than 20,000 years before large human
populations reached the area."
This in any case fails to support Dr. LaViolette's theory of a rapid
extinction event around 14,000 years ago.
Although the loss of such large mammal species as the mastodon and
sabre-toothed cat is striking, is does not qualify as the worst animal
extinction event of the Tertiary period, as LaViolette put it, for two
reasons.
Most trivially, this is the Quaternary period, not the Tertiary
period. (The mass extinction that killed off dinosaurs was at the KT
or Cretaceous-Tertiary Boundary.)
Most importantly, while humans may not be the proximate cause of the
mastodon's disappearance, we can certainly take a good deal of the
responsiblity for the rapid rate at which species have begun to die
off in the last 200 years:
[Geologic Time Chart with Mass Extinctions]
http://www.geocities.com/RainForest/8471/geology.html
"Humans dominate near the very end (last 100,000 years), and in the
last 200 years there is another mass extinction. Rate of species loss
is now estimated at 4000 species/year."
So if you throw it open to all animal species, not just the megafaunal
mammals, there's no doubt we're in the midst of a mass extinction
worse than that one.
Summary
=======
It looks to me like the absence of independent confirmation for Dr.
LaViolette's theories is pretty compelling. Twenty years ago he
predicted that polar ice cores and other isotope measurements would
confirm his ideas, but they haven't. Of course exactly what he means
by "galactic superwave" appears to be vague by design, so that no one
specific study will be able to disprove it. But this is a critical
element for a theory to be considered scientific, ie. falsifiability.
If Dr. LaViolette indulges in speculations that are never precise
enough to be plain wrong, it's not science, but it might help sell
some books.
If I hear from Dr. LaViolette, I'll be glad to facilitate his reply here.
regards, mathtalk-ga |
