Don
L. Anderson1 & Warren
B. Hamilton2
1Seismological
Laboratory, California Institute of Technology,
Pasadena, CA 91125, dla@gps.caltech.edu
2Department
of Geophysics, Colorado School of Mines, Golden CO
80401, whamilto@mines.edu
"In science, conventional
wisdom is difficult to overturn…some implications
of plate tectonics have yet to be fully appreciated
by isotope geochemists…and
by geologists and geophysicsts who have followed
their lead"–Armstrong, 1991
Zombies are reanimated, shambling
and catatonic corpses of voodoo and video that know
not when they are dead. Zombies have analogs in obsolete
conjectures–propped
up as conventional wisdom–in science and maintained
for reasons and methods outside of science (Charlton,
2008). Zombie hypotheses are unproductive (they
do not produce useful results) but are not completely
sterile (uncreative). They need to evolve and morph
to keep up with the facts that threaten to bury them;
they spawn rationalization, exceptions, paradoxes,
adjectives and other zombies, often in creative ways
that diverge from real science. Aether, phlogiston,
and Lamarckian inheritance of acquired characteristics
are among examples of zombie science that are now extinct.
Phlogiston, the magic elixir of alchemy, became endowed
with many mysterious qualities but when it was discovered
that adding phlogiston to burning solids added to their
weight, a small group of alchemists defected and founded
chemistry. Aether was similiarly discarded when it
was required to be rigid, fluid, weightless
and invisible. Ptolomaic motions of Sun and the planets
around a fixed Earth survived generations of complications
with epicycles, eccentrics, and equants, but were demoted
from science centuries before they were rejected by
the Vatican. Even before better models were fully in
place the Ptolomaic system became so complicated with
gears-within-gears, and spheres-within-spheres that
some astrologers looked elsewhere for solutions and
became astronomers. Fixity (of aether, Earth, Euler
poles, geographic poles, "hot spots", continents,
species) is a simple and testable hypothesis that can
make numerous predictions. If every observation requires
an adjustment, or a new parameter, then the hypothesis
is no longer simple or elegant and it cannot make predictions.
But it is hard to recognize the final straw, the smoking
gun, or the nail in the coffin–so dead things
stick around.
Editors, reviewers and funding agencies
unwittingly perpetuate zombie science, which differs
from simply bad science in that it is immune to evidence.
As a result, zombie science becomes entrenched as conventional
wisdom, and even mainstream science. Speculations that
may have been reasonable when proposed become cemented
by constant repetition to dogma, impervious to disproof
and defended passionately by committed advocates.
In real science, assumptions
are formulated clearly, tested rigorously, and applied
to as many situations as possible. The assumptions
self-destruct if nature resists. Assumptions and hypotheses
are not laws of nature, but are made to be tested and,
when broken, abandoned. Controversial science, ideas
that conflict with our own, and wrong hypotheses can
all be good science. Zombie science, in contrast, cannot
be falsified or killed, and instead exists in a nether
world of dogma and superstition that lies between paradigm
shifts. Contradicting facts are ignored and added as
new, unpredicted properties or adjustments to earlier
speculations. The underlying assumptions, which are
no longer believed by anyone, are forgotten in the
process.
A well-known geoscience example was
the "permanent
continents–rigid mantle" ideology,
retained by most geologists and geophysicists
long after continental drift and a flowing mantle,
with no fixed points, were established by empirical
evidence. We look with disbelief on 20th century scientists
who believed that gigantic continents were fixed to
the mantle. However, the view is now adopted that small
islands are tethered to the deep, rigid mantle by narrow
umbilical cords. We accept the views that while oceanic
crust recycles to the lowermost mantle, continental
crust is permanent. Future scientists may regard present-day
belief in absolute reference systems, fertile fixed
points, narrow 3000-km-tall mantle jets, and one-way
continental growth from “the convecting mantle” as
persistent myths (Armstrong,
1991).
Geologists had long
since given up on the young Earth hypothesis before
the news filtered up to physicists. Mineral physicists
and petrologists dismiss the geochemical dogma that
low seismic velocity and large magma volumes are unique
proxies for high absolute temperature. Geodynamicists
no longer believe that convection implies chaotic stirring
and homogeneity, or that plates are passive passengers
on the backs of convection cells driven by core heat.
Geologists do not believe that the upper mantle is
homogeneous or that oceanic crust, delivered up by
plumes from the lower mantle, is the only contaminating
material. Planetary scientists do not believe that
Earth accreted cold and homogeneous and only later
warmed up and differentiated. Yet these old ideas are
still entrenched in dependent disciplines. Complex
conjectures are built on the assumption that early
Earth was cold, the lower mantle “unfractionated” and “undegassed”,
that the crust grew gradually and, once formed, was
permanent and that there was no recycling. Because
the model required two "reservoirs", the
mantle was early thought by geochemists to be two-layered.
Later it was thought to be one-layered based on suggestive
visual chromotomography wherein the assumption that “red
is hot and blue is not” was unconciously accepted.
Continuous recycling of oceanic crust from the surface
to the core-mantle boundary and back was presumed.
Geodynamicists supported these speculations with modeling.
Sometimes in science it is hard to know
when to “put the last nail in the coffin” of
an attractive hypothesis that has failed all
tests. “…before we nail any more coffins,
let’s first be sure that there is a body to be
buried” (Hofmann & Hart,
2007). The temptation
is to add more assumptions and parameters to prop up
dead theories. Just like munchkins
in the Wizard of Oz, we often wait and see if it is truly dead; "Let
the joyous news be spread, The Wicked Old Witch at
last is dead!…not only merely dead…she's
really most sincerely dead.” Specialists are
often unaware when developments in other fields have
falsified the assumptions on which their work relies.
The fixed "hot spot" postulate
was based on the southeastward younging of Hawaiian
volcanoes, previously attributed to fissures and propagating
cracks that were also able to account for the age progression.
Many modern advocates say that the plume concept is
validated by the fit of Hawaii and other “hot
spot tracks” to fixed-hot-spot predictions, a
circular rationale. Speculation expanded to include
myriad features of magmatism, geochemistry and dynamics
that had previously been explained by top-down processes
such as plate tectonics, continental dynamics and crustal
stoping.
Rationalizations of the observed characteristics of
hypothetical plumes have generated continuously changing
predictions regarding fixity, hot-spot motion, age progressions
of island chains, heatflow, style of mantle convection,
uplift prior to magmatism, temperatures of magmas,
and geochemistry. These predictions are rarely successful,
so the concepts have been modified to allow as many
exceptions, and as many kinds of plumes, as there are
"hot spots". The guiding principles are non-physical.
The products of plumes are whatever is observed where
plumes are postulated. Amendments to the fixed "hot
spot" hypothesis now include mantle winds, polar wander,
mantle roll, lithosphere drift, lateral flow, magma
tunnels, group motions of "hot spots", plume head decapitation
and superplumes. Mantle winds are used to explain non-fixity
of "hot spots". “Fixed hot spots" may
be large regions or long "hot lines" within
which volcanoes can pop up anywhere and in any sequence.
Plumes are postulated to feed volcanoes thousands of
kilometers distant, and they no longer need fit Euler
geometry or global reference frames. If age progressions
are non-uniform, new co-linear plumes are added. Most “plume
tracks” are missing a “plume head”,
and most “plume heads” are missing a track.
The lack of evidence for “plume heads”, “plume
tracks”, high heatflow and precursory uplift
is ignored or rationalized. Evidence for the uplift
predicted to precede the Siberian flood basalt is assumed
to be hidden beneath the west Siberian lowlands, whereas
that for Hawaii is assumed to have been subducted.
Findings that defy such ad hoc adjustments
became official paradoxes: the Lead Paradox, the Helium
Paradox, and the Heat Flow Paradox. New observations
are labeled surprising, unexpected, counter-intuitive
or anomalous.
All of this signals a failed hypothesis–zombie
science–but the conjecture is sustained outside
the domain of science. A simple, elegant, satisfyingly
neat, concise, falsifiable hypothesis has become a
complicated, awkward, messy, unfalsifiable monster
that refuses to lie down and die. According to the
more cynical philosophers of science, failed hypotheses,
heaped high with anomalies, paradoxes and auxiliary
conjectures, are perpetuated by repetition and self-referencing
because too many adherents have invested their careers
in them. Although many scientists have moved on plumeology
remains entrenched conventional wisdom, supported by
the publishing industry, with alternative opinions
discouraged and made to jump a higher bar. Young scientists
who should be encouraged to question dogma are kept
in line via hiring, promotion, grant proposal and publication
decisions. Zombie research programs defy burial.
References
last updated 11th
December, 2008 |