Saturday, November 26, 2011

Can Opposing Scientific Theories Be Reconciled?

An intriguing question posed by WSJ columnist Mat Ridley today ('New Suspects in a 65-Million Year Old Mystery'), is that in certain cases "scientific tribal polarization" can be trumped and two competing theories reconciled or bought together to become one. His premise is that the polarization occurs because excessive "academic tribal energy" goes into one or both theories and hence any full bodied compromise yielding a hybrid theory becomes impossible.

As an example, he uses the extinction of the dinosaurs some 65 million years ago, accepted by most astronomers as being caused by an asteroid impact that delivered an explosion equal to two million hydrogen bombs and forming the 110-mile diameter Chicxulub crater. The explosion would not have been the immediate cause of the dinosaur's demise, but rather the injection of more than 4 trillion tonnes of dust and debris into the atmosphere because of it. This then led to the phenomenon of "nuclear winter" in which so much sunlight would have been impeded by the atmsopheric debris that most of the green flora would have perished. This would have led to the extinction of the vegetarian dinos, and thence the meat eaters which depended on them in the food chain.

Another competing theory for the dinosaurs' extinction, proposes massive volcanic eruptions that burst through the skin of the Indian subcontinent at about the same time and poisoned the dinos and 67% of other life via high concentrations of sulphur and CO2 in the atmosphere. Ridley then cites new "more powerful evidence" for this volcanic theory, though more work clearly needs to be done.

Ridley then asks why both theories might not simply be unified, and thereby we have "an impact and a consequent eruption, both of which contributed to poisoning the atmosphere and the ocean to the point that few species could survive".

To be sure, this might have merit, depending on whether further work shows that: a) the volcanic eruptions were really consequent on the impact, and b) the eruptions delivered the needed levels of toxicity to claim two thirds of all the then life on Earth. Another question to be addressed: Could the volcanic eruptions alone have been enough to cause mass extinction?

Even if the two extinction theories can be integrated into a workable hybrid, it doesn't mean all scientific theories can be handled in the same way. For example, Newton's theory of gravitation and Einstein's are impossible to reconcile because one (Einstein's) is a tensor theory predicated on the geometry of space -time being curved in the vicinity of large masses, while Newton's is a scalar theory dependend on "action at a distance" within an absolute space, no space-time!

In like manner, it would have been impossible to reconcile the Big Bang theory with Fred Hoyle's steady state theory. The reason is that each mandates separate predictions which must be validated for the theory's acceptance. There are no overlapping predictions! Since the Big Bang theory was vindicated by postulating a 2.7 K isotropic background radiation, it was the winner.

In the field of solar flares, meanwhile, two divergent paradigms have emerged, one (B-v) peculiar to solar physics and based on the magnetic field intensity (B) and surface flow vector velocity (v) and the other (E-J) peculiar to space physics which is based on the electric field intensity and the current density.

One implication of the E-J paradigm models is that adequate power for flares can be provided once sufficiently large field-aligned potential drops can occur (as in double layers) arising from sufficiently large longitudinal (J‖) current densities. (cf. Kan et al, Solar Physics, Oct. 1983). Unfortunately, there seems to be no way to track these changes in the pre-flare phase, at least for specific solar active regions and sunspots.

Meanwhile, the unloading force-free field energy system, for the B- v paradigm, has become the centerpiece template for use in most solar physics applications. According to this view, convective fluid motions with characteristic velocity v warp and deform the magnetic field B, leading directly to

curl B = u_o J

Where B is the magnetic induction, J the current density, and u_o is the magnetic permeability of free space (u_o = 4π x 10^-7 H/m) . In this paradigm, free magnetic energy accumulated during the shearing of force-free fields incepted by (v x B) , or the cross product of the velocity flow and the magnetic field strength. (Imagine the local magnetic fields being twisted up like you would a rubber band. The more twist imparted to the rubber band the more "free energy" it's stored. When you let it go, that energy gets released).

Most models based on the B-v paradigm concentrate on the energy generation (or storage) aspects, while ignoring energy dissipation other than as a passing afterthought. Clearly, this is unsatisfactory and leaves unanswered the question of detailed energy balance in a specified flare volume (coronal loop, arcade etc.). In particular, it leaves unanswered whether driven flare energy models (based on release of magnetic free energy from force-free fields) are adequate to ever be refined into full, self-consistent theoretical descriptions, as opposed to assorted ansatzes cobbled together or “cartoon” depictions.

The E-J models DO address the energy balance issues, but in most cases invoke artifacts common to magnetic substorms - such as V, -S potentials, and "neutral winds" which are not receognized by solar physicists as integral and physical parts of the flare process.

In a 1994 paper session for the joint meeting of the American Geophysical Union and Solar Physics Division in Baltimore, I presented a theoretical model that melded aspects of solar and space physics, by incorporating the respective B-v and E-J themes. Though numerous observers were “shocked” that a space physics basis could be incorporated to describe the flare process, others expressed interest and curiosity.

The basic model, depicted in Fig. 2, entailed successive weak double layer (WDL) formation in a Vlasov-Maxwell (upper coronal loop) plasma subject to anisotropic distribution of electrons in velocity space. The key point in the above model is that WDLs are needed to confine potential drops to extremely localized regions (in this case, also characterized by anomalous resistivity) . Meanwhile, the "feet' of the loop were anchored in a high beta plasma regime which was subject to the distorting motions of convective flows and their action in twisting the ambient (phnotospheric) magnetic field - leading to mutual polarity intrusion and magnetic gradients that could trigger flares. The activation arose when the potential drops in the upper part of the loop became large enough to tip the overall loop into instability. For example, if the twist of the loop was near T = 2π, then even a small micro-instability might act as the specific trigger.

The gist of the above illustrations is that yes, it is certainly possible in some cases to achieve a hybrid model or theory, but one must be aware all the time of the contexts, and also whether the resulting hybrid can make the predictions needed for acceptance. Alas, cross checking my theory must await the arrival of a higher resolution solar telescope that can identify the weak double layers in the upper corona.

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