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[This immediate blog discussion follows a forum discussion on gyrodynamics and the principle of juji, the "cross shape" +. It is put here in blog form for those who care about the technical intricacies of such things and exploring non-aiki analogues of aiki principles, and other observations that may shed light on Aiki priciples and WHY they work the way they do. I will repost the gyrodynamics portions of this discussion immediately following. While the facts related are sound as far as they go, the application of everything here is speculative and subject verification in actual aikido practice. Choose wisely, therefore, and ask your own teacher. ]
You cannot have magnetic flux without electric current somewhere within meaningful inverse square law range, and you cannot have electrical current without magnetic flux similarly situated. But they are always 90 degrees out of phase from one another. (right hand rule) But you can have observed purely electrical action or observed purely magnetic action because of their existence in differing phases. The potential always exists for the correlative action of the other at the same field strength in each circumstance; but it remains potential (virtual) until realized by appropriate conversion of its form or phase.
Of course, you cannot measure a field directly without inducing current or flux. Heisenberg's law still applies. An electric field exists without magnetic flux. Magnetic flux is only created by those electrons starting to move and thus creating current. One can be used to measure the other. But electric fields can be measured indirectly without inducing current or flux.
Photons possess neither mass nor charge and yet they excite electrons and electrons, when sufficiently excited, emit them without creating current, but revealing their charge state. Because of two potential polarizations, photons also preserve the phase distinction between the joint magnetic and electric fields to which they relate. In a sufficiently strong electric field, electrons spontaneuously emit photons and tend to ionize as they do that (with a local deielectric current, but none globally). So there are proxies to field strength measurement that allow the inference of the field, even if undetectable directly. For example, charge distribution (and thus field potential), may be inferred from the distribution of color of plasma ionization discharges in the atmosphere. See: http://www.atmo.arizona.edu/students...y_Nov_2001.pdf
One guage of magnetic field is incomplete but only propagates at the speed of light, and thus may be deemed "actual" in relativistic terms, since we can directly observe its components. The other guage for magnetic field is complete, but has unobservable, inferred components, which are capable of travelling faster than the speed of light, but because they are not observable, does not matter. It can thus be deemed "virtual" in relativistic terms, since going faster than light is not allowable in actuality.
The Aharanov-Bohm effect directly demonstrates that eletromagnetic effects occur to particles in a region from which the "actual" field at issue is expressly excluded. The " virtual" mathematical field apparently has more demonstrable reality than the "actual" field, even though it is non-relativistic. And now we know that quantum non-locality does not require forces at all to "communicate" state variables (an acknowledged overstatement).
The potential field vector is there whether there is actual electrical current or magnetic flux or not. If the path of the realized current is known (and it can be demonstrated or inferred), even if unrealized, the potential (virtual) field is as defined mathematically as if current and flux actually existed at the time of the analysis. It is thus is the proper topic for the method of virtual work to compute a resultant without disturbing the field any more than is necessary to detect its orientation until the action is applied.
In aikido, the analogue is the connection (ki musubi), which harmonizes tori/nage to uke's state at contact and allows the creation at that moment (takemusu aiki) of appropriate technique based on the detected orientation. The connection does not disturb the attack, but joins with it in order to establish orientation, which then leads to a technique appropriate to that flow.
Only at this moment of connection is anything like "strategy" in existence, much less "tactic." And even then, the only "strategy" is to let the state of forces at play define the action to be accomplished. Chinese would describe this as following "li" 理 the principle of the grain of wood, which shaped itself to the forces under which it grew.