Given that FF is invisible, why is no one else looking for the clearly physical effect it is said to have on an opponent?
If it's invisible and also has no observable effect, it's indistinguishable from something that doesn't even happen.
Hi. Force Flow is technically not 'invisible' if you have the right instrumentation. For example, if I had a very powerful microscope, perhaps electron, you can see, albeit interpreted, a force passing through an object.
In branches of mathematics 'force flow' would be referred to as a vector and here a force vector. There are some materials that enable one to see the distribution of a load and the force exerted throughout the material.
For example please see this video.
03:56 is where you see some photoelastic material put under stress and the force flow through it. If your bones were made of this material or other parts of your body you would be able to see the force vectors pass through. Likewise, if you had good instrumentation you could 'see it' pass through bones and flesh too.
We can either talk physics properly and use the correct terms or choose a half way house such as force flow as most don't do mathematics and physics.
In sum, yes, to the human eye it is invisible but it is there and I hope to have provided some thoughts that may allow some to understand the idea of force flow a little better.
Sometimes when we talk about having good structure we are talking about the ratio of a force vector that passes through the skeletal structure as opposed to the more fleshy parts and if your body had the same properties of that photoelastic material, you would be able see how that ratio changes as you position and reposition your body to be more structurally aligned or not.
It is true, when we have incorrect tension the force vector will distribute to the fleshy parts over the skeletal structure and this is what some people mean by it becoming 'jammed'. There is nothing mystical it is all just science. The issue is always one of articulation and the extent to which some will exploit ignorance here to insert their own frameworks. Others, as stated, attempt a half way house because most folk are not good with overly technical and 'scientific' terminology. 'Reaching/attaining Song' helps prevent 'jamming' in my view and allows one to 'feel' a vector force and to use it more efficiently.
This is why SLT is so important as one is dealing with just gravity and the ground reaction force and the meditative aspect trains you to attend to the sensations in your body and to identify the force vectors passing through, whilst allowing you to play with body positions to experience changes in that ratio and to reach Song in this very basic mechanical system; gravity and the ground reaction force i.e. just those simple force vectors.
I hope some find what I write above useful.
Cheers