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Logic & First Principles 8: Bridging the Wigner MATH-PHYSICS GAP (with help from phase/ configuration/ state space)

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In order to conceptually bridge the Wigner MATH-PHYSICS GAP, it is helpful to see how deeply embedded quantitative and structural properties are in the physical world. The phase space approach is helpful, and a vid on how colliding blocks compute digits of pi (under ideal circumstances) will help. The vid:

It helps to look at some screenshots:

In this first shot (from a part 1 vid) we see a setup where we have a frictionless plane with a rigid wall to the left and two masses that collide. On the first hitting the second, it will hit and bounce back (elastically) from the wall. A second collision with the first block follows and rebound from the wall. This will continue until the second block cannot catch up with the first. Amazingly, depending on the mass ratio, the number of collisions between blocks or with the wall will give digits of pi.

Such suggests that there is a hidden circle, and there is, in an associated phase space — which allows us to see the dynamics from a geometric viewpoint in an associated abstract space:

Here, we see blocks moving so that kinetic energy and momentum are conserved. The circle shows constant kinetic energy and the zigzag jumps come from momentum conservation during collision — the vertical one being due to collisions with the wall of effectively infinite mass (rigidity). Due to collisions, they are switching directions and points on the circle on collisions. And, the angle at the centre will be twice that at the circumference standing on the same arc, here marking three successive collisions:

This continues until a critical value is left. It turns out, that this is when the arc-jump around the circle can no longer achieve a critical value:

The result of all this is that we move, depending on mass ratio, from 3 to 31 to 314 collisions and onward. Which computes pi’s digits.

Of course, we have idealised the system to be friction-free. (In the video, clacks are added as an audio effect, with energy conservation there would obviously be no noise.)

We see here how a physical situation (admittedly idealised) obeys laws of physics which were empirically discovered. These reveal a deeply embedded logic of structure and quantity manifest in phenomena of the world. Where, we may freely move to an abstract, phase space which allows further insight and analysis.

In this case, geometry counts.

Counts to the point that an idealised case would allow computation of digits of pi.

Of course, we could not actually build such a system, but the laws we infer from the observed world help us to form abstract model logic worlds that give us insights and which often help us to understand real world cases with friction etc.

Why all of this is possible is because the physical world is governed by logic of being constraints that are structural and quantitative. Laws, that turn out in aggregate to be fine tuned in ways that enable C-Chemistry, aqueous medium, cell based life. END

PS: Mobius strip cutting exercise:

https://www.youtube.com/watch?v=gXsgkojxkdY
Comments
F/N: Maybe I should add a note on kinetic energy i/l/o kinematics and some basic dynamics of force and work. 1: It is easy to see from uniformly accelerated motion: v^2 = u^2 + 2*a*x, 2: So, rearranging: v^2 - u^2 = 2*a*x, 1/2[v^2 - u^2] = a*x, 3: Where F = m*a (where m is constant) and increment of work, dW = F*dx, so too: 1/2*m*[v^2 - u^2] = m*a*x = F*x = W --> Work done by F applied to a body is linked to change in a velocity-square term, so set u = 0: 1/2*m*v^2 = m*a*x = F*x = W --> 1/2*m*v^2 or kinetic energy, is the net work done to give a body of mass m its velocity v, starting from rest and it is manifest also in the forced motion through relevant distance moved, x. This gives some background to the OP. It also helps us see why kinetic energy will be conserved in the idealised case, KE change comes from forces changing the speed of massive bodies. (BTW, this can be extended to rotational motion.) KF PS: Momentum conservation can be similarly analysed, given that empirically bodies interact in pairs, exerting equal magnitude, oppositely directed forces, where too momentum is in effect cumulative effect of force acting across time. So momentum change in body A of an interacting pair will be equal size but oppositely directed to that of body B. In the cases above, the rigid wall has effectively infinite mass and all momentum change is in the body that hits it. The two moving bodies interact in ways dependent on relative masses and velocities. All of this then has its dual in the phase space view.kairosfocus
January 22, 2019
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Things like this make me look forward even more keenly to being able to question the designer.ScuzzaMan
January 22, 2019
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Logic & First Principles 8: Bridging the Wigner MATH-PHYSICS GAP (with help from phase/ configuration/ state space)kairosfocus
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