If a particle has spin angular momentum of 1hbar then if the particle's spin axis flips from up spin to down spin and then to up spin again then it will be in the same quantum state meaning that how it interacts with all the other particles around it will be the same as before it flipped twice or a total of 360 degrees of spin axis flip. The unit of measure "h bar" is related to Planck's constant.
If a particle has spin angular momentum of 1 hbar/2 like the electron then if the particle's spin axis flips from up spin to down spin and then back to up spin again then it is only 1/2 way back to being back in the same quantum state even though its spin axis and associated North-South magnetic dipole field is pointed back in the same direction again. The way it interacts with its environment has changed. This is evident in a 2 slit experiment because destructive interference occurs where constructive interference had occurred and vice versa when creating an interference pattern between electron's that haven't been flipped by 360 degrees with those that have 360 degrees of flip. But after 720 degrees of flip, the electrons passing through a 2 slit apparatus show the original interference pattern again when interfering with electrons that haven't been flipped at all.
These characteristics of an electron can be explained in a classical way by analyzing how all particles precess all the time and by analyzing the precessional phases of all the particles involved and the EM (electromagnetic) waves exchanged between them all by their precessional motions. This gives rise to a sea of standing waves among all matter that is not readily apparent. Similar EM standing waves develop from precessional motions of quarks within protons and neutrons. Not all EM radiation to/from sets of particles is compensated. Some is just not apparent. The wave characteristics of particles are not from abstract probability waves but from these unique electromagnetic waves.
When describing the spin of the electron, quantum physics suggests that it is "as if" the electron has a precessional angle and has precessional motion. What modern science has not realized is that in fact it really does. EM energy radiated and absorbed due to this precessional motion is continuously exchanged with all other particles with similar precessional motions. This EM interaction between the electrons passing through a 2 slit apparatus and the particles of the atoms of the 2 slit apparatus is what causes a particular interference pattern to develop.
If 2 free electrons are precessing in phase and 1-electron experiences 360 degrees of spin axis flip then its precessional phase is also shifted relative to the other electron. Two free electrons precessing will tend to naturally move to a state of either precessing in phase or 180 degrees out of phase due to the EM waves exchanged between them by their precessional motions. At any other precessional phase the EM forces developed between them will tend to push them back to positions where they are either precessing in phase or 180 out of phase. These EM forces developed between them from EM energy exchanged between them due to the precession of their magnetic dipoles is what moves them into quantized states.
To visualize precessional phase, imagine looking down into the axis of precession of 2 particles and then see (in a 2D plane from that eye point) the precessing of them both frozen in a snap shot of time and see the spin axis of each pointing the same direction (zero phase difference) or opposite directoins (180 degrees precessional phase difference).
Quantum physics describes exchange coupling and exchange energy in a purely mathematical way without any real world processes and characteristics of particles or classical analog that accounts for the spin characteristics of particles. It is possible that there are real processes and spin characteristics of particles and particle interactions and that a valid classical description exists. In this case, compensating precessional motions are involved of paired electrons with up and down spin or simply precessional motion of unpaired electrons. There is EM energy that is radiated to and from the precessional rotation of the magnetic dipoles of all these precessing charged particles, even from spins normally thought of as compensated, such that energy is continuously exchanged between them all and there is always an amount of EM coupling between all precessing particles. EM coupling and energy exchange from precessional motion occurs even among quarks of protons and neutrons but at much higher precessional frequencies than with electrons.
Once any particular particle has achieved synchronous precessional motion with all other particles then the energy stored in the difference in phase of the EM emissions between them will reduce towards zero. It would be hard to detect even any EM energy between them since as long as they are in sync there is very little energy stored in the difference in phase of EM emissions from them all.
However as soon as you attempt to make that particle move to a new position in space its EM emissions from its precessional motion will not be in phase with emissions of all other precessing particles around it near or far. The EM forces that develop due to this difference in phase between their precessional motions will cause a resistance to its motion to a new location and force must be applied against this resistance in order to successfully move any precessing particle to a new location. This is the cause of inertial resistance to the acceleration of matter.
All charged particles precess due to the EM emission exchange that has already been setup among them all. Also angular momentum is kept the same for all same type particles because if any particle emits too much energy from its precessional motion so as to start precessing slower then that energy is immediately replaced with energy absorbed from all EM emissions of all other precessing particles everywhere of similar type.
If by a man made device a large group of precessing particles making up all the atoms of a vehicle and its contents could be made to precess at a shifted phase relative to the phase of EM emissions of all other matter then a sudden and swift motion of the vehicle could be achieved by the forces that develop on all the particles of the vehicle due to the phase shift of the EM emissions of all the particles of the vehicle relative to all the EM emissions of all other matter in the area.
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Particle Spin and Propulsion