In this short series of my blogs, I like to shed a light on **Quantum Mechanics** (QM)
and in particular **Quantum Particles** and how their behaviour interferes
with our normal word. After month of Corona shutdown, I thought it is
beneficial to recall the principles of nature and learn from the facts.

So let's start! First, lets discuss our scope and where we are: In fig 1 I've tried to summarise the 'global' or even more 'cosmic' scale of the subjects in physics. Here, we have:

- The micro cosmos determined by the physical laws of Quantum Mechanics. Of course, this is our primary subject.
- Our visible world which is determined by Newton's mechanics; and since mankind is knowledgable about electro-magnetism, we need to consider those, though it rules our daily live by means of chemistry.
- The Universe as such, which is still out-of-reach except for exploring our solar system, is ruled be the gravitational forces and at extreme edges by Einstein's General Relativity.

Fig 1 makes an attempt to put it all together. We see, that we talk about a
scale of 10^{45} magnitudes of size, starting from the 'size' of an electron
and reaching the diameter of the Universe. The forces span almost the same order
from gravitation to strong interaction. It is interesting to note, that the
stronger the force the more restricted (in terms of spatial dimension) it is,
while the - principally - very weak force of gravitation 'rules' the Universe!

However, we see that forces - together with all quantum particles - carry
an intrinsic property called 'spin' which rules indeed their behaviour.
Let's come to that point later. For now, we me recognise that we - given our
experiences and instruments - are sitting 'in between' the scales. Both
**experience** and **instruments** need to be adjusted in order not only to
understand and analyse the given physics but in addition interact with the
analysed subjects. In case of the universe, interaction can be neglected;
but for the quantum world it is most significant since it impacts the
observed behaviour.

**Quantum Mechanics** tries to cope with this interdependency, because it is
formulated as a theory of 'observables': What we do measure is not the
quantum 'object' by itself, but rather its behaviour measured at our 'scale'.

If you take a ride with your bike you've noticed (fig 2 bottom): Your motion is stable unless you stop. The physical source which keeps your bike straight is given by the energy conserved in the motion or your wheels: An energy conversation force is given once the wheels turn; and the amount of energy is proportional to the size (radius) of the wheels and the rotating speed.

In essence, energy can be conserved by a rotating system. Even the
quantum world follows this principle introducing the *spin* of a particle.
This spin - and any other angular momentum - in the quantum world is
however (though) quantised, thus possessing discrete levels, starting with * 1/2*.

Actually, the *1/2* is just an artefact of you math describing those
particles. However, the rules QM particles follow are strict.

- A spin
*1/2*particle can only (given the same quantum state) only concurrently twice. - A particle with natural spin {0, 1, 2} may exist in the very same quantum state with indefinite copies.

Basically, this is why we have a 'material girl': Quantum exclusion rules forbid spin 1/2 particles to fill up the quantum states regardless. On the other hand, that is the reason why 'Luke Skywalker's' light sober never will work the photons, because they are spin 1 particles and thus infinite photons may exist in the same quantum state and would not interact.

Angular momentum is present in our daily life, since this the reason
why the earth is circulating around the sun and why planet systems do
exit over a very long period. Even the order (= distance) of planets
relative to the sun is determined well defined
by a physical theorem, the **Titus-Bode law**,
although we are outside any quantum rules.

However, it shows that a many-body system's energy can be conserved.
It is however not clear, whether this is the reasons why fermions have
finite mass ... Looking at the other scale, we can say that
the long-time existence of objects like galaxies really depends on the
bound energy given by their angular momentum. In (fig 1 bottom) this is called the
*Virial theorem*: If you observe some object and you can measure
their (radial) velocity and estimate the radius relative to it's center,
you can calculate the mass (within the given radius) forcing the objects
to circulate around the center.

The fact, that I can beat on my desk is basically due to the fact that the
quantum particles building my desk are *spin* 1/2 particles. The need to follow
the *exclusion rule* that only 2 particles can be in the same quantum state
(at the very same moment). We call these particles **Fermions**, since they
obey the *Fermi/Dirac statistics*. The entire 'matter' is build from
fermions as shown in fig 2. On the opposite; even spin (or zero spin) particles
are used as *force* particles, in particular the photons and gluons.

The question is now: Is this behaviour exclusive. The answer is: No.
We do have *mesons* which may have integer spin values (among others) and
we observe spin 1/2 particles to act as exchange particles. However, the
underlying reason is still not clear.

Within your known world (the middle lane) we experience the following forces:

Interesting to note, that the gravitational and electro-magnetic forces
behave almost alike, since observe a dependence of the force
given by `F ∝ a*b/r ^{2}`

These forces behave differently depending on the scale (fig 3). In particular,
physicists *assume* that all forces can be derived from a primary primeval force,
which was split up during the birth of the universe. Assuming that, we my conclude
that all the different forces behave identical in case we can 'reconstruct' the
primeval circumstances. The unification of the electro-magnetic and the weak force
acts here as a blueprint and has been achieved already.

Let's try to explore this word! I've planned to discuss the following topics:

- Quantum Water
- Proton
- Superposition
- Neutrinos
- Quasiparticles
- Antimatter
- Phonons
- Pentaquarks
- The Higgs