Entropy, fluctuations, HUP as an “arrow of time ”
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‘Arrow of time’ reversed in quantum experiment

'' ... heat can spontaneously flow from a cold quantum particle to
a hotter one under certain conditions:. . .''

https://www.sciencenews.org/article/...eriment?tgt=nr

In my opinion, this conditions are so called:
entropy,* quantum fluctuations, vacuum transformations,
Heisenberg uncertainty principle

Entropy is a very weird and misunderstood quantity.
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Between 1850 - 1865 Rudolf Clausius published a paper
in which he called " The energy conservation law" as
" The first law of thermodynamics". But in our nature the
heat always flows from the higher temperature to the
lower one and never back. In our everyday life we don't see
the heat itself rises from cold to hot. So, it seemed that
in thermodynamics " The energy conservation law"
wasn’t kept, this law was broken. But Clausius had another
opinion. He thought:
I know people believe that this process is
irreversible, but I am sure that " The energy conservation law"
is universal law and it must be correct also for thermodynamic
process. So, how can I save this law ?
Probably, in the thermodynamic process there is something
that we don't know. Maybe, there is some degradation
of the total energy in the system which never disappears .
Perhaps, there is some non-useful heat, some unseen process ,
some unknown dark energy , some another form of potential
energy/heat itself which can transform heat from the cold
body to the warm one. I will call this conception as " entropy"
and it will mean that changes of entropy (dS) can be calculated
for reversible process and may be defined as the ratio of the
quantity of energy taken up (dQ) to the thermodynamic
temperature (T), i.e. dS= dQ /T.
And because I don't know how this process goes I won't call
it as a law, but as " The second principle of thermodynamics "
which says that " the entropy of an isolated system always
increases ". Another version: " No process is possible
in which the only result is the transfer of heat from a hotter
to a colder body. It is possible some reversible process which
is unknown now ."
Later, Ludwig Boltzmann described ''entropy'' by a formula: S= k log W.
And, finally, Max Planck described ''entropy'' as: h*f = kT logW .
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So, ''entropy'' saves us from ''cold death'' by creating hot systems (stars, planets ).
But, it is a pity, that until today we cannot understand how this process is going:
not from hot ''big bang'' but vice versa - from zero cold tob 'singular point''.

Scientists cannot explain how using Planck's formula h*f = kT logW is possible
to create at first ''singular point'' as E=h*f
and then a ''big bang'' as a hot system of star formation: S= kT logW.
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Quantum fluctuations, vacuum transformations . . . as a “arrow of time ”
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Heisenberg uncertainty principle connects the measurement of
energy and time: when the time can be arrow or to past or to future.

best wishes
Israel sadovnik socratus

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If we use an “arrow of time ” to cold reference frame then we know,
the “arrow of time ” disappears at concrete parameter: T=0K.
If we use an “arrow of time ” to hot reference frame then “arrow of time ”
disappears in a '' singular point'' - in an abstract, no concrete parameter.
So, if a science is the science of Physics then it is better to think about
the '' arrow of time'' from the concrete physical parameter: T=0K.

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