Thank you for your answer. I have thought more and I believe that now I
understand the paper better.
I would agree that an ideal potential barrier, provided it is created
intelligently, does not inject the energy in a micro- and a macrosystem.
Well, if a potential barrier has some thickness, then when we insert it,
it should move the medium away. Also if we do not know the position of
the bead exactly then it well might be that the wall will push the bead
directly. Hence one cannot exclude that the potential wall inject the
energy as well, but presumably one can neglect it.
Still, I do not understand exactly how to describe the influence of the
wall on the physical system. In the ideal case, it does not change the
energy of the system but it definitely changes the momentum in the case
with the ball. In a microsystem, provided the wall goes through the
medium only, the momentum could stay the same though as the change from
both sides of the wall might cancel each other. It could be.
In any case, it is more interesting what happens with information. I
also agree that in this case the information is processed by the
controller, that is, there are some measurements, the results go into
the controller, and after some processing it makes an action.
Thereafter in my view, the title of the paper is misleading:
"information-to-energy conversion". By the way the authors are talking
about the energy, not the entropy.
What happens is that we have a multidomain system where there are
different interactions between different subsystems. Using some very
specific vocabulary one can presumably find a meaning in such a
statement "information-to-energy conversion" (or if you want it ot
"information-to-entropy conversion"). As I have already mentioned, this
could work if we limit the analysis for one subsystem of the whole
system. Yet, then information will be context dependent, so I am not
sure if it will be possible to bring a strict definition of information
as a property of a physical system from such an experiment.
Again, I have nothing against of the experiment as such. It looks
interesting. What is missing is a good theoretical analysis when one
starts from the whole system, including the controller (I guess, there
are computations there) and write down all the assumptions made to come
to the conclusion "information-to-energy conversion". It would be nice
to understand how information emerges from the movements of atoms and
molecules in the whole system including the controller.
On 27.03.2012 22:50 meekerdb said the following:
On 3/27/2012 11:26 AM, Evgenii Rudnyi wrote:
I have nothing against of fundamental science and I do not expect
practical application for this paper.
Yet, I do not see fundamental results. What is in the paper is just a
change of vocabulary. I would say that we are free to choose a
definition. Well, right now when free will is under question such a
statement might be ill-posed but I guess that you understand what I mean.
Let me start with "extracting energy from random molecular motion".
Let us consider the next example. A macroscopic ball is flying in one
direction. We suddenly make a potential barrier on its way and it
flies back after the collision with this potential wall. Do we inject
the energy in the system to change the ball trajectory or not?
Could you please compare this example with the experiment described in
the paper? What is the difference between the wall in the example and
potential walls in the experiment?
To be like the experiment the ball would have it's trajectory changed
again by the random heat energy of the medium.
My point above is that I am not convinced yet, that the energy in the
experiment is extracted from random molecular motion.
As I read it, not energy was actually extracted. It was a demonstration
of principle. In principle one could have a tiny shaft attached to the
bead so that as it rotated the shaft could be used to do work. But of
course this is impractical.
It might be possible to state this but then, in my view, some change
in the normal vocabulary is needed. This has been taken in the paper
for granted. Hence, I am not convinced.
"What you asked for was an example of using information to reduce
entropy: not obtaining information AND using it to reduce entropy."
What do you mean here? I see two statements
"using information to reduce entropy"
"obtaining information AND using it to reduce entropy"
What in your view has been done in the paper and what difference do
you see between these two statements.
The latter is of course what is done in the paper. The difference is
that if you include the obtaining the information in the balance sheets
that costs free energy, so even though you use information to gain free
energy the second law is still upheld for the whole system.
Finally when I have quoted a statement from the paper
"In microscopic systems, thermodynamic quantities such as work, heat
and internal energy do not remain constant"
I have meant the following. A thermodynamic system has an internal
energy, the Gibbs energy, the entropy and other state functions.
However a thermodynamic system does not possess work or heat, they are
not state functions. A thermodynamic system can perform work or
produce heat when it goes from one state to another. Hence the
statement above as such is just sloppy.
Complain to the authors.
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