On Sep 3, 1:12=A0pm, Jarek Duda
gmail.com> wrote:> I've simplified above counterexample - there shouldn't be any doubts
> now.
>
> Everything is in vacuum, without gravity.
> Take a tube with interior covered with mirror.
> Fix two transparent separators inside and place hot gas between them.
> Now place two mirrors on both sides, which can freely move inside the
> tube.
>
> Some of thermal infrared photons will be bounced by a mirror - giving
> part of own momentum, thanks of momentum conservation law.
> The heat of the gas will be slowly converted into momentum of mirrors,
> which can be converted into work.
>
> After infinite time all heat energy will be converted into kinetic
> energy of mirrors - we will have only gas with T=3D0 and moving mirrors.
After an infinite time, the mirrors are an infinite distance
apart. Therefore, there is nothing outside the mirrors upon which work
can be done. By your assumption, the only way for the mirrors to do
work is if they were to come into contact with something. Something
has to get in their way.
Furthermore, the radiation pressure at infinite time is zero.
There is no way to push the two mirrors together again. So the energy
between the two mirrors is used up.
I think you have this problem wrong. The word "system" has at its
root, "stem" (Ouch!) The two mirrors are like a "stem" extending
between two heat reservoirs: the volume initially between the two
mirrors and the volume initially outside the two mirrors. The "system"
is the two mirrors. The two mirrors are the objects that do the work
and permit the flow of energy.
Actually, this is a version of the free expansion problem. The
photon gas initially between the two mirrors is expanding into space
because of the motion of the mirrors. Entropy is increasing because
energy is being transferred from the hot reservoir to the cold
reservoir. The mirrors are forming a type of heat engine. Free energy
is being used up. Once those mirrors have expanded to their fullest
extent, there is no free energy. The heat engine will stop working.
There is no way to cycle the energy. You haven't come up with any way
to recycle the energy when the mirrors have expanded.
>
> Returning to practical use/biology ...
> I was thinking about 2nd law of thermodynamics and crystallization.
> During this process we get higher ordering (lower entropy), but the
> cost is energy difference between free and bind molecule - this energy
> is usually just dispersed around, increasing general temperature.
> But what if we wouldn't allow this energy to run away randomly ... for
> example storing it in chemical energy of some molecule, like ATP ...
That is not the cost. The cost was when you cooled the crystal,
you took energy from a high temperature reservoir to a low temperature
reservoir. You couldn't store the energy in a molecule.
>
> That lead me to mechanisms that could allow organisms to feed directly wi=
th heat (not using thermal infrared):
>
> Let say that we have two molecules(A,B) which has larger total > energy =
separated(E1) than when they are bind (E2
> Additionally there is energy barrier between these states.
There is no "temperature" defined by two molecules.
> Now when they are bind in solution, their thermal energy statistically s=
ometimes exceed the =A0barrier, and they split (reducing temperature!).
The temperature isn't reduced. The kinetic energy of the two
molecules is reduced. Temperature is not the same as kinetic energy.
> But to bind them back, they not only have to reach the barrier, >but they=
have also to find each other in the solution
Yes they do have to find each other. You haven't explained how
they do so. There are many wrong directions that lead to moving far
apart, and only a few paths that lead toward each other. The molecules
are blind: unless they send out pulses of something (light?) they
don't know the ways back together.
> - it's not >very likely, so statistically concentration of AB is >relativ=
ely small comparing to concentration of separated molecules.
Yes, so you have described a system with an excess of reactants
and a deficiency of product. The reaction proceeds forward. AB is
formed, while A and B separately decrease.
>
> Now we will need a catalyst which reduce the barrier, but then >use the e=
nergy difference for example to bind ADP and phosphate.
> For example it catches all required molecules and uses energy >stored in =
own structure to take A and B closer, to make them reach >the top of the ba=
rrier, then use energy they produce to bind ADP + >P and restore own energy=
..
The catalyst molecule is blind. It can swing its arms. However, it
is as likely to separate A and B as to bring them together. Unless the
catalyst molecule can send out probes, it speeds up both the formation
of AB and the destruction of AB equally. The increase per molecule of
both reactions is equal.
>
> I know - this enzyme would work in both directions,
Exactly.
>but concentration of AB should be small, such that the wanted >direction s=
hould dominate.
Impossible. The enzyme molecule is blind. The blindness of the
enzyme causes the following rule. An enzyme by itself can never change
the equilibrium constant.
Google the phrase: equilibrium constant. A catalyst can't change
the equilibrium constant. It can only increase the rate of reaction
while the system is far from equilibrium.
None of the enzymes in a living thing change the equilibrium
constants. They can't make a reaction that is thermodynamically
impossible occur. This is why plants need sunlight and animals eat
plants. The enzyme can only make a reaction occur faster, it can't
make the impossible happen.
