On Aug 25, 1:47 am, Jarek Duda
gmail.com> wrote:> Phenomenological thermodynamics is like Newton's physics - a few
> century old theory ... and is tried to be adjust to experiments
> because physicists have to trust old authorities ... ?
> It is only an approximation! Something like mean field - it assumes
> only simple interactions and usually that particles are independent...
> it forgets that the molecules can organize in some specific
> patterns ... like life :)
> Even forgetting about for example emission of thermal photons, it
> already has problems - for example how You explain that while
> spontaneous crystallization entropy goes into 'forbidden'
>
direction...?http://www.garai-research.com/research%%20statement/Entropy/Entropy...
>
> You can argue, but the have working machines which are
> counterexamples :)
> Which can change heat into sound wave and then into electricity and
> then eventually to work!
> Or in given temperatures change naturally produced thermal infrared
> into periodic movement of electrons in wires and than into regular
> movement of electrons...
> If it can be done electronically, it should be doable using single
> molecules ... biology should have found it...
>
> I believe the problem is with the last part ... in electronics we use
> diodes for it ... could single molecules do it?
> If we can make single molecule transistors ...
http://www.physorg.com/news4345.html
>
> How could such infrared photosynthesis look like? We need
>about ten times more photons ...
The problem with infrared photosynthesis isn't the number of
photons necessary to be absorbed. The problem is that a colder heat
reservoir is needed.
Lets consider standard visible light photosynthesis. The light
shining on a green plant comes from the surface of the sun, which is
about 5000 degrees Kelvin. The origin of this light is "marked" by its
spectrum. The molecules of the green plants "know" (figuratively
speaking) the temperature of the source through the spectrum. The
spectrum of sunlight reaching the earth matches in shape that of a
black body radiator at 5000 degrees Kelvin. There are a few
differences related to narrow spectral lines, and the intensity of the
radiation is far down from what one would expect. However, to first
order the sunlight has the "mark" of a 5000 degree Kelvin source.
The green leaf absorbs the light. Whether it uses it in
photosynthesis or not, most of the light is turned into "heat energy"
at By heat I mean infrared radiation with a spectrum the same as a
300 Kelvin black body source. So the leaf "knows" (figuratively
speaking) that the radiation it emits comes from a 300 K source (the
leaf itself).
Thus the leaf generates entropy consistent with a heat reservori
at 5000 K transferring energy to a heat source at 300 K. That is a BIG
increase in entropy. Whether or not the leaf is photosynthesizing
doesn't matter as far as the second law of thermodynamics is
concerned. Any reaction that decreases the entropy less than the leaf
is making entropy is possible according to the second law, as long as
that system is connected to the leaf.
However, a leaf that absorbed infrared radiation would not be
so fortunate. If a leaf absorbs IR from the atmosphere at 300 K, it
soon emits IR to the atmosphere at 300 K. That is NO increase in
entropy. Thus, there is no reaction that decreases entropy that is
possible, even for a system connected to the leaf.
Now, this is a bit of an oversimplification. There may be organisms
out there which is heated to a high temperature on one side and a cold
temperature on the other. Maybe some type of "IR photosynthesis" is
possible under those conditions. However, I am fairly sure based on
these arguments that IR photosynthesis can't be as efficient as
visible light photosynthesis.
Good luck if you think you know a way.
> There should be many (similar?) molecules which catch these photons. I
> know - they should emit the same photon back... and it's where some
> kind of nanodiode is needed!
You are not thinking about the stimulated emission and stimulated
absorption. Having a larger number of photons around increases the
chances that an absorbed photon will be remitted. Diodes have been
studied thermodynamically. I don't know what will be different about
nanodiodes.
Are you claiming that the laws of thermodynamics are wrong? If
so, I don't know how to analyze it. If you know a nanodiode that can
violate the Second Law, then please sell it or do something. We need
it rather badly.
