From: schinder@leprss.gsfc.nasa.gov (Paul J. Schinder)
Newsgroups: talk.origins
Subject: Re: Thermodynamics FAQ
Date: 31 Jul 92 16:54:21 GMT
Reply-To: schinder@leprss.gsfc.nasa.gov
Organization: Goddard Space Flight Center

In <henley.920731102303@wilbur.eng.auburn.edu> henley@eng.auburn.edu (James Paul Henley) writes:

>In article <1992Jul31.071648.10927@murdoch.acc.Virginia.EDU> lfoard@Turing.ORG (Lawrence C. Foard) writes:
>>In article <henley.920730124402@wilbur.eng.auburn.edu> henley@eng.auburn.edu (James Paul Henley) writes:
>>>Actually, the entropy will have increased.  What happened is that the work
>>>being done by the Sun was chemical.  That increased entropy is in the form
>>>of chemical entropy.  If the plant does not grow, or reaches a state in
>>>which it sheds leaves as fast as it grows new one, and there is sufficient
>>>microbial activity to cause the leaves to decay as fast as they are being
>>>shed, then you have reached steady state.  As long as you can complete the
>>>biological food cycle, the system can continue to live.
>>>
>>>Try the following experiment:
>>>
>>>Take the same sealed container, surround it with artificial sunlight 24 hours
>>>a day.  The second law of thermodynamics predicts that the plant will not
>>>be able to survive - you will reach equilibrium, and all internal processes
>>>will cease.  This should be easy enough to try. 
>>
>>The plant only needs a heat differential, light comes in at a high energy
>>(equivalent to 1000K or so), and is then reradiated by the plant into the

>That is why I specified that it was surrounded - a uniform radiation field
>in.  I should have also specified that it was insulated against conductive
>and convective heat transfer out - limited only to radiative heat transfer
>out.  What would happen in that situation?

The same thing that would happen if you tossed a plant into a furnace.
So what?  If you heat a plant to 1000 K, it'll die, and it doesn't matter
how you cook it.

>>air at room tempature. Only if the plant was as hot as the light source
>>would there be a problem (and plants tend not to like 1000K) :-)
>>
>If the radiation in is uniform, you've got a *BIG* problem.  No differential.
>>
>>Try it you will be surprised :-)

>As amended, I still stand by the prediction.  Any biologists want to prove
>me wrong?  Should be very very easy.  Suspend a glass container inside
>another glass container with a vacuum.  That should prevent conductive
>heat transfer out.  Completely surround the plant with artificial sunlight
>so that the intensity is uniform.  You can use any intensity you choose,
>but it must be uniform.   See how long the plant lives.  It can
>grow, but it cannot go through the O2 breathing night cycle, so it will 
>always breath CO2.  Once the CO2 is gone,  finito.

Uhh, I thought plants produced O2 from C02, more than they use in
respiration (that's why the atmosphere of the earth is polluted with
O2 and out of equilibrium).  *Eventually* the plant will eat up the
carbon supply, and I suppose it'll die then.  So?

>Oh, You can put anything inside the container you want,  plants, animals,
>microbes, or any device of any kind that you chose.  But that device can
>not receive any external source of energy except the artificial sunlight.
>You can even put mirrors to shield part of the system, or to selectively
>reflect sunlight.  If that system can survive, you will have proven
>that the laws of thermodynamics do not apply to biological systems.
>(what would that mean?)

You mean that it can vent radiation to the universe?  We're talking
about a something like a source of (approximately solar) light, and
the container is permitted to radiate to the night sky, such that the
radiation balance keeps an approximately earth like temperature inside
the container (we don't want to kill the plant and animals)?  The
earth itself is one such system, and things have been living on it for
about 3 billion years.  I believe that people actually *have*
constructed such small closed systems trying to learn how to build
self contained micro ecosystems for spaceflight, although I don't know
offhand how many years they can survive.

How do you suppose the space shuttle gets rid of its excess heat?  Do
you know *why* they open the cargo bay doors as soon as possible?

>The system that I just described is known as a perpetual motion machine
>of the second kind.  One of the statements of the second law is:
>"A perpetual motion machine of the second kind is impossible"

Yes, but you can run an engine so long as there's an energy supply.

>>-- 
>>>>Unix/C Contract worker available 5 years C/unix work experience<<  ______
>>Available for Telecommuting/Travel and contracts on the T Line       \    /
>>in the Boston MA area. Send me e-mail for a copy of my Resume.        \  /
>>       -- VWIS 508-793-9568 (2400 baud), Linux support BBS.--          \/


>James P. Henley Jr.
>Chemical Engineering Dept
>Auburn University

--
--------
Paul J. Schinder
NASA Goddard Space Flight Center
schinder@leprss.gsfc.nasa.gov
Newsgroups: talk.origins,sci.astro