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RE: 2nd Law of Thermodynamics



On 27 March 1997, Nathan Myhrvold wrote:

> Also, since it is mentioned in the inclusion in the mail, the biosphere
> is NOT entirely powered by the sun.   Bacteria, tube worms and other
> creatures that live on the ocean bottom near deep sea vents are powered
> by heat from the earth. 

Talking about the second law of thermodynamics, here's a question 
from one of its greatest fans:

These bacteria, tube worms etc. on the ocean bottom are powered by heat from 
the earth ? 
Great, but please tell me, how exactly does this work ? I don't know 
how hot it's down there, let's just suppose the temperature is 350 K.
So our little bacterium is surrounded by an environment 
of 350 K, but who cares ? The environment offers a great amount of 
energy, but this kind of energy has no value because of the second 
law of thermodynamics. Everybody familiar with 
the concept of exergy and anergy (I hope those terms exist in 
English) will know this. The bacterium needs valuable energy 
(exergy) for moving, growing, reproduction etc. A source of heat can 
only be used for getting such valuable energy if it has a temperature
higher than the environment.

We human beings have the same problem. We live at a temperature of 
about 290 K, which means our whole environment is full of thermic energy, which 
however 
cannot be used. It only works if something else exists which has a 
lower level of temperature. This may be the ultimate solution of my 
question, as the organisms could use the difference of temperature 
between the hot ground and the cool surrounding ocean, but this still 
does not explain how they do it. (Photosynthesis is a completely 
different case, as radiation from the sun contains a high percentage 
of valuable energy.)

I'm looking forward to any explanations !



Martin Jehle, Dipl.-Ing.(FH)
martin.jehle@klinik.uni-regensburg.de
Regensburg, Germany